Geomorphological and geotechnical issues affecting the seismic slope stability of the Duwamish River Delta, Port of Seattle, Washington

USGS Publications Warehouse

Kayen, Robert E.; Barnhardt, Walter A.; Palmer, Stephen P.

1999-01-01

Young Holocene deposits of the Duwamish River valley underlie a highly developed transportation-industrial corridor, extending from the City of Kent to the Elliott Bay-Harbor Island marine terminal facilities. The deposits have been shaped by relative sea-level rise, but also by episodic volcanism and seismicity. A geologic and geotechnical investigation of these river-mouth deposits indicates high initial liquefaction susceptibility during earthquakes, and possibly the potential for unlimited-strain disintegrative flow failure of the delta front.

[Infiltration characteristics of soil water on loess slope land under intermittent and repetitive rainfall conditions].

PubMed

Li, Yi; Shao, Ming-An

2008-07-01

Based on the experiments of controlled intermittent and repetitive rainfall on slope land, the infiltration and distribution characteristics of soil water on loess slope land were studied. The results showed that under the condition of intermittent rainfall, the cumulative runoff during two rainfall events increased linearly with time, and the wetting front also increased with time. In the interval of the two rainfall events, the wetting front increased slowly, and the infiltration rate was smaller on steeper slope than on flat surface. During the second rainfall event, there was an obvious decreasing trend of infiltration rate with time. The cumulative infiltration on 15 degrees slope land was larger than that of 25 degrees slope land, being 178 mm and 88 mm, respectively. Under the condition of repetitive rainfall, the initial infiltration rate during each rainfall event was relatively large, and during the first rainfall, both the infiltration rate and the cumulative infiltration at various stages were larger than those during the other three rainfall events. However, after the first rainfall, there were no obvious differences in the infiltration rate among the next three rainfall events. The more the rainfall event, the deeper the wetting front advanced.

Landslide Probability Assessment by the Derived Distributions Technique

NASA Astrophysics Data System (ADS)

Muñoz, E.; Ochoa, A.; Martínez, H.

2012-12-01

Landslides are potentially disastrous events that bring along human and economic losses; especially in cities where an accelerated and unorganized growth leads to settlements on steep and potentially unstable areas. Among the main causes of landslides are geological, geomorphological, geotechnical, climatological, hydrological conditions and anthropic intervention. This paper studies landslides detonated by rain, commonly known as "soil-slip", which characterize by having a superficial failure surface (Typically between 1 and 1.5 m deep) parallel to the slope face and being triggered by intense and/or sustained periods of rain. This type of landslides is caused by changes on the pore pressure produced by a decrease in the suction when a humid front enters, as a consequence of the infiltration initiated by rain and ruled by the hydraulic characteristics of the soil. Failure occurs when this front reaches a critical depth and the shear strength of the soil in not enough to guarantee the stability of the mass. Critical rainfall thresholds in combination with a slope stability model are widely used for assessing landslide probability. In this paper we present a model for the estimation of the occurrence of landslides based on the derived distributions technique. Since the works of Eagleson in the 1970s the derived distributions technique has been widely used in hydrology to estimate the probability of occurrence of extreme flows. The model estimates the probability density function (pdf) of the Factor of Safety (FOS) from the statistical behavior of the rainfall process and some slope parameters. The stochastic character of the rainfall is transformed by means of a deterministic failure model into FOS pdf. Exceedance probability and return period estimation is then straightforward. The rainfall process is modeled as a Rectangular Pulses Poisson Process (RPPP) with independent exponential pdf for mean intensity and duration of the storms. The Philip infiltration model is used along with the soil characteristic curve (suction vs. moisture) and the Mohr-Coulomb failure criteria in order to calculate the FOS of the slope. Data from two slopes located on steep tropical regions of the cities of Medellín (Colombia) and Rio de Janeiro (Brazil) where used to verify the model's performance. The results indicated significant differences between the obtained FOS values and the behavior observed on the field. The model shows relatively high values of FOS that do not reflect the instability of the analyzed slopes. For the two cases studied, the application of a more simple reliability concept (as the Probability of Failure - PR and Reliability Index - β), instead of a FOS could lead to more realistic results.

Quadrupedal gaits in hexapod animals - inter-leg coordination in free-walking adult stick insects.

PubMed

Grabowska, Martyna; Godlewska, Elzbieta; Schmidt, Joachim; Daun-Gruhn, Silvia

2012-12-15

The analysis of inter-leg coordination in insect walking is generally a study of six-legged locomotion. For decades, the stick insect Carausius morosus has been instrumental for unravelling the rules and mechanisms that control leg coordination in hexapeds. We analysed inter-leg coordination in C. morosus that freely walked on straight paths on plane surfaces with different slopes. Consecutive 1.7 s sections were assigned inter-leg coordination patterns (which we call gaits) based on footfall patterns. Regular gaits, i.e. wave, tetrapod or tripod gaits, occurred in different proportions depending on surface slopes. Tetrapod gaits were observed most frequently, wave gaits only occurred on 90 deg inclining slopes and tripod gaits occurred most often on 15 deg declining slopes, i.e. in 40% of the sections. Depending on the slope, 36-66% of the sections were assigned irregular gaits. Irregular gaits were mostly due to multiple stepping by the front legs, which is perhaps probing behaviour, not phase coupled to the middle legs' cycles. In irregular gaits, middle leg and hindleg coordination was regular, related to quadrupedal walk and wave gaits. Apparently, front legs uncouple from and couple to the walking system without compromising middle leg and hindleg coordination. In front leg amputees, the remaining legs were strictly coordinated. In hindleg and middle leg amputees, the front legs continued multiple stepping. The coordination of middle leg amputees was maladapted, with front legs and hindlegs performing multiple steps or ipsilateral legs being in simultaneous swing. Thus, afferent information from middle legs might be necessary for a regular hindleg stepping pattern.

Time shift in slope failure prediction between unimodal and bimodal modeling approaches

NASA Astrophysics Data System (ADS)

Ciervo, Fabio; Casini, Francesca; Nicolina Papa, Maria; Medina, Vicente

2016-04-01

Together with the need to use more appropriate mathematical expressions for describing hydro-mechanical soil processes, a challenge issue relates to the need of considering the effects induced by terrain heterogeneities on the physical mechanisms, taking into account the implications of the heterogeneities in affecting time-dependent hydro-mechanical variables, would improve the prediction capacities of models, such as the ones used in early warning systems. The presence of the heterogeneities in partially-saturated slopes results in irregular propagation of the moisture and suction front. To mathematically represent the "dual-implication" generally induced by the heterogeneities in describing the hydraulic terrain behavior, several bimodal hydraulic models have been presented in literature and replaced the conventional sigmoidal/unimodal functions; this presupposes that the scale of the macrostructure is comparable with the local scale (Darcy scale), thus the Richards' model can be assumed adequate to mathematically reproduce the processes. The purpose of this work is to focus on the differences in simulating flow infiltration processes and slope stability conditions originated from preliminary choices of hydraulic models and contextually between different approaches to evaluate the factor of safety (FoS). In particular, the results of two approaches are compared. The first one includes the conventional expression of the FoS under saturated conditions and the widespread used hydraulic model of van Genuchten-Mualem. The second approach includes a generalized FoS equation for infinite-slope model under variably saturated soil conditions (Lu and Godt, 2008) and the bimodal Romano et al.'s (2011) functions to describe the hydraulic response. The extension of the above mentioned approach to the bimodal context is based on an analytical method to assess the effects of the hydraulic properties on soil shear developed integrating a bimodal lognormal hydraulic function within the Bishop stress theory framework (Ciervo et al., 2015). The proposed work tends to emphasize how a more accurate slope stability analysis that accounts dual-structure could be useful to reach a more accurate definition of the stability conditions. The effects in practical analysis may be significant. The highlighted discrepancies between the different approaches in describing the timing processes and strength contribution due to capillary forces may entail no negligible differences in slope stability predictions, especially in those cases where the possibility of a failure in unsaturated terrains is contemplated.

Final Scientific/Technical Report: Characterizing the Response of the Cascadia Margin Gas Hydrate Reservoir to Bottom Water Warming Along the Upper Continental Slope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Solomon, Evan A.; Johnson, H. Paul; Salmi, Marie

The objective of this project is to understand the response of the WA margin gas hydrate system to contemporary warming of bottom water along the upper continental slope. Through pre-cruise analysis and modeling of archive and recent geophysical and oceanographic data, we (1) inventoried bottom simulating reflectors along the WA margin and defined the upper limit of gas hydrate stability, (2) refined margin-wide estimates of heat flow and geothermal gradients, (3) characterized decadal scale temporal variations of bottom water temperatures at the upper continental slope of the Washington margin, and (4) used numerical simulations to provide quantitative estimates of howmore » the shallow boundary of methane hydrate stability responds to modern environmental change. These pre-cruise results provided the context for a systematic geophysical and geochemical survey of methane seepage along the upper continental slope from 48° to 46°N during a 10-day field program on the R/V Thompson from October 10-19, 2014. This systematic inventory of methane emissions along this climate-sensitive margin corridor and comprehensive sediment and water column sampling program provided data and samples for Phase 3 of this project that focused on determining fluid and methane sources (deep-source vs. shallow; microbial, thermogenic, gas hydrate dissociation) within the sediment, and how they relate to contemporary intermediate water warming. During the 2014 research expedition, we sampled nine seep sites between ~470 and 520 m water depth, within the zone of predicted methane hydrate retreat over the past 40 years. We imaged 22 bubble plumes with heights commonly rising to ~300 meters below sea level with one reaching near the sea surface. We collected 22 gravity cores and 20 CTD/hydrocasts from the 9 seeps and at background locations (no acoustic evidence of seepage) within the depth interval of predicted downslope retreat of the methane hydrate stability zone. Approximately 300 pore water samples were extracted from the gravity cores, and the pore water was analyzed for a comprehensive suite of solutes, gases, and stable isotope ratios. This comprehensive geochemical dataset was used to characterize the fluid and gas source(s) at each of the seep sites surveyed. The primary results of this project are: 1) Bottom simulating reflector-derived heat flow values decrease from 95 mW/m2 10 km east of the deformation front to ~60 mW/m2 60 km landward of the deformation front, with anomalously low values of ~25 mW/m2 on a prominent mid-margin terrace off central Washington. 2) The temperature of the incoming sediment/ocean crust interface at the deformation front ranges between 164-179 oC off central Washington, and the 350 oC isotherm at the top of the subducting ocean crust occurs 95 km landward of the deformation front. Differences between BSR-derived heat flow and modeled conductive heat flow suggest mean upward fluid flow rates of 0.4 cm/yr across the margin, with local regions (e.g. fault zones) exhibiting fluid flow rates up to 3.5 cm/yr. 3) A compilation of 2122 high-resolution CTD, glider, and Argo float temperature profiles spanning the upper continental slope of the Washington margin from the years 1968 to 2013 show a long-term warming trend that ranges from 0.006-0.008 oC/yr. Based on this long-term bottom water warming, we developed a 2-D thermal model to simulate the change in sediment temperature distribution over this period, along with the downslope retreat of the methane hydrate stability field. Over the 43 years of the simulation, the thermal disturbance propagated 30 m into the sediment column, causing the base of the methane hydrate stability field to shoal ~13 m and to move ~1 km downslope. 4) A preliminary analysis of seafloor observations and mid-water column acoustic data to detect bubble plumes was used to characterize the depth distribution of seeps along the Cascadia margin. These results indicate high bubble plume densities along the continental shelf at water depths <180 m and at the upper limit of methane hydrate stability along the Washington margin. 5) The majority of the seeps cored during the 2014 research expedition on the R/V Thompson contained abundant authigenic carbonate indicating that they are locations of long-lived seepage rather than emergent seep systems related to methane hydrate dissociation. Despite the evidence for enhanced methane seepage at the upper limit of methane hydrate stability along the Washington margin, we found no unequivocal evidence for active methane hydrate dissociation as a source of fluid and gas at the seeps surveyed. The pore fluid and bottom water chemistry shows that the seeps are fed by a variety of fluid and methane sources, but that methane hydrate dissociation, if occurring, is not widespread and is only a minor source (below the detection limit of our methods). Collectively, these results provide a significant advance in our understanding of the thermal structure of the Cascadia subduction zone and the fluid and methane sources feeding seeps along the upper continental slope of the Washington-sector of the Cascadia margin. Though we did not find unequivocal evidence for methane hydrate dissociation as a source of water and methane at the upper pressure-temperature limit of methane hydrate stability at present, continued warming of North Pacific Intermediate Water in the future has the potential to impact the methane hydrate reservoir in sediments at greater depths along the slope. Thus, this study provides a strong foundation and the necessary characterization of the background state of seepage at the upper limit of methane hydrate stability for future investigations of this important process.« less

Hydrologic behavior of model slopes with synthetic water repellent soils

NASA Astrophysics Data System (ADS)

Zheng, Shuang; Lourenço, Sérgio D. N.; Cleall, Peter J.; Chui, Ting Fong May; Ng, Angel K. Y.; Millis, Stuart W.

2017-11-01

In the natural environment, soil water repellency decreases infiltration, increases runoff, and increases erosion in slopes. In the built environment, soil water repellency offers the opportunity to develop granular materials with controllable wettability for slope stabilization. In this paper, the influence of soil water repellency on the hydrological response of slopes is investigated. Twenty-four flume tests were carried out in model slopes under artificial rainfall; soils with various wettability levels were tested, including wettable (Contact Angle, CA < 90°), subcritical water repellent (CA ∼ 90°) and water repellent (CA > 90°). Various rainfall intensities (30 mm/h and 70 mm/h), slope angles (20° and 40°) and relative compactions (70% and 90%) were applied to model the response of natural and man-made slopes to rainfall. To quantitatively assess the hydrological response, a number of measurements were made: runoff rate, effective rainfall rate, time to ponding, time to steady state, runoff acceleration, total water storage and wetting front rate. Overall, an increase in soil water repellency reduces infiltration and shortens the time for runoff generation, with the effects amplified for high rainfall intensity. Comparatively, the slope angle and relative compaction had only a minor contribution to the slope hydrology. The subcritical water repellent soils sustained infiltration for longer than both the wettable and water repellent soils, which presents an added advantage if they are to be used in the built environment as barriers. This study revealed substantial impacts of man-made or synthetically induced soil water repellency on the hydrological behavior of model slopes in controlled conditions. The results shed light on our understanding of hydrological processes in environments where the occurrence of natural soil water repellency is likely, such as slopes subjected to wildfires and in agricultural and forested slopes.

Distribution patterns of the mesozooplankton, principally siphonophores and medusae, in the vicinity of the Antarctic Slope Front (eastern Weddell Sea)

NASA Astrophysics Data System (ADS)

Pagès, Francesc; Schnack-Schiel, Sigrid B.

1996-12-01

The composition, abundance and vertical distribution of mesozooplankton, particularly siphonophores and medusae (27 species), collected along two transects in the eastern Weddell Sea have been analysed. Both transects were characterized by a steep thermocline that on approaching the coastline defined the Antarctic Slope Front. The front acted as a strong boundary in the shelf-slope and caused a pronounced cross frontal gradient in the populations of cnidarians. Few species and low abundances were found in the upper cold waters and most of the populations concentrated in and below the thermocline. The analysis of the gastrozooids of the physonect siphonophore Pyrostephos vanhoeffeni showed a wide variety of prey but the relatively high contribution of krill larvae reveals a substantial trophic impact when both organisms co-occur.

Influence of the posterior tibial slope on the flexion gap in total knee arthroplasty.

PubMed

Okazaki, Ken; Tashiro, Yasutaka; Mizu-uchi, Hideki; Hamai, Satoshi; Doi, Toshio; Iwamoto, Yukihide

2014-08-01

Adjusting the joint gap length to be equal in both extension and flexion is an important issue in total knee arthroplasty (TKA). It is generally acknowledged that posterior tibial slope affects the flexion gap; however, the extent to which changes in the tibial slope angle directly affect the flexion gap remains unclear. This study aimed to clarify the influence of tibial slope changes on the flexion gap in cruciate-retaining (CR) or posterior-stabilizing (PS) TKA. The flexion gap was measured using a tensor device with the femoral trial component in 20 cases each of CR- and PS-TKA. A wedge plate with a 5° inclination was placed on the tibial cut surface by switching its front-back direction to increase or decrease the tibial slope by 5°. The flexion gap after changing the tibial slope was compared to that of the neutral slope measured with a flat plate that had the same thickness as that of the wedge plate center. When the tibial slope decreased or increased by 5°, the flexion gap decreased or increased by 1.9 ± 0.6mm or 1.8 ± 0.4mm, respectively, with CR-TKA and 1.2 ± 0.4mm or 1.1 ± 0.3mm, respectively, with PS-TKA. The influence of changing the tibial slope by 5° on the flexion gap was approximately 2mm with CR-TKA and 1mm with PS-TKA. This information is useful when considering the effect of manipulating the tibial slope on the flexion gap when performing CR- or PS-TKA. Copyright © 2014 Elsevier B.V. All rights reserved.

A downslope propagating thermal front over the continental slope

NASA Astrophysics Data System (ADS)

van Haren, Hans; Hosegood, Phil J.

2017-04-01

In the ocean, internal frontal bores above sloping topography have many appearances, depending on the local density stratification, and on the angle and source of generation of the carrier wave. However, their common characteristics are a backward breaking wave, strong sediment resuspension, and relatively cool (denser) water moving more or less upslope underneath warm (less dense) water. In this paper, we present a rare example of a downslope moving front of cold water moving over near-bottom warm water. Large backscatter is observed in the downslope moving front's trailing edge, rather than the leading edge as is common in upslope moving fronts. Time series observations have been made during a fortnight in summer, using a 101 m long array of high-resolution temperature sensors moored with an acoustic Doppler current profiler at 396 m depth in near-homogeneous waters, near a small canyon in the continental slope off the Malin shelf (West-Scotland, UK). Occurring between fronts that propagate upslope with tidal periodicity, the rare downslope propagating one resembles a gravity current and includes strong convective turbulence coming from the interior rather than the more usual frictionally generated turbulence arising from interaction with the seabed. Its turbulence is 3-10 times larger than that of more common upslope propagating fronts. As the main turbulence is in the interior with a thin stratified layer close to the bottom, little sediment is resuspended by a downslope propagating front. The downslope propagating front is suggested to be generated by oblique propagation of internal (tidal) waves and flow over a nearby upstream promontory.

On the Antarctic Slope Front and Current crossing of the South Scotia Ridge

NASA Astrophysics Data System (ADS)

Orsi, A. H.; Palmer, M.; Gomis, D.; Flexas, M. M.; Kim, Y.-S.; Jordà, G.; Wiederwohl, C.; Álvarez, M.

2012-04-01

To unveil the contorted path followed by the Antarctic Slope Current connecting the Weddell and Scotia Seas, hydrographic stations with unprecedented spatial resolution were occupied on a series of sections across the slope and multiple channels in the double-pronged western portion of the South Scotia Ridge. Fieldwork consisted of two cruises from the ESASSI (January 2008) and ACROSS (February 2009) programs, the Spanish and USA/Argentina components of the International Polar Year core project SASSI (Synoptic Antarctic Shelf-Slope Interaction study). In this region the Antarctic Slope Current can be located by the pronounced in-shore deepening of isopycnals over the continental slope, rendering the strong subsurface temperature and salinity gradients characteristic of the Antarctic Slope Front. Before reaching the gaps in the southern Ridge near 51°W and 50°W, the ASC carries about 3 Sv of upper layer waters, but it splits into shallow and deep branches upon turning north through these two gaps. The shallower branch enters the Hesperides Trough at 51°W, then shows a tight cyclonic loop back to that longitude roughly following the slope's 700-m isobath, and turns again westward through a similar gap in the northern Ridge. In the Scotia Sea the westward-flowing Antarctic Slope Current is found as far west as the Elephant Island along slightly deeper levels of slope (1100 m) before it is blocked by the Antarctic Circumpolar Current south of the Shackleton Fracture Zone (56°W). The deeper branch of the ASC in the Powell Basin crosses the southern Ridge near 50°W and roughly follows the 1600-m isobath before entering the Scotia Sea through the Hesperides Gap farther to the east (49°W). Thereafter the deeper waters carried westward by this branch become undistinguishable from those circulating farther offshore. Repeat cross-slope sections at both southern and northern flanks of the South Scotia Ridge showed significant temporal variability in the characteristics of the Antarctic Slope Front/Current system.

Implementation of the pyramid wavefront sensor as a direct phase detector for large amplitude aberrations

NASA Astrophysics Data System (ADS)

Kupke, Renate; Gavel, Don; Johnson, Jess; Reinig, Marc

2008-07-01

We investigate the non-modulating pyramid wave-front sensor's (P-WFS) implementation in the context of Lick Observatory's Villages visible light AO system on the Nickel 1-meter telescope. A complete adaptive optics correction, using a non-modulated P-WFS in slope sensing mode as a boot-strap to a regime in which the P-WFS can act as a direct phase sensor is explored. An iterative approach to reconstructing the wave-front phase, given the pyramid wave-front sensor's non-linear signal, is developed. Using Monte Carlo simulations, the iterative reconstruction method's photon noise propagation behavior is compared to both the pyramid sensor used in slope-sensing mode, and the traditional Shack Hartmann sensor's theoretical performance limits. We determine that bootstrapping using the P-WFS as a slope sensor does not offer enough correction to bring the phase residuals into a regime in which the iterative algorithm can provide much improvement in phase measurement. It is found that both the iterative phase reconstructor and the slope reconstruction methods offer an advantage in noise propagation over Shack Hartmann sensors.

The Barents Sea Polar Front in summer

NASA Astrophysics Data System (ADS)

Parsons, A. Rost; Bourke, Robert H.; Muench, Robin D.; Chiu, Ching-Sang; Lynch, James F.; Miller, James H.; Plueddemann, Albert J.; Pawlowicz, Richard

1996-06-01

In August 1992 a combined physical oceanography and acoustic tomography experiment was conducted to describe the Barents Sea Polar Front (BSPF) and investigate its impact on the regional oceanography. The study area was an 80 × 70 km grid east of Bear Island where the front exhibits topographic trapping along the northern slope of the Bear Island Trough. Conductivity-temperature-depth, current meter, and acoustic Doppler current profiler (ADCP) data, combined with tomographic cross sections, presented a highly resolved picture of the front in August. All hydrographic measurements were dominated by tidal signals, with the strongest signatures associated with the M2 and S2 semidiurnal species. Mean currents in the warm saline water to the south of the front, derived from a current meter mooring and ADCP data, were directed to the southwest and may be associated with a barotropic recirculation of Norwegian Atlantic Water (NAW) within the Bear Island Trough. The geostrophic component of the velocity was well correlated with the measured southwestward mean surface layer flow north of the front. The frontal structure was retrograde, as the frontal isopleths sloped opposite to the bathymetry. The surface signature of the front was dominated by salinity gradients associated with the confluence of Atlantic and Arctic water masses, both warmed by insolation to a depth of about 20 m. The surface manifestation of the front varied laterally on the order of 10 km associated with tidal oscillations. Below the mixed layer, temperature and salinity variations were compensating, defining a nearly barotropic front. The horizontal scale of the front in this region was ˜3 km or less. At middepth beneath the frontal interface, tomographic cross sections indicated a high-frequency (˜16 cpd) upslope motion of filaments of NAW origin. The summertime BSPF was confirmed to have many of the general characteristics of a shelf-slope frontal system [Mooers et al., 1978] as well as a topographic-circulatory front [Federov, 1983].

Evaluating the Effect of Rainfall Infiltration on the Slope Stability of T16 tower of Taipei Mao-kong Gondola by Numerical Methods

NASA Astrophysics Data System (ADS)

RUNG, J.

2013-12-01

In this study, a series of rainfall-stability analyses were performed to simulate the failure mechanism and the function of remediation works of the down slope of T-16 tower pier, Mao-Kong gondola (or T-16 Slope) at the hillside of Taipei City using two-dimensional finite element method. The failure mechanism of T-16 Slope was simulated using the rainfall hyetograph of Jang-Mi typhoon in 2008 based on the field investigation data, monitoring data, soil/rock mechanical testing data and detail design plots of remediation works. Eventually, the numerical procedures and various input parameters in the analysis were verified by comparing the numerical results with the field observations. In addition, 48 hrs design rainfalls corresponding to 5, 10, 25 and 50 years return periods were prepared using the 20 years rainfall data of Mu-Zha rainfall observation station, Central Weather Bureau for the rainfall-stability analyses of T-16 Slope to inspect the effect of the compound stabilization works on the overall stability of the slope. At T-16 Slope, without considering the longitudinal and transverse drainages on the ground surface, there totally 4 types of stabilization works were installed to stabilize the slope. From the slope top to the slope toe, the stabilization works of T-16 Slope consists of RC-retaining wall with micro-pile foundation at the up-segment, earth anchor at the up-middle-segment, soil nailing at the middle-segment and retaining pile at the down-segment of the slope. The effect of each individual stabilization work on the slope stability under rainfall condition was examined and evaluated by raising field groundwater level.

Instabilities in rapid solidification of multi-component alloys

NASA Astrophysics Data System (ADS)

Altieri, Anthony L.; Davis, Stephen H.

2017-10-01

Rapid solidification of multi-component liquids occurs in many modern applications such as additive manufacturing. In the present work the interface departures from equilibrium consist of the segregation coefficient and liquidus slope depending on front speed, the one-sided, frozen-temperature approximation, and the alloy behaving as the superposition of individual components. Linear-stability theory is applied, showing that the cellular and oscillatory instabilities of the binary case are modified. The addition of components tends to destabilize the interface while the addition of a single large-diffusivity material can entirely suppress the oscillatory mode. Multiple minima in the neutral curve for the cellular mode occur.

The Hydromechanics of Vegetation for Slope Stabilization

NASA Astrophysics Data System (ADS)

Mulyono, A.; Subardja, A.; Ekasari, I.; Lailati, M.; Sudirja, R.; Ningrum, W.

2018-02-01

Vegetation is one of the alternative technologies in the prevention of shallow landslide prevention that occurs mostly during the rainy season. The application of plant for slope stabilization is known as bioengineering. Knowledge of the vegetative contribution that can be considered in bioengineering was the hydrological and mechanical aspects (hydromechanical). Hydrological effect of the plant on slope stability is to reduce soil water content through transpiration, interception, and evapotranspiration. The mechanical impact of vegetation on slope stability is to stabilize the slope with mechanical reinforcement of soils through roots. Vegetation water consumption varies depending on the age and density, rainfall factors and soil types. Vegetation with high ability to absorb water from the soil and release into the atmosphere through a transpiration process will reduce the pore water stress and increase slope stability, and vegetation with deep root anchoring and strong root binding was potentially more significant to maintain the stability of the slope.

30 CFR 56.3130 - Wall, bank, and slope stability.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Wall, bank, and slope stability. 56.3130... Mining Methods § 56.3130 Wall, bank, and slope stability. Mining methods shall be used that will maintain wall, bank, and slope stability in places where persons work or travel in performing their assigned...

Structural and Geomorphic Controls in Altitudinal Treeline: a Case Study in the Front Ranges of the Canadian Rocky Mountains

NASA Astrophysics Data System (ADS)

Macias Fauria, M.; Johnson, E. A.

2009-12-01

Altitudinal treelines occur on mountain slopes. The geological history of mountain systems sets both the distribution of slope angles, aspects and lengths, and the physical characteristics of the bedrock and regolith on which trees have to establish and grow. We show that altitudinal treeline is largely controlled at an ecosystem level by structural and slope (i.e. gravitational) geomorphic processes operating at a range of temporal and spatial scales, which have direct influence on the hydrological properties of the substrate (affecting the trees’ water and energy budget), as well as on substrate stability, both of which affect recruitment and growth of trees. The study was conducted over a relatively large area of > 200 km2 in the Front Ranges of the Canadian Rocky Mountains, selected to contain the regional diversity of slopes and substrates, which is the result of hundreds of millions of years of sea deposition, subsequent mountain building, and deep erosion by glaciations. Very high-resolution remote sensing data (LiDAR), aerial orthophotos taken at several times since the late 1940s, and ground truthing were employed to classify the terrain into process-based geomorphic units. High resolution, landscape-scale treeline studies are able avoid potential biases in site selection (i.e. selection of sites that are not representative of the overall regional treeline), and consequently capture the coupling between trees and the environment at an ecosystem (regional) level. Moreover, explicitly accounting for slope and substrate-related processes occurring in the studied mountain region is paramount in order to understand the dynamics of trees at their altitudinal distribution limit. Presence of trees in each unit was found to be controlled by a set of parameters relevant to both hydrological and slope processes, such as contributing area, slope angle, regolith transmissivity, and aspect. Our results show no treeline advance over the last 60 years in the region, as most of the area is controlled by geological processes and not by physiological temperature thresholds. Temperature could potentially affect presence of trees at high elevations through its effects on the physical properties of the slopes on which trees grow. However, this effect is at a much longer timescale than those implied in current studies of treeline response to global warming. Finally, continuous recruitment of trees following lightning-caused wildfires during the first half of the 20th century has resulted in increased high altitude forest stand density.

Spirit's Course

NASA Technical Reports Server (NTRS)

2004-01-01

[figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2

This digital elevation map shows the topography of the 'Columbia Hills,' just in front of the Mars Exploration Rover Spirit's current position. Rover planners have plotted the safest route for Spirit to climb to the front hill, called 'West Spur.' The black line in the middle of the image represents the rover's traverse path, which starts at 'Hank's Hollow' and ends at the top of 'West Spur.' Scientists are sending Spirit up the hill to investigate the interesting rock outcrops visible in images taken by the rover. Data from the Mars Orbital Camera on the orbiting Mars Global Surveyor were used to create this 3-D map.

In figure 1, the digital map shows the slopes of the 'Columbia Hills,' just in front of the Mars Exploration Rover Spirit's current position. Colors indicate the slopes of the hills, with red areas being the gentlest and blue the steepest. Rover planners have plotted the safest route for Spirit to climb the front hill, called 'West Spur.' The path is indicated here with a curved black line. Stereo images from the Mars Orbital Camera on the orbiting Mars Global Surveyor were used to create this 3-D map.

In figure 2, the map shows the north-facing slopes of the 'Columbia Hills,' just in front of the Mars Exploration Rover Spirit's current position. Bright areas indicate surfaces sloping more toward the north than dark areas. To reach the rock outcrop at the top of the hill, engineers will aim to drive the rover around the dark areas, which would yield less solar power. The curved black line in the middle represents the rover's planned traverse path.

A nomogram for interpreting slope stability of fine-grained deposits in modern and ancient-marine environments.

USGS Publications Warehouse

Booth, J.S.; Sangrey, D.A.; Fugate, J.K.

1985-01-01

This nomogram was designed to aid in interpreting the causes of mass movement in modern and ancient settings, to provide a basis for evaluating and predicting slope stability under given conditions and to further the understanding of the relationships among the several key factors that control slope stability. Design of the nomogram is based on effective stress and combines consolidation theory as applicable to depositional environments with the infinite-slope model of slope-stability analysis. If infinite-slope conditions are assumed to exist, the effective overburden stress can be used to derive a factor of safety against static slope failure by using the angle of internal friction and the slope angle. -from Authors

The Contribution of Particle Swarm Optimization to Three-Dimensional Slope Stability Analysis

PubMed Central

A Rashid, Ahmad Safuan; Ali, Nazri

2014-01-01

Over the last few years, particle swarm optimization (PSO) has been extensively applied in various geotechnical engineering including slope stability analysis. However, this contribution was limited to two-dimensional (2D) slope stability analysis. This paper applied PSO in three-dimensional (3D) slope stability problem to determine the critical slip surface (CSS) of soil slopes. A detailed description of adopted PSO was presented to provide a good basis for more contribution of this technique to the field of 3D slope stability problems. A general rotating ellipsoid shape was introduced as the specific particle for 3D slope stability analysis. A detailed sensitivity analysis was designed and performed to find the optimum values of parameters of PSO. Example problems were used to evaluate the applicability of PSO in determining the CSS of 3D slopes. The first example presented a comparison between the results of PSO and PLAXI-3D finite element software and the second example compared the ability of PSO to determine the CSS of 3D slopes with other optimization methods from the literature. The results demonstrated the efficiency and effectiveness of PSO in determining the CSS of 3D soil slopes. PMID:24991652

The contribution of particle swarm optimization to three-dimensional slope stability analysis.

PubMed

Kalatehjari, Roohollah; Rashid, Ahmad Safuan A; Ali, Nazri; Hajihassani, Mohsen

2014-01-01

Over the last few years, particle swarm optimization (PSO) has been extensively applied in various geotechnical engineering including slope stability analysis. However, this contribution was limited to two-dimensional (2D) slope stability analysis. This paper applied PSO in three-dimensional (3D) slope stability problem to determine the critical slip surface (CSS) of soil slopes. A detailed description of adopted PSO was presented to provide a good basis for more contribution of this technique to the field of 3D slope stability problems. A general rotating ellipsoid shape was introduced as the specific particle for 3D slope stability analysis. A detailed sensitivity analysis was designed and performed to find the optimum values of parameters of PSO. Example problems were used to evaluate the applicability of PSO in determining the CSS of 3D slopes. The first example presented a comparison between the results of PSO and PLAXI-3D finite element software and the second example compared the ability of PSO to determine the CSS of 3D slopes with other optimization methods from the literature. The results demonstrated the efficiency and effectiveness of PSO in determining the CSS of 3D soil slopes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

DE GERONIMO,G.; FRIED, J.; FROST, E.

We describe a front-end application specific integrated circuit (ASIC) developed for a silicon Compton telescope. Composed of 32 channels, it reads out signals in both polarities from each side of a Silicon strip sensor, 2 mm thick 27 cm long, characterized by a strip capacitance of 30 pF. Each front-end channel provides low-noise charge amplification, shaping with a stabilized baseline, discrimination, and peak detection with an analog memory. The channels can process events simultaneously, and the read out is sparsified. The charge amplifier makes uses a dual-cascode configuration and dual-polarity adaptive reset, The low-hysteresis discriminator and the multi-phase peak detectormore » process signals with a dynamic range in excess of four hundred. An equivalent noise charge (ENC) below 200 electrons was measured at 30 pF, with a slope of about 4.5 electrons/pF at a peaking time of 4 {micro}s. With a total dissipated power of 5 mW the channel covers an energy range up to 3.2 MeV.« less

Fiber optic vibration sensor using bifurcated plastic optical fiber

NASA Astrophysics Data System (ADS)

Abdullah, M.; Bidin, N.; Yasin, M.

2016-11-01

An extrinsic fiber optic vibration sensor is demonstrated for a fiber optic displacement sensor based on a bundled multimode fiber to measure a vibration frequency ranging from 100 until 3000 Hz. The front slope has a sensitivity of 0.1938mV/mm and linearity of 99.7% within a measurement range between 0.15-3.00 mm. By placing the diaphragm of the concave load-speaker within the linear range from the probe, the frequency of the vibration can be measured with error percentage of less than 1.54%. The graph of input against output frequency for low, medium and high frequency range show very high linearity up to 99%. Slope for low, medium, and high frequency range are calculated as 1.0026, 0.9934, and 1.0007 respectively. Simplicity, long term stability, low power consumption, wide dynamic and frequency ranges, noise reduction, ruggedness, linearity and light weight make it promising alternative to other well-establish methods for vibration frequency measurement.

Slope stabilization guide for Minnesota local government engineers.

DOT National Transportation Integrated Search

2017-06-01

This user guide provides simple, costeffective methods for stabilizing locally maintained slopes along roadways in Minnesota. Eight slope stabilization techniques are presented that local government engineers can undertake using locally available ...

A simplified approach for slope stability analysis of uncontrolled waste dumps.

PubMed

Turer, Dilek; Turer, Ahmet

2011-02-01

Slope stability analysis of municipal solid waste has always been problematic because of the heterogeneous nature of the waste materials. The requirement for large testing equipment in order to obtain representative samples has identified the need for simplified approaches to obtain the unit weight and shear strength parameters of the waste. In the present study, two of the most recently published approaches for determining the unit weight and shear strength parameters of the waste have been incorporated into a slope stability analysis using the Bishop method to prepare slope stability charts. The slope stability charts were prepared for uncontrolled waste dumps having no liner and leachate collection systems with pore pressure ratios of 0, 0.1, 0.2, 0.3, 0.4 and 0.5, considering the most critical slip surface passing through the toe of the slope. As the proposed slope stability charts were prepared by considering the change in unit weight as a function of height, they reflect field conditions better than accepting a constant unit weight approach in the stability analysis. They also streamline the selection of slope or height as a function of the desired factor of safety.

Conceptualization of preferential flow for hillslope stability assessment

NASA Astrophysics Data System (ADS)

Kukemilks, Karlis; Wagner, Jean-Frank; Saks, Tomas; Brunner, Philip

2018-03-01

This study uses two approaches to conceptualize preferential flow with the goal to investigate their influence on hillslope stability. Synthetic three-dimensional hydrogeological models using dual-permeability and discrete-fracture conceptualization were subsequently integrated into slope stability simulations. The slope stability simulations reveal significant differences in slope stability depending on the preferential flow conceptualization applied, despite similar small-scale hydrogeological responses of the system. This can be explained by a local-scale increase of pore-water pressures observed in the scenario with discrete fractures. The study illustrates the critical importance of correctly conceptualizing preferential flow for slope stability simulations. It further demonstrates that the combination of the latest generation of physically based hydrogeological models with slope stability simulations allows for improvement to current modeling approaches through more complex consideration of preferential flow paths.

75 FR 65366 - Recovery Policy RP9524.2, Landslides and Slope Stability Related to Public Facilities

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-22

...] Recovery Policy RP9524.2, Landslides and Slope Stability Related to Public Facilities AGENCY: Federal... the final Recovery Policy RP9524.2, Landslides and Slope Stability Related to Public Facilities, which... facilities threatened by landslides or slope failures; as well as the eligibility of permanent repairs to...

Influences of geological parameters to probabilistic assessment of slope stability of embankment

NASA Astrophysics Data System (ADS)

Nguyen, Qui T.; Le, Tuan D.; Konečný, Petr

2018-04-01

This article considers influences of geological parameters to slope stability of the embankment in probabilistic analysis using SLOPE/W computational system. Stability of a simple slope is evaluated with and without pore–water pressure on the basis of variation of soil properties. Normal distributions of unit weight, cohesion and internal friction angle are assumed. Monte Carlo simulation technique is employed to perform analysis of critical slip surface. Sensitivity analysis is performed to observe the variation of the geological parameters and their effects on safety factors of the slope stability.

Regional variability of slope stability: Application to the Eel margin, California

USGS Publications Warehouse

Lee, H.; Locat, J.; Dartnell, P.; Israel, K.; Florence, Wong

1999-01-01

Relative values of downslope driving forces and sediment resisting forces determine the locations of submarine slope failures. Both of these vary regionally, and their impact can be addressed when the data are organized in a Geographic Information System (GIS). The study area on the continental margin near the Eel River provides an excellent opportunity to apply GIS spatial analysis techniques for evaluation of slope stability. In this area, swath bathymetric mapping shows seafloor morphology and distribution of slope steepness in fine detail, and sediment analysis of over 70 box cores delineates the variability of sediment density near the seafloor surface. Based on the results of ten geotechnical studies of submarine study areas, we developed an algorithm that relates surface sediment density to the shear strength appropriate to the type of cyclic loading produced by an earthquake. Strength and stress normalization procedures provide results that are conceptually independent of subbottom depth. Results at depth are rigorously applicable if sediment lithology does not vary significantly and consolidation state can be estimated. Otherwise, the method applies only to shallow-seated slope failure. Regional density, slope, and level of anticipated seismic shaking information were combined in a GIS framework to yield a map that illustrates the relative stability of slopes in the face of seismically induced failure. When a measure of predicted relative slope stability is draped on an oblique view of swath bathymetry, a variation in this slope stability is observed on an otherwise smooth slope along the mid-slope region north of a plunging anticline. The section of slope containing diffuse, pockmarked gullies has a lower measure of stability than a separate section containing gullies that have sharper boundaries and somewhat steeper sides. Such an association suggests that our slope-stability analysis relates to the stability of the gully sides. The remainder of the study area shows few obvious indications of slope instability except for a feature that has become known as the 'Humboldt Slide,' but it is too deep-seated to be amenable to the slope-stability-prediction techniques presented herein. In general, few slope failures have been mapped in the Eel margin study area despite the high level of seismicity, the relatively high rates of sediment accumulation, and the extent of gas charging observed by others.

Impact of slope inclination on salt accumulation

NASA Astrophysics Data System (ADS)

Nachshon, Uri

2017-04-01

Field measurements indicated on high variability in salt accumulation along natural and cultivated slopes, even for relatively homogeneous soil conditions. It was hypothesised that slope inclination has an impact on the location of salt accumulation along the slope. A set of laboratory experiments and numerical models were used to explore the impact of slope inclination on salt accumulation. It was shown, experimentally, that for conditions of saline water source at the lower boundary of the slope - salt accumulates in low concentrations and homogeneously along the entire slope, for moderate slopes. However, as inclination increases high salt concentrations were observed at the upper parts of the slope, leaving the lower parts of the slope relatively free of salt. The traditional flow and transport models did not predict the experimental observations as they indicated also for the moderate slopes on salt accumulation in the elevated parts of the slope, away of the saline water source. Consequently - a conceptual model was raised to explain the laboratory observations. It was suggested that the interactions between slope angle, evaporation rates, hydraulic conductivity of the medium and distribution of wetness along the slope affect the saline water flow path through the medium. This lead to preferential flow path close to the soil-atmosphere interface for the steep slopes, which leads to constant wash of the salts from the evaporation front upward towards the slope upper parts, whereas for the moderate slopes, flow path is below the soil-atmosphere interface, therefore salt that accumulates at the evaporation front is not being transported upward. Understanding of salt dynamics along slopes is important for agricultural and natural environments, as well as for civil engineering purposes. Better understanding of the salt transport processes along slopes will improve our ability to minimize and to cope with soil salinization processes. The laboratory experiments and the new conceptual model fit the field observations and may explain the high variability of salt accumulation along slopes as observed in the field.

Rainfall thresholds for the initiation of shallow landslides in the Wiśnicz Foothills region (the Flysch Carpathians Mountain, Poland)

NASA Astrophysics Data System (ADS)

Demczuk, Piotr; Zydroń, Tymoteusz; Siłuch, Marcin

2017-04-01

Determination of the magnitude of the rainfall threshold is a complex task, as it depends on the properties of the engineering-geological formations deposited on slopes and lithological conditions; it is also a resultant of the intensity and duration of precipitation. Meteorological monitoring and knowledge of the geological structure and adequate engineering tools (models of the soil and rock substrate) can greatly contribute to identification of the magnitude of rainfall that can pose a threat to slope stability. Calculation programs, which include the physical description of changes in the stress state in the soil substrate, are widely used tools for assessment of the slope stability conditions. Such programs take into account only the impact of rainfall on slope stability conditions and disregard the role of other meteorological factors. Development of a model that would be able to estimate these values is difficult; hence, this paper presents an attempt to determine the impact of precipitation on slope stability of selected shallow landslide slopes located in the area of the Wiśnicz Foothills (Outer Carpathians, Poland) using physically-based model taking into account meteorological conditions. Firstly, based on the meteorological data from 2004-2013 calculations of slope stability were performed to verify the geotechnical parameters of the soils. The calculations also yielded the range of pore pressure changes in the analysed period of 2004-2013, which simultaneously facilitated determination of extreme slope stability conditions prevailing during the growing seasons in the analysed years. Further investigations were focused on determination of changes in slope stability induced in response to 120-day long rainfalls with increasing, constant, and decreasing intensities characterised by a 1-99% probability of occurrence. For the analysis, three systems of pore pressure distribution in the slope were employed. Two of them corresponded to the maximum and minimum soil wetness values at the beginning of the growing seasons in 2004-2013 (period between late March and late July, which substantially coincides with periods of intensification of mass movements in Polish Flysch Carpathians). The analyses were performed with the calculation modules of the GeoSlope Inc. package: - Vadose/W was used to determine the impact of meteorological conditions (temperature, humidity, wind speed, precipitation) on the pore pressure distribution in the slope, - Slope/W - calculations of slope stability. The stability calculations have confirmed that the rainfall threshold values are a function of many variables, primarily the hydraulic properties of slope covers and rock substratum, temporal distribution of precipitation, and wetness conditions (degree of slope cover saturation). The major mechanism of stability failure by the analysed slopes in the Wiśnicz Foothills is the saturation of slope covers. Given this mechanism, observations of the groundwater table can be an important factor in assessment of the susceptibility of slopes to mass movements, besides meteorological observations. It also seems that slope stability calculations can be an important tool for assessment of landslide hazards. Importantly, the calculations have to take into account not only precipitation data but also other meteorological factors, which have impact on the amount of water accumulated in slope covers.

Study of the influence of fuel load and slope on a fire spreading across a bed of pine needles by using oxygen consumption calorimetry

NASA Astrophysics Data System (ADS)

Tihay, V.; Morandini, F.; Santoni, P. A.; Perez-Ramirez, Y.; Barboni, T.

2012-11-01

A set of experiments using a Large Scale Heat Release Rate Calorimeter was conducted to test the effects of slope and fuel load on the fire dynamics. Different parameters such as the geometry of the flame front, the rate of spread, the mass loss rate and the heat release rate were investigated. Increasing the fuel load or the slope modifies the fire behaviour. As expected, the flame length and the rate of spread increase when fuel load or slope increases. The heat release rate does not reach a quasi-steady state when the propagation takes place with a slope of 20° and a high fuel load. This is due to an increase of the length of the fire front leading to an increase of fuel consumed. These considerations have shown that the heat release can be estimated with the mass loss rate by considering the effective heat of combustion. This approach can be a good alternative to estimate accurately the fireline intensity when the measure of oxygen consumption is not possible.

Stability Calculation Method of Slope Reinforced by Prestressed Anchor in Process of Excavation

PubMed Central

Li, Zhong; Wei, Jia; Yang, Jun

2014-01-01

This paper takes the effect of supporting structure and anchor on the slope stability of the excavation process into consideration; the stability calculation model is presented for the slope reinforced by prestressed anchor and grillage beam, and the dynamic search model of the critical slip surface also is put forward. The calculation model of the optimal stability solution of each anchor tension of the whole process is also given out, through which the real-time analysis and checking of slope stability in the process of excavation can be realized. The calculation examples indicate that the slope stability is changed with the dynamic change of the design parameters of anchor and grillage beam. So it is relatively more accurate and reasonable by using dynamic search model to determine the critical slip surface of the slope reinforced by prestressed anchor and grillage beam. Through the relationships of each anchor layout and the slope height of various stages of excavation, and the optimal stability solution of prestressed bolt tension design value in various excavation stages can be obtained. The arrangement of its prestressed anchor force reflects that the layout of the lower part of bolt and the calculation of slope reinforcement is in line with the actual. These indicate that the method is reasonable and practical. PMID:24683319

Stability calculation method of slope reinforced by prestressed anchor in process of excavation.

PubMed

Li, Zhong; Wei, Jia; Yang, Jun

2014-01-01

This paper takes the effect of supporting structure and anchor on the slope stability of the excavation process into consideration; the stability calculation model is presented for the slope reinforced by prestressed anchor and grillage beam, and the dynamic search model of the critical slip surface also is put forward. The calculation model of the optimal stability solution of each anchor tension of the whole process is also given out, through which the real-time analysis and checking of slope stability in the process of excavation can be realized. The calculation examples indicate that the slope stability is changed with the dynamic change of the design parameters of anchor and grillage beam. So it is relatively more accurate and reasonable by using dynamic search model to determine the critical slip surface of the slope reinforced by prestressed anchor and grillage beam. Through the relationships of each anchor layout and the slope height of various stages of excavation, and the optimal stability solution of prestressed bolt tension design value in various excavation stages can be obtained. The arrangement of its prestressed anchor force reflects that the layout of the lower part of bolt and the calculation of slope reinforcement is in line with the actual. These indicate that the method is reasonable and practical.

16. VIEW OF ROAD AND LEVELED AREA IN FRONT OF ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

16. VIEW OF ROAD AND LEVELED AREA IN FRONT OF HATCH ADIT (FEATURE B-28) WHICH IS ON THE RIGHT SIDE OF PHOTOGRAPH. (OCTOBER, 1995) - Nevada Lucky Tiger Mill & Mine, East slope of Buckskin Mountain, Paradise Valley, Humboldt County, NV

Seasonal variability in ice-front position, glacier speed, and surface elevation at Helheim Glacier, SE Greenland, from 2010-2016

NASA Astrophysics Data System (ADS)

Kehrl, L. M.; Joughin, I. R.; Shean, D. E.

2016-12-01

Marine-terminating glaciers can be very sensitive to changes in ice-front position, depending on their geometry. If a nearly grounded glacier retreats into deeper water, the glacier typically must speed up to produce the additional longitudinal and lateral stress gradients necessary to restore force balance. This speedup often causes thinning, which can increase the glacier's susceptibility to further retreat. In this study, we combine satellite observations and numerical modeling (Elmer/Ice) to investigate how seasonal changes in ice-front position affect glacier speed and surface elevation at Helheim Glacier, SE Greenland, from 2010-2016. Helheim's calving front position fluctuated about a mean position from 2010-2016. During 2010/11, 2013/14, and 2015/16, Helheim seasonally retreated and advanced along a reverse bed slope by > 3 km. During these years, the glacier retreated from winter/spring to late summer and then readvanced until winter/spring. During the retreat, Helheim sped up by 20-30% and thinned by 20 m near its calving front. This thinning caused the calving front to unground, and a floating ice tongue was then able to readvance over the following winter with limited iceberg calving. The advance, which continued until the glacier reached the top of the bathymetric high, caused the glacier to slow and thicken. During years when Helheim likely did not form a floating ice tongue, iceberg calving continued throughout the winter. Consequently, the formation of this floating ice tongue may have helped stabilize Helheim after periods of rapid retreat and dynamic thinning. Helheim's rapid retreat from 2001-2005 also ended when a floating ice tongue formed and readvanced over the 2005/06 winter. These seasonal retreat/advance cycles may therefore be important for understanding Helheim's long-term behavior.

An alternative soil nailing system for slope stabilization: Akarpiles

NASA Astrophysics Data System (ADS)

Lim, Chun-Lan; Chan, Chee-Ming

2017-11-01

This research proposes an innovative solution for slope stabilization with less environmental footprint: AKARPILES. In Malaysia, landslide has become common civil and environmental problems that cause impacts to the economy, safety and environment. Therefore, effective slope stabilization method helps to improve the safety of public and protect the environment. This study focused on stabilizing surfacial slope failure. The idea of AKARPILES was generated from the tree roots system in slope stabilization. After the piles are installed in the slope and intercepting the slip plane, grout was pumped in and discharged through holes on the piles. The grout then filled the pores in the soil with random flow within the slip zone. SKW mixture was used to simulate the soil slope. There were two designs being proposed in this study and the prototypes were produced by a 3D printer. Trial mix of the grout was carried out to obtain the optimum mixing ratio of bentonite: cement: water. A series of tests were conducted on the single-pile-reinforced slope under vertical slope crest loading condition considering different slope gradients and nail designs. Parameters such as ultimate load, failure time and failure strain were recorded and compared. As comparison with the unreinforced slope, both designs of AKARPILES showed better but different performances in the model tests.

Asymmetric Effects of Subaerial and Subaqueous Basement Slopes on Self-Similar Morphology of Prograding Deltas

NASA Astrophysics Data System (ADS)

Lai, Steven Yueh Jen; Hsiao, Yung-Tai; Wu, Fu-Chun

2017-12-01

Deltas form over basements of various slope configurations. While the morphodynamics of prograding deltas over single-slope basements have been studied previously, our understanding of delta progradation over segmented basements is still limited. Here we use experimental and analytical approaches to investigate the deltaic morphologies developing over two-slope basements with unequal subaerial and subaqueous slopes. For each case considered, the scaled profiles of the evolving delta collapse to a single profile for constant water and sediment influxes, allowing us to use the analytical self-similar profiles to investigate the individual effects of subaerial/subaqueous slopes. Individually varying the subaerial/subaqueous slopes exerts asymmetric effects on the morphologies. Increasing the subaerial slope advances the entire delta; increasing the subaqueous slope advances the upstream boundary of the topset yet causes the downstream boundary to retreat. The delta front exhibits a first-retreat-then-advance migrating trend with increasing subaqueous slope. A decrease in subaerial topset length is always accompanied by an increase in subaqueous volume fraction, no matter which segment is steepened. Applications are presented for estimating shoreline retreat caused by steepening of basement slopes, and estimating subaqueous volume and delta front using the observed topset length. The results may have implications for real-world delta systems subjected to upstream tectonic uplift and/or downstream subsidence. Both scenarios would exhibit reduced topset lengths, which are indicative of the accompanied increases in subaqueous volume and signal tectonic uplift and/or subsidence that are at play. We highlight herein the importance of geometric controls on partitioning of sediment between subaerial and subaqueous delta components.

3D Modeling of Landslide in Open-pit Mining on Basis of Ground-based LIDAR Data

NASA Astrophysics Data System (ADS)

Hu, H.; Fernandez-Steeger, T. M.; Azzam, R.; Arnhardt, C.

2009-04-01

Slope stability is not only an important problem which is related to production and safety in open-pit mining, but also very complex task. There are three main reasons which affect the slope stability as follows: geotechnical factors: Geological structure, lithologic characteristics, water, cohesion, friction, etc.; climate factors: Rainfall and temperature; and external factors: Open-pit mining process, explosion vibration, dynamic load, etc.. The 3rd reason, as a specially one in open-pit mining, not only causes some dynamic problems but also induces the fast geometry changing which must be considered in the following research using numerical simulation and stability analysis. Recently, LIDAR technology has been applied in many fields and places in the world wide. Ground-based LIDAR technology with high accuracy up to 3mm increasingly accommodates to monitoring landslides and detecting changing. LIDAR data collection and preprocessing research have been carried out by Department of Engineering Geology and Hydrogeology at RWTH Aachen University. LIDAR data, so-called a point-cloud of mass data in high density can be obtained in short time for the sensitive open-pit mining area by using ground-based LIDAR. To obtain a consistent surface model, it is necessary to set up multiple scans with the ground-based LIDAR. The framework of data preprocessing which can be implemented by Poly-Works is introduced as follows: gross error detection and elimination, integration of reference frame, model fusion of different scans (re-sampled in overlap region), data reduction without removing the useful information which is a challenge and research front in LIDAR data processing. After data preprocessing, 3D surface model can be directly generated in Poly-Works or generated in other software by building the triangular meshes. The 3D surface landslide model can be applied to further researches such as: real time landslide geometry monitoring due to the fast data collection and processing; change detecting by means of overlying different periods of topographic or geometric data; FEM (Finite Element Method) numerical simulation on basis of combining with the geotechnical properties and parameters to analyze slope stability and predict future movements for designing and rectifying the open-pit mining process; using the reverse engineering thought for developing constitutive models. An improved 3D surface model (HRDEM) which is based on fast data collection and precise data processing on basis of ground-based LIDAR technology is important contribution for further researches of slope stability in open-pit mining area.

Rock Slope Stability Evaluation in a Steep-Walled Canyon: Application to Elevator Construction in the Yunlong River Valley, Enshi, China

NASA Astrophysics Data System (ADS)

Xiao, Lili; Chai, Bo; Yin, Kunlong

2015-09-01

A passenger elevator is to be built on a nearly vertical slope in the National Geological Park in Enshi, Hubei province, China. Three steps comprise the construction: excavating the slope toe for the elevator platform, building the elevator on the platform, and affixing the elevator to the slope using anchors. To evaluate the rock slope stability in the elevator area and the safety of the elevator construction, we applied three techniques: qualitative analysis, formula calculation, and numerical simulation methods, based on field investigation and parameter selection, and considering both wet and dry conditions, pre- and post-construction. Qualitative stability factors for sliding and falling were calculated using the limit equilibrium method; the results show that the slope as a whole is stable, with a few unstable blocks, notably block BT1. Formula-based stability factors were calculated for four sections on block BT1, revealing the following: anchors will decrease the stability of certain rock pieces; the lowest average stability factor after anchoring will be K f = 1.36 in wet conditions; block BT1 should be reinforced during elevator construction, up to a first-class slope stability factor of K f = 1.40; and the slope as a whole is stable. Numerical simulation using FLAC3D indicated that the stress distribution will reach equilibrium for all steps before and after construction, and that the factor of safety (FOS) is within the general slope safety range (FOS > 1.05). We suggest that unstable pieces in block BT1 be reinforced during construction to a first-class slope safety range (FOS > 1.3), and that deformation monitoring on the slope surface be implemented.

Effect of hydraulic hysteresis on the stability of infinite slopes under steady infiltration

USGS Publications Warehouse

Chen, Pan; Mirus, Benjamin B.; Lu, Ning; Godt, Jonathan W.

2017-01-01

Hydraulic hysteresis, including capillary soil water retention (SWR), air entrapment SWR, and hydraulic conductivity, is a common phenomenon in unsaturated soils. However, the influence of hydraulic hysteresis on suction stress, and subsequently slope stability, is generally ignored. This paper examines the influence of each of these three types of hysteresis on slope stability using an infinite slope stability analysis under steady infiltration conditions. First, hypothetical slopes for representative silty and sandy soils are examined. Then a monitored hillslope in the San Francisco Bay Area, California is assessed, using observed rainfall conditions and measured hydraulic and geotechnical properties of the colluvial soil. Results show that profiles of suction stress and the corresponding factor of safety are generally strongly affected by hydraulic hysteresis. Results suggest that each of the three types of hydraulic hysteresis may play a major role in the occurrence of slope failure, indicating that ignoring hydraulic hysteresis will likely lead to underestimates of failure potential and hence to inaccurate slope stability analysis.

Assessment of Slope Stability of Various Cut Slopes with Effects of Weathering by Using Slope Stability Probability Classification (SSPC)

NASA Astrophysics Data System (ADS)

Ersöz, Timur; Topal, Tamer

2017-04-01

Rocks containing pore spaces, fractures, joints, bedding planes and faults are prone to weathering due to temperature differences, wetting-drying, chemistry of solutions absorbed, and other physical and chemical agents. Especially cut slopes are very sensitive to weathering activities because of disturbed rock mass and topographical condition by excavation. During and right after an excavation process of a cut slope, weathering and erosion may act on this newly exposed rock material. These acting on the material may degrade and change its properties and the stability of the cut slope in its engineering lifetime. In this study, the effect of physical and chemical weathering agents on shear strength parameters of the rocks are investigated in order to observe the differences between weathered and unweathered rocks. Also, slope stability assessment of cut slopes affected by these weathering agents which may disturb the parameters like strength, cohesion, internal friction angle, unit weight, water absorption and porosity are studied. In order to compare the condition of the rock materials and analyze the slope stability, the parameters of weathered and fresh rock materials are found with in-situ tests such as Schmidt hammer and laboratory tests like uniaxial compressive strength, point load and direct shear. Moreover, slake durability and methylene blue tests are applied to investigate the response of the rock to weathering and presence of clays in rock materials, respectively. In addition to these studies, both rock strength parameters and any kind of failure mechanism are determined by probabilistic approach with the help of SSPC system. With these observations, the performances of the weathered and fresh zones of the cut slopes are evaluated and 2-D slope stability analysis are modeled with further recommendations for the cut slopes. Keywords: 2-D Modeling, Rock Strength, Slope Stability, SSPC, Weathering

Gravity-induced stresses in finite slopes

USGS Publications Warehouse

Savage, W.Z.

1994-01-01

An exact solution for gravity-induced stresses in finite elastic slopes is presented. This solution, which is applied for gravity-induced stresses in 15, 30, 45 and 90?? finite slopes, has application in pit-slope design, compares favorably with published finite element results for this problem and satisfies the conditions that shear and normal stresses vanish on the ground surface. The solution predicts that horizontal stresses are compressive along the top of the slopes (zero in the case of the 90?? slope) and tensile away from the bottom of the slopes, effects which are caused by downward movement and near-surface horizontal extension in front of the slope in response to gravity loading caused by the additional material associated with the finite slope. ?? 1994.

Dynamic stabilization of Rayleigh-Taylor instability: Experiments with Newtonian fluids as surrogates for ablation fronts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez Prieto, G.; Piriz, A. R.; Lopez Cela, J. J.

2013-01-15

A previous theory on dynamic stabilization of Rayleigh-Taylor instability at interfaces between Newtonian fluids is reformulated in order to make evident the analogy of this problem with the related one on dynamic stabilization of ablation fronts in the framework of inertial confinement fusion. Explicit analytical expressions are obtained for the boundaries of the dynamically stable region which turns out to be completely analogue to the stability charts obtained for the case of ablation fronts. These results allow proposing experiments with Newtonian fluids as surrogates for studying the case of ablation fronts. Experiments with Newtonian fluids are presented which demonstrate themore » validity of the theoretical approach and encourage to pursue experimental research on ablation fronts to settle the feasibility of dynamic stabilization in the inertial confinement fusion scenario.« less

Influence of filling-drawdown cycles of the Vajont reservoir on Mt. Toc slope stability

NASA Astrophysics Data System (ADS)

Paronuzzi, Paolo; Rigo, Elia; Bolla, Alberto

2013-06-01

In the present work, the 1963 Vajont landslide has been back-analyzed in detail to examine the influence of reservoir operations (filling and drawdown) on Mt. Toc slope stability. The combined seepage-slope stability analyses carried out show that the main destabilizing factor that favored the 1963 Vajont landslide was the reservoir-induced water table that formed as a consequence of rapid seepage inflow within the submerged toe of the slope — decrease in the factor of safety (FOS) up to 12% compared to the initial slope stability condition, i.e., in the absence of the Vajont reservoir. Rainfall would only have been a decisive factor if the initial stability condition of the Mt. Toc slope had already been very close to failure (decrease in FOS caused by heavy or prolonged rainfall is about 3-4%, for the worst case scenario analyzed). The permeability of the shear zone material occurring at the base of the prehistoric Vajont rockslide has been evaluated at 5 × 10- 4 m/s, and back-calculated values of the friction angles Φ range from 17.5° to 27.5°. When considering mountain reservoirs, slope failures can occur during both filling and drawdown phases. In the Vajont case, owing to the highly permeable materials of the shear zone, slope stability decreased during filling and increased during drawdown. Another displacement-dependent phenomenon of a mechanical nature - progressive failure of the NE landslide constraint - has to be considered to understand the slope collapse that occurred during the last drawdown (26 September-9 October 1963). The results of the combined seepage-slope stability models indicate that permeability of bank-forming material and filling-drawdown rates of reservoirs can strongly influence slope stability. Slow lowering of the reservoir level is a necessary measure to reduce the occurrence of very dangerous transient negative peaks of FOS.

A parametric study of golf car and personal transport vehicle braking stability and their deficiencies.

PubMed

Seluga, Kristopher J; Baker, Lowell L; Ojalvo, Irving U

2009-07-01

This paper describes research and parametric analyses of braking effectiveness and directional stability for golf cars, personal transport vehicles (PTVs) and low speed vehicles (LSVs). It is shown that current designs, which employ brakes on only the rear wheels, can lead to rollovers if the brakes are applied while traveling downhill. After summarizing the current state of existing safety standards and brake system designs, both of which appear deficient from a safety perspective, a previously developed dynamic simulation model is used to identify which parameters have the greatest influence on the vehicles' yaw stability. The simulation results are then used to parametrically quantify which combination of these factors can lead to yaw induced rollover during hard braking. Vehicle velocity, steering input, path slope and tire friction are all identified as important parameters in determining braking stability, the effects of which on rollover propensity are presented graphically. The results further show that when vehicles are equipped with front brakes or four-wheel brakes, the probability of a yaw induced rollover is almost entirely eliminated. Furthermore, the parametric charts provided may be used as an aid in developing guidelines for golf car and PTV path design if rear brake vehicles are used.

Assessing Subaqueous Mudflow Hazard on the Mississippi River Delta Front, Part 1: A Historical Perspective on Mississippi River Delta Front Sedimentation

NASA Astrophysics Data System (ADS)

Maloney, J. M.; Bentley, S. J.; Obelcz, J.; Xu, K.; Miner, M. D.; Georgiou, I. Y.; Hanegan, K.; Keller, G.

2014-12-01

Subaqueous mudflows are known to be ubiquitous across the Mississippi River delta front (MRDF) and have been identified as a hazard to offshore infrastructure. Among other factors, sediment accumulation rates and patterns play an important role in governing the stability of delta front sediment. High sedimentation rates result in underconsolidation, slope steepening, and increased biogenic gas production, which are all known to decrease stability. Sedimentation rates are highly variable across the MRDF, but are highest near the mouth of Southwest Pass, which carries the largest percentage of Mississippi River sediment into the Gulf of Mexico. Since the 1950s, the sediment load of the Mississippi River has decreased by ~50% due to dam construction upstream. The impact of this decreased sediment load on MRDF mudflow dynamics has yet to be examined. We compiled MRDF bathymetric datasets, including historical charts, industry and academic surveys, and NOAA data, collected between 1764 and 2009, in order to identify historic trends in sedimentation patterns. The progradation of Southwest Pass (measured at 10 m depth contour) has slowed from ~66 m/yr between 1764 and 1940 to ~25 m/yr between 1940 and 1979, with evidence of further deceleration from 1979-2009. Decreased rates of progradation are also observed at South Pass and Pass A Loutre. Advancement of the delta also decelerated in deeper water (15-90 m) offshore from Southwest Pass. In this area, from 1940-1979, depth contours advanced seaward ~25 m/yr, but did not advance from 1979-2005. Furthermore, over the same area and time ranges, the sediment accumulation rate decreased by ~82%. We expect these sedimentation trends are occurring across the delta front, with potential impacts on spatial and temporal patterns of subaqueous mudflows. The MRDF appears to be entering a phase of decline, which will likely be accelerated by future upstream sediment diversion projects. New geophysical data will be required to assess potential mudflow hazards associated with new MRDF sedimentation rates and patterns (See Part 2, Obelcz et al.).

Slope Stability Analysis of Mountain Pine Beetle Impacted Areas

NASA Astrophysics Data System (ADS)

Bogenschuetz, N. M.; Bearup, L. A.; Maxwell, R. M.; Santi, P. M.

2015-12-01

The mountain pine beetle (MPB), Dendroctonus ponderosae, has caused significant tree mortality within North America. Specifically, the MPB affects ponderosa pine and lodgepole pine forests within the Rocky Mountains with approximately 3.4 million acres of forest impacted over the past 20 years. The full impacts of such unprecedented tree mortality on hydrology and slope stability is not well understood. This work studies the affects of MPB infestation on slope instability. A large-scale statistical analysis of MPB and slope stability is combined with a more in-depth analysis of the factors that contribute to slope stability. These factors include: slope aspect, slope angle, root decay, regrowth and hydrologic properties, such as water table depth and soil moisture. Preliminary results show that MPB may affect a greater number of north- and east-facing slopes. This is in accordance with more water availability and a higher MPB impacted tree density on north-facing slopes which, in turn, could potentially increase the probability of slope failure. Root strength is predicted to decrease as the roots stop transpiring 3-4 years proceeding infestation. However, this effect on the hillslope is likely being counterbalanced by the regrowth of grasses, forbs, shrubs, and trees. In addition, the increase in water table height from the lack of transpiring trees is adding a driving force to the slopes. The combination of all these factors will be used in order to assess the effects of MPB tree mortality on slope stability.

Enhancement of slope efficiency and output power in GaN-based vertical-cavity surface-emitting lasers with a SiO2-buried lateral index guide

NASA Astrophysics Data System (ADS)

Kuramoto, Masaru; Kobayashi, Seiichiro; Akagi, Takanobu; Tazawa, Komei; Tanaka, Kazufumi; Saito, Tatsuma; Takeuchi, Tetsuya

2018-03-01

We have achieved a high output power of 6 mW from a 441 nm GaN-based vertical-cavity surface-emitting laser (VCSEL) under continuous wave (CW) operation, by reducing both the internal loss and the reflectivity of the front cavity mirror. A preliminary analysis of the internal loss revealed an enormously high transverse radiation loss in a conventional GaN-based VCSEL without lateral optical confinement (LOC). Introducing an LOC structure enhanced the slope efficiency by a factor of 4.7, with a further improvement to a factor of 6.7 upon reducing the front mirror reflectivity. The result was a slope efficiency of 0.87 W/A and an external differential quantum efficiency of 32% under pulsed operation. A flip-chip-bonded VCSEL also exhibited a high slope efficiency of 0.64 W/A and an external differential quantum efficiency of 23% for the front-side output under CW operation. The reflectivity of the cavity mirror was adjusted by varying the number of AlInN/GaN distributed Bragg reflector pairs from 46 to 42, corresponding to reflectivity values from 99.8% to 99.5%. These results demonstrate that a combination of internal loss reduction and cavity mirror control is a very effective way of obtaining a high output GaN-based VCSEL.

Slope Stability. CEGS Programs Publication Number 15.

ERIC Educational Resources Information Center

Pestrong, Raymond

Slope Stability is one in a series of single-topic problem modules intended for use in undergraduate and earth science courses. The module, also appropriate for use in undergraduate civil engineering and engineering geology courses, is a self-standing introduction to studies of slope stability. It has been designed to supplement standard…

Ocean processes at the Antarctic continental slope

PubMed Central

Heywood, Karen J.; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D.; Queste, Bastien Y.; Stevens, David P.; Wadley, Martin; Thompson, Andrew F.; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K.; Smith, Walker

2014-01-01

The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean–atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system. PMID:24891389

Ocean processes at the Antarctic continental slope.

PubMed

Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

2014-07-13

The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system.

Test matrices for evaluating cable median barriers placed in v-ditches.

DOT National Transportation Integrated Search

2012-07-01

Cable barrier systems designed to be used in median ditches have been traditionally full-scale crash tested placed either : within 4 ft from the slope break point (SBP) of a 4H:1V front slope or near the bottom of the ditch. Recently, there has been ...

Slope stability radar for monitoring mine walls

NASA Astrophysics Data System (ADS)

Reeves, Bryan; Noon, David A.; Stickley, Glen F.; Longstaff, Dennis

2001-11-01

Determining slope stability in a mining operation is an important task. This is especially true when the mine workings are close to a potentially unstable slope. A common technique to determine slope stability is to monitor the small precursory movements, which occur prior to collapse. The slope stability radar has been developed to remotely scan a rock slope to continuously monitor the spatial deformation of the face. Using differential radar interferometry, the system can detect deformation movements of a rough wall with sub-millimeter accuracy, and with high spatial and temporal resolution. The effects of atmospheric variations and spurious signals can be reduced via signal processing means. The advantage of radar over other monitoring techniques is that it provides full area coverage without the need for mounted reflectors or equipment on the wall. In addition, the radar waves adequately penetrate through rain, dust and smoke to give reliable measurements, twenty-four hours a day. The system has been trialed at three open-cut coal mines in Australia, which demonstrated the potential for real-time monitoring of slope stability during active mining operations.

Application of FBG Sensing Technology in Stability Analysis of Geogrid-Reinforced Slope.

PubMed

Sun, Yijie; Xu, Hongzhong; Gu, Peng; Hu, Wenjie

2017-03-15

By installing FBG sensors on the geogrids, smart geogrids can both reinforce and monitor the stability for geogrid-reinforced slopes. In this paper, a geogrid-reinforced sand slope model test is conducted in the laboratory and fiber Bragg grating (FBG) sensing technology is used to measure the strain distribution of the geogrid. Based on the model test, the performance of the reinforced soil slope is simulated by finite element software Midas-GTS, and the stability of the reinforced soil slope is analyzed by strength reduction method. The relationship between the geogrid strain and the factor of safety is set up. The results indicate that the measured strain and calculated results agree very well. The geogrid strain measured by FBG sensor can be applied to evaluate the stability of geogrid-reinforced sand slopes.

Application of FBG Sensing Technology in Stability Analysis of Geogrid-Reinforced Slope

PubMed Central

Sun, Yijie; Xu, Hongzhong; Gu, Peng; Hu, Wenjie

2017-01-01

By installing FBG sensors on the geogrids, smart geogrids can both reinforce and monitor the stability for geogrid-reinforced slopes. In this paper, a geogrid-reinforced sand slope model test is conducted in the laboratory and fiber Bragg grating (FBG) sensing technology is used to measure the strain distribution of the geogrid. Based on the model test, the performance of the reinforced soil slope is simulated by finite element software Midas-GTS, and the stability of the reinforced soil slope is analyzed by strength reduction method. The relationship between the geogrid strain and the factor of safety is set up. The results indicate that the measured strain and calculated results agree very well. The geogrid strain measured by FBG sensor can be applied to evaluate the stability of geogrid-reinforced sand slopes. PMID:28294995

Multidimensional stability of traveling fronts in combustion and non-KPP monostable equations

NASA Astrophysics Data System (ADS)

Bu, Zhen-Hui; Wang, Zhi-Cheng

2018-02-01

This paper is concerned with the multidimensional stability of traveling fronts for the combustion and non-KPP monostable equations. Our study contains two parts: in the first part, we first show that the two-dimensional V-shaped traveling fronts are asymptotically stable in R^{n+2} with n≥1 under any (possibly large) initial perturbations that decay at space infinity, and then, we prove that there exists a solution that oscillates permanently between two V-shaped traveling fronts, which implies that even very small perturbations to the V-shaped traveling front can lead to permanent oscillation. In the second part, we establish the multidimensional stability of planar traveling front in R^{n+1} with n≥1.

The Influence of Increasing Rain and Earthquake Activities on Landslide Slope Stability in Forest Areas

NASA Astrophysics Data System (ADS)

Kubota, T.; Aditian, A.

2014-12-01

Deriving the analysis of rainfall data in various mountainous locations, increase in rainfall that is deemed to be induced by the global climate change is obvious in Kyushu district, western Japan. On this point of view, its long term impact on the forest slope stability is analyzed with field investigation and numerical simulation such as finite element method (FEM). On the other hand, the influence of earthquake such as cracks on the slope due to seismic vibration was also analyzed with FEM. In this case, the slope stability analysis to obtain the factor of safety "Fs" is conducted. Here, in case of the Fs > 1.0, the slope is stable. In addition, the slope stabilizing effect of the forest mainly due to the roots strength is evaluated on some unstable slopes. Simultaneously, a holistic estimation over landslide groups is conducted by comparing "Fs" on forest slopes with non- forest slopes. Therefore, the following conclusions are obtained: 1) Comparing the Fs without increased rainfall from the previous decade and the one with actual rainfall, the former case is 1.04 ~1.06 times more stable than the latter. 2) On the other hand, the forest slopes are estimated to be up to approximately 1.5 to 2.5 times more stable than the slope without forest. Therefore, the slope stabilizing effect by the forest is much higher than the increasing rainfall influence i.e. the climate change effect. These results imply that an appropriate forest existence is important under the climate change condition to prevent forest slope degradation. 3) Comparing with the destabilization of the slope by seismic activities (vibration) due to the reduction of soil strength and "cracks = slope deformation" (8~9 % to 30% reduction in Fs even after an earthquake of 490gal), the influence of the long term rainfall increase on slopes (such as 1% decrease in Fs) is relatively small in the study area.

Poro-mechanical coupling influences on potential for rainfall-induced shallow landslides in unsaturated soils

NASA Astrophysics Data System (ADS)

Wu, L. Z.; Selvadurai, A. P. S.; Zhang, L. M.; Huang, R. Q.; Huang, Jinsong

2016-12-01

Rainfall-induced landslides are a common occurrence in terrain with steep topography and soils that have degradable strength. Rainfall infiltration into a partially saturated slope of infinite extent can lead to either a decrease or complete elimination of soil suction, compromising the slopes' stability. In this research the rainfall infiltration coupled with deformation of a partially saturated soil slope during rainfall infiltration is analyzed. The limit equilibrium conditions and the shear strength relationship of a partially saturated soil are employed to develop an analytical solution for calculating the stability of an infinite partially saturated slope due to rainfall infiltration. The analytical solutions are able to consider the influence of the coupled effects on the stability of the slope. The factors that affect the safety of a partially saturated slope of infinite extent are discussed. The results indicate that the poro-mechanical coupling of water infiltration and deformation has an important effect on the stability of the infinite unsaturated slope.

The effects of soil suction on shallow slope stability.

DOT National Transportation Integrated Search

2013-07-01

This study investigates the slope failures associated with clayey soils so engineers can better : understand the problem and better predict shallow slope stability, and implement preventive : measures if necessary. This research also examines the mec...

Geological hazard zonation in a marble exploitation area (Apuan Alps, Italy)

NASA Astrophysics Data System (ADS)

Francioni, M.; Salvini, R.; Riccucci, S.

2011-12-01

The present paper describes the hazard mapping of an exploitation area sited in the Apuan Alps marble district (Italy) carried out by the integration of various survey and analysis methodologies. The research, supported by the Massa and Carrara Local Sanitary Agency responsible for workplace health and safety activities, aimed to reduce the high degree hazard of rock fall caused by the presence of potentially unstable blocks located on slopes overhanging the marble quarries. The study of rocky fronts bases on the knowledge of both the structural setting and the physical-mechanical properties of intact material and its discontinuities. In this work the main difficulty in obtaining this information was the inaccessibility of the slope overhanging the area (up to 500 meters high). For this reason, the structural and geological-engineering surveys were integrated by outcomes from digital photogrammetry carried out through terrestrial stereoscopic photos acquired from an aerostatic balloon and a helicopter. In this way, it was possible to derive the geometrical characteristics of joints (such as discontinuities dip, dip direction, spacing and persistence), blocks volumes and slopes morphology also in inaccessible areas. This information, combined with data coming from the geological-engineering survey, was used to perform the stability analysis of the slope. Subsequently, using the topographic map at the scale of 1:2,000, the Digital Terrain Model (DTM) of the slopes and several topographic profiles along it were produced. Assuming that there is a good correspondence between travelling paths and maximum down slope angle, probable trajectories of rock fall along the slope were calculated on the DTM by means of a GIS procedure which utilizes the ArcHydro module of EsriTM ArcMap software. When performing such a 2D numerical modelling of rock falls, lateral dispersion of trajectories has often been hampered by the "a priori" choice of the travelling path. Such a choice can be assessed largely subjective and it leads to possible errors. Thus, rock fall hazard zonation needs spatially distributed analyses including a reliable modelling of lateral dispersion. In this research Conefall software, a freeware QuanterraTM code that estimates the potential run out areas by means of a "so-called" cone method, was used to compute the spatial distribution of rock falls frequency, velocities and kinetic energies. In this way, a modelling approach based on local morphologies was employed to assess the accuracy of the 2D analysis by profiles created "a priori" along the maximum down slope angle. Final results about slope stability and run out analysis allowed to create rock fall hazard map and to advise the most suitable protection works to mitigate the hazard in the most risky sites.

A Gulf Stream-derived pycnocline intrusion on the Middle Atlantic Bight shelf

NASA Astrophysics Data System (ADS)

Gawarkiewicz, Glen; McCarthy, Robert K.; Barton, Kenneth; Masse, Ann K.; Church, Thomas M.

1990-12-01

Saline intrusions from the upper slope onto the outer shelf are frequently observed at the pycnocline along the shelfbreak front in the Middle Atlantic Bight during the summer. A brief cruise was conducted in July, 1986 between Baltimore and Washington Canyons to examine along-shelf variability of pycnocline salinity intrusions. A particularly saline intrusion of 35.8 Practical Salinity Units (PSU) was observed between 20 and 40 m in a water depth of 70 to 80 m. The along-shelf extent was at least 40 km. The cooler, sub-pycnocline outer shelf water was displaced 15 km shoreward of the shelfbreak. A Gulf Stream filament was present in the slope region prior to the hydrographic sampling, but was not visible in thermal imagery during the hydrographic sampling. Temperature-salinity characteristics of the intrusion suggest that it was a mixture of Gulf Stream water and slope water, possibly from the filament. The shoreward penetration of saline water was most pronounced at the pycnocline and penetrated the shelfbreak front, with salinities as high as 35.0 PSU reaching as far shoreward as the 35 m isobath. These pycnocline intrusions may be an important mechanism for the transport of Gulf Stream-derived water onto the shelf during the summer. The presence of filaments or other Gulf Stream-derived water on the upper slope may account for some of the along-front variability of the pycnocline salinity maximum that has previously been observed.

PARTIAL RESTRAINING FORCE INTRODUCTION METHOD FOR DESIGNING CONSTRUCTION COUNTERMESURE ON ΔB METHOD

NASA Astrophysics Data System (ADS)

Nishiyama, Taku; Imanishi, Hajime; Chiba, Noriyuki; Ito, Takao

Landslide or slope failure is a three-dimensional movement phenomenon, thus a three-dimensional treatment makes it easier to understand stability. The ΔB method (simplified three-dimensional slope stability analysis method) is based on the limit equilibrium method and equals to an approximate three-dimensional slope stability analysis that extends two-dimensional cross-section stability analysis results to assess stability. This analysis can be conducted using conventional spreadsheets or two-dimensional slope stability computational software. This paper describes the concept of the partial restraining force in-troduction method for designing construction countermeasures using the distribution of the restraining force found along survey lines, which is based on the distribution of survey line safety factors derived from the above-stated analysis. This paper also presents the transverse distributive method of restraining force used for planning ground stabilizing on the basis of the example analysis.

The study on length and diameter ratio of nail as preliminary design for slope stabilization

NASA Astrophysics Data System (ADS)

Gunawan, Indra; Silmi Surjandari, Niken; Muslih Purwana, Yusep

2017-11-01

Soil nailing technology has been widely applied in practice for reinforced slope. The number of studies for the effective design of nail-reinforced slopes has also increased. However, most of the previous study was focused on a safety factor of the slope; the ratio of length and diameter itself has likely never been studied before. The aim of this study is to relate the length and diameter ratio of the nail with the safety factor of the 20 m height of sand slope in the various angle of friction and steepness of the slope. Simplified Bishop method was utilized to analyze the safety factor of the slope. This study is using data simulation to calculate the safety factor of the slope with soil nailing reinforcement. The results indicate that safety factor of slope stability increases with the increase of length and diameter ratio of the nail. At any angle of friction and steepness of the slope, certain effective length and diameter ratio was obtain. These results may be considered as a preliminary design for slope stabilization.

Modern configuration of the southwest Florida carbonate slope: Development by shelf margin progradation

USGS Publications Warehouse

Brooks, G.R.; Holmes, C.W.

1990-01-01

Depositional patterns and sedimentary processes influencing modern southwest Florida carbonate slope development have been identified based upon slope morphology, seismic facies and surface sediment characteristics. Three slope-parallel zones have been identified: (1) an upper slope progradational zone (100-500 m) characterized by seaward-trending progradational clinoforms and sediments rich in shelf-derived carbonate material, (2) a lower gullied slope zone (500-800 m) characterized by numerous gullies formed by the downslope transport of gravity flows, and (3) a base-of-slope zone (> 800 m) characterized by thin, lens-shaped gravity flow deposits and irregular topography interpreted to be the result of bottom currents and slope failure along the basal extensions of gullies. Modern slope development is interpreted to have been controlled by the offshelf transport of shallow-water material from the adjacent west Florida shelf, deposition of this material along a seaward advancing sediment front, and intermittent bypassing of the lower slope by sediments transported in the form of gravity flows via gullies. Sediments are transported offshelf by a combination of tides and the Loop Current, augmented by the passage of storm frontal systems. Winter storm fronts produce cold, dense, sediment-laden water that cascades offshelf beneath the strong, eastward flowing Florida Current. Sediments are eventually deposited in a relatively low energy transition zone between the Florida Current on the surface and a deep westward flowing counter current. The influence of the Florida Current is evident in the easternmost part of the study area as eastward prograding sediments form a sediment drift that is progressively burying the Pourtales Terrace. The modern southwest Florida slope has seismic reflection and sedimentological characteristics in common with slopes bordering both the non-rimmed west Florida margin and the rimmed platform of the northern Bahamas, and shows many similarities to the progradational Miocene section along the west Florida slope. As with rimmed platform slopes, development of non-rimmed platform slopes can be complex and controlled by a combination of processes that result in a variety of configurations. Consequently, the distinction between the two slope types based solely upon seismic and sedimentological characteristics may not be readily discernible. ?? 1990.

Bio-engineering for land stabilization : executive summary report.

DOT National Transportation Integrated Search

2010-06-30

Soil-bioengineering, or simply : bioengineering, is the use of vegetation for : slope stabilization. Currently, a large : number of slopes near Ohio highways are : experiencing stability problems. These : failures usually begin as local erosion...

Determination of strength behaviour of slope supported by vegetated crib walls using centrifuge model testing

NASA Astrophysics Data System (ADS)

Sudan Acharya, Madhu

2010-05-01

The crib retaining structures made of wooden/bamboo logs with live plants inside are called vegetative crib walls which are now becoming popular due to their advantages over conventional civil engineering walls. Conventionally, wooden crib walls were dimensioned based on past experiences. At present, there are several guidelines and design standards for machine finished wooden crib walls, but only few guidelines for the design and construction of vegetative log crib walls are available which are generally not sufficient for an economic engineering design of such walls. Analytical methods are generally used to determine the strength of vegetated crib retaining walls. The crib construction is analysed statically by satisfying the condition of static equilibrium with acceptable level of safety. The crib wall system is checked for internal and external stability using conventional monolithic and silo theories. Due to limitations of available theories, the exact calculation of the strength of vegetated wooden/bamboo crib wall cannot be made in static calculation. Therefore, experimental measurements are generally done to verify the static analysis. In this work, a model crib construction (1:20) made of bamboo elements is tested in the centrifuge machine to determine the strength behaviour of the slope supported by vegetated crib retaining wall. A geotechnical centrifuge is used to conduct model tests to study geotechnical problems such as the strength, stiffness and bearing capacity of different structures, settlement of embankments, stability of slopes, earth retaining structures etc. Centrifuge model testing is particularly well suited to modelling geotechnical events because the increase in gravitational force creates stresses in the model that are equivalent to the much larger prototype and hence ensures that the mechanisms of ground movements observed in the tests are realistic. Centrifuge model testing provides data to improve our understanding of basic mechanisms of deformation and failure and provides benchmarks useful for verification of numerical models. In this case this test is mainly carried out to verify the stability analysis and deformation characteristics of a bamboo crib wall. Models of crib wall of dimensions 37x13x10 cm and 37x13x14cm were placed inside a Plexiglas box of internal dimensions of 42.5x42.5x30 cm and slope was formed leaving a space about 10 cm in the front. The model crib wall tests were all performed at 40-70 times earth's gravity. This means that the 5 mm diameters bamboo rods in model used represents a prototype diameter of 20-35 cm. The horizontal and vertical displacements were measured with the help of three displacements sensor fixed horizontally and one sensor fixed vertically at the top of the model crib wall. All together nine tests were carried out with varying model parameters. Standard medium sand and coarse sand were used as fill material in the testing. Two wall heights variations and three slopes variations were used in the testing. The test model was constructed either compacted or uncompacted. The compaction in the model was carried out by hand to about 90% of the Proctor density. Three slopes inclinations were used. For flat slope the slope angle was less than 25° , and for steep slope it was 25° -35° and for extremely steep slope it was > 35° . The test results and conclusions are presented in this paper.

Effect of Tibial Posterior Slope on Knee Kinematics, Quadriceps Force, and Patellofemoral Contact Force After Posterior-Stabilized Total Knee Arthroplasty.

PubMed

Okamoto, Shigetoshi; Mizu-uchi, Hideki; Okazaki, Ken; Hamai, Satoshi; Nakahara, Hiroyuki; Iwamoto, Yukihide

2015-08-01

We used a musculoskeletal model validated with in vivo data to evaluate the effect of tibial posterior slope on knee kinematics, quadriceps force, and patellofemoral contact force after posterior-stabilized total knee arthroplasty. The maximum quadriceps force and patellofemoral contact force decreased with increasing posterior slope. Anterior sliding of the tibial component and anterior impingement of the anterior aspect of the tibial post were observed with tibial posterior slopes of at least 5° and 10°, respectively. Increased tibial posterior slope contributes to improved exercise efficiency during knee extension, however excessive tibial posterior slope should be avoided to prevent knee instability. Based on our computer simulation we recommend tibial posterior slopes of less than 5° in posterior-stabilized total knee arthroplasty. Copyright © 2015 Elsevier Inc. All rights reserved.

Application of soil nails to the stability of mine waste slopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tant, C.R.; Drumm, E.C.; Mauldon, M.

1996-12-31

The traditional soil nailed structure incorporates grouted or driven nails, and a wire mesh reinforced shotcrete facing to increase the stability of a slope or wall. This paper describes the construction and monitoring of a full-scale demonstration of nailing to stabilize coal mine spoil. The purpose of the investigation is to evaluate the performance of nailed slopes in mine spoil using methods proven for the stabilization of soil walls and slopes. The site in eastern Tennessee is a 12 meter high slope of dumped fill, composed of weathered shale chips, sandstone, and coal. The slope was formed by {open_quotes}pre-regulatory{close_quotes} contourmore » surface mining operations and served as a work bench during mining. The material varies in size from silt to boulders, and has a small amount of cohesion. Portions of the mine spoil slope have experienced slope instability and erosion which have hampered subsequent reclamation activities. Three different nail spacings and three different nail lengths were used in the design. The 12 meter high structure is instrumented to permit measurement of nail strain, and vertical inclinometer readings and survey measurements will be used for the detection of ground movement. The results of this study will aid in the development of design recommendations and construction guidelines for the application of soil nailing to stabilize mine spoil.« less

[Composition and stability of soil aggregates in hedgerow-crop slope land].

PubMed

Pu, Yu-Lin; Lin, Chao-Wen; Xie, De-Ti; Wei, Chao-Fu; Ni, Jiu-Pai

2013-01-01

Based on a long-term experiment of using hedgerow to control soil and water loss, this paper studied the composition and stability of soil aggregates in a hedgerow-crop slope land. Compared with those under routine contour cropping, the contents of > 0.25 mm soil mechanical-stable and water-stable aggregates under the complex mode hedgerow-crop increased significantly by 13.3%-16.1% and 37.8% -55.6%, respectively. Under the complex mode, the contents of > 0.25 mm soil water-stable aggregates on each slope position increased obviously, and the status of > 0.25 mm soil water-stable aggregates being relatively rich at low slope and poor at top slope was improved. Planting hedgerow could significantly increase the mean mass diameter and geometric mean diameter of soil aggregates, decrease the fractal dimension of soil aggregates and the destruction rate of > 0.25 mm soil aggregates, and thus, increase the stability and erosion-resistance of soil aggregates in slope cropland. No significant effects of slope and hedgerow types were observed on the composition, stability and distribution of soil aggregates.

Using three-dimensional plant root architecture in models of shallow-slope stability.

PubMed

Danjon, Frédéric; Barker, David H; Drexhage, Michael; Stokes, Alexia

2008-05-01

The contribution of vegetation to shallow-slope stability is of major importance in landslide-prone regions. However, existing slope stability models use only limited plant root architectural parameters. This study aims to provide a chain of tools useful for determining the contribution of tree roots to soil reinforcement. Three-dimensional digitizing in situ was used to obtain accurate root system architecture data for mature Quercus alba in two forest stands. These data were used as input to tools developed, which analyse the spatial position of roots, topology and geometry. The contribution of roots to soil reinforcement was determined by calculating additional soil cohesion using the limit equilibrium model, and the factor of safety (FOS) using an existing slope stability model, Slip4Ex. Existing models may incorrectly estimate the additional soil cohesion provided by roots, as the spatial position of roots crossing the potential slip surface is usually not taken into account. However, most soil reinforcement by roots occurs close to the tree stem and is negligible at a distance >1.0 m from the tree, and therefore global values of FOS for a slope do not take into account local slippage along the slope. Within a forest stand on a landslide-prone slope, soil fixation by roots can be minimal between uniform rows of trees, leading to local soil slippage. Therefore, staggered rows of trees would improve overall slope stability, as trees would arrest the downward movement of soil. The chain of tools consisting of both software (free for non-commercial use) and functions available from the first author will enable a more accurate description and use of root architectural parameters in standard slope stability analyses.

Using Three-dimensional Plant Root Architecture in Models of Shallow-slope Stability

PubMed Central

Danjon, Frédéric; Barker, David H.; Drexhage, Michael; Stokes, Alexia

2008-01-01

Background The contribution of vegetation to shallow-slope stability is of major importance in landslide-prone regions. However, existing slope stability models use only limited plant root architectural parameters. This study aims to provide a chain of tools useful for determining the contribution of tree roots to soil reinforcement. Methods Three-dimensional digitizing in situ was used to obtain accurate root system architecture data for mature Quercus alba in two forest stands. These data were used as input to tools developed, which analyse the spatial position of roots, topology and geometry. The contribution of roots to soil reinforcement was determined by calculating additional soil cohesion using the limit equilibrium model, and the factor of safety (FOS) using an existing slope stability model, Slip4Ex. Key Results Existing models may incorrectly estimate the additional soil cohesion provided by roots, as the spatial position of roots crossing the potential slip surface is usually not taken into account. However, most soil reinforcement by roots occurs close to the tree stem and is negligible at a distance >1·0 m from the tree, and therefore global values of FOS for a slope do not take into account local slippage along the slope. Conclusions Within a forest stand on a landslide-prone slope, soil fixation by roots can be minimal between uniform rows of trees, leading to local soil slippage. Therefore, staggered rows of trees would improve overall slope stability, as trees would arrest the downward movement of soil. The chain of tools consisting of both software (free for non-commercial use) and functions available from the first author will enable a more accurate description and use of root architectural parameters in standard slope stability analyses. PMID:17766845

A Simple and Accurate Rate-Driven Infiltration Model

NASA Astrophysics Data System (ADS)

Cui, G.; Zhu, J.

2017-12-01

In this study, we develop a novel Rate-Driven Infiltration Model (RDIMOD) for simulating infiltration into soils. Unlike traditional methods, RDIMOD avoids numerically solving the highly non-linear Richards equation or simply modeling with empirical parameters. RDIMOD employs infiltration rate as model input to simulate one-dimensional infiltration process by solving an ordinary differential equation. The model can simulate the evolutions of wetting front, infiltration rate, and cumulative infiltration on any surface slope including vertical and horizontal directions. Comparing to the results from the Richards equation for both vertical infiltration and horizontal infiltration, RDIMOD simply and accurately predicts infiltration processes for any type of soils and soil hydraulic models without numerical difficulty. Taking into account the accuracy, capability, and computational effectiveness and stability, RDIMOD can be used in large-scale hydrologic and land-atmosphere modeling.

The effect of speaking style on a locus equation characterization of stop place of articulation.

PubMed

Sussman, H M; Dalston, E; Gumbert, S

1998-01-01

Locus equations were employed to assess the phonetic stability and distinctiveness of stop place categories in reduced speech. Twenty-two speakers produced stop consonant + vowel utterances in citation and spontaneous speech. Coarticulatory increases in hypoarticulated speech were documented only for /dV/ and [gV] productions in front vowel contexts. Coarticulatory extents for /bV/ and [gV] in back vowel contexts remained stable across style changes. Discriminant analyses showed equivalent levels of correct classification across speaking styles. CV reduction was quantified by use of Euclidean distances separating stop place categories. Despite sensitivity of locus equation parameters to articulatory differences encountered in informal speech, stop place categories still maintained a clear separability when plotted in a higher-order slope x y-intercept acoustic space.

The Three-Dimensional (3D) Numerical Stability Analysis of Hyttemalmen Open-Pit

NASA Astrophysics Data System (ADS)

Cała, Marek; Kowalski, Michał; Stopkowicz, Agnieszka

2014-10-01

The purpose of this paper was to perform the 3D numerical calculations allowing slope stability analysis of Hyttemalmen open pit (location Kirkenes, Finnmark Province, Norway). After a ramp rock slide, which took place in December 2010, as well as some other small-scale rock slope stability problems, it proved necessary to perform a serious stability analyses. The Hyttemalmen open pit was designed with a depth up to 100 m, a bench height of 24 m and a ramp width of 10 m. The rock formation in the iron mining district of Kirkenes is called the Bjornevaten Group. This is the most structurally complicated area connected with tectonic process such as folding, faults and metamorphosis. The Bjornevaten Group is a volcano-sedimentary sequence. Rock slope stability depends on the mechanical properties of the rock, hydro-geological conditions, slope topography, joint set systems and seismic activity. However, rock slope stability is mainly connected with joint sets. Joints, or general discontinuities, are regarded as weak planes within rock which have strength reducing consequences with regard to rock strength. Discontinuities within the rock mass lead to very low tensile strength. Several simulations were performed utilising the RocLab (2007) software to estimate the gneiss cohesion for slopes of different height. The RocLab code is dedicated to estimate rock mass strength using the Hoek-Brown failure criterion. Utilising both the GSI index and the Hoek-Brown strength criterion the equivalent Mohr-Coulomb parameters (cohesion and angle of internal friction) can be calculated. The results of 3D numerical calculations (with FLA3D code) show that it is necessary to redesign the slope-bench system in the Hyttemalmen open pit. Changing slope inclination for lower stages is recommended. The minimum factor of safety should be equal 1.3. At the final planned stage of excavation, the factor of safety drops to 1.06 with failure surface ranging through all of the slopes. In the case of a slope angle 70° for lower stages, FS = 1.26, which is not enough to provide slope stability. Another series of calculations were therefore performed taking water table lowering into consideration, which increases the global safety factor. It was finally evaluated, that for a water table level of 72 m the factor of safety equals 1.3, which is enough to assure global open-pit stability.

Influence of Analyte Concentration on Stability Constant Values Determined by Capillary Electrophoresis.

PubMed

Sursyakova, Viktoria V; Burmakina, Galina V; Rubaylo, Anatoly I

2016-08-01

The influence of analyte concentration when compared with the concentration of a charged ligand in background electrolyte (BGE) on the measured values of electrophoretic mobilities and stability constants (association, binding or formation constants) is studied using capillary electrophoresis (CE) and a dynamic mathematical simulator of CE. The study is performed using labile complexes (with fast kinetics) of iron (III) and 5-sulfosalicylate ions (ISC) as an example. It is shown that because the ligand concentration in the analyte zone is not equal to that in BGE, considerable changes in the migration times and electrophoretic mobilities are observed, resulting in systematic errors in the stability constant values. Of crucial significance is the slope of the dependence of the electrophoretic mobility decrease on the ligand equilibrium concentration. Without prior information on this dependence to accurately evaluate the stability constants for similar systems, the total ligand concentration must be at least >50-100 times higher than the total concentration of analyte. Experimental ISC peak fronting and the difference between the direction of the experimental pH dependence of the electrophoretic mobility decrease and the mathematical simulation allow assuming the presence of capillary wall interaction. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Slope Stabilization Using Recycled Plastic Pins, Phase III.

DOT National Transportation Integrated Search

2007-01-01

A new technique for stabilizing surficial slope failures using recycled plastic reinforcing members has been developed. The : objective of the project described in this report has been to develop, evaluate, and document a technique for stabilization ...

A DESIGN METHOD FOR RETAINING WALL BASED ON RETURN PERIOD OF RAINFALL AND SNOWMELT

NASA Astrophysics Data System (ADS)

Ebana, Ryo; Uehira, Kenichiro; Yamada, Tadashi

The main purpose of this study is to develop a new design method for the retaining wall in a cold district. In the cold district, snowfall and snowmelt is one of the main factors in sediment related disaster. However, the effect of the snowmelt is not being taken account of sediment disasters precaution and evacuation system. In this study, we target at past slope failure disaster and quantitatively evaluate that the effect of rainfall and snowmelt on groundwater level and then verify the stability of slope. Water supplied on the slope was determined from the probabilistic approach of the snowmelt using DegreeDay method in this study. Furthermore, a slope stability analysis was carried out based on the ground water level that was obtained from the unsaturated infiltration flow with the saturated seepage flow simulations. From the result of the slope stability analysis, it was found that the effect of ground water level on the stability of slope is much bigger than that of other factors.

Three-dimensional modelling of slope stability using the Local Factor of Safety concept

NASA Astrophysics Data System (ADS)

Moradi, Shirin; Huisman, Sander; Beck, Martin; Vereecken, Harry; Class, Holger

2017-04-01

Slope stability is governed by coupled hydrological and mechanical processes. The slope stability depends on the effective stress, which in turn depends on the weight of the soil and the matrix potential. Therefore, changes in water content and matrix potential associated with infiltration will affect slope stability. Most available models describing these coupled hydro-mechanical processes either rely on a one- or two-dimensional representation of hydrological and mechanical properties and processes, which obviously is a strong simplification in many applications. Therefore, the aim of this work is to develop a three-dimensional hydro-mechanical model that is able to capture the effect of spatial and temporal variability of both mechanical and hydrological parameters on slope stability. For this, we rely on DuMux, which is a free and open-source simulator for flow and transport processes in porous media that facilitates coupling of different model approaches and offers flexibility for model development. We use the Richards equation to model unsaturated water flow. The simulated water content and matrix potential distribution is used to calculate the effective stress. We only consider linear elasticity and solve for statically admissible fields of stress and displacement without invoking failure or the redistribution of post-failure stress or displacement. The Local Factor of Safety concept is used to evaluate slope stability in order to overcome some of the main limitations of commonly used methods based on limit equilibrium considerations. In a first step, we compared our model implementation with a 2D benchmark model that was implemented in COMSOL Multiphysics. In a second step, we present in-silico experiments with the newly developed 3D model to show the effect of slope morphology, spatial variability in hydraulic and mechanical material properties, and spatially variable soil depth on simulated slope stability. It is expected that this improved physically-based three-dimensional hydro-mechanical model is able to provide more reliable slope instability predictions in more complex situations.

Plant Functional Type Shifts in Big Sagebrush Ecosystems: Impacts on Dryland Ecosystem Water Balance

NASA Astrophysics Data System (ADS)

Bogenschuetz, N. M.; Bearup, L. A.; Maxwell, R. M.; Santi, P. M.

2014-12-01

The mountain pine beetle (MPB), Dendroctonus ponderosae, has caused significant tree mortality within North America. Specifically, the MPB affects ponderosa pine and lodgepole pine forests within the Rocky Mountains with approximately 3.4 million acres of forest impacted over the past 20 years. The full impacts of such unprecedented tree mortality on hydrology and slope stability is not well understood. This work studies the affects of MPB infestation on slope instability. A large-scale statistical analysis of MPB and slope stability is combined with a more in-depth analysis of the factors that contribute to slope stability. These factors include: slope aspect, slope angle, root decay, regrowth and hydrologic properties, such as water table depth and soil moisture. Preliminary results show that MPB may affect a greater number of north- and east-facing slopes. This is in accordance with more water availability and a higher MPB impacted tree density on north-facing slopes which, in turn, could potentially increase the probability of slope failure. Root strength is predicted to decrease as the roots stop transpiring 3-4 years proceeding infestation. However, this effect on the hillslope is likely being counterbalanced by the regrowth of grasses, forbs, shrubs, and trees. In addition, the increase in water table height from the lack of transpiring trees is adding a driving force to the slopes. The combination of all these factors will be used in order to assess the effects of MPB tree mortality on slope stability.

The morphology and evolution of the Stromboli 2002-2003 lava flow field--An example of a basaltic flow field emplaced on a steep slope

USGS Publications Warehouse

Lodato, Luigi; Harris, A.; Spampinato, L.; Calvari, Sonia; Dehn, J.; Patrick, M.

2007-01-01

The use of a hand-held thermal camera during the 2002–2003 Stromboli effusive eruption proved essential in tracking the development of flow field structures and in measuring related eruption parameters, such as the number of active vents and flow lengths. The steep underlying slope on which the flow field was emplaced resulted in a characteristic flow field morphology. This comprised a proximal shield, where flow stacking and inflation caused piling up of lava on the relatively flat ground of the vent zone, that fed a medial–distal lava flow field. This zone was characterized by the formation of lava tubes and tumuli forming a complex network of tumuli and flows linked by tubes. Most of the flow field was emplaced on extremely steep slopes and this had two effects. It caused flows to slide, as well as flow, and flow fronts to fail frequently, persistent flow front crumbling resulted in the production of an extensive debris field. Channel-fed flows were also characterized by development of excavated debris levees in this zone (Calvari et al. 2005). Collapse of lava flow fronts and inflation of the upper proximal lava shield made volume calculation very difficult. Comparison of the final field volume with that expecta by integrating the lava effusion rates through time suggests a loss of ~70% erupted lava by flow front crumbling and accumulation as debris flows below sea level. Derived relationships between effusion rate, flow length, and number of active vents showed systematic and correlated variations with time where spreading of volume between numerous flows caused an otherwise good correlation between effusion rate, flow length to break down. Observations collected during this eruption are useful in helping to understand lava flow processes on steep slopes, as well as in interpreting old lava–debris sequences found in other steep-sided volcanoes subject to effusive activity.

Slope Stability of Geosynthetic Clay Liner Test Plots

EPA Science Inventory

Fourteen full-scale field test plots containing five types of geosynthetic clay liners (GCLs) were constructed on 2H:IV and 3H:IV slopes for the purpose of assessing slope stability. The test plots were designed to simulate typical final cover systems for landfill. Slides occurr...

76 FR 13546 - Airworthiness Directives; The Boeing Company Model MD-90-30 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-14

...We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require a detailed inspection to detect distress and existing repairs to the leading edge structure of the vertical stabilizer at the splice at Station Zfs=52.267; repetitive inspections for cracking in the front spar cap forward flanges of the vertical stabilizer, and either the aft flanges or side skins; repetitive inspections for loose and missing fasteners; and related investigative and corrective actions if necessary. This proposed AD was prompted by reports of cracked vertical stabilizer skin, a severed front spar cap, elongated fastener holes at the leading edge of the vertical stabilizer, and a cracked front spar web and front spar cap bolt holes in the vertical stabilizer. We are proposing this AD to detect and correct such cracking damage, which could result in the structure being unable to support limit load, and could lead to the loss of the vertical stabilizer.

76 FR 41651 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-15

...We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires a detailed inspection to detect distress and existing repairs to the leading edge structure of the vertical stabilizer at the splice at Station Zfs = 52.267; repetitive inspections for cracking in the front spar cap forward flanges of the vertical stabilizer, and either the aft flanges or side skins; repetitive inspections for loose and missing fasteners; and related investigative and corrective actions if necessary. This AD was prompted by reports of cracked vertical stabilizer skin, a severed front spar cap, elongated fastener holes at the leading edge of the vertical stabilizer, and a cracked front spar web and front spar cap bolt holes in the vertical stabilizer. We are issuing this AD to detect and correct such cracking damage, which could result in the structure being unable to support limit load, and could lead to the loss of the vertical stabilizer.

76 FR 35342 - Airworthiness Directives; The Boeing Company Model MD-90-30 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-17

...We are adopting a new airworthiness directive (AD) for the products listed above. This AD requires a detailed inspection to detect distress and existing repairs to the leading edge structure of the vertical stabilizer at the splice at Station Zfs=52.267; repetitive inspections for cracking in the front spar cap forward flanges of the vertical stabilizer, and either the aft flanges or side skins; repetitive inspections for loose and missing fasteners; and related investigative and corrective actions if necessary. This AD was prompted by reports of cracked vertical stabilizer skin, a severed front spar cap, elongated fastener holes at the leading edge of the vertical stabilizer, and cracked front spar web and front spar cap bolt holes in the vertical stabilizer. We are issuing this AD to detect and correct such cracking damage, which could result in the structure being unable to support limit load, and could lead to the loss of the vertical stabilizer.

Physically-based landslide assessment for railway infrastructure

NASA Astrophysics Data System (ADS)

Heyerdahl, Håkon; Høydal, Øyvind

2017-04-01

A new high-speed railway line in Eastern Norway passes through areas with Quaternary soil deposits where stability of natural slopes poses considerable challenges. The ground typically consist of thick layers of marine clay deposits, overlain by 8-10 m of silt and sand. Both shallow landslides in the top layers of silt and sand and deep-seated failures in clay must be accounted for. In one section of the railway, the potential for performing stabilizing measures is limited due to existing cultural heritage on top of the slope. Hence, the stability of a steep top section of the slope needs to be evaluated. Assessment of the slope stability for rainfall-triggered slides relies on many parameters. An approach based only on empirical relations will not comply with the design criteria, which only allows deterministic safety margins. From a classic geotechnical approach, the slope would also normally be considered unsafe. However, considerable suction is assumed to exist in the silty and sandy deposits above ground-water level, which will improve the stability. The stabilizing effect however is highly dependent on rainfall, infiltration and soil moisture, and thereby varies continuously. An unsaturated geomechanical approach was taken to assess the slope stability. Soil moisture sensors were installed to monitor changes of in situ water content in the vadose zone. Retention curves for silt/sand specimens samples were measured by pressure plate tests. Some triaxial tests soil strength were performed to check the effect of suction on soil shear strength (performed as drained constant water content tests on compacted specimens). Based on the performed laboratory tests, the unsaturated response of the slope will be modelled numerically and compared with measured soil moisture in situ. Work is still on-going. Initial conditions after respectively dry and wet periods need to be coupled with selected rainfall intensities and duration to see the effect on slope stability. The aim of the work is to reach a result informing the client about the probability of a landslide in the slope, based on expected critical rainfall. A strictly deterministic criterion for minimum safety margin may need to be replaced by scenarios for probability and geometry of potential failures for given return periods and rainfall events.

Impact of vegetation on stability of slopes subjected to rainfall - numerical aspect

NASA Astrophysics Data System (ADS)

Switala, Barbara Maria; Tamagnini, Roberto; Sudan Acharya, Madhu; Wu, Wei

2015-04-01

Recent years brought a significant development of soil bioengineering methods, considered as an ecological and economically effective measure for slope stabilization. This work aims to show the advantages of the soil bioengineering solutions for a slope subjected to a heavy rainfall, with the help of a numerical model, which integrates most of the significant plant and slope features. There are basically two different ways in which vegetation can affect stability of a slope: root reinforcement (mechanical impact) and root water uptake (evapotranspiration). In the numerical model, the first factor is modelled using the Cam-Clay model extended for unsaturated conditions by Tamagnini (2004). The original formulation of a constitutive model is modified by introducing an additional constitutive parameter, which causes an expansion of the yield surface as a consequence of an increase in root mass in a representative soil element. The second factor is the root water uptake, which is defined as a volumetric sink term in the continuity equation of groundwater flow. Water removal from the soil mass causes an increase in suction in the vicinity of the root zone, which leads to an increase in the soil cohesion and provides additional strength to the soil-root composite. The developed numerical model takes into account the above mentioned effects of plants and thus considers the multi-phase nature of the soil-plant-water relationship. Using the developed method, stability of some vegetated and non-vegetated slopes subjected to rainfall are investigated. The performance of each slope is evaluated by the time at which slope failure occurs. Different slope geometries and soil mechanical and hydrological properties are considered. Comparison of the results obtained from the analyses of vegetated and non-vegetated slopes leads to the conclusion, that the use of soil bioengineering methods for slope stabilization can be effective and can significantly delay the occurrence of a rainfall induced landslide. On the contrary, vegetation removal can have serious consequences, especially on steep and forested slopes.

Debris flows as geomorphic agents in the Huachuca Mountains of southeastern Arizona

USGS Publications Warehouse

Wohl, E.E.; Pearthree, P.P.

1991-01-01

Numerous debris flows occurred in the Huachuca Mountains of southeastern Arizona during the summer rainy season of 1988 in areas that were burned by a forest fire earlier in the summer. Debris flows occurred following a major forest fire in 1977 as well, suggesting a causal link between fires and debris flows. Abundant evidence of older debris flows preserved along channels and in mountain front fans indicates that debris flows have occurred repeteadly during the late Quaternary in this environment. Soil development in sequences of debris-flow deposits indicates that debris flows probably recur over time intervals of several hundred to a thousand years in individual drainage basins in the study area. Surface runoff in the steep drainage basins of the Huachuca Mountains is greatly enhanced following forest fires, as the hillslopes are denuded of their vegetative cover. Water and sediment eroded from the hillslope regolith are rapidly introduced into the upper reaches of tributary channels by widespread rilling and slope wash during rainfall events. This influx of water and sediment destabilizes regolith previously accumulated in the channel, triggering debris flows that scour the channel to bedrock in the upper reaches. Following a debris flow, the scoured, trapezoidally-shaped channel gradually assumes a swale shape and the percentage of exposed bedrock declines, as material is introduced from the slopes. Debris flows do a tremendous amount of work in a very short time, however, and are the major channel-forming events. Where the tributary channels enter larger, trunk channels, the debris flows serve as the main source of very coarse sediment. The local slope and coarse particle distribution of the trunk channel depend on the competence of water flows in the channel to transport the material introduced by debris flows. Where the smaller channels drain directly to the mountain front, debris flows create extensive alluvial fans which dominate the morphology of the basin-range boundary. Time intervals between debris flows in the drainage basins of the Huachuca Mountains are probably controlled by complex interactions among climate, forest fires and slope processes. Fires destroy the protective vegetation that stabilizes the upper catchment slopes and inhibits erosion. However, not every fire that burns a catchment causes debris flows, because sufficient weathered material must accumulate in the upper channel reaches to initiate a large debris flow. If such accumulation has not occurred, the material introduced to a channel following a forest fire will move only a short distance down the channel. Thus, the episodic nature of debris flows probably depends on rates of slope weathering and erosion, which are in turn controlled by climate, both directly and through vegetation and forest fires. ?? 1991.

An engineering rock classification to evaluate seismic rock-fall susceptibility and its application to the Wasatch Front

USGS Publications Warehouse

Harp, E.L.; Noble, M.A.

1993-01-01

Investigations of earthquakes world wide show that rock falls are the most abundant type of landslide that is triggered by earthquakes. An engineering classification originally used in tunnel design, known as the rock mass quality designation (Q), was modified for use in rating the susceptibility of rock slopes to seismically-induced failure. Analysis of rock-fall concentrations and Q-values for the 1980 earthquake sequence near Mammoth Lakes, California, defines a well-constrained upper bound that shows the number of rock falls per site decreases rapidly with increasing Q. Because of the similarities of lithology and slope between the Eastern Sierra Nevada Range near Mammoth Lakes and the Wasatch Front near Salt Lake City, Utah, the probabilities derived from analysis of the Mammoth Lakes region were used to predict rock-fall probabilities for rock slopes near Salt Lake City in response to a magnitude 6.0 earthquake. These predicted probabilities were then used to generalize zones of rock-fall susceptibility. -from Authors

Assessing slope stability in unplanned settlements in developing countries.

PubMed

Anderson, Malcolm G; Holcombe, Liz; Renaud, Jean-Philippe

2007-10-01

Unplanned housing in developing countries is often located on steep slopes. Frequently no building code is enforced for such housing and mains water is provided with no drainage provision. Both of these factors can be particularly significant in terms of landslide risk if, as is so often the case, such slopes lack any planned drainage provision. There is thus a need to develop a model that facilitates the assessment of slope stability in an holistic context, incorporating a wide range of factors (including surface cover, soil water topographic convergence, slope loading and point source water leakage) in order that appropriate advice can be given as to the general controls on slope stability in such circumstances. This paper outlines a model configured for this specific purpose and describes an application to a site in St. Lucia, West Indies, where there is active slope movement in an unplanned housing development on relatively steep topography. The model findings are in accord with the nature of the current failure at the site, provide guidance as to the significance of slope drainage and correspond to inferences drawn from an application of resistance envelope methods to the site. In being able to scenario test a uniquely wide range of combinations of factors, the model structure is shown to be highly valuable in assessing dominant slope stability process controls in such complex environments.

The Stability Analysis Method of the Cohesive Granular Slope on the Basis of Graph Theory.

PubMed

Guan, Yanpeng; Liu, Xiaoli; Wang, Enzhi; Wang, Sijing

2017-02-27

This paper attempted to provide a method to calculate progressive failure of the cohesivefrictional granular geomaterial and the spatial distribution of the stability of the cohesive granular slope. The methodology can be divided into two parts: the characterization method of macro-contact and the analysis of the slope stability. Based on the graph theory, the vertexes, the edges and the edge sequences are abstracted out to characterize the voids, the particle contact and the macro-contact, respectively, bridging the gap between the mesoscopic and macro scales of granular materials. This paper adopts this characterization method to extract a graph from a granular slope and characterize the macro sliding surface, then the weighted graph is analyzed to calculate the slope safety factor. Each edge has three weights representing the sliding moment, the anti-sliding moment and the braking index of contact-bond, respectively, . The safety factor of the slope is calculated by presupposing a certain number of sliding routes and reducing Weight repeatedly and counting the mesoscopic failure of the edge. It is a kind of slope analysis method from mesoscopic perspective so it can present more detail of the mesoscopic property of the granular slope. In the respect of macro scale, the spatial distribution of the stability of the granular slope is in agreement with the theoretical solution.

Sequential deconvolution from wave-front sensing using bivariate simplex splines

NASA Astrophysics Data System (ADS)

Guo, Shiping; Zhang, Rongzhi; Li, Jisheng; Zou, Jianhua; Xu, Rong; Liu, Changhai

2015-05-01

Deconvolution from wave-front sensing (DWFS) is an imaging compensation technique for turbulence degraded images based on simultaneous recording of short exposure images and wave-front sensor data. This paper employs the multivariate splines method for the sequential DWFS: a bivariate simplex splines based average slopes measurement model is built firstly for Shack-Hartmann wave-front sensor; next, a well-conditioned least squares estimator for the spline coefficients is constructed using multiple Shack-Hartmann measurements; then, the distorted wave-front is uniquely determined by the estimated spline coefficients; the object image is finally obtained by non-blind deconvolution processing. Simulated experiments in different turbulence strength show that our method performs superior image restoration results and noise rejection capability especially when extracting the multidirectional phase derivatives.

Slope Stability Estimation of the Kościuszko Mound in Cracow

NASA Astrophysics Data System (ADS)

Wrana, Bogumił; Pietrzak, Natalia

2015-06-01

In the paper, the slope stability problem of the Kościuszko Mound in Cracow, Poland is considered. The slope stability analysis was performed using Plaxis FEM program. The outer surface of the mound has complex geometry. The slope of the cone is not uniform in all directions, on the surface of the cone are pedestrian paths. Due to its complicated geometry it was impossible to do computing by Plaxis input pre-procesor. The initial element mesh was generated using Autodesk Autocad 3D and next it was updated by Plaxis program. The soil parameters were adopted in accordance with the detailed geological soil testing performed in 2012. Calculating model includes geogrids. The upper part was covered by MacMat geogrid, while the lower part of the Mound was reinforced using Terramesh Matt geogrid. The slope analysis was performed by successives reduction of φ /c parameters. The total multiplayer ΣMsf is used to define the value of the soil strength parameters. The article presents the results of slope stability before and after the rainfall during 33 days of precipitation in flood of 2010.

Physical Analysis Work for Slope Stability at Shah Alam, Selangor

NASA Astrophysics Data System (ADS)

Ishak, M. F.; Zaini, M. S. I.

2018-04-01

Slope stability analysis is performed to assess the equilibrium conditions and the safe design of a human-made or natural slope to find the endangered areas. Investigation of potential failure and determination of the slope sensitivity with regard to safety, reliability and economics were parts of this study. Ground anchor is designed to support a structure in this study. Ground anchor were implemented at the Mechanically Stabilized Earth (MSE) wall along Anak Persiaran Jubli Perak to overcome the further cracking of pavement parking, concrete deck and building of the Apartments. A result from the laboratory testing of soil sample such as index test and shear strength test were applied to the Slope/W software with regard to the ground anchors that were implemented. The ground anchors were implemented to increase the value of the factor of safety (FOS) of the MSE Wall. The value of the factor of safety (FOS) before implementing the ground anchor was 0.800 and after the ground anchor was implemented the value increase to 1.555. The increase percentage of factor of safety by implementing on stability of slope was 94.38%.

Design of Rock Slope Reinforcement: An Himalayan Case Study

NASA Astrophysics Data System (ADS)

Tiwari, Gaurav; Latha, Gali Madhavi

2016-06-01

The stability analysis of the two abutment slopes of a railway bridge proposed at about 359 m above the ground level, crossing a river and connecting two hill faces in the Himalayas, India, is presented. The bridge is located in a zone of high seismic activity. The rock slopes are composed of a heavily jointed rock mass and the spacing, dip and dip direction of joint sets are varying at different locations. Geological mapping was carried out to characterize all discontinuities present along the slopes. Laboratory and field investigations were conducted to assess the geotechnical properties of the intact rock, rock mass and joint infill. Stability analyses of these rock slopes were carried out using numerical programmes. Loads from the foundations resting on the slopes and seismic accelerations estimated from site-specific ground response analysis were considered. The proposed slope profile with several berms between successive foundations was simulated in the numerical model. An equivalent continuum approach with Hoek and Brown failure criterion was initially used in a finite element model to assess the global stability of the slope abutments. In the second stage, finite element analysis of rock slopes with all joint sets with their orientations, spacing and properties explicitly incorporated into the numerical model was taken up using continuum with joints approach. It was observed that the continuum with joints approach was able to capture the local failures in some of the slope sections, which were verified using wedge failure analysis and stereographic projections. Based on the slope deformations and failure patterns observed from the numerical analyses, rock anchors were designed to achieve the target factors of safety against failure while keeping the deformations within the permissible limits. Detailed design of rock anchors and comparison of the stability of slopes with and without reinforcement are presented.

Slope Stability Analysis In Seismic Areas Of The Northern Apennines (Italy)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lo Presti, D.; Fontana, T.; Marchetti, D.

2008-07-08

Several research works have been published on the slope stability in the northern Tuscany (central Italy) and particularly in the seismic areas of Garfagnana and Lunigiana (Lucca and Massa-Carrara districts), aimed at analysing the slope stability under static and dynamic conditions and mapping the landslide hazard. In addition, in situ and laboratory investigations are available for the study area, thanks to the activities undertaken by the Tuscany Seismic Survey. Based on such a huge information the co-seismic stability of few ideal slope profiles have been analysed by means of Limit equilibrium method LEM - (pseudo-static) and Newmark sliding block analysismore » (pseudo-dynamic). The analysis--results gave indications about the most appropriate seismic coefficient to be used in pseudo-static analysis after establishing allowable permanent displacement. Such indications are commented in the light of the Italian and European prescriptions for seismic stability analysis with pseudo-static approach. The stability conditions, obtained from the previous analyses, could be used to define microzonation criteria for the study area.« less

Denudational slope processes on weathered basalt in northern California: 130 ka history of soil development, periods of slope stability and colluviation, and climate change

NASA Astrophysics Data System (ADS)

McDonald, Eric; Harrison, Bruce; Baldwin, John; Page, William; Rood, Dylan

2017-04-01

The geomorphic history of hillslope evolution is controlled by multiple types of denudational processes. Detailed analysis of hillslope soil-stratigraphy provides a means to identify the timing of periods of slope stability and non-stability, evidence of the types of denudational processes, and possible links to climatic drivers. Moreover, the degree of soil formation and the presence of buried or truncated soils provide evidence of the relative age of alternating periods of colluviation and stability. We use evaluation of soil stratigraphy, for a small forested hillslope (<500 m of slope length) located in the Cascades of northern California, to elucidate both the timing and processes controlling 130 ka of hillslope evolution. The soils and slope colluvium are derived from highly weathered basalt. Stratigraphic interpretation is reinforced with soil profile development index (PDI) derived age estimates, tephrochronology, luminescence ages on colluvium, and He3 nuclide exposure dates. Soils formed along hilltop ridges are well developed and reflect deep (>2-3 m) in-situ weathering of the basalt bedrock. PDI age estimates and He3 exposure dates indicate that these hilltop soils had been in place for 100-130 ka, implying a long period of relative surface stability. At about 40-30 ka, soil stratigraphy indicates the onset of 3 distinct cycles of denudation of the hilltop and slopes. Evidence for changes in stability and onset of soil erosion is the presence of several buried soils formed in colluvium downslope of the hilltop. These buried soils have formed in sediment derived from erosion of the hilltop soils (i.e. soil parent material of previously weathered soil matrix and basalt cobbles). The oldest buried soil indicates that slope stability was re-established between 32-23 ka, with stability and soil formation lasting to about 10 ka. Soil-stratigraphy indicates that two additional intervals of downslope transport of sediment between 6-10 ka, and 2-5 ka. Soil properties indicate that the primary method of downslope transport is largely due to tree throw and faunal burrowing. Onset of slope instability at 40-30 ka appears to be related to changes in vegetation with establishment of a pine dominated forest (increase in tree throw) and/or onset of local faulting. By comparison, slope stability from 30-10 ka appears to be a related to the formation of a shrub dominated steppe and a decrease in tree throw. The two periods of slope erosion after 10 ka appear related to regional periods of pronounced channel incision. Results indicate that soil stratigraphy can provide a key record of slope evolution and related paleoenvironmental changes.

Stability analysis and hazard assessment of the northern slopes of San Vicente Volcano in central El Salvador

NASA Astrophysics Data System (ADS)

Smith, Daniel M.

Geologic hazards affect the lives of millions of people worldwide every year. El Salvador is a country that is regularly affected by natural disasters, including earthquakes, volcanic eruptions and tropical storms. Additionally, rainfall-induced landslides and debris flows are a major threat to the livelihood of thousands. The San Vicente Volcano in central El Salvador has a recurring and destructive pattern of landslides and debris flows occurring on the northern slopes of the volcano. In recent memory there have been at least seven major destructive debris flows on San Vicente volcano. Despite this problem, there has been no known attempt to study the inherent stability of these volcanic slopes and to determine the thresholds of rainfall that might lead to slope instability. This thesis explores this issue and outlines a suggested method for predicting the likelihood of slope instability during intense rainfall events. The material properties obtained from a field campaign and laboratory testing were used for a 2-D slope stability analysis on a recent landslide on San Vicente volcano. This analysis confirmed that the surface materials of the volcano are highly permeable and have very low shear strength and provided insight into the groundwater table behavior during a rainstorm. The biggest factors on the stability of the slopes were found to be slope geometry, rainfall totals and initial groundwater table location. Using the results from this analysis a stability chart was created that took into account these main factors and provided an estimate of the stability of a slope in various rainfall scenarios. This chart could be used by local authorities in the event of a known extreme rainfall event to help make decisions regarding possible evacuation. Recommendations are given to improve the methodology for future application in other areas as well as in central El Salvador.

The long-term hydrological effect of forest stands on the stability of slopes

NASA Astrophysics Data System (ADS)

Bogaard, T. A.; Meng, W.; van Beek, L. P. H.

2012-04-01

Forest is widely known to improve slope stability as a result of mechanical and hydrological effects. While the mechanics underlying the stabilizing process of root reinforcement are well understood and quantified, the influence of forest on the occurrence of critical hydrological conditions in terms of suction or pore pressure remains uncertain. Due to seasonal and inter-annual fluctuations, the stabilizing influence of evaporation and transpiration is difficult to isolate from the overall noise of the hydrological signal. More long-term effects of forest stands on soil development are highly variable and thus difficult to observe and quantify. Often these effects are ambivalent, having potentially a stabilizing or destabilizing influence on a slope under particular conditions (e.g., more structured soils leading to both rapid infiltration and drainage). Consequently, it can be postulated that forests will hydrologically influence the magnitude-frequency distribution of landsliding, not only at the stand level but also on a regional scale through the groundwater system. The overall aim of this research is to understand and quantify the stabilizing hydrological effect of forests on potentially unstable slopes. To this end, we focus on the changes in the magnitude-frequency distribution of landsliding that arise as a result of variations in evapotranspiration losses over the life cycle of stands. Temporal variations in evapotranspiration comprise first of all the interception that can account for an important amount of evaporation from a forest, and that changes with seasonal and annual variations in the interception capacity of the canopy and forest floor. Transpiration also represents an important loss that varies over the various growth stages of a forest stand. Based on a literature review of water consumption by tree species and water balance studies of forested catchments we defined the potential transpiration for different growth stages. This information we used in a spatially distributed, physical-based, dynamical model to simulate the hydrology and resulting stability for a catchment on a daily scale. The results can be used to identify end members of the hydrological influence of forests on slope stability and the typical variations in stability associated with the various growth stages. They indicate that the influence of forest stand age on the water consumption can be significant and has clear consequences for the antecedent soil moisture condition within a slope and thus on the potential for slope destabilization. The outcome should help to understand the long-term impact of vegetation on slope hydrology and define sustainable and reliable management strategies at the scale of forest stands. Keywords: slope stability, hydrology, vegetation, long-tem effect

Robustness for slope stability modelling under deep uncertainty

NASA Astrophysics Data System (ADS)

Almeida, Susana; Holcombe, Liz; Pianosi, Francesca; Wagener, Thorsten

2015-04-01

Landslides can have large negative societal and economic impacts, such as loss of life and damage to infrastructure. However, the ability of slope stability assessment to guide management is limited by high levels of uncertainty in model predictions. Many of these uncertainties cannot be easily quantified, such as those linked to climate change and other future socio-economic conditions, restricting the usefulness of traditional decision analysis tools. Deep uncertainty can be managed more effectively by developing robust, but not necessarily optimal, policies that are expected to perform adequately under a wide range of future conditions. Robust strategies are particularly valuable when the consequences of taking a wrong decision are high as is often the case of when managing natural hazard risks such as landslides. In our work a physically based numerical model of hydrologically induced slope instability (the Combined Hydrology and Stability Model - CHASM) is applied together with robust decision making to evaluate the most important uncertainties (storm events, groundwater conditions, surface cover, slope geometry, material strata and geotechnical properties) affecting slope stability. Specifically, impacts of climate change on long-term slope stability are incorporated, accounting for the deep uncertainty in future climate projections. Our findings highlight the potential of robust decision making to aid decision support for landslide hazard reduction and risk management under conditions of deep uncertainty.

Field instrumentation, monitoring of drilled shafts for landslide stabilization and development of pertinent design method : executive summary report.

DOT National Transportation Integrated Search

2010-11-01

The use of a row of spaced drilled shafts to stabilize unstable slopes along the highways offers many advantages compared to other slope stabilization techniques. Some of these advantages may include: (1) various construction techniques are available...

Mapping Mountain Front Recharge Areas in Arid Watersheds Based on a Digital Elevation Model and Land Cover Types

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowen, Esther E.; Hamada, Yuki; O’Connor, Ben L.

Here, a recent assessment that quantified potential impacts of solar energy development on water resources in the southwestern United States necessitated the development of a methodology to identify locations of mountain front recharge (MFR) in order to guide land development decisions. A spatially explicit, slope-based algorithm was created to delineate MFR zones in 17 arid, mountainous watersheds using elevation and land cover data. Slopes were calculated from elevation data and grouped into 100 classes using iterative self-organizing classification. Candidate MFR zones were identified based on slope classes that were consistent with MFR. Land cover types that were inconsistent with groundwatermore » recharge were excluded from the candidate areas to determine the final MFR zones. No MFR reference maps exist for comparison with the study’s results, so the reliability of the resulting MFR zone maps was evaluated qualitatively using slope, surficial geology, soil, and land cover datasets. MFR zones ranged from 74 km2 to 1,547 km2 and accounted for 40% of the total watershed area studied. Slopes and surficial geologic materials that were present in the MFR zones were consistent with conditions at the mountain front, while soils and land cover that were present would generally promote groundwater recharge. Visual inspection of the MFR zone maps also confirmed the presence of well-recognized alluvial fan features in several study watersheds. While qualitative evaluation suggested that the algorithm reliably delineated MFR zones in most watersheds overall, the algorithm was better suited for application in watersheds that had characteristic Basin and Range topography and relatively flat basin floors than areas without these characteristics. Because the algorithm performed well to reliably delineate the spatial distribution of MFR, it would allow researchers to quantify aspects of the hydrologic processes associated with MFR and help local land resource managers to consider protection of critical groundwater recharge regions in their development decisions.« less

Mapping Mountain Front Recharge Areas in Arid Watersheds Based on a Digital Elevation Model and Land Cover Types

DOE PAGES

Bowen, Esther E.; Hamada, Yuki; O’Connor, Ben L.

2014-06-01

Here, a recent assessment that quantified potential impacts of solar energy development on water resources in the southwestern United States necessitated the development of a methodology to identify locations of mountain front recharge (MFR) in order to guide land development decisions. A spatially explicit, slope-based algorithm was created to delineate MFR zones in 17 arid, mountainous watersheds using elevation and land cover data. Slopes were calculated from elevation data and grouped into 100 classes using iterative self-organizing classification. Candidate MFR zones were identified based on slope classes that were consistent with MFR. Land cover types that were inconsistent with groundwatermore » recharge were excluded from the candidate areas to determine the final MFR zones. No MFR reference maps exist for comparison with the study’s results, so the reliability of the resulting MFR zone maps was evaluated qualitatively using slope, surficial geology, soil, and land cover datasets. MFR zones ranged from 74 km2 to 1,547 km2 and accounted for 40% of the total watershed area studied. Slopes and surficial geologic materials that were present in the MFR zones were consistent with conditions at the mountain front, while soils and land cover that were present would generally promote groundwater recharge. Visual inspection of the MFR zone maps also confirmed the presence of well-recognized alluvial fan features in several study watersheds. While qualitative evaluation suggested that the algorithm reliably delineated MFR zones in most watersheds overall, the algorithm was better suited for application in watersheds that had characteristic Basin and Range topography and relatively flat basin floors than areas without these characteristics. Because the algorithm performed well to reliably delineate the spatial distribution of MFR, it would allow researchers to quantify aspects of the hydrologic processes associated with MFR and help local land resource managers to consider protection of critical groundwater recharge regions in their development decisions.« less

Karstic slope "breathing": morpho-structural influence and hazard implications

NASA Astrophysics Data System (ADS)

Devoti, Roberto; Falcucci, Emanuela; Gori, Stefano; Eliana Poli, Maria; Zanferrari, Adriano; Braitenberg, Carla; Fabris, Paolo; Grillo, Barbara; Zuliani, David

2016-04-01

The study refers to the active slope deformation detected by GPS and tiltmeter stations in the Cansiglio karstic plateau located in the western Carnic Prealps (NE Italy). The observed transient deformation clearly correlates with the rainfall, so that the southernmost border of the Plateau reacts instantly to heavy rains displaying a "back and forth" deformation up to a few centimeters wide, with different time constants, demonstrating a response to different catchment volumes. We carried out a field survey along the southern Cansiglio slope, to achieve structural characterization of the relief and to verify the possible relation between structural features and the peculiar geomorphological setting dominated by widespread karstic features. The Cansiglio plateau develops on the frontal ramp anticline of the Cansiglio thrust, an about ENE-WSW trending, SSE-verging, low angle thrust, belonging to the Neogene-Quaternary front of the eastern Southern Alps. The Cansiglio thrust outcrops at the base of the Cansiglio plateau, where it overlaps the Mesozoic carbonates on the Miocene-Quaternary terrigenous succession. All along its length cataclastic limestone largely outcrop. The Cansiglio thrust is bordered by two transfer zones probably inherited from the Mesozoic paleogeography: the Caneva fault in the west and the Col Longone fault in the east. The carbonatic massif is also characterized by a series of about northward steeply dipping reverse minor faults and a set of subvertical joints parallel to the axes of the Cansiglio anticline. Other NNW-SSE and NNE-SSW conjugate faults and fractures perpendicular to the Cansiglio southern slope are also identified. This structural setting affect pervasively the whole slope and may determine centimetre- to metre-scale rock prisms. Interestingly, along the topmost portion of the slope, some dolines and swallow holes show an incipient coalescence, that trends parallel to the massif front and to the deformation zones related to the reverse fault. Such a dolines alignment forms a ridge parallel elongated trench, about 4 km long, which is a typical morpho-structural feature of slopes undergoing large scale gravitational instability (deep seated gravitational slope deformations). The trench is interrupted towards the NE by several coalescent and slide scarps. Such geomorphic evidence testifies to the occurrence of landslides events (mainly rockslides and rock falls) that sourced from the top portion of the slope, as local collapses of the sector affected by the trench. Our observations, as a whole, suggest that morpho-structural framework of the Cansiglio south-eastern slope is highly influenced by tectonic features related to the complex tectonic deformation. The structural setting is locally favoring the nucleation of karstic landforms (dolines, swallow holes and ipokarstic features). Moreover, the presence of widespread tectonic features lead gravitational instability affecting the slope, linked to the high local relief of the mountain front, may trigger collapse of sectors of the slope in rock falls phenomena. In this perspective, therefore, the continuous "back and forth" movements of the slope observed by GPS time series analysis induced by rainfall may progressively weaken the slope and render it prone to landsliding.

76 FR 13543 - Airworthiness Directives; The Boeing Company Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-14

...We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD would require a detailed inspection to detect distress and existing repairs to the leading edge structure of the vertical stabilizer at the splice at Station Zfs = 52.267; repetitive inspections for cracking in the front spar cap forward flanges of the vertical stabilizer, and either the aft flanges or side skins; repetitive inspections for loose and missing fasteners; and related investigative and corrective actions if necessary. This proposed AD was prompted by reports of cracked vertical stabilizer skin, a severed front spar cap, elongated fastener holes at the leading edge of the vertical stabilizer, and a cracked front spar web and front spar cap bolt holes in the vertical stabilizer. We are proposing this AD to detect and correct such cracking damage, which could result in the structure being unable to support limit load, and could lead to the loss of the vertical stabilizer.

On the influence of tyre and structural properties on the stability of bicycles

NASA Astrophysics Data System (ADS)

Doria, Alberto; Roa Melo, Sergio Daniel

2018-06-01

In recent years the Whipple Carvallo Bicycle Model has been extended to analyse high speed stability of bicycles. Various researchers have developed models taking into account the effects of front frame compliance and tyre properties, nonetheless, a systematic analysis has not been yet carried out. This paper aims at analysing parametrically the influence of front frame compliance and tyre properties on the open loop stability of bicycles. Some indexes based on the eigenvalues of the dynamic system are defined to evaluate quantitatively bicycle stability. The parametric analysis is carried out with a factorial design approach to determine the most influential parameters. A commuting and a racing bicycle are considered and numerical results show different effects of the various parameters on each bicycle. In the commuting bicycle, the tyre properties have greater influence than front frame compliance, and the weave mode has the main effect on stability. Conversely, in the racing bicycle, the front frame compliance parameters have greater influence than tyre properties, and the wobble mode has the main effect on stability.

Vorticity and turbulence observations during a wildland fire on sloped terrain

NASA Astrophysics Data System (ADS)

Contezac, J.; Clements, C. B.; Hall, D.; Seto, D.; Davis, B.

2013-12-01

Fire-atmosphere interactions represent an atmospheric boundary-layer regime typically associated with complex circulations that interact with the fire front. In mountainous terrain, these interactions are compounded by terrain-driven circulations that often lead to extreme fire behavior. To better understand the role of complex terrain on fire behavior, a set of field experiments was conducted in June 2012 in the Coast Range of central California. The experiments were conducted on steep valley sidewalls to allow fires to spread upslope. Instrumentation used to measure fire-atmosphere interactions included three micrometeorological towers arranged along the slope and equipped with sonic anemometers, heat flux radiometers, and fine-wire thermocouples. In addition, a scanning Doppler lidar was used to measured winds within and above the valley, and airborne video imagery was collected to monitor fire behavior characteristics. The experimental site was located on the leeside of a ridge where terrain-induced flow and opposing mesoscale winds aloft interacted to create a zone of high wind shear. During the burn, the interaction between the fire and atmosphere caused the generation of several fire whirls that develop as a result of several environmental conditions including shear-generated vorticity and fire front geometry. Airborne video imagery indicated that upon ignition, the plume tilted in the opposite direction from the fire movement suggesting that higher horizontal momentum from aloft was brought to the surface, resulting in much slower fire spread rates due to opposing winds. However, after the fire front had passed the lowest tower located at the base of the slope, a shift in wind speed and direction caused a fire whirl to develop near an L-shaped kink in the fire front. Preliminary results indicate that at this time, winds at the bottom of the slope began to rotate with horizontal vorticity values of -0.2 s^-1. Increased heat flux values at this time indicated that winds were continuing to transport heat towards the slope. As the winds shifted with the fire whirl, heat flux values returned to ambient indicating the passage of the fire plume. A 0.15 hPa decrease in pressure was also observed at the first tower during this period. Further analyses to be presented include vorticity estimates from the Doppler lidar and turbulence kinetic energy measurements from the in situ towers.

Subducted seamounts and recent earthquakes beneath the central Cascadia forearc

USGS Publications Warehouse

Tréhu, Anne M.; Blakely, Richard J.; Williams, Mark C.

2012-01-01

Bathymetry and magnetic anomalies indicate that a seamount on the Juan de Fuca plate has been subducted beneath the central Cascadia accretionary complex and is now located ∼45 km landward of the deformation front. Passage of this seamount through the accretionary complex has resulted in a pattern of uplift followed by subsidence that has had a profound influence on slope morphology, gas hydrate stability, and sedimentation. Based on potential-field data and a new three-dimensional seismic velocity model, we infer that this is the most recent of several seamounts subducted over the past several million years beneath this segment of Cascadia. More deeply subducted seamounts may be responsible for recent earthquake activity on the plate boundary in this region and for along-strike variations in the thickness of the subduction channel, which may affect coupling across the plate boundary.

The Stability Analysis Method of the Cohesive Granular Slope on the Basis of Graph Theory

PubMed Central

Guan, Yanpeng; Liu, Xiaoli; Wang, Enzhi; Wang, Sijing

2017-01-01

This paper attempted to provide a method to calculate progressive failure of the cohesive-frictional granular geomaterial and the spatial distribution of the stability of the cohesive granular slope. The methodology can be divided into two parts: the characterization method of macro-contact and the analysis of the slope stability. Based on the graph theory, the vertexes, the edges and the edge sequences are abstracted out to characterize the voids, the particle contact and the macro-contact, respectively, bridging the gap between the mesoscopic and macro scales of granular materials. This paper adopts this characterization method to extract a graph from a granular slope and characterize the macro sliding surface, then the weighted graph is analyzed to calculate the slope safety factor. Each edge has three weights representing the sliding moment, the anti-sliding moment and the braking index of contact-bond, respectively, E1E2E3E1E2E3. The safety factor of the slope is calculated by presupposing a certain number of sliding routes and reducing Weight E3 repeatedly and counting the mesoscopic failure of the edge. It is a kind of slope analysis method from mesoscopic perspective so it can present more detail of the mesoscopic property of the granular slope. In the respect of macro scale, the spatial distribution of the stability of the granular slope is in agreement with the theoretical solution. PMID:28772596

End user evaluation of a Kneeling Wheelchair with "on the fly" adjustable seating functions.

PubMed

Mattie, Johanne; Wong, Angie; Leland, Danny; Borisoff, Jaimie

2018-04-18

A "kneeling" ultralight wheelchair prototype has been developed that allows users to adjust seat position "on the fly" for different activities throughout the day. The wheelchair includes independent adjustment functions for rear seat height, front seat height ("kneeling") and backrest angle.  Aim: This work aimed to gather feedback about the wheelchair's functionality and performance through end user evaluation trials.  Methods: Eight manual wheelchair users evaluated the prototype Kneeling Wheelchair for a range of activities. User perspectives on parameters such as usability, comfort, stability and effectiveness were obtained through both open-ended and Likert-scale rating questions.  Results: Results indicate several potential benefits of the adjustment functions of the Kneeling Wheelchair. Rear seat height adjustment may facilitate a number of activities of daily living, as well as provide benefits for comfort and social interactions. Back rest adjustment may increase comfort and stability on slopes. Front seat height adjustment may be beneficial for transfers and conducting sustained low-to-the-ground activities. While benefits of this adjustment function were described by many participants, some struggled with usability of the kneeling mechanism and rated this function less favourably than the other two.  Conclusion: The findings of this study will inform future iterations of the Kneeling Wheelchair design and may spur future developments in wheeled mobility. In the long-term, it is anticipated that novel wheelchair solutions, such as the one described in this paper, may support improved health, quality of life and community participation for people with mobility impairments. Implications for rehabilitation Wheelchairs that allow users to easily adjust seat and backrest position "on the fly" to better suit different tasks throughout the day may provide benefits such as facilitating activities of daily living. A front seat height adjustment feature on a new wheelchair prototype may be beneficial for transfers and conducting sustained low-to-the ground activities. End user evaluations can provide valuable insight to direct future design modifications and innovation.

Physically-based slope stability modelling and parameter sensitivity: a case study in the Quitite and Papagaio catchments, Rio de Janeiro, Brazil

NASA Astrophysics Data System (ADS)

de Lima Neves Seefelder, Carolina; Mergili, Martin

2016-04-01

We use the software tools r.slope.stability and TRIGRS to produce factor of safety and slope failure susceptibility maps for the Quitite and Papagaio catchments, Rio de Janeiro, Brazil. The key objective of the work consists in exploring the sensitivity of the geotechnical (r.slope.stability) and geohydraulic (TRIGRS) parameterization on the model outcomes in order to define suitable parameterization strategies for future slope stability modelling. The two landslide-prone catchments Quitite and Papagaio together cover an area of 4.4 km², extending between 12 and 995 m a.s.l. The study area is dominated by granitic bedrock and soil depths of 1-3 m. Ranges of geotechnical and geohydraulic parameters are derived from literature values. A landslide inventory related to a rainfall event in 1996 (250 mm in 48 hours) is used for model evaluation. We attempt to identify those combinations of effective cohesion and effective internal friction angle yielding the best correspondence with the observed landslide release areas in terms of the area under the ROC Curve (AUCROC), and in terms of the fraction of the area affected by the release of landslides. Thereby we test multiple parameter combinations within defined ranges to derive the slope failure susceptibility (fraction of tested parameter combinations yielding a factor of safety smaller than 1). We use the tool r.slope.stability (comparing the infinite slope stability model and an ellipsoid-based sliding surface model) to test and to optimize the geotechnical parameters, and TRIGRS (a coupled hydraulic-infinite slope stability model) to explore the sensitivity of the model results to the geohydraulic parameters. The model performance in terms of AUCROC is insensitive to the variation of the geotechnical parameterization within much of the tested ranges. Assuming fully saturated soils, r.slope.stability produces rather conservative predictions, whereby the results yielded with the sliding surface model are more conservative than those yielded with the infinite slope stability model. The sensitivity of AUCROC to variations in the geohydraulic parameters remains small as long as the calculated degree of saturation of the soils is sufficient to result in the prediction of a significant amount of landslide release pixels. Due to the poor sensitivity of AUCROC to variations of the geotechnical and geohydraulic parameters it is hard to optimize the parameters by means of statistics. Instead, the results produced with many different combinations of parameters correspond reasonably well with the distribution of the observed landslide release areas, even though they vary considerably in terms of their conservativeness. Considering the uncertainty inherent in all geotechnical and geohydraulic data, and the impossibility to capture the spatial distribution of the parameters by means of laboratory tests in sufficient detail, we conclude that landslide susceptibility maps yielded by catchment-scale physically-based models should not be interpreted in absolute terms. Building on the assumption that our findings are generally valid, we suggest that efforts to develop better strategies for dealing with the uncertainties in the spatial variation of the key parameters should be given priority in future slope stability modelling efforts.

Formation of a katabatic induced cold front at the east Andean slopes

NASA Astrophysics Data System (ADS)

Trachte, K.; Nauss, T.,; Rollenbeck, R.; Bendix, J.

2009-04-01

Within the DFG research unit 816, climate dynamics in a tropical mountain rain forest in the national reserve of the Reserva Biósfera de San Francisco in South Ecuador are investigated. Precipitation measurements in the mountain environment of the Estación Científica de San Francisco (ECSF) with a vertical rain radar profiler have been made over the last seven years. They reveal unexpected constant early morning rainfall events. On the basis of cloud top temperatures from corresponding GOES satellite imageries, a Mesoscale Convective System could be derived. Its formation region is located south-east of the ECSF in the Peruvian Amazon basin. The generation of the MCS is assumed to results from an interaction of both local and mesoscale conditions. Nocturnal drainage air from the Andean slopes and valleys confluences in the Amazon basin due to the concave lined terrain. This cold air converges with the warm-moist air of the Amazon inducing a local cold front. This process yields to deep convection resulting in a MCS. With the numerical model ARPS the hypothesized formation of a cloud cluster due to a katabatic induced cold front is shown in an ideal case study. Therefor an ideal terrain model representing the features of the Andes in the target area has been used. The simplification of the oprography concerns a concave lined slope and a valley draining into the basin. It describes the confluence of the cold drainage air due to the shape of the terrain. Inside the basin the generation of a local cold front is shown, which triggers the formation of a cloud cluster.

Rock slope stability analysis along the North Carolina section of the Blue Ridge Parkway: Using a geographic information system (GIS) to integrate site data and digital geologic maps

USGS Publications Warehouse

Latham, R.S.; Wooten, R.M.; Cattanach, B.L.; Merschat, C.E.; Bozdog, G.N.

2009-01-01

In 2008, the North Carolina Geological Survey (NCGS) completed a five-year geologic and geohazards inventory of the 406-km long North Carolina segment of the Blue Ridge Parkway (BRP). The ArcGIS??? format deliverables for rock slopes include a slope movement and slope movement deposit database and maps and site-specific rock slope stability assessments at 158 locations. Database entries for known and potential rock slope failures include: location data, failure modes and dimensions, activity dates and levels, structural and lithologic data, the occurrence of sulfide minerals and acid-producing potential test results. Rock slope stability assessments include photographs of the rock cuts and show locations and orientations of rock data, seepage zones, and kinematic stability analyses. Assigned preliminary geologic hazard ratings of low, moderate and high indicate the generalized relative probability of rock fall and/or rock slide activity at a given location. Statistics compiled based on the database indicate some general patterns within the data. This information provides the National Park Service with tools that can aid in emergency preparedness, and in budgeting mitigation, maintenance and repair measures. Copyright 2009 ARMA, American Rock Mechanics Association.

Hydrological effect of vegetation against rainfall-induced landslides

NASA Astrophysics Data System (ADS)

Gonzalez-Ollauri, Alejandro; Mickovski, Slobodan B.

2017-06-01

The hydrological effect of vegetation on rainfall-induced landslides has rarely been quantified and its integration into slope stability analysis methods remains a challenge. Our goal was to establish a reproducible, novel framework to evaluate the hydrological effect of vegetation on shallow landslides. This was achieved by accomplishing three objectives: (i) quantification in situ of the hydrological mechanisms by which woody vegetation (i.e. Salix sp.) might impact slope stability under wetting and drying conditions; (ii) to propose a new approach to predict plant-derived matric suctions under drying conditions; and (iii) to evaluate the suitability of the unified effective stress principle and framework (UES) to quantify the hydrological effect of vegetation against landslides. The results revealed that plant water uptake was the main hydrological mechanism contributing to slope stability, as the vegetated slope was, on average, 12.84% drier and had matric suctions three times higher than the fallow slope. The plant-related mechanisms under wetting conditions had a minimal effect on slope stability. The plant aerial parts intercepted up to 26.73% of the rainfall and concentrated a further 10.78% of it around the stem. Our approach successfully predicted the plant-derived matric suctions and UES proved to be adequate for evaluating the hydrological effect of vegetation on landslides. Although the UES framework presented here sets the basis for effectively evaluating the hydrological effect of vegetation on slope stability, it requires knowledge of the specific hydro-mechanical properties of plant-soil composites and this in itself needs further investigation.

Investigating the performance of LiDAR-derived biomass information in hydromechanic slope stability modelling

NASA Astrophysics Data System (ADS)

Schmaltz, Elmar; Steger, Stefan; Bogaard, Thom; Van Beek, Rens; Glade, Thomas

2017-04-01

Hydromechanic slope stability models are often used to assess the landslide susceptibility of hillslopes. Some of these models are able to account for vegetation related effects when assessing slope stability. However, spatial information of required vegetation parameters (especially of woodland) that are defined by land cover type, tree species and stand density are mostly underrepresented compared to hydropedological and geomechanical parameters. The aim of this study is to assess how LiDAR-derived biomass information can help to distinguish distinct tree stand-immanent properties (e.g. stand density and diversity) and further improve the performance of hydromechanic slope stability models. We used spatial vegetation data produced from sophisticated algorithms that are able to separate single trees within a stand based on LiDAR point clouds and thus allow an extraordinary detailed determination of the aboveground biomass. Further, this information is used to estimate the species- and stand-related distribution of the subsurface biomass using an innovative approach to approximate root system architecture and development. The hydrological tree-soil interactions and their impact on the geotechnical stability of the soil mantle are then reproduced in the dynamic and spatially distributed slope stability model STARWARS/PROBSTAB. This study highlights first advances in the approximation of biomechanical reinforcement potential of tree root systems in tree stands. Based on our findings, we address the advantages and limitations of highly detailed biomass information in hydromechanic modelling and physically based slope failure prediction.

Slope stability of bioreactor landfills during leachate injection: effects of heterogeneous and anisotropic municipal solid waste conditions.

PubMed

Giri, Rajiv K; Reddy, Krishna R

2014-03-01

In bioreactor landfills, leachate recirculation can significantly affect the stability of landfill slope due to generation and distribution of excessive pore fluid pressures near side slope. The current design and operation of leachate recirculation systems do not consider the effects of heterogeneous and anisotropic nature of municipal solid waste (MSW) and the increased pore gas pressures in landfilled waste caused due to leachate recirculation on the physical stability of landfill slope. In this study, a numerical two-phase flow model (landfill leachate and gas as immiscible phases) was used to investigate the effects of heterogeneous and anisotropic nature of MSW on moisture distribution and pore-water and capillary pressures and their resulting impacts on the stability of a simplified bioreactor landfill during leachate recirculation using horizontal trench system. The unsaturated hydraulic properties of MSW were considered based on the van Genuchten model. The strength reduction technique was used for slope stability analyses as it takes into account of the transient and spatially varying pore-water and gas pressures. It was concluded that heterogeneous and anisotropic MSW with varied unit weight and saturated hydraulic conductivity significantly influenced the moisture distribution and generation and distribution of pore fluid pressures in landfill and considerably reduced the stability of bioreactor landfill slope. It is recommended that heterogeneous and anisotropic MSW must be considered as it provides a more reliable approach for the design and leachate operations in bioreactor landfills.

Texas lignite mining: Groundwater and slope stability control in the nineties and beyond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lawrence J.

As lignite mining in Texas approaches and exceeds depths of 200 feet below ground level, rising costs demand that innovative mining approaches be used in order to maintain the economic viability of lignite mining. Groundwater and slope stability problems multiply at these depths, resulting in increasing focus on how to control these costs. Dewatering costs are consistently rising for the lignite industry, as deeper mining encounters more and larger saturated sand bodies. These sands require dewatering in order to improve slope stability. Planning and analysis become more important as the number of wells grows beyond what can be managed withmore » a simple {open_quotes}cookie-cutter{close_quotes} approach. Slope stability plays an increasing role in mining concerns as deeper lignite is recovered. Slope stability causes several problems, including loss of lignite, increased rehandle, and hazards to personnel and equipment. Traditional lignite mine planning involved a fairly {open_quotes}generic{close_quotes} pit design with one design highwall angle, one design spoil angle, and little geotechnical evaluation of the deposit. This {open_quotes}one mine-one design{close_quotes} approach, while cost-effective in the past, is now being replaced by a more critical analysis of the design requirements of each area. Geotechnical evaluation plays an increasing role in the planning and operational aspects of lignite mining. Laboratory core sample test results can be used for slope stability modeling, in order to obtain more accurate design and operational information.« less

75 FR 7945 - Airworthiness Directives; Augustair, Inc. Models 2150, 2150A, and 2180 Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-23

... inspect the vertical stabilizer front spar for cracks and loose fasteners, repair any cracks and loose fasteners found, and reinforce the vertical stabilizer spar regardless if cracks are found. This AD results from six reports of airplanes with a cracked vertical stabilizer front spar. We are issuing this AD to...

Flow patterns and bathymetric signatures on the delta front of a prograding river delta

NASA Astrophysics Data System (ADS)

Shaw, J.; Mohrig, D. C.; Wagner, R. W.

2016-02-01

The transition of water between laterally confined channels and the unchannelized delta front controls the growth pattern of river deltas, but is difficult to measure on field-scale deltas. We quantify flow patterns, bathymetry and bathymetric evolution for the subaqueous delta front on the Wax Lake Delta (WLD), a rapidly prograding delta in coastal Louisiana. The flow direction field, mapped using streaklines composed of biogenic slicks on the water surface, shows that a significant portion of flow ( 59%) departs subaqueous channels laterally over the subaqueous margins of the channel seaward of the shoreline. Synoptic datasets of bathymetry and flow direction allow spatial changes in flow velocity to be quantified. Most lateral flow divergence and deceleration occurs within 3-8 channel widths outboard of subaqueous channel margins, rather than downstream of channel tips. In interdistributary bays, deposit elevation decreases with a basinward slope of 2.4 x 10-4 with distance from a channel margin along any flow path. Flow patterns and this slope produce constructional features called interdistributary troughs - topographic lows in the center of interdistributary bays. These data show that flow patterns and bathymetry on the delta front are coupled both at the transition from channelized to unchannelized flow and in the depositional regions outside the distributary network.

Reliability-Based Stability Analysis of Rock Slopes Using Numerical Analysis and Response Surface Method

NASA Astrophysics Data System (ADS)

Dadashzadeh, N.; Duzgun, H. S. B.; Yesiloglu-Gultekin, N.

2017-08-01

While advanced numerical techniques in slope stability analysis are successfully used in deterministic studies, they have so far found limited use in probabilistic analyses due to their high computation cost. The first-order reliability method (FORM) is one of the most efficient probabilistic techniques to perform probabilistic stability analysis by considering the associated uncertainties in the analysis parameters. However, it is not possible to directly use FORM in numerical slope stability evaluations as it requires definition of a limit state performance function. In this study, an integrated methodology for probabilistic numerical modeling of rock slope stability is proposed. The methodology is based on response surface method, where FORM is used to develop an explicit performance function from the results of numerical simulations. The implementation of the proposed methodology is performed by considering a large potential rock wedge in Sumela Monastery, Turkey. The accuracy of the developed performance function to truly represent the limit state surface is evaluated by monitoring the slope behavior. The calculated probability of failure is compared with Monte Carlo simulation (MCS) method. The proposed methodology is found to be 72% more efficient than MCS, while the accuracy is decreased with an error of 24%.

Locating Critical Circular and Unconstrained Failure Surface in Slope Stability Analysis with Tailored Genetic Algorithm

NASA Astrophysics Data System (ADS)

Pasik, Tomasz; van der Meij, Raymond

2017-12-01

This article presents an efficient search method for representative circular and unconstrained slip surfaces with the use of the tailored genetic algorithm. Searches for unconstrained slip planes with rigid equilibrium methods are yet uncommon in engineering practice, and little publications regarding truly free slip planes exist. The proposed method presents an effective procedure being the result of the right combination of initial population type, selection, crossover and mutation method. The procedure needs little computational effort to find the optimum, unconstrained slip plane. The methodology described in this paper is implemented using Mathematica. The implementation, along with further explanations, is fully presented so the results can be reproduced. Sample slope stability calculations are performed for four cases, along with a detailed result interpretation. Two cases are compared with analyses described in earlier publications. The remaining two are practical cases of slope stability analyses of dikes in Netherlands. These four cases show the benefits of analyzing slope stability with a rigid equilibrium method combined with a genetic algorithm. The paper concludes by describing possibilities and limitations of using the genetic algorithm in the context of the slope stability problem.

The horizontal transport of pollutants from a slope wind layer into the valley core as a function of atmospheric stability

NASA Astrophysics Data System (ADS)

Leukauf, Daniel; Gohm, Alexander; Rotach, Mathias W.; Posch, Christian

2016-04-01

Slope winds provide a mechanism for the vertical exchange of air between the valley and the free atmosphere aloft. By this means, heat, moisture and pollutants are exported or imported. However, it the static stability of the valley atmosphere is strong, one part of the up-slope flow is redirected towards the valley center and pollutants are recirculated within the valley. This may limit the venting potential of slope winds severely. The main objective of this study is to quantify the horizontal transport of pollutants from the slope wind layer into the stable valley core and to determine the dependency of this flux as a function of the initial stability of the atmosphere. For this purpose, we conducted large eddy simulations with the Weather Research and Forecasting (WRF) model for a quasi-two-dimensional valley. The valley geometry consists of two slopes with constant slope angle rising to a crest height of 1500 m and a 4 km wide flat valley floor in between. The valley is 20 km long and homogeneous in along-valley direction. Hence, only slope winds but no valley winds can evolve. The surface sensible heat flux is prescribed by a sine function with an amplitude of 125 W m-2. The initial sounding characterized by an atmosphere at rest and by a constant Brunt-Väisälä frequency which is varied between 0.006 s-1 and 0.02 s-1. A passive tracer is released with an arbitrary but constant rate at the valley floor. As expected, the atmospheric stability has a strong impact on the vertical and horizontal transport of tracer mass. A horizontal intrusion forms at the top of the mixed layer due to outflow from the slope wind layer. Tracer mass is transported from the slope towards the center of the valley. The efficiency of this mechanism increases with increasing stability N. For the lowest value of N, about 70% of the tracer mass released at the valley bottom is exported out of the valley. This value drops to about 12% in the case of the strongest stability. Hence, most of the tracer mass, which enters the slope wind layer at the valley bottom, is leaving it again through horizontal fluxes at the height of the intrusion and therefore remains inside the valley.

Front fingering and complex dynamics driven by the interaction of buoyancy and diffusive instabilities.

PubMed

D'Hernoncourt, J; Merkin, J H; De Wit, A

2007-09-01

Traveling fronts can become transversally unstable either because of a diffusive instability arising when the key variables diffuse at sufficiently different rates or because of a buoyancy-driven Rayleigh-Taylor mechanism when the density jump across the front is statically unfavorable. The interaction between such diffusive and buoyancy instabilities of fronts is analyzed theoretically for a simple model system. Linear stability analysis and nonlinear simulations show that their interplay changes considerably the stability properties with regard to the pure Rayleigh-Taylor or diffusive instabilities of fronts. In particular, an instability scenario can arise which triggers convection around statically stable fronts as a result of differential diffusion. Moreover, spatiotemporal chaos can be observed when both buoyancy and diffusive effects cooperate to destabilize the front. Experimental conditions to test our predictions are suggested.

Quantification of Urban Environment's Role in Slope Stability for Landslide Events.

NASA Astrophysics Data System (ADS)

Bozzolan, E.; Holcombe, E.; Wagener, T.; Pianosi, F.

2017-12-01

The combination of a rapid and unplanned urban development with a likely future climate change could significantly affect landslide occurrences in the humid tropics, where rainfall events of high intensity and duration are the dominant trigger for landslide risk. The attention of current landslide hazard studies is largely focussed on natural slope processes based on combinations of environmental factors, excluding the role of urbanisation on slope stability. This project aims to understand the relative influence of urbanisation features on local slope stability and to translate the findings to a wider region. Individual slopes are firstly analysed with the software CHASM, a physically based model which combines soil hydrology and slope stability assessment. Instead of relying on existing records, generally lacking for landslides, ranges of plausible preparatory (such as slope, cohesion, friction angles), triggering (rainfall) and aggravating factors (deforestation, house density and water network) are defined and possible combinations of these factors are created by sampling from those ranges. The influence of urban features on site hydrology and stability mechanisms are evaluated and then implemented in denser urban contexts, characteristic of unplanned settlements. The results of CHASMS can be transferred to regional maps in order to identify the areas belonging to the triggering combinations of factors previously found. In this way, areas susceptible to landslides can be detected not only in terms of natural factors but also in relation to the degree of urbanisation. Realistic scenarios can be extrapolated from the areas considered and then analysed again with CHASM. This permits to adapt (and improve) the initial variability ranges of the factors, creating a general-specific cycle able to identify the landslide susceptibility regions and outline a hazard map. Once the triggers are understood, possible consequences can be assessed and mitigation strategies can be evaluated. The ability to define local urban rainfall threshold for landslide slope stability helps the decision-making process to prioritize the areas of interest and locally define the main causes of instability.

Delay-slope-dependent stability results of recurrent neural networks.

PubMed

Li, Tao; Zheng, Wei Xing; Lin, Chong

2011-12-01

By using the fact that the neuron activation functions are sector bounded and nondecreasing, this brief presents a new method, named the delay-slope-dependent method, for stability analysis of a class of recurrent neural networks with time-varying delays. This method includes more information on the slope of neuron activation functions and fewer matrix variables in the constructed Lyapunov-Krasovskii functional. Then some improved delay-dependent stability criteria with less computational burden and conservatism are obtained. Numerical examples are given to illustrate the effectiveness and the benefits of the proposed method.

Multigrid preconditioned conjugate-gradient method for large-scale wave-front reconstruction.

PubMed

Gilles, Luc; Vogel, Curtis R; Ellerbroek, Brent L

2002-09-01

We introduce a multigrid preconditioned conjugate-gradient (MGCG) iterative scheme for computing open-loop wave-front reconstructors for extreme adaptive optics systems. We present numerical simulations for a 17-m class telescope with n = 48756 sensor measurement grid points within the aperture, which indicate that our MGCG method has a rapid convergence rate for a wide range of subaperture average slope measurement signal-to-noise ratios. The total computational cost is of order n log n. Hence our scheme provides for fast wave-front simulation and control in large-scale adaptive optics systems.

Laboratory and 3-D distinct element analysis of the failure mechanism of a slope under external surcharge

NASA Astrophysics Data System (ADS)

Li, N.; Cheng, Y. M.

2015-01-01

Landslide is a major disaster resulting in considerable loss of human lives and property damages in hilly terrain in Hong Kong, China and many other countries. The factor of safety and the critical slip surface for slope stabilization are the main considerations for slope stability analysis in the past, while the detailed post-failure conditions of the slopes have not been considered in sufficient detail. There is however increasing interest in the consequences after the initiation of failure that includes the development and propagation of the failure surfaces, the amount of failed mass and runoff and the affected region. To assess the development of slope failure in more detail and to consider the potential danger of slopes after failure has initiated, the slope stability problem under external surcharge is analyzed by the distinct element method (DEM) and a laboratory model test in the present research. A more refined study about the development of failure, microcosmic failure mechanisms and the post-failure mechanisms of slopes will be carried out. The numerical modeling method and the various findings from the present work can provide an alternate method of analysis of slope failure, which can give additional information not available from the classical methods of analysis.

Laboratory and 3-D-distinct element analysis of failure mechanism of slope under external surcharge

NASA Astrophysics Data System (ADS)

Li, N.; Cheng, Y. M.

2014-09-01

Landslide is a major disaster resulting in considerable loss of human lives and property damages in hilly terrain in Hong Kong, China and many other countries. The factor of safety and the critical slip surface for slope stabilization are the main considerations for slope stability analysis in the past, while the detailed post-failure conditions of the slopes have not been considered in sufficient details. There are however increasing interest on the consequences after the initiation of failure which includes the development and propagation of the failure surfaces, the amount of failed mass and runoff and the affected region. To assess the development of slope failure in more details and to consider the potential danger of slopes after failure has initiated, the slope stability problem under external surcharge is analyzed by the distinct element method (DEM) and laboratory model test in the present research. A more refined study about the development of failure, microcosmic failure mechanism and the post-failure mechanism of slope will be carried out. The numerical modeling method and the various findings from the present work can provide an alternate method of analysis of slope failure which can give additional information not available from the classical methods of analysis.

Dip-slope and Dip-slope Failures in Taiwan - a Review

NASA Astrophysics Data System (ADS)

Lee, C.

2011-12-01

Taiwan is famous for dip-slope and dip-slope slides. Dip-slopes exist at many places in the fold-and-thrust belt of Taiwan. Under active cutting of stream channels and man-made excavations, a dip-slope may become unstable and susceptible for mass sliding. Daylight of a bedding parallel clay seam is the most dangerous type for dip-slope sliding. Buckling or shear-off features may also happen at toe of a long dip-slope. Besides, a dip-slope is also dangerous for shallow debris slides, if the slope angle is between 25 to 45 degrees and the debris (colluvium or slope wash) is thick (>1m). These unstable slopes may slide during a triggering event, earthquake or typhoon storm; or even slide without a triggering event, like the 2010 Tapu case. Initial buckling feature had been found in the dip-slope of the Feitsui arch dam abutment after detailed explorations. Shear-off feature have also been found in dip-slope located in right bank of the Nahua reservoir after field investigation and drilling. The Chiufengerhshan slide may also be shear-off type. On the other hand, the Tapu, the Tsaoling slides and others are of direct slide type. The Neihoo Bishan slide is a shallow debris slide on dip-slope. All these cases demonstrate the four different types of dip-slope slide. The hazard of a dip-slope should be investigated to cover these possible types of failure. The existence of bedding parallel clay seams is critical for the stability of a dip-slope, either for direct slide or buckling or shear-off type of failure, and is a hot point during investigation. Because, the stability of a dip-slope is changing with time, therefore, detailed explorations to including weathering and erosion rates are also very necessary to ensure the long-term stability of a dip-slope.

Integrating the effects of forest cover on slope stability in a deterministic landslide susceptibility model (TRIGRS 2.0)

NASA Astrophysics Data System (ADS)

Zieher, T.; Rutzinger, M.; Bremer, M.; Meissl, G.; Geitner, C.

2014-12-01

The potentially stabilizing effects of forest cover in respect of slope stability have been the subject of many studies in the recent past. Hence, the effects of trees are also considered in many deterministic landslide susceptibility models. TRIGRS 2.0 (Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability; USGS) is a dynamic, physically-based model designed to estimate shallow landslide susceptibility in space and time. In the original version the effects of forest cover are not considered. As for further studies in Vorarlberg (Austria) TRIGRS 2.0 is intended to be applied in selected catchments that are densely forested, the effects of trees on slope stability were implemented in the model. Besides hydrological impacts such as interception or transpiration by tree canopies and stems, root cohesion directly influences the stability of slopes especially in case of shallow landslides while the additional weight superimposed by trees is of minor relevance. Detailed data on tree positions and further attributes such as tree height and diameter at breast height were derived throughout the study area (52 km²) from high-resolution airborne laser scanning data. Different scenarios were computed for spruce (Picea abies) in the study area. Root cohesion was estimated area-wide based on published correlations between root reinforcement and distance to tree stems depending on the stem diameter at breast height. In order to account for decreasing root cohesion with depth an exponential distribution was assumed and implemented in the model. Preliminary modelling results show that forest cover can have positive effects on slope stability yet strongly depending on tree age and stand structure. This work has been conducted within C3S-ISLS, which is funded by the Austrian Climate and Energy Fund, 5th ACRP Program.

The effect of proximal tibial slope on dynamic stability testing of the posterior cruciate ligament- and posterolateral corner-deficient knee.

PubMed

Petrigliano, Frank A; Suero, Eduardo M; Voos, James E; Pearle, Andrew D; Allen, Answorth A

2012-06-01

Proximal tibial slope has been shown to influence anteroposterior translation and tibial resting point in the posterior cruciate ligament (PCL)-deficient knee. The effect of proximal tibial slope on rotational stability of the knee is unknown. Change in proximal tibial slope produced via osteotomy can influence both static translation and dynamic rotational kinematics in the PCL/posterolateral corner (PLC)-deficient knee. Controlled laboratory study. Posterior drawer, dial, and mechanized reverse pivot-shift (RPS) tests were performed on hip-to-toe specimens and translation of the lateral and medial compartments measured utilizing navigation (n = 10). The PCL and structures of the PLC were then sectioned. Stability testing was repeated, and compartmental translation was recorded. A proximal tibial osteotomy in the sagittal plane was then performed achieving either +5° or -5° of tibial slope variation, after which stability testing was repeated (n = 10). Analysis was performed using 1-way analysis of variance (ANOVA; α = .05). Combined sectioning of the PCL and PLC structures resulted in a 10.5-mm increase in the posterior drawer, 15.5-mm increase in the dial test at 30°, 14.5-mm increase in the dial test at 90°, and 17.9-mm increase in the RPS (vs intact; P < .05). Increasing the posterior slope (high tibial osteotomy [HTO] +5°) in the PCL/PLC-deficient knee reduced medial compartment translation by 3.3 mm during posterior drawer (vs deficient; P < .05) but had no significant effect on the dial test at 30°, dial test at 90°, or RPS. Conversely, reversing the slope (HTO -5°) caused a 4.8-mm increase in medial compartment translation (vs deficient state; P < .05) during posterior drawer and an 8.6-mm increase in lateral compartment translation and 9.0-mm increase in medial compartment translation during RPS (vs deficient state; P < .05). Increasing posterior tibial slope diminished static posterior instability of the PCL/PLC-deficient knee as measured by the posterior drawer test but had little effect on rotational or dynamic multiplanar stability as assessed by the dial and RPS tests, respectively. Conversely, decreasing posterior slope resulted in increased posterior instability and a significant increase in the magnitude of the RPS. These results suggest that increasing posterior tibial slope may improve sagittal stability in the PCL/PLC-deficient knee. Moreover, a knee with diminished posterior tibial slope may demonstrate greater multiplanar instability in this setting. Consequently, proximal tibial slope should be considered when treating combined PCL/PLC injuries of the knee.

Submarine slope failures due to pipe structure formation.

PubMed

Elger, Judith; Berndt, Christian; Rüpke, Lars; Krastel, Sebastian; Gross, Felix; Geissler, Wolfram H

2018-02-19

There is a strong spatial correlation between submarine slope failures and the occurrence of gas hydrates. This has been attributed to the dynamic nature of gas hydrate systems and the potential reduction of slope stability due to bottom water warming or sea level drop. However, 30 years of research into this process found no solid supporting evidence. Here we present new reflection seismic data from the Arctic Ocean and numerical modelling results supporting a different link between hydrates and slope stability. Hydrates reduce sediment permeability and cause build-up of overpressure at the base of the gas hydrate stability zone. Resulting hydro-fracturing forms pipe structures as pathways for overpressured fluids to migrate upward. Where these pipe structures reach shallow permeable beds, this overpressure transfers laterally and destabilises the slope. This process reconciles the spatial correlation of submarine landslides and gas hydrate, and it is independent of environmental change and water depth.

Postural Stability Margins as a Function of Support Surface Slopes.

PubMed

Dutt-Mazumder, Aviroop; Slobounov, Seymon M; Challis, John Henry; Newell, Karl Maxim

2016-01-01

This investigation examined the effects of slope of the surface of support (35°, 30°, 20°, 10° Facing(Toe) Down, 0° Flat and 10°, 20°, 25° Facing (Toe) Up) and postural orientation on the margins of postural stability in quiet standing of young adults. The findings showed that the center of pressure-CoP (displacement, area and length) had least motion at the baseline (0° Flat) platform condition that progressively increased as a function of platform angle in both facing up and down directions. The virtual time to collision (VTC) dynamics revealed that the spatio-temporal margins to the functional stability boundary were progressively smaller and the VTC time series also more regular (SampEn-Sample Entropy) as slope angle increased. Surface slope induces a restricted stability region with lower dimension VTC dynamics that is more constrained when postural orientation is facing down the slope. These findings provide further evidence that VTC acts as a control variable in standing posture that is influenced by the emergent dynamics of the individual-environment-task interaction.

Proportioning the airplane for lateral stability

NASA Technical Reports Server (NTRS)

Donlan, C. J.

1976-01-01

Proportioning for lateral aircraft control included: (1) directional stability (slope of curve of yawing moment coefficient against sideslip), and (2) effective dihedral factor (slope of curve of rolling moment coefficient against sideslip). Basic forces influencing the directional stability of aircraft are indicated. Propeller side force, basic fuselage yaw, and vertical tail side force contributed to yaw moment about center of gravity.

Can we use ice calving on glacier fronts as a proxy for rock slope failures?

NASA Astrophysics Data System (ADS)

Abellan, Antonio; Penna, Ivanna; Daicz, Sergio; Carrea, Dario; Derron, Marc-Henri; Jaboyedoff, Michel; Riquelme, Adrian; Tomas, Roberto

2015-04-01

Ice failures on glacier terminus show very similar fingerprints to rock-slope failure (RSF) processes, nevertheless, the investigation of gravity-driven instabilities that shape rock cliffs and glacier's fronts are currently dissociated research topics. Since both materials (ice and rocks) have very different rheological properties, the development of a progressive failure on mountain cliffs occurs at a much slower rate than that observed on glacier fronts, which leads the latter a good proxy for investigating RSF. We utilized a terrestrial Laser Scanner (Ilris-LR system from Optech) for acquiring successive 3D point clouds of one of the most impressive calving glacier fronts, the Perito Moreno glacier located in the Southern Patagonian Ice Fields (Argentina). We scanned the glacier terminus during five days (from 10th to 14th of March 2014) with very high accuracy (0.7cm standard deviation of the error at 100m) and a high density of information (200 points per square meter). Each data series was acquired at a mean interval of 20 minutes. The maximum attainable range for the utilized wavelength of the Ilris-LR system (1064 nm) was around 500 meters over massive ice (showing no-significant loss of information), being this distance considerably reduced on crystalline or wet ice short after the occurrence of calving events. As for the data treatment, we have adapted our innovative algorithms originally developed for the investigation of both precursory deformation and rockfalls to study calving events. By comparing successive three-dimensional datasets, we have investigated not only the magnitude and frequency of several ice failures at the glacier's terminus (ranging from one to thousands of cubic meters), but also the characteristic geometrical features of each failure. In addition, we were able to quantify a growing strain rate on several areas of the glacier's terminus shortly after their final collapse. For instance, we investigated the spatial extent of the differential pre-failure deformation, together with its length and duration, showing very similar acceleration patterns than that observed on rock slopes at their 3rd creep stage. We then documented the differential strain rates observed at different parts of the glacier's terminus, and correlated the areas affected with a progressive acceleration on the strain rate with those that had finally calved. Finally, we also observed that, similarly as it occurs on rock slopes, the investigation of the mechanical discontinuities (crevasses) observed at the glacier controlled the different front failure mechanisms observed at the glacier front. Thanks to the so-built analogies between rock and ice gravity driven instability phenomena, this interdisciplinary research could constitute a great insight in the investigation of RSF endangering human population and infrastructures.

Traveling waves in a spring-block chain sliding down a slope

NASA Astrophysics Data System (ADS)

Morales, J. E.; James, G.; Tonnelier, A.

2017-07-01

Traveling waves are studied in a spring slider-block model. We explicitly construct front waves (kinks) for a piecewise-linear spinodal friction force. Pulse waves are obtained as the matching of two traveling fronts with identical speeds. Explicit formulas are obtained for the wavespeed and the wave form in the anticontinuum limit. The link with localized waves in a Burridge-Knopoff model of an earthquake fault is briefly discussed.

Traveling waves in a spring-block chain sliding down a slope.

PubMed

Morales, J E; James, G; Tonnelier, A

2017-07-01

Traveling waves are studied in a spring slider-block model. We explicitly construct front waves (kinks) for a piecewise-linear spinodal friction force. Pulse waves are obtained as the matching of two traveling fronts with identical speeds. Explicit formulas are obtained for the wavespeed and the wave form in the anticontinuum limit. The link with localized waves in a Burridge-Knopoff model of an earthquake fault is briefly discussed.

New insights into debris-flow hazards from an extraordinary event in the Colorado Front Range

USGS Publications Warehouse

Coe, Jeffrey A.; Kean, Jason W.; Godt, Jonathan W.; Baum, Rex L.; Jones, Eric S.; Gochis, David; Anderson, Gregory S

2016-01-01

Rainfall on 9–13 September 2013 triggered at least 1,138 debris flows in a 3430 km2 area of the Colorado Front Range. The historical record reveals that the occurrence of these flows over such a large area in the interior of North America is highly unusual. Rainfall that triggered the debris flows began after ~75 mm of antecedent rain had fallen, a relatively low amount compared to other parts of the United States. Most flows were triggered in response to two intense rainfall periods, one 12.5-hour-long period on 11–12 September, and one 8-hour-long period on 12 September. The maximum 10 min. intensities during these periods were 67 and 39 mm/hr. Ninety-five percent of flows initiated in canyons and on hogbacks at elevations lower than a widespread erosion surface of low slope and relief (25°), predominantly south- and east-facing slopes with upslope contributing areas 3300 m2. Areal concentrations of debris flows revealed that colluvial soils formed on sedimentary rocks were more susceptible to flows than soils on crystalline rocks. This event should serve as an alert to government authorities, emergency responders, and residents in the Front Range and other interior continental areas with steep slopes. Widespread debris flows in these areas occur infrequently but may pose a greater risk than in areas with shorter return periods, because the public is typically unprepared for them.

Modelling wetting and drying effects over complex topography

NASA Astrophysics Data System (ADS)

Tchamen, G. W.; Kahawita, R. A.

1998-06-01

The numerical simulation of free surface flows that alternately flood and dry out over complex topography is a formidable task. The model equation set generally used for this purpose is the two-dimensional (2D) shallow water wave model (SWWM). Simplified forms of this system such as the zero inertia model (ZIM) can accommodate specific situations like slowly evolving floods over gentle slopes. Classical numerical techniques, such as finite differences (FD) and finite elements (FE), have been used for their integration over the last 20-30 years. Most of these schemes experience some kind of instability and usually fail when some particular domain under specific flow conditions is treated. The numerical instability generally manifests itself in the form of an unphysical negative depth that subsequently causes a run-time error at the computation of the celerity and/or the friction slope. The origins of this behaviour are diverse and may be generally attributed to:1. The use of a scheme that is inappropriate for such complex flow conditions (mixed regimes).2. Improper treatment of a friction source term or a large local curvature in topography.3. Mishandling of a cell that is partially wet/dry.In this paper, a tentative attempt has been made to gain a better understanding of the genesis of the instabilities, their implications and the limits to the proposed solutions. Frequently, the enforcement of robustness is made at the expense of accuracy. The need for a positive scheme, that is, a scheme that always predicts positive depths when run within the constraints of some practical stability limits, is fundamental. It is shown here how a carefully chosen scheme (in this case, an adaptation of the solver to the SWWM) can preserve positive values of water depth under both explicit and implicit time integration, high velocities and complex topography that may include dry areas. However, the treatment of the source terms: friction, Coriolis and particularly the bathymetry, are also of prime importance and must not be overlooked. Linearization with a combination of switching between explicit-implicit integration can overcome the stiffness of the friction and Coriolis terms and provide stable numerical integration. The treatment of the bathymetry source term is much more delicate. For cells undergoing a transient wet-dry process, the imposition of zero velocity stabilizes most of the approximations. However, this artificial zero velocity condition can be the cause of considerable error, especially when fast moving fronts are involved. Besides these difficulties linked with the internal position of the front within a cell versus the limited resolution of a numerical grid, it appears that the second derivative that defines whether the bed is locally convex or concave is a key indicator for stability. A convex bottom may lead to unbounded solutions. It appears that this behaviour is not linked to the numerics (numerical scheme) but rather to the mathematical theory of the SWWM. These concerns about stability have taken precedence, until now, over the crucial and related question of accuracy, especially near a moving front, and how these possible inaccuracies at the leading edge may affect the solution at interior points within the domain.This paper presents an in depth, fully two-dimensional space analysis of the aforementioned problem that has not been addressed before. The purpose of the present communication is not to propose what could be viewed as a final solution, but rather to provide some key considerations that may reveal the ingredients and insight necessary for the development of accurate and robust solutions in the future.

Effect of cement injection on sandy soil slope stability, case study: slope in Petang district, Badung regency

NASA Astrophysics Data System (ADS)

Arya, I. W.; Wiraga, I. W.; GAG Suryanegara, I.

2018-01-01

Slope is a part of soil topography formed due to elevation difference from two soil surface. Landslides is frequently occur in natural slope, it is because shear force is greater than shear strength in the soil. There are some factor that influence slope stability such as: rain dissipation, vibration from earthquake, construction and crack in the soil. Slope instability can cause risk in human activity or even threaten human lives. Every years in rainy season, landslides always occur in Indonesia. In 2016, there was some landslide occurred in Bali. One of the most damaging is landslide in Petang district, Badung regency. This landslide caused main road closed entirely. In order to overcome and prevent landslide, a lot of method have been practiced and still looking for more sophisticated method for forecasting slope stability. One of the method to strengthen soil stability is filling the soil pores with some certain material. Cement is one of the material that can be used to fill the soil pores because when it is in liquid form, it can infiltrate into soil pores and fill the gap between soil particles. And after it dry, it can formed a bond with soil particle so that soil become stronger and the slope as well. In this study, it will use experimental method, slope model in laboratory to simulate a real slope behavior in the field. The first model is the slope without any addition of cement. This model will be become a benchmark for the other models. The second model is a slope with improved soil that injects the slope with cement. Injection of cement is done with varying interval distance of injection point is 5 cm and 10 cm. Each slope model will be given a load until the slope collapses. The slope model will also be analyzed with slope stability program. The test results on the improved slope models will be compared with unimproved slope. In the initial test will consist of 3 model. First model is soil without improvement or cement injection, second model is soil with cement injection interval 5 cm and third model is soil with cement injection interval 10 cm. The result is the shear strength (ϕ value) the soil is increase from 32.02° to 47.57°. The increase value of internal friction angle (ϕ) shows that an increase in shear strength of the cement improved soil. While, the value of cohesion (c) is zero indicating there is no cohesion in the soil. This is common for sand soil or sandy soil. The calculation of safety factor with GeoStructural Analysis obtained an increase of safety factor from 0.78 if the soil without cement injection to 1.07 and 1.17 if the soil is injected with cement at a distance of 10 cm and 5 cm.

Application of Soil Nailing Technique for Protection and Preservation Historical Buildings

NASA Astrophysics Data System (ADS)

Kulczykowski, Marek; Przewłócki, Jarosław; Konarzewska, Bogusława

2017-10-01

Soil nailing is one of the recent in situ techniques used for soil improvement and in stabilizing slopes. The process of soil nailing consists of reinforcing the natural ground with relatively small steel bars or metal rods, grouted in the pre-drilled holes. This method has a wide range of applications for stabilizing deep excavations and steep slopes. Soil nailing has recently become a very common method of slope stabilisation especially where situated beneath or adjacent to historical buildings. Stabilisation by nails drilled into existing masonry structures such as failing retaining walls abutments, provide long term stability without demolition and rebuilding costs. Two cases of soil nailing technology aimed at stabilising slopes beneath old buildings in Poland are presented in this paper. The first concerns application of this technology to repair a retaining wall supporting the base of the dam at the historic hydroelectric power plant in Rutki. The second regards a concept of improving the slope of the Castle Hill in Sandomierz. An analysis of the slope stability for the latter case, using stabilisation technique with the piling system and soil nailing was performed. Some advantages of soil nailing especially for protection of historical buildings, are also underlined. And, the main results of an economic comparison analysis are additionally presented.

Optimization of stabilization of highway embankment slopes using driven piles : phase I.

DOT National Transportation Integrated Search

2010-12-01

This study determined the feasibility of using driven piles to stabilize highway embankment slopes. The activities : performed under this study were a detailed literature review, a national survey of state DOTs, a review of inspection and : stabiliza...

Geospatial Data Integration for Assessing Landslide Hazard on Engineered Slopes

NASA Astrophysics Data System (ADS)

Miller, P. E.; Mills, J. P.; Barr, S. L.; Birkinshaw, S. J.

2012-07-01

Road and rail networks are essential components of national infrastructures, underpinning the economy, and facilitating the mobility of goods and the human workforce. Earthwork slopes such as cuttings and embankments are primary components, and their reliability is of fundamental importance. However, instability and failure can occur, through processes such as landslides. Monitoring the condition of earthworks is a costly and continuous process for network operators, and currently, geospatial data is largely underutilised. The research presented here addresses this by combining airborne laser scanning and multispectral aerial imagery to develop a methodology for assessing landslide hazard. This is based on the extraction of key slope stability variables from the remotely sensed data. The methodology is implemented through numerical modelling, which is parameterised with the slope stability information, simulated climate conditions, and geotechnical properties. This allows determination of slope stability (expressed through the factor of safety) for a range of simulated scenarios. Regression analysis is then performed in order to develop a functional model relating slope stability to the input variables. The remotely sensed raster datasets are robustly re-sampled to two-dimensional cross-sections to facilitate meaningful interpretation of slope behaviour and mapping of landslide hazard. Results are stored in a geodatabase for spatial analysis within a GIS environment. For a test site located in England, UK, results have shown the utility of the approach in deriving practical hazard assessment information. Outcomes were compared to the network operator's hazard grading data, and show general agreement. The utility of the slope information was also assessed with respect to auto-population of slope geometry, and found to deliver significant improvements over the network operator's existing field-based approaches.

Slope effects on the fluid dynamics of a fire spreading across a fuel bed: PIV measurements and OH* chemiluminescence imaging

NASA Astrophysics Data System (ADS)

Morandini, F.; Silvani, X.; Honoré, D.; Boutin, G.; Susset, A.; Vernet, R.

2014-08-01

Slope is among the most influencing factor affecting the spread of wildfires. A contribution to the understanding of the fluid dynamics of a fire spreading in these terrain conditions is provided in the present paper. Coupled optical diagnostics are used to study the slope effects on the flow induced by a fire at laboratory scale. Optical diagnostics consist of particle image velocimetry, for investigating the 2D (vertical) velocity field of the reacting flow and chemiluminescence imaging, for visualizing the region of spontaneous emission of OH radical occurring during gaseous combustion processes. The coupling of these two techniques allows locating accurately the contour of the reaction zone within the computed velocity field. The series of experiments are performed across a bed of vegetative fuel, under both no-slope and 30° upslope conditions. The increase in the rate of fire spread with increasing slope is attributed to a significant change in fluid dynamics surrounding the flame. For horizontal fire spread, flame fronts exhibit quasi-vertical plume resulting in the buoyancy forces generated by the fire. These buoyancy effects induce an influx of ambient fresh air which is entrained laterally into the fire, equitably from both sides. For upward flame spread, the induced flow is strongly influenced by air entrainment on the burnt side of the fire and fire plume is tilted toward unburned vegetation. A particular attention is paid to the induced air flow ahead of the spreading flame. With increasing the slope angle beyond a threshold, highly dangerous conditions arise because this configuration induces wind blows away from the fire rather than toward it, suggesting the presence of convective heat transfers ahead of the fire front.

[Effects of posterior tibial slope on non-contact anterior cruciate ligament rupture and stability of anterior cruciate ligament rupture knee].

PubMed

Yue, De-bo; E, Sen; Wang, Bai-liang; Wang, Wei-guo; Guo, Wan-shou; Zhang, Qi-dong

2013-05-07

To retrospectively explore the correlation between anterior cruciate ligament (ACL)-ruptured knees, stability of ACL-rupture knee and posterior tibial slope (PTS). From January 2008 to October 2012, 150 knees with ACL rupture underwent arthroscopic surgery for ACL reconstruction. A control group was established for subjects undergoing arthroscopic surgery without ACL rupture during the same period. PTS was measured on a digitalized lateral radiograph. Lachman and mechanized pivot shift tests were performed for assessing the stability of knee. There was significant difference (P = 0.007) in PTS angle between the patients with ACL rupture (9.5 ± 2.2 degrees) and the control group (6.6 ± 1.8 degrees). Only among females, increased slope of tibial plateau had effect on the Lachman test. There was a higher positive rate of pivot shift test in patients of increased posterior slope in the ACL rupture group. Increased posterior tibial slope (>6.6) appears to contribute to non-contact ACL injuries in females. And the changes of tibial slope have no effect upon the Lachman test. However, large changes in tibial slope affect pivot shift.

Slope Stability Analysis of Mountainous/Hilly regions of Nepal: A case study of Bhotekoshi Hydropower site

NASA Astrophysics Data System (ADS)

Acharya, A.; Gautam, S.; Kafle, K. R.

2017-12-01

Nepal is a mountainous, developing country that straddles the boundary between the Indian and Himalayan tectonic plates. In Nepal, landslides represent a major constraint on development, causing high levels of economic loss and substantial number of fatalities each year. There is a general consensus that the impacts of landslides in mountainous countries such as Nepal are increasing with time due to unstable slopes. The present study deals with the field investigation of slope stability in mountainous/hilly region of Nepal. Among the natural hazards that occur in regularly in Nepal, flood and landslides due to unstable slopes are by far the serious ones. They claim many human lives every year and cause other damages such as destruction and blockage of highway, destruction of hydropower, losses of livestock, crops and agricultural land. Slope Mass Rating system and stereographic projection has been carried out for analysis of slope stability using standard formats and parameters. It has been found that there are few major discontinuities that play the role for the rock/soil slides around the area. The major discontinuities are 235°/67°. These joint sets play the main role to the plane as well as wedge failures around the area. The rock mass rating of the slope has been found to be 27 and the slope mass rating has been found to be 37.8. The obtained slope mass rating value lies on IV class (Bad) that represents unstable slope having planner or big wedge failure and needs to be corrective measures in the slope. From stereographic projection, wedge failure of the slope has been seen according to the conditions of slope failure.

Seismic response of rock slopes: Numerical investigations on the role of internal structure

NASA Astrophysics Data System (ADS)

Arnold, L.; Applegate, K.; Gibson, M.; Wartman, J.; Adams, S.; Maclaughlin, M.; Smith, S.; Keefer, D. K.

2013-12-01

The stability of rock slopes is significantly influenced and often controlled by the internal structure of the slope created by such discontinuities as joints, shear zones, and faults. Under seismic conditions, these discontinuities influence both the resistance of a slope to failure and its response to dynamic loading. The dynamic response, which can be characterized by the slope's natural frequency and amplification of ground motion, governs the loading experienced by the slope in a seismic event and, therefore, influences the slope's stability. In support of the Network for Earthquake Engineering Simulation (NEES) project Seismically-Induced Rock Slope Failure: Mechanisms and Prediction (NEESROCK), we conducted a 2D numerical investigation using the discrete element method (DEM) coupled with simple discrete fracture networks (DFNs). The intact rock mass is simulated with a bonded assembly of discrete particles, commonly referred to as the bonded-particle model (BPM) for rock. Discontinuities in the BPM are formed by the insertion of smooth, unbonded contacts along specified planes. The influence of discontinuity spacing, orientation, and stiffness on slope natural frequency and amplification was investigated with the commercially available Particle Flow Code (PFC2D). Numerical results indicate that increased discontinuity spacing has a non-linear effect in decreasing the amplification and increasing the natural frequency of the slope. As discontinuity dip changes from sub-horizontal to sub-vertical, the slope's level of amplification increases while the natural frequency of the slope decreases. Increased joint stiffness decreases amplification and increases natural frequency. The results reveal that internal structure has a strong influence on rock slope dynamics that can significantly change the system's dynamic response and stability during seismic loading. Financial support for this research was provided by the United States National Science Foundation (NSF) under grant CMMI-1156413.

Vibration waveform effects on dynamic stabilization of ablative Rayleigh-Taylor instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piriz, A. R.; Lucchio, L. Di; Rodriguez Prieto, G.

2011-08-15

An analysis of dynamic stabilization of Rayleigh-Taylor instability in an ablation front is performed by considering a general square wave for modulating the vertical acceleration of the front. Such a kind of modulation allows for clarifying the role of thermal conduction in the mechanism of dynamic stabilization. In addition, the study of the effect of different modulations by varying the duration and amplitude of the square wave in each half-period provides insight on the optimum performance of dynamic stabilization.

Focus expansion and stability of the spread parameter estimate of the power law model for dispersal gradients

PubMed Central

Gent, David H.; Mehra, Lucky K.; Christie, David; Magarey, Roger

2017-01-01

Empirical and mechanistic modeling indicate that pathogens transmitted via aerially dispersed inoculum follow a power law, resulting in dispersive epidemic waves. The spread parameter (b) of the power law model, which is an indicator of the distance of the epidemic wave front from an initial focus per unit time, has been found to be approximately 2 for several animal and plant diseases over a wide range of spatial scales under conditions favorable for disease spread. Although disease spread and epidemic expansion can be influenced by several factors, the stability of the parameter b over multiple epidemic years has not been determined. Additionally, the size of the initial epidemic area is expected to be strongly related to the final epidemic extent for epidemics, but the stability of this relationship is also not well established. Here, empirical data of cucurbit downy mildew epidemics collected from 2008 to 2014 were analyzed using a spatio-temporal model of disease spread that incorporates logistic growth in time with a power law function for dispersal. Final epidemic extent ranged from 4.16 ×108 km2 in 2012 to 6.44 ×108 km2 in 2009. Current epidemic extent became significantly associated (P < 0.0332; 0.56 < R2 < 0.99) with final epidemic area beginning near the end of April, with the association increasing monotonically to 1.0 by the end of the epidemic season in July. The position of the epidemic wave-front became exponentially more distant with time, and epidemic velocity increased linearly with distance. Slopes from the temporal and spatial regression models varied with about a 2.5-fold range across epidemic years. Estimates of b varied substantially ranging from 1.51 to 4.16 across epidemic years. We observed a significant b ×time (or distance) interaction (P < 0.05) for epidemic years where data were well described by the power law model. These results suggest that the spread parameter b may not be stable over multiple epidemic years. However, b ≈ 2 may be considered the lower limit of the distance traveled by epidemic wave-fronts for aerially transmitted pathogens that follow a power law dispersal function. PMID:28649473

Stability Analysis of Landslide on the R1 Expressway by Limit Equilibrium and Finite Element Methods

NASA Astrophysics Data System (ADS)

Janták, Viktor

2017-12-01

The most difficult problem by designing the superior infrastructure is tracing the expressways and higways in an environment of Quaternary and Neogene complexes of finegrained cohesive and non-cohesive soils. At the last time the typical examples are stability problems on the R1 Nitra - Tekovské Nemce Expressway. The article is focused on the description of reasons of stability loss in the deep earth cut in the 79,000 km of expressway R1, the course of the landslide, slide correction and especially slope-stability assessment before and after the occurrence of slope failures by limit equilibrium and finite elements methods by comparing the behaviour of the slope in the various model situations.

Stability analysis of unsteady ablation fronts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Betti, R.; McCrory, R.L.; Verdon, C.P.

1993-08-01

The linear stability analysis of unsteady ablation fronts, is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

Stability analysis of unsteady ablation fronts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Betti, R.; McCrory, R.L.; Verdon, C.P.

1993-11-08

The linear stability analysis of unsteady ablation fronts is carried out for a semi-infinite uniform medium. For a laser accelerated target, it is shown that a properly selected modulation of the laser intensity can lead to the dynamic stabilization or growth-rate reduction of a large portion of the unstable spectrum. The theory is in qualitative agreement with the numerical results obtained by using the two-dimensional hydrodynamic code ORCHID.

Comparison of Accuracy between Side-Cutting Instruments and Front-Cutting Instruments in Minimally Invasive Total Knee Arthroplasty.

PubMed

Pinsornsak, Piya; Harnroongroj, Thos

2016-11-01

The specialized instrument system used in minimally invasive surgery (MIS) has been developed for reducing soft tissue trauma in total knee arthroplasty (TKA). Compared with front-cutting MIS instruments, side-cutting quadriceps sparing MIS instruments have the advantage of creating a smaller incision and causing fewer traumas to the quadriceps tendon. However, the accuracy of side-cutting instruments concerns surgeons in prosthesis malalignment. To compare the accuracy of side-cutting quadriceps sparing instruments versus front-cutting instruments in MIS-TKA. In this prospective randomized controlled study, we compared the accuracy of side-cutting quadriceps sparing instruments versus the front-cutting instruments used in MIS-TKA. Sixty knees were included in the study, with 30 knees in each group. All the operations were performed by single surgeon. Coronal alignment (tibiofemoral angle, lateral distal femoral angle, and medial proximal tibial angle), and sagittal alignment (femoral component flexion and tibial posterior slope) were measured and compared. Tibiofemoral angle, lateral distal femoral angle, and medial proximal tibial angle, all of which are considered in the assessment of acceptable coronal radiographic alignment, were not different between groups (p = 0.353, 0.500, and 0.177, respectively). However, side-cutting quadriceps sparing instruments produced less acceptable sagittal radiographic alignment, femoral component flexion (63% vs. 93%, p = 0.005), and tibial posterior slope (73% vs. 93%, p = 0.04). Side-cutting quadriceps sparing MIS-TKA instruments had similar accuracy to front-cutting MIS-TKA instruments for coronal alignment but is less accurate for sagittal alignment.

Best practices of using shotcrete for wall fascia and slope stabilization (phase 1 study)

DOT National Transportation Integrated Search

2017-06-01

Shotcrete has become attractive and holds potential to replace cast-in-place (CIP) concrete for elements like retaining walls and slope stabilization. However, this practice is still limited due to concerns of drying shrinkage cracking, long-term dur...

Parameterization experiments performed via synthetic mass movements prototypes generated by 3D slope stability simulator

NASA Astrophysics Data System (ADS)

Colangelo, Antonio C.

2010-05-01

The central purpose of this work is to perform a reverse procedure in the mass movement conventional parameterization approach. The idea is to generate a number of synthetic mass movements by means of the "slope stability simulator" (Colangelo, 2007), and compeer their morphological and physical properties with "real" conditions of effective mass movements. This device is an integrated part of "relief unity emulator" (rue), that permits generate synthetic mass movements in a synthetic slope environment. The "rue" was build upon fundamental geomorphological concepts. These devices operate with an integrated set of mechanical, geomorphic and hydrological models. The "slope stability simulator" device (sss) permits to perform a detailed slope stability analysis in a theoretical three dimensional space, by means of evaluation the spatial behavior of critical depths, gradients and saturation levels in the "potential rupture surfaces" inferred along a set of slope profiles, that compounds a synthetic slope unity. It's a meta-stable 4-dimensional object generated by means of "rue", that represents a sequence evolution of a generator profile applied here, was adapted the infinite slope model for slope. Any slope profiles were sliced by means of finite element solution like in Bishop method. For the synthetic slope systems generated, we assume that the potential rupture surface occurs at soil-regolith or soil-rock boundary in slope material. Sixteen variables were included in the "rue-sss" device that operates in an integrated manner. For each cell, the factor of safety was calculated considering the value of shear strength (cohesion and friction) of material, soil-regolith boundary depth, soil moisture level content, potential rupture surface gradient, slope surface gradient, top of subsurface flow gradient, apparent soil bulk density and vegetation surcharge. The slope soil was considered as cohesive material. The 16 variables incorporated in the models were analyzed for each cell in synthetic slope systems performed by relief unity emulator. The central methodological strategy is to locate the potential rupture surfaces (prs), main material discontinuities, like soil-regolith or regolith-rock transitions. Inner these "prs", we would to outline the effective potential rupture surfaces (eprs). This surface is a sub-set of the "prs" that presents safety factor less than unity (f<1), the sub-region in the "prs" equal or deeper than critical depths. When the effective potential rupture surface acquires significant extension with respect the thickness of critical depth and retaining walls, the "slope stability simulator" generates a synthetic mass movement. The overlay material will slide until that a new equilibrium be attained at residual shear strength. These devices generate graphic 3D cinematic sequences of experiments in synthetic slope systems and numerical results about physical and morphological data about scars and deposits. Thus, we have a detailed geotechnical, morphological, topographic and morphometric description of these mass movements prototypes, for deal with effective mass movements found in the real environments.

Implications of the USGS analysis of slope stability at Sulphur Creek

Treesearch

L. M. Reid

1998-01-01

The slope stability equation and values for material properties recommended by USGS geologist Dr. Raymond Wilson were used to map the stability regime of the four units of THP 1-97-307 HUM and the two units of THP 1-96-413 HUM. When calculations are carried out for conditions without trees, results indicate that each unit includes significant areas that would be...

Geotechnical Asset Management Plan : Technical Report

DOT National Transportation Integrated Search

2017-06-30

Geotechnical assets which include rock and soil slopes, retaining walls, and material sites support and protect the Department's pavements and bridges, and provide the material from which these assets are built. They are the front line of the...

Optimization of Stabilization of Highway Embankment Slopes Using Driven Piles (Phase II – Development and Verification)

DOT National Transportation Integrated Search

2015-01-01

This study examines the feasibility of using driven piles to stabilize highway embankment slopes. The literature review showed that there has been significant research done concerning the lateral capacity of piles. This research tends to be focused o...

Modeling landslide recurrence in Seattle, Washington, USA

USGS Publications Warehouse

Salciarini, Diana; Godt, Jonathan W.; Savage, William Z.; Baum, Rex L.; Conversini, Pietro

2008-01-01

To manage the hazard associated with shallow landslides, decision makers need an understanding of where and when landslides may occur. A variety of approaches have been used to estimate the hazard from shallow, rainfall-triggered landslides, such as empirical rainfall threshold methods or probabilistic methods based on historical records. The wide availability of Geographic Information Systems (GIS) and digital topographic data has led to the development of analytic methods for landslide hazard estimation that couple steady-state hydrological models with slope stability calculations. Because these methods typically neglect the transient effects of infiltration on slope stability, results cannot be linked with historical or forecasted rainfall sequences. Estimates of the frequency of conditions likely to cause landslides are critical for quantitative risk and hazard assessments. We present results to demonstrate how a transient infiltration model coupled with an infinite slope stability calculation may be used to assess shallow landslide frequency in the City of Seattle, Washington, USA. A module called CRF (Critical RainFall) for estimating deterministic rainfall thresholds has been integrated in the TRIGRS (Transient Rainfall Infiltration and Grid-based Slope-Stability) model that combines a transient, one-dimensional analytic solution for pore-pressure response to rainfall infiltration with an infinite slope stability calculation. Input data for the extended model include topographic slope, colluvial thickness, initial water-table depth, material properties, and rainfall durations. This approach is combined with a statistical treatment of rainfall using a GEV (General Extreme Value) probabilistic distribution to produce maps showing the shallow landslide recurrence induced, on a spatially distributed basis, as a function of rainfall duration and hillslope characteristics.

Geotechnical approach for occupational safety risk analysis of critical slope in open pit mining as implication for earthquake hazard

NASA Astrophysics Data System (ADS)

Munirwansyah; Irsyam, Masyhur; Munirwan, Reza P.; Yunita, Halida; Zulfan Usrina, M.

2018-05-01

Occupational safety and health (OSH) is a planned effort to prevent accidents and diseases caused by work. In conducting mining activities often occur work accidents caused by unsafe field conditions. In open mine area, there is often a slump due to unstable slopes, which can disrupt the activities and productivity of mining companies. Based on research on stability of open pit slopes conducted by Febrianti [8], the Meureubo coal mine located in Aceh Barat district, on the slope of mine was indicated unsafe slope conditions, it will be continued research on OSH for landslide which is to understand the stability of the excavation slope and the shape of the slope collapse. Plaxis software was used for this research. After analyzing the slope stability and the effect of landslide on OSH with Job Safety Analysis (JSA) method, to identify the hazard to work safety, risk management analysis will be conducted to classified hazard level and its handling technique. This research aim is to know the level of risk of work accident at the company and its prevention effort. The result of risk analysis research is very high-risk value that is > 350 then the activity must be stopped until the risk can be reduced to reach the risk value limit < 20 which is allowed or accepted.

On the impact of atmospheric thermal stability on the characteristics of nocturnal downslope flows

NASA Astrophysics Data System (ADS)

Ye, Z. J.; Garratt, J. R.; Segal, M.; Pielke, R. A.

1990-04-01

The impacts of background (or ambient) and local atmospheric thermal stabilities, and slope steepness, on nighttime thermally induced downslope flow in meso-β domains (i.e., 20 200 km horizontal extent) have been investigated using analytical and numerical model approaches. Good agreement between the analytical and numerical evaluations was found. It was concluded that: (i) as anticipated, the intensity of the downslope flow increases with increased slope steepness, although the depth of the downslope flow was found to be insensitive to slope steepness in the studied situations; (ii) the intensity of the downslope flow is generally independent of background atmospheric thermal stability; (iii) for given integrated nighttime cooling across the nocturnal boundary layer (NBL), Q s the local atmospheric thermal stability exerts a strong influence on downslope flow behavior: the downslope flow intensity increases when local atmospheric thermal stability increases; and (iv) the downslope flow intensity is proportional to Q s 1/2.

Slope instability in complex 3D topography promoted by convergent 3D groundwater flow

NASA Astrophysics Data System (ADS)

Reid, M. E.; Brien, D. L.

2012-12-01

Slope instability in complex topography is generally controlled by the interaction between gravitationally induced stresses, 3D strengths, and 3D pore-fluid pressure fields produced by flowing groundwater. As an example of this complexity, coastal bluffs sculpted by landsliding commonly exhibit a progression of undulating headlands and re-entrants. In this landscape, stresses differ between headlands and re-entrants and 3D groundwater flow varies from vertical rainfall infiltration to lateral groundwater flow on lower permeability layers with subsequent discharge at the curved bluff faces. In plan view, groundwater flow converges in the re-entrant regions. To investigate relative slope instability induced by undulating topography, we couple the USGS 3D limit-equilibrium slope-stability model, SCOOPS, with the USGS 3D groundwater flow model, MODFLOW. By rapidly analyzing the stability of millions of potential failures, the SCOOPS model can determine relative slope stability throughout the 3D domain underlying a digital elevation model (DEM), and it can utilize both fully 3D distributions of pore-water pressure and material strength. The two models are linked by first computing a groundwater-flow field in MODFLOW, and then computing stability in SCOOPS using the pore-pressure field derived from groundwater flow. Using these two models, our analyses of 60m high coastal bluffs in Seattle, Washington showed augmented instability in topographic re-entrants given recharge from a rainy season. Here, increased recharge led to elevated perched water tables with enhanced effects in the re-entrants owing to convergence of groundwater flow. Stability in these areas was reduced about 80% compared to equivalent dry conditions. To further isolate these effects, we examined groundwater flow and stability in hypothetical landscapes composed of uniform and equally spaced, oscillating headlands and re-entrants with differing amplitudes. The landscapes had a constant slope for both headlands and re-entrants to minimize slope effects on stability. Despite these equal slopes, our analyses, given dry conditions, illustrated that the headlands can be 5-7% less stable than the re-entrants, owing to the geometry of the 3D failure mass with the lowest stability. We then simulated groundwater flow in these landscapes; flow was caused by recharge perching on a horizontal low permeability layer with discharge at the bluff faces. By systematically varying recharge, hydraulic conductivity of the material, and conductance at the bluffs, we created different 3D pore-pressure fields. Recharge rates and hydraulic conductivities controlled the height of the water table, whereas bluff conductance influenced the gradient of the water table near the bluff face. Given elevated water tables with steep gradients, bluffs in the re-entrants became unstable where flow converged. Thus, with progressively stronger effects from water flow, overall instability evolved from relatively unstable headlands to more uniform stability to relatively unstable re-entrants. Larger re-entrants led to more 3D flow convergence and greater localized instability. One- or two-dimensional models cannot fully characterize slope instability in complex topography.

Dealing with deep uncertainties in landslide modelling for disaster risk reduction under climate change

NASA Astrophysics Data System (ADS)

Almeida, Susana; Holcombe, Elizabeth Ann; Pianosi, Francesca; Wagener, Thorsten

2017-02-01

Landslides have large negative economic and societal impacts, including loss of life and damage to infrastructure. Slope stability assessment is a vital tool for landslide risk management, but high levels of uncertainty often challenge its usefulness. Uncertainties are associated with the numerical model used to assess slope stability and its parameters, with the data characterizing the geometric, geotechnic and hydrologic properties of the slope, and with hazard triggers (e.g. rainfall). Uncertainties associated with many of these factors are also likely to be exacerbated further by future climatic and socio-economic changes, such as increased urbanization and resultant land use change. In this study, we illustrate how numerical models can be used to explore the uncertain factors that influence potential future landslide hazard using a bottom-up strategy. Specifically, we link the Combined Hydrology And Stability Model (CHASM) with sensitivity analysis and Classification And Regression Trees (CART) to identify critical thresholds in slope properties and climatic (rainfall) drivers that lead to slope failure. We apply our approach to a slope in the Caribbean, an area that is naturally susceptible to landslides due to a combination of high rainfall rates, steep slopes, and highly weathered residual soils. For this particular slope, we find that uncertainties regarding some slope properties (namely thickness and effective cohesion of topsoil) are as important as the uncertainties related to future rainfall conditions. Furthermore, we show that 89 % of the expected behaviour of the studied slope can be characterized based on only two variables - the ratio of topsoil thickness to cohesion and the ratio of rainfall intensity to duration.

Effect of tibial slope on the stability of the anterior cruciate ligament-deficient knee.

PubMed

Voos, James E; Suero, Eduardo M; Citak, Musa; Petrigliano, Frank P; Bosscher, Marianne R F; Citak, Mustafa; Wickiewicz, Thomas L; Pearle, Andrew D

2012-08-01

We aimed to quantify the effect of changes in tibial slope on the magnitude of anterior tibial translation (ATT) in the anterior cruciate ligament (ACL)-deficient knee during the Lachman and mechanized pivot shift tests. We hypothesized that increased posterior tibial slope would increase the amount of ATT of an ACL-deficient knee, while leveling the slope of the tibial plateau would decrease the amount of ATT. Lachman and mechanized pivot shift tests were performed on hip-to-toe cadaveric specimens, and ATT of the lateral and the medial compartments was measured using navigation (n = 11). The ACL was then sectioned. Stability testing was repeated, and ATT was recorded. A proximal tibial osteotomy in the sagittal plane was then performed achieving either +5 or -5° of tibial slope variation after which stability testing was repeated (n = 10). Sectioning the ACL resulted in a significant increase in ATT in both the Lachman and mechanized pivot shift tests (P < 0.05). Increasing or decreasing the slope of the tibial plateau had no effect on ATT during the Lachman test (n.s.). During the mechanized pivot shift tests, a 5° increase in posterior slope resulted in a significant increase in ATT compared to the native knee (P < 0.05), while a 5° decrease in slope reduced ATT to a level similar to that of the intact knee. Tibial slope changes did not affect the magnitude of translation during a Lachman test. However, large changes in tibial slope variation affected the magnitude of the pivot shift.

Steering Dynamics of Tilting Narrow Track Vehicle with Passive Front Wheel Design

NASA Astrophysics Data System (ADS)

TAN, Jeffrey Too Chuan; ARAKAWA, Hiroki; SUDA, Yoshihiro

2016-09-01

In recent years, narrow track vehicle has been emerged as a potential candidate for the next generation of urban transportation system, which is greener and space effective. Vehicle body tilting has been a symbolic characteristic of such vehicle, with the purpose to maintain its stability with the narrow track body. However, the coordination between active steering and vehicle tilting requires considerable driving skill in order to achieve effective stability. In this work, we propose an alternative steering method with a passive front wheel that mechanically follows the vehicle body tilting. The objective of this paper is to investigate the steering dynamics of the vehicle under various design parameters of the passive front wheel. Modeling of a three-wheel tilting narrow track vehicle and multibody dynamics simulations were conducted to study the effects of two important front wheel design parameters, i.e. caster angle and trail toward the vehicle steering dynamics in steering response time, turning radius, steering stability and resiliency towards external disturbance. From the results of the simulation studies, we have verified the relationships of these two front wheel design parameters toward the vehicle steering dynamics.

Prediction of slope stability based on numerical modeling of stress–strain state of rocks

NASA Astrophysics Data System (ADS)

Kozhogulov Nifadyev, KCh, VI; Usmanov, SF

2018-03-01

The paper presents the developed technique for the estimation of rock mass stability based on the finite element modeling of stress–strain state of rocks. The modeling results on the pit wall landslide as a flow of particles along a sloped surface are described.

Field instrumentation, monitoring of drilled shafts for landslide stabilization and development of pertinent design method.

DOT National Transportation Integrated Search

2010-11-01

The design method for using a single row, spaced drilled shafts, socketed into a firm rock strata, to stabilize : an unstable slope has been developed in this research. The soil arching due to the presence of spaced : drilled shafts in a slope was ob...

Stabilization of erodible slopes with geofibers and nontraditional liquid additives.

DOT National Transportation Integrated Search

2013-05-01

Instability of erodible slopes due to extreme climate events and of permafrost slopes due degradation and thawing is a significant : engineering problem for northern transportation infrastructure. Engineers continually look for mitigation alternative...

Study on Stability Analysis and Monitoring Technology of Deep Concave Open-Pit Mine Slope

NASA Astrophysics Data System (ADS)

Xue, Dinglong; Ren, Fenghua; Li, Yuan

2018-05-01

In this paper, using the FLAC3D software to establish the numerical model of the rock slope in the south of Washan stope and to compare and verify with the monitoring result, reference is made to the original engineering and hydrogeological data of Washan stope. The results show that the stability of the South slope is mainly affected by the dominant structural plane, and the potential slip surface and the dominant structure surface are the same. During the recovery period of -120m platform residual mine, the disturbance stress is increasing but the overall amplitude is small and the slope is relatively stable.

Infinite slope stability under steady unsaturated seepage conditions

USGS Publications Warehouse

Lu, Ning; Godt, Jonathan W.

2008-01-01

We present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions. The analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions. The framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil. The factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone. Slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework. These analyses indicate that for hillslopes of both sandy and silty soils, failure can occur above the water table under steady infiltration conditions, which is consistent with some field observations that cannot be predicted by the classical infinite slope theory. A case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near Seattle, Washington, is presented to examine the predictive utility of the proposed framework.

Historic bluff retreat and stabilization at Flag Harbor, Chesapeake Bay, Maryland

USGS Publications Warehouse

Clark, Inga; Larsen, Curtis E.; McRae, Michele

2002-01-01

Studies of bluff erosion and slope stability along the western shore of Chesapeake Bay suggest relative evolution from steep, eroding coastal bluffs to stable slopes at angles of repose ca. 35 degrees over decades. Because of the dating methods in those studies, it was impossible to precisely define rates of change. The present study provides historic age control. A pair of small harbor structures were constructed in the early 1950's at Chesapeake Beach, MD to maintain a dredged channel to a small marina occupying a ravine in the Calvert Cliffs. Prior to construction, this section of shoreline was comprised of eroding steep bluffs cut into Miocene-age sediments. Downdrift erosion is now apparent south of the structures as is updrift deposition behind the northern jetty. Since construction the updrift sand body has prograded northward and progressively deposited protective beaches along the toes of the bluffs. Former eroding bluffs nearest the harbor are now stable, vegetated slopes at angles near 35 degrees. Slope angles widen to the north and to the northern limit of the sand body. Beyond this are eroding bluffs standing at angles of 70-80 degrees. The relative time required for eroding bluffs to reach stability is estimated by interpolating the distance and time for the sand body to prograde northward since harbor construction. We measured slope angles at intervals northward from the updrift structure for a distance of 2000 feet. A least squares regression of slope angle vs distance showed progressive decrease in angle from north to south. Actively eroding 70-80 degree bluffs gave way to vegetated, but slumping slopes, and finally to stable 35-degree slopes at the harbor. A relationship between time and distance along the shore allowed us to estimate a stabilization time for this location of 35-40 years. The shortness of this time scale allows us to suggest that attempts to artificially stabilize eroding bluffs along this coast is not a simple task of protecting the toes of slopes from wave action. Once shoreline retreat ends, sloughing of sediment from bluff faces gives way to longer-term landslide processes. The bluff top recedes until a stable 35-degree slope is attained. Thus, simple shoreline protection methods may not preserve property at the bluff edge.

Slope Stability Analysis of Waste Dump in Sandstone Open Pit Osielec

NASA Astrophysics Data System (ADS)

Adamczyk, Justyna; Cała, Marek; Flisiak, Jerzy; Kolano, Malwina; Kowalski, Michał

2013-03-01

This paper presents the slope stability analysis for the current as well as projected (final) geometry of waste dump Sandstone Open Pit "Osielec". For the stability analysis six sections were selected. Then, the final geometry of the waste dump was designed and the stability analysis was conducted. On the basis of the analysis results the opportunities to improve the stability of the object were identified. The next issue addressed in the paper was to determine the proportion of the mixture containing mining and processing wastes, for which the waste dump remains stable. Stability calculations were carried out using Janbu method, which belongs to the limit equilibrium methods.

Scale dependence of the diversity-stability relationship in a temperate grassland.

PubMed

Zhang, Yunhai; He, Nianpeng; Loreau, Michel; Pan, Qingmin; Han, Xingguo

2018-05-01

A positive relationship between biodiversity and ecosystem stability has been reported in many ecosystems; however, it has yet to be determined whether and how spatial scale affects this relationship. Here, for the first time, we assessed the effects of alpha, beta and gamma diversity on ecosystem stability and the scale dependence of the slope of the diversity-stability relationship.By employing a long-term (33 years) dataset from a temperate grassland, northern China, we calculated the all possible spatial scales with the complete combination from the basic 1-m 2 plots.Species richness was positively associated with ecosystem stability through species asynchrony and overyielding at all spatial scales (1, 2, 3, 4 and 5 m 2 ). Both alpha and beta diversity were positively associated with gamma stability.Moreover, the slope of the diversity-area relationship was significantly higher than that of the stability-area relationship, resulting in a decline of the slope of the diversity-stability relationship with increasing area. Synthesis. With the positive species diversity effect on ecosystem stability from small to large spatial scales, our findings demonstrate the need to maintain a high biodiversity and biotic heterogeneity as insurance against the risks incurred by ecosystems in the face of global environmental changes.

SINMAP Modeling of an active landslide area in the Swabian Alb

NASA Astrophysics Data System (ADS)

Terhorst, Birgit; Jaeger, Daniel

2015-04-01

Landslides are a common hazard in German low mountain areas such as the Swabian Alb. As areas of former landslides are highly prone to secondary movements, this study aims to assess the susceptibility for landslide hazard around Mössingen-Öschingen, a region consistently affected by landslides during the last decades. Based on the history and development of mass movements and a detailed geomorphological map, slope stability was calculated using SINMAP (Stability Index Mapping). SINMAP (Pack et al., 1998; Tarboton, 1997) is based on the "infinite slope stability model" by Hammond et al. (1992) and Montgomery and Dietrich (1994) describing the ratio of slope stabilizing factors (e.g. cohesion) and slope destabilizing factors (e.g. gravitation) on a slip surface parallel to the slope. Most input parameters are determined by the relief and therefore, can be calculated from a digital terrain model (DTM, resolution 5 m). Based on the local morphology and geology, a total of 10 'calibration regions', each with similar hydrogeological characteristics, were defined. Further input parameters were: Shear strength via friction angle (Phi), cohesion (C) and hydraulic conductivity (T/R). The data was obtained from soil mechanical assessments and field/laboratory analyses. As a result, a specific stability index is calculated, describing the susceptibility of a slope movement. In a first step, the 'topographic wetness index' (derived from catchment area, slope gradient and hydraulic conductivity) was calculated. Results show several preferred (natural) drainage channels with generally higher water saturations in morphological depressions. Several of them can be linked to the location of damaged houses in the settlement area on the lower slope. The SINMAP calculation clearly revealed the impermeable Callovian clay layers as most prone to slope movements. A comparison of the susceptibility map with slide masses which were mapped during a field survey showed generally good agreements. This was in particular true for the slopes of the "Landhaussiedlung", a small settlement area east of Mössingen-Öschingen. In the uphill areas, a large landslide was triggered on June 3rd, 2013, mainly caused by heavy rainfalls during the days before. The scarp/slip surface was situated in the Callovian clay layers and in an area which was shown as susceptible for slope movements by the SINMAP model earlier Terhorst and Kreja (2009). The movement processes reactivated an old slide mass, which reached the outermost parts of the settlement area and damaged the densely built-up underground of the Landhaussiedlung. Although no house was destroyed completely by the slide mass, the induced pressure caused severe damages, rendering the buildings uninhabitable and leading to the evacuation of the Landhaussiedlung. The results show, that the modeling provided a solid identification of the vulnerable slope areas. The recent landslide area is almost completely situated in a region modeled as vulnerable for slope movements. Therefore, the landslide event of 2013 practically validated the susceptibility map. On the base of solid data and under consideration of detailed and differentiated information, SINMAP is a powerful tool for the assessment of susceptibilities for translational slides. Hammond, C., Hall, D., Miller, S., Swetik, P., 1992. Level I Stability Analysis (LISA) documentation for version 2.0. General Technical Report, INT-285. U.S. Deptartment of Agriculture, Forest Service, Intermountain Research Station, Ogden. Montgomery, D.R., Dietrich, W.E., 1994. A Physically Based Model for the Topographic Control on Shallow Landsliding. Water Resources Research, 30(4), 1153-1171. Pack, R.T., Tarboton, D.G., Goodwin, C.N., 1998. The SINMAP approach to terrain stability mapping, 8th Congress of the International Association of Engineering Geology, Vancouver, Canada, pp. 8. Tarboton, D.G., 1997. A new method for the determination of flow directions and upslope areas in grid digital elevation models. Water Resources Research, 33(2), 309-319. Terhorst, B., Kreja, R., 2009. Slope stability modelling with SINMAP in a settlement area of the Swabian Alb. Landslides, 6(4), 309-319.

Analysis of slope stabilization by soil bioengineering method

NASA Astrophysics Data System (ADS)

Switala, Barbara Maria; Wu, Wei

2013-04-01

The aim of the project is to create a numerical model which will include the impact of vegetation on the slope stability analysis, considering both mechanical and hydrological factors. This will enrich the current knowledge about how roots reinforce the soil layers on the slope and how it influences the increase of shear strength of the soil. This has to be combined together with hydrological effects caused by evapotranspiration: modified soil moisture regime, dissipation of excess pore pressure and established matric suction. Coupled analyses (mechanical and hydrological) are rarely conducted, or only outdated models are used, which leads to overestimation of the additional shear strength of soil. That is why there is a need to support this branch of landslide hazard assessment and develop a new model. This research will help to raise awareness, that soil bioengineering methods of slope stabilization can in some cases be more appropriate and less expensive than traditional methods. As an input to the model, the appropriate slope geometry and soil properties have to be chosen. It is also important to consider different plant types and root properties, as well as different levels of groundwater table. To assess the effect of evapotranspiration it is necessary to know the geographical location of the slope and the weather conditions in the chosen region. The final output of the model, which will help to quantitatively assess the impact of vegetation on the slope stability, is the factor of safety (FOS) for vegetated slope for different types of soil and degrees of saturation. Results may then be compared with different conditions and factors of safety, calculated for the corresponding non-vegetated slope. It will be possible to specify the most favorable and unfavorable conditions. Moreover, the calculations provide also information on changes of cohesion, caused by mechanical and hydrological effects, as well as the change in the friction angle of soil.

Seafloor morphology of the continental slope in front the Petacalco Bay and its tsunamigenic relationship at the Mexican sector of the Middle American subduction zone

NASA Astrophysics Data System (ADS)

Mortera-Gutierrez, C. A.; Bandy, W. L.; Millan-Motolinia, C.; Ponce-Nuñez, F.; Ortega-Ramirez, J.

2014-12-01

The recent occurrence of offshore, large, earthquake ruptures in the western limit of the Guerrero Seismic Gap and the scattered data of seafloor morphology of the continental slope along this sector at the Mexican Mid American subduction zone have encouraged the UNAM marine geophysical group to initiate a mapping program at the Guerrero margin, from the shelf break to the Middle American Trench. The main objective of this initiative is to have a complete cover of the seafloor morphology of the Guerrero slope as the background data for comparative studies of the seafloor deformation in case of future offshore earthquake ruptures in this region. At he first stage of this initiative, we have mapped the continental slope in front the Petacalco Bay, west of the Guerrero Seismic Gap, where three important large earthquakes occurred and caused great damages in Mexico City: Petatlán earthquake (Mw=7.6) at 1979, Michoacán earthquake (Mw=8.1) and its aftershock (Mw=7.9) at 1985. Geophysical results of two campaigns carry in 2012 (MAMRIV12) and 2013 (BABPET13) on board the BO EL PUMA are presented which include multibeam data and subbottom profiles. These data sets cover an area between 101°W and 103°W, and from the shelf-slope break to the trench. The multibeam chart shows details of the hydrological erosion induced by many submarine cannons at the upper slope, whereas the seafloor relief in the lower slope is dominated by tectonic structures. The subbottom profiles and the seafloor morphology evidence zones of big slumps and faults. For first time the Rio Balsas submarine cannon is completed chart, reaching the trench basin. The river course is deflected, possibly by shear faulting. There are slump sites near the trench that probably one is associated to the 1925 tsunami at Zihuatanejo, Guerrero. The 1985 Michoacán aftershock was accompany by a small Tsunami. At that time, the lack of morphology data in this slope inhibited further studies of seafloor-deformation and its tsunamigenic relationship. Funding providing by UNAM-DGAPA-PAPIIT grants: IN115613 and IN115513

Analysis of Rainfall Infiltration Law in Unsaturated Soil Slope

PubMed Central

Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

2014-01-01

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θ s - θ r), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process. PMID:24672332

Analysis of rainfall infiltration law in unsaturated soil slope.

PubMed

Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

2014-01-01

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θs - θr), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process.

Construction of a Dry Ash Dam with Soilbags and Slope Stability Analysis

NASA Astrophysics Data System (ADS)

Li, Hui; Song, Yingjun; Gao, Jiaorong; Li, Longhua; Zhou, Yuqi; Qi, Hui

2017-12-01

In thermal power plants, it is necessary to build ash dams to store fly ash, which is the by-product after the combustion of coals. To solve the problem of lacking rockfill materials in Africa, A new technology of constructing ash dams using solibags filled with local sands is proposed and the method of analyzing its slope stability is suggested. The design of the ash dam using soilbags in Lamb Thermal Power Plant of Kenya is introduced in detail. The slope stability of the soilbags-constructed ash dam was analyzed by adopting the suggested method. The results show that the soilbags filled with ash or sands have high compressive strength, and the primary dam constructed with soilbags can effectively retain the backfill ash and the stacking dam reinforced with soilbags can stand stable even with the slope of 1:1.5.

Efficient Meshfree Large Deformation Simulation of Rainfall Induced Soil Slope Failure

NASA Astrophysics Data System (ADS)

Wang, Dongdong; Li, Ling

2010-05-01

An efficient Lagrangian Galerkin meshfree framework is presented for large deformation simulation of rainfall-induced soil slope failure. Detailed coupled soil-rainfall seepage equations are given for the proposed formulation. This nonlinear meshfree formulation is featured by the Lagrangian stabilized conforming nodal integration method where the low cost nature of nodal integration approach is kept and at the same time the numerical stability is maintained. The initiation and evolution of progressive failure in the soil slope is modeled by the coupled constitutive equations of isotropic damage and Drucker-Prager pressure-dependent plasticity. The gradient smoothing in the stabilized conforming integration also serves as a non-local regularization of material instability and consequently the present method is capable of effectively capture the shear band failure. The efficacy of the present method is demonstrated by simulating the rainfall-induced failure of two typical soil slopes.

Effects of Structural Flexibility on Motorcycle Straight Running Stability by using Energy Flow Method

NASA Astrophysics Data System (ADS)

Marumo, Yoshitaka; Katayama, Tsuyoshi

This study uses the energy flow method to analyze how structural flexibility affects the motorcycle wobble and weave modes. Lateral bending of the front fork and torsion of the main frame affect the wobble mode stability. These are based on the gyroscopic effect of the front wheel in the steering motion by considering structural flexibility. At high speeds, lateral bending of the front fork and torsion of the rear swing arm more significantly affect the weave mode stability. These are primarily due to the phase changes of the external force generated by the yaw rate in the lateral motion. The phase change of the yaw rate force in the lateral motion originates from the phase change of the tire side forces.

Bio-engineering traits of Pinus radiata D.Don

NASA Astrophysics Data System (ADS)

Giadrossich, Filippo; Marden, Michael; Marrosu, Roberto; Schwarz, Massimiliano; Phillips, Chris John; Cohen, Denis; Niedda, Marcello

2017-04-01

Pinus radiata is widely cultivated in New Zealand. Due to steep slopes and intense rainfall, the silviculture of Pinus radiata forests is important to control erosion and slope stability. Bio-engineering traits such as root distribution and root tensile strength are fundamental to understand the effectiveness of Pinus radiata. This information is needed to use the state of the art root reinforcement model (the Root Bundle Model) and the physically-based slope stability model SOSlope. Yet, little is known about root distribution and tensile strength for this specie. We measured soil moisture and carried out 30 field tensile tests on roots of Pinus radiata. We also measured root distribution data from 5 plants, digging arc of circles 0.6 radian around the trees in four opposite directions. We fully excavated the root system of two trees. Using the Root Bundle Model, results of our measurements allow estimation of root reinforcement. With the slope stability model SOSlope, information on the intensity and frequency of harvesting and on the development of weak zones that can be supported by a stand of Pinus radiata in relation to slope stability can be calculated. An added value is that the collected data allow us to make inferences between number and sizes of roots, and growth direction.

At similar angles, slope walking has a greater fall risk than stair walking.

PubMed

Sheehan, Riley C; Gottschall, Jinger S

2012-05-01

According to the CDC, falls are the leading cause of injury for all age groups with over half of the falls occurring during slope and stair walking. Consequently, the purpose of this study was to compare and contrast the different factors related to fall risk as they apply to these walking tasks. More specifically, we hypothesized that compared to level walking, slope and stair walking would have greater speed standard deviation, greater ankle dorsiflexion, and earlier peak activity of the tibialis anterior. Twelve healthy, young male participants completed level, slope, and stair trials on a 25-m walkway. Overall, during slope and stair walking, medial-lateral stability was less, anterior-posterior stability was less, and toe clearance was greater in comparison to level walking. In addition, there were fewer differences between level and stair walking than there were between level and slope walking, suggesting that at similar angles, slope walking has a greater fall risk than stair walking. Copyright © 2011 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Supersymmetry across the light and heavy-light hadronic spectrum. II.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dosch, Hans Gunter; de Téramond, Guy F.; Brodsky, Stanley J.

We extend our analysis of the implications of hadronic supersymmetry for heavy-light hadrons in light-front holographic QCD. Although conformal symmetry is strongly broken by the heavy quark mass, supersymmetry and the holographic embedding of semiclassical light-front dynamics derived from five-dimensional anti-de Sitter space nevertheless determine the form of the confining potential in the light-front Hamiltonian to be harmonic. The resulting light-front bound-state equations lead to a heavy-light Regge-like spectrum for both mesons and baryons. The confinement hadron mass scale and their Regge slopes depend, however, on the mass of the heavy quark in the meson or baryon as expected frommore » heavy quark effective theory. Furthermore, this procedure reproduces the observed spectra of heavy-light hadrons with good precision and makes predictions for yet unobserved states.« less

Supersymmetry across the light and heavy-light hadronic spectrum. II.

DOE PAGES

Dosch, Hans Gunter; de Téramond, Guy F.; Brodsky, Stanley J.

2017-02-15

We extend our analysis of the implications of hadronic supersymmetry for heavy-light hadrons in light-front holographic QCD. Although conformal symmetry is strongly broken by the heavy quark mass, supersymmetry and the holographic embedding of semiclassical light-front dynamics derived from five-dimensional anti-de Sitter space nevertheless determine the form of the confining potential in the light-front Hamiltonian to be harmonic. The resulting light-front bound-state equations lead to a heavy-light Regge-like spectrum for both mesons and baryons. The confinement hadron mass scale and their Regge slopes depend, however, on the mass of the heavy quark in the meson or baryon as expected frommore » heavy quark effective theory. Furthermore, this procedure reproduces the observed spectra of heavy-light hadrons with good precision and makes predictions for yet unobserved states.« less

The effect of posterior tibial slope on knee flexion in posterior-stabilized total knee arthroplasty.

PubMed

Shi, Xiaojun; Shen, Bin; Kang, Pengde; Yang, Jing; Zhou, Zongke; Pei, Fuxing

2013-12-01

To evaluate and quantify the effect of the tibial slope on the postoperative maximal knee flexion and stability in the posterior-stabilized total knee arthroplasty (TKA). Fifty-six patients (65 knees) who had undergone TKA with the posterior-stabilized prostheses were divided into the following 3 groups according to the measured tibial slopes: Group 1: ≤4°, Group 2: 4°-7° and Group 3: >7°. The preoperative range of the motion, the change in the posterior condylar offset, the elevation of the joint line, the postoperative tibiofemoral angle and the preoperative and postoperative Hospital for Special Surgery (HSS) scores were recorded. The tibial anteroposterior translation was measured using the Kneelax 3 Arthrometer at both the 30° and the 90° flexion angles. The mean values of the postoperative maximal knee flexion were 101° (SD 5), 106° (SD 5) and 113° (SD 9) in Groups 1, 2 and 3, respectively. A significant difference was found in the postoperative maximal flexion between the 3 groups (P < 0.001). However, no significant differences were found between the 3 groups in the postoperative HSS scores, the changes in the posterior condylar offset, the elevation of the joint line or the tibial anteroposterior translation at either the 30° or the 90° flexion angles. A 1° increase in the tibial slope resulted in a 1.8° flexion increment (r = 1.8, R (2) = 0.463, P < 0.001). An increase in the posterior tibial slope can significantly increase the postoperative maximal knee flexion. The tibial slope with an appropriate flexion and extension gap balance during the operation does not affect the joint stability.

Stability of a flow down an incline with respect to two-dimensional and three-dimensional disturbances for Newtonian and non-Newtonian fluids.

PubMed

Allouche, M H; Millet, S; Botton, V; Henry, D; Ben Hadid, H; Rousset, F

2015-12-01

Squire's theorem, which states that the two-dimensional instabilities are more dangerous than the three-dimensional instabilities, is revisited here for a flow down an incline, making use of numerical stability analysis and Squire relationships when available. For flows down inclined planes, one of these Squire relationships involves the slopes of the inclines. This means that the Reynolds number associated with a two-dimensional wave can be shown to be smaller than that for an oblique wave, but this oblique wave being obtained for a larger slope. Physically speaking, this prevents the possibility to directly compare the thresholds at a given slope. The goal of the paper is then to reach a conclusion about the predominance or not of two-dimensional instabilities at a given slope, which is of practical interest for industrial or environmental applications. For a Newtonian fluid, it is shown that, for a given slope, oblique wave instabilities are never the dominant instabilities. Both the Squire relationships and the particular variations of the two-dimensional wave critical curve with regard to the inclination angle are involved in the proof of this result. For a generalized Newtonian fluid, a similar result can only be obtained for a reduced stability problem where some term connected to the perturbation of viscosity is neglected. For the general stability problem, however, no Squire relationships can be derived and the numerical stability results show that the thresholds for oblique waves can be smaller than the thresholds for two-dimensional waves at a given slope, particularly for large obliquity angles and strong shear-thinning behaviors. The conclusion is then completely different in that case: the dominant instability for a generalized Newtonian fluid flowing down an inclined plane with a given slope can be three dimensional.

Volcano collapse promoted by hydrothermal alteration and edifice shape, Mount Rainier, Washington

USGS Publications Warehouse

Reid, M.E.; Sisson, T.W.; Brien, D.L.

2001-01-01

Catastrophic collapses of steep volcano flanks threaten many populated regions, and understanding factors that promote collapse could save lives and property. Large collapses of hydrothermally altered parts of Mount Rainier have generated far-traveled debris flows; future flows would threaten densely populated parts of the Puget Sound region. We evaluate edifice collapse hazards at Mount Rainier using a new three-dimensional slope stability method incorporating detailed geologic mapping and subsurface geophysical imaging to determine distributions of strong (fresh) and weak (altered) rock. Quantitative three-dimensional slope stability calculations reveal that sizeable flank collapse (>0.1 km3) is promoted by voluminous, weak, hydrothermally altered rock situated high on steep slopes. These conditions exist only on Mount Rainier's upper west slope, consistent with the Holocene debris-flow history. Widespread alteration on lower flanks or concealed in regions of gentle slope high on the edifice does not greatly facilitate collapse. Our quantitative stability assessment method can also provide useful hazard predictions using reconnaissance geologic information and is a potentially rapid and inexpensive new tool for aiding volcano hazard assessments.

A Dynamic Hydrology-Critical Zone Framework for Rainfall-triggered Landslide Hazard Prediction

NASA Astrophysics Data System (ADS)

Dialynas, Y. G.; Foufoula-Georgiou, E.; Dietrich, W. E.; Bras, R. L.

2017-12-01

Watershed-scale coupled hydrologic-stability models are still in their early stages, and are characterized by important limitations: (a) either they assume steady-state or quasi-dynamic watershed hydrology, or (b) they simulate landslide occurrence based on a simple one-dimensional stability criterion. Here we develop a three-dimensional landslide prediction framework, based on a coupled hydrologic-slope stability model and incorporation of the influence of deep critical zone processes (i.e., flow through weathered bedrock and exfiltration to the colluvium) for more accurate prediction of the timing, location, and extent of landslides. Specifically, a watershed-scale slope stability model that systematically accounts for the contribution of driving and resisting forces in three-dimensional hillslope segments was coupled with a spatially-explicit and physically-based hydrologic model. The landslide prediction framework considers critical zone processes and structure, and explicitly accounts for the spatial heterogeneity of surface and subsurface properties that control slope stability, including soil and weathered bedrock hydrological and mechanical characteristics, vegetation, and slope morphology. To test performance, the model was applied in landslide-prone sites in the US, the hydrology of which has been extensively studied. Results showed that both rainfall infiltration in the soil and groundwater exfiltration exert a strong control on the timing and magnitude of landslide occurrence. We demonstrate the extent to which three-dimensional slope destabilizing factors, which are modulated by dynamic hydrologic conditions in the soil-bedrock column, control landslide initiation at the watershed scale.

Submarine landslides triggered by destabilization of high-saturation hydrate anomalies

NASA Astrophysics Data System (ADS)

Handwerger, Alexander L.; Rempel, Alan W.; Skarbek, Rob M.

2017-07-01

Submarine landslides occur along continental margins at depths that often intersect the gas hydrate stability zone, prompting suggestions that slope stability may be affected by perturbations that arise from changes in hydrate stability. Here we develop a numerical model to identify the conditions under which the destabilization of hydrates results in slope failure. Specifically, we focus on high-saturation hydrate anomalies at fine-grained to coarse-grained stratigraphic boundaries that can transmit bridging stresses that decrease the effective stress at sediment contacts and disrupt normal sediment consolidation. We evaluate slope stability before and after hydrate destabilization. Hydrate anomalies act to significantly increase the overall slope stability due to large increases in effective cohesion. However, when hydrate anomalies destabilize there is a loss of cohesion and increase in effective stress that causes the sediment grains to rapidly consolidate and generate pore pressures that can either trigger immediate slope failure or weaken the surrounding sediment until the pore pressure diffuses away. In cases where failure does not occur, the sediment can remain weakened for months. In cases where failure does occur, we quantify landslide dynamics using a rate and state frictional model and find that landslides can display either slow or dynamic (i.e., catastrophic) motion depending on the rate-dependent properties, size of the stress perturbation, and the size of the slip patch relative to a critical nucleation length scale. Our results illustrate the fundamental mechanisms through which the destabilization of gas hydrates can pose a significant geohazard.

Relationships between slope erosion processes and aggregate stability of Ultisols from subtropical China during rainstorms

NASA Astrophysics Data System (ADS)

Liu, Gang; Xiao, Hai; Liu, Puling

2017-04-01

Soil aggregates, being a key soil structural unit, influence several soil physical properties such as water infiltration, runoff and erosion. The relationship between soil aggregate stability and interrill and rill erodibility is unclear but critical to process-based erosion prediction models. One obvious reason is that it is hard to distinguish between interrill and rill-eroded sediment during the erosion process. This study was designed to partition interrill and rill erosion rates and relates them to the aggregate stability of Ultisols in subtropical China. Six kinds of rare earth element (REE) were applied as tracers mixed with two cultivated soils derived from the Quaternary red clay soil and the shale soil at six slope positions. Soil aggregate stability was determined by the Le Bissonnais (LB)-method. Simulated rainfall with three intensities (60, 90 and 120 mm/h) were applied to a soil plot (2.25 m long, 0.5 m wide, 0.2 m deep) at three slope gradients (10°, 20° and 30°) with duration of 30 min after runoff initiation. The results indicated that interrill and rill erosion increased with increasing rainfall intensity and slope gradient for both types of soil. Rill and interrill erosion rates of the shale soil were much higher than those of the Quaternary red clay soil. Rill erosion contribution enhanced with increasing rainfall intensity and slope gradient for both soils. Percentage of the downslope area erosion to total erosion was the largest, followed by the mid-slope area and then upslope area. Equations using an aggregate stability index As to replace the erodibility factor of interrill and rill erosion in the Water Erosion Prediction Project (WEPP) model were constructed after analyzing the relationships between estimated and measured rill and interrill erosion data. It was shown that these equations based on the stability index, As, have the potential to improve methods for assessing interrill and rill erosion erodibility synchronously for the subtropical Ultisols by using REE tracing method.

Posterior tibial slope as a risk factor for anterior cruciate ligament rupture in soccer players.

PubMed

Senişik, Seçkin; Ozgürbüz, Cengizhan; Ergün, Metin; Yüksel, Oğuz; Taskiran, Emin; Işlegen, Cetin; Ertat, Ahmet

2011-01-01

Anterior cruciate ligament (ACL) is the primary stabilizer of the knee. An impairment of any of the dynamic or static stability providing factors can lead to overload on the other factors and ultimately to deterioration of knee stability. This can result in anterior tibial translation and rupture of the ACL. The purpose of this study was to examine the influence of tibial slope on ACL injury risk on soccer players. A total of 64 elite soccer players and 45 sedentary controls were included in this longitudinal and controlled study. The angle between the tibial mid-diaphysis line and the line between the anterior and posterior edges of the medial tibial plateau was measured as the tibial slope via lateral radiographs. Individual player exposure, and injuries sustained by the participants were prospectively recorded. Eleven ACL injuries were documented during the study period. Tibial slope was not different between soccer players and sedentary controls. Tibial slope in the dominant and non-dominant legs was greater for the injured players compared to the uninjured players. The difference reached a significant level only for the dominant legs (p < 0.001). While the tibial slopes of the dominant and non-dominant legs were not different on uninjured players (p > 0.05), a higher tibial slope was observed in dominant legs of injured players (p < 0.05). Higher tibial slope on injured soccer players compared to the uninjured ones supports the idea that the tibial slope degree might be an important risk factor for ACL injury. Key pointsDominant legs' tibial slopes of the injured players were significantly higher compared to the uninjured players (p < 0.001).Higher tibial slope was determined in dominant legs compared to the non-dominant side, for the injured players (p = 0.042). Different tibial slope measures in dominant and non-dominant legs might be the result of different loading and/or adaptation patterns in soccer.

Front and pulse solutions for the complex Ginzburg-Landau equation with higher-order terms.

PubMed

Tian, Huiping; Li, Zhonghao; Tian, Jinping; Zhou, Guosheng

2002-12-01

We investigate one-dimensional complex Ginzburg-Landau equation with higher-order terms and discuss their influences on the multiplicity of solutions. An exact analytic front solution is presented. By stability analysis for the original partial differential equation, we derive its necessary stability condition for amplitude perturbations. This condition together with the exact front solution determine the region of parameter space where the uniformly translating front solution can exist. In addition, stable pulses, chaotic pulses, and attenuation pulses appear generally if the parameters are out of the range. Finally, applying these analysis into the optical transmission system numerically we find that the stable transmission of optical pulses can be achieved if the parameters are appropriately chosen.

100. Catalog HHistory 1, C.C.C., 34 Landscaping, Negative No. P ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

100. Catalog H-History 1, C.C.C., 34 Landscaping, Negative No. P 733c (Photographer and date unknown) SLOPE MAINTENANCE WORK BY CCC. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

Instabilities and finger formation in replacement fronts driven by an oversaturated solution

NASA Astrophysics Data System (ADS)

Kondratiuk, Paweł; Tredak, Hanna; Upadhyay, Virat; Ladd, Anthony J. C.; Szymczak, Piotr

2017-08-01

We consider a simple model of infiltration-driven mineral replacement, in which the chemical coupling between precipitation and dissolution leads to the appearance of a reaction front advancing into the system. Such fronts are usually accompanied by a local increase of porosity. We analyze the linear stability of the replacement front to establish whether such a localized porosity increase can lead to global instability and pattern formation in these systems. We find that for a wide range of control parameters such fronts are unstable. However, both short- and long-wavelength perturbations are stabilized, whereas in a purely dissolutional instability only short wavelengths are stable. We analyze the morphologies of the dissolution patterns emerging in the later stages of the evolution of the system, when the dynamics are beyond the linear regime. Implications of these results for the natural systems are discussed, particularly in the context of karst formation in terra rossa-covered carbonate bedrock.

The role of vegetation in the stability of forested slopes

Treesearch

Robert R. Ziemer

1981-01-01

Summary - Vegetation helps stabilize forested slopes by providing root strength and by modifying the saturated soil water regime. Plant roots can anchor through the soil mass into fractures in bedrock, can cross zones of weakness to more stable soil, and can provide interlocking long fibrous binders within a weak soil mass. In Mediterranean-type climates, having warm...

Stability analysis of nonlinear systems with slope restricted nonlinearities.

PubMed

Liu, Xian; Du, Jiajia; Gao, Qing

2014-01-01

The problem of absolute stability of Lur'e systems with sector and slope restricted nonlinearities is revisited. Novel time-domain and frequency-domain criteria are established by using the Lyapunov method and the well-known Kalman-Yakubovich-Popov (KYP) lemma. The criteria strengthen some existing results. Simulations are given to illustrate the efficiency of the results.

Assessing the effectiveness of seeding and fertilization treatments for reducing erosion potential following severe wildfires

Treesearch

David W. Peterson; Erich Kyle Dodson; Richy J. Harrod

2007-01-01

Postfire slope stabilization treatments are often prescribed following high‑severity wildfires on public lands to reduce erosion, maintain soil productivity, protect water quality, and reduce risks to human life and property. However, the effectiveness of slope stabilization treatments remains in question. For this study, tests were on effectiveness of...

Statistical anisotropy in free turbulence for mixing layers at high Reynolds numbers

NASA Astrophysics Data System (ADS)

Gardner, Patrick J.; Roggemann, Michael C.; Welsh, Byron M.; Bowersox, Rodney D.; Luke, Theodore E.

1996-08-01

A lateral shearing interferometer was used to measure the slope of perturbed wave fronts after propagating through free turbulent mixing layers. Shearing interferometers provide a two-dimensional flow visualization that is nonintrusive. Slope measurements were used to reconstruct the phase of the turbulence-corrupted wave front. The random phase fluctuations induced by the mixing layer were captured in a large ensemble of wave-front measurements. Experiments were performed on an unbounded, plane shear mixing layer of helium and nitrogen gas at fixed velocities and high Reynolds numbers for six locations in the flow development. Statistical autocorrelation functions and structure functions were computed on the reconstructed phase maps. The autocorrelation function results indicated that the turbulence-induced phase fluctuations were not wide-sense stationary. The structure functions exhibited statistical homogeneity, indicating that the phase fluctuations were stationary in first increments. However, the turbulence-corrupted phase was not isotropic. A five-thirds power law is shown to fit orthogonal slices of the structure function, analogous to the Kolmogorov model for isotropic turbulence. Strehl ratios were computed from the phase structure functions and compared with classical estimates that assume isotropy. The isotropic models are shown to overestimate the optical degradation by nearly 3 orders of magnitude compared with the structure function calculations.

Comparison of measured and computed Strehl ratios for light propagated through a channel flow of a He N 2 mixing layer at high Reynolds numbers

NASA Astrophysics Data System (ADS)

Gardner, Patrick J.; Roggemann, Michael C.; Welsh, Byron M.; Bowersox, Rodney D.; Luke, Theodore E.

1997-04-01

A lateral shearing interferometer was used to measure the slope of perturbed wave fronts after they propagated through a He N 2 mixing layer in a rectangular channel. Slope measurements were used to reconstruct the phase of the turbulence-corrupted wave front. The random phase fluctuations induced by the mixing layer were captured in a large ensemble of wave-front measurements. Phase structure functions, computed from the reconstructed phase surfaces, were stationary in first increments. A five-thirds power law is shown to fit streamwise and cross-stream slices of the structure function, analogous to the Kolmogorov model for isotropic turbulence, which describes the structure function with a single parameter. Strehl ratios were computed from the phase structure functions and compared with a measured experiment obtained from simultaneous point-spread function measurements. Two additional Strehl ratios were calculated by using classical estimates that assume statistical isotropy throughout the flow. The isotropic models are a reasonable estimate of the optical degradation only within a few centimeters of the initial mixing, where the Reynolds number is low. At higher Reynolds numbers, Strehl ratios calculated from the structure functions match the experiment much better than Strehl ratio calculations that assume isotropic flow.

Finite Element analyses of soil bioengineered slopes

NASA Astrophysics Data System (ADS)

Tamagnini, Roberto; Switala, Barbara Maria; Sudan Acharya, Madhu; Wu, Wei; Graf, Frank; Auer, Michael; te Kamp, Lothar

2014-05-01

Soil Bioengineering methods are not only effective from an economical point of view, but they are also interesting as fully ecological solutions. The presented project is aimed to define a numerical model which includes the impact of vegetation on slope stability, considering both mechanical and hydrological effects. In this project, a constitutive model has been developed that accounts for the multi-phase nature of the soil, namely the partly saturated condition and it also includes the effects of a biological component. The constitutive equation is implemented in the Finite Element (FE) software Comes-Geo with an implicit integration scheme that accounts for the collapse of the soils structure due to wetting. The mathematical formulation of the constitutive equations is introduced by means of thermodynamics and it simulates the growth of the biological system during the time. The numerical code is then applied in the analysis of an ideal rainfall induced landslide. The slope is analyzed for vegetated and non-vegetated conditions. The final results allow to quantitatively assessing the impact of vegetation on slope stability. This allows drawing conclusions and choosing whenever it is worthful to use soil bioengineering methods in slope stabilization instead of traditional approaches. The application of the FE methods show some advantages with respect to the commonly used limit equilibrium analyses, because it can account for the real coupled strain-diffusion nature of the problem. The mechanical strength of roots is in fact influenced by the stress evolution into the slope. Moreover, FE method does not need a pre-definition of any failure surface. FE method can also be used in monitoring the progressive failure of the soil bio-engineered system as it calculates the amount of displacements and strains of the model slope. The preliminary study results show that the formulated equations can be useful for analysis and evaluation of different soil bio-engineering methods of slope stabilization.

Widespread gas hydrate instability on the upper U.S. Beaufort margin

NASA Astrophysics Data System (ADS)

Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.

2014-12-01

The most climate-sensitive methane hydrate deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for gas hydrate stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to gas hydrate dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope gas hydrates and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope gas hydrate distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from gas hydrate stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed gas hydrate stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of gas hydrates in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the gas hydrate stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating gas hydrates into the sediments underlying an area of ~5-7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.

Spirit Paige Panorama of the Interior of Home Plate False Color

NASA Image and Video Library

2006-03-06

This panorama shows two rock-strewn slopes on the left and right sides of a broad, U-shaped dip in the middle. The sandy surface in front of the rover is reddish brown; individual rocks and more distant features are blue-gray

Morphological stability of sapphire crystallization front

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baranov, V. V., E-mail: baranov.isc@gmail.com; Nizhankovskyi, S. V.

2016-03-15

The main factors and specificity of growth conditions for sapphire and Ti:sapphire crystals, which affect the morphological stability of the crystal–melt interface, have been investigated with allowance for the concentration and radiative melt supercooling. It is shown that the critical sapphire growth rate is determined to a great extent by the optical transparency of the melt and the mixing conditions near the crystallization front.

Observations of seasonal exchange in the Celtic Sea slope region from underwater gilders

NASA Astrophysics Data System (ADS)

Porter, Marie; Inall, Mark; Smeed, David; Palmer, Matthew; Dumont, Estelle; Aleynik, Dmitry

2015-04-01

Between June 2012 and January 2013, four underwater gliders, profiling to a maximum depth of 1000m, occupied a transect between 47.6°N, 10.3°W and 48.4°N, 9.3°W, perpendicular to the Celtic Sea continental slope. Due to the significant and well-documented internal tide activity in this region and the relatively slow through-water speed of gliders it is first demonstrated that the chosen sampling methodology minimised aliasing of the internal tide. Gliders were flown along a repeat transect and care was taken to ensure that each location was sampled at a different phase of the tide on repeat occupations. Through monthly averaging of the transect data, the effects of the internal tide are minimised and the lower frequency processes made visible. In this presentation we highlight the importance of the lower frequency variability in contributing to cross-slope exchange. Analysis of monthly averaged glider transect data suggests two distinct regimes; 1) Summer, June - October, when the surface water was temperature stratified and, 2) Winter, from October to January, when the seasonal thermocline was mixed down to below the depth of the shelf break (200 m). During the stratified summer months a well-defined shelf break salinity front limits the exchange of water between the ocean and the shelf, preventing the spread of the more saline, sub-surface ocean water (centred at ~150m) onto the shelf. Nevertheless, some cross-slope flow is identified during these months: an intermediate depth salinity minimum (centred at ~600m) is observed to upwell (from 600m to 200-300m) up the slope, sometimes continuing onto the shelf. As the stratification is eroded during the winter months, subsurface upwelling switches to downwelling, and the intermediate depth salinity minimum (~600m) retreats away from the slope region removing it as a potential source of oceanic water on the shelf. Downwelling near to the slope does however allow for an intrusion of the shallower high salinity water onto the shelf reducing the control of the shelf break salinity front, although it has not been ascertained whether this extends further onto the shelf than the shelf break region.

Slope Reinforcement with the Utilization of the Coal Waste Anthropogenic Material

NASA Astrophysics Data System (ADS)

Gwóźdź-Lasoń, Monika

2017-10-01

The protection of the environment, including waste management, is one of the pillars of the policy of the Europe. The application which is presented in that paper tries to show a trans-disciplinary way to design geotechnical constructions - slope stability analysis. The generally accepted principles that the author presents are numerous modelling patterns of earth retaining walls as slope stabilization system. The paper constitutes an attempt to summarise and generalise earlier researches which involved FEM numeric procedures and the Z_Soil package. The design of anthropogenic soil used as a material for reinforced earth retaining walls, are not only of commercial but of environmental importance as well and consistent with the concept of sustainable development and the need to redevelop brownfield. This paper tries to show conceptual and empirical modelling approaches to slope stability system used in anthropogenic soil formation such as heaps, resulting from mining, with a special focus on urban areas of South of Poland and perspectives of anthropogenic materials application in geotechnical engineering are discussed.

Subsurface Characterization using Geophysical Seismic Refraction Survey for Slope Stabilization Design with Soil Nailing

NASA Astrophysics Data System (ADS)

Ashraf Mohamad Ismail, Mohd; Ng, Soon Min; Hazreek Zainal Abidin, Mohd; Madun, Aziman

2018-04-01

The application of geophysical seismic refraction for slope stabilization design using soil nailing method was demonstrated in this study. The potential weak layer of the study area is first identify prior to determining the appropriate length and location of the soil nail. A total of 7 seismic refraction survey lines were conducted at the study area with standard procedures. The refraction data were then analyzed by using the Pickwin and Plotrefa computer software package to obtain the seismic velocity profiles distribution. These results were correlated with the complementary borehole data to interpret the subsurface profile of the study area. It has been identified that layer 1 to 3 is the potential weak zone susceptible to slope failure. Hence, soil nails should be installed to transfer the tensile load from the less stable layer 3 to the more stable layer 4. The soil-nail interaction will provide a reinforcing action to the soil mass thereby increasing the stability of the slope.

Coir geotextile for slope stabilization and cultivation - A case study in a highland region of Kerala, South India

NASA Astrophysics Data System (ADS)

Vishnudas, Subha; Savenije, Hubert H. G.; Van der Zaag, Pieter; Anil, K. R.

A sloping field is not only vulnerable to soil erosion it may also suffer from soil moisture deficiency. Farmers that cultivate on slopes everywhere face similar problems. Conservation technologies may reduce soil and nutrient losses, and thus enhance water holding capacity and soil fertility. But although these technologies promote sustainable crop production on steep slopes, the construction of physical structure such as bench terraces are often labour intensive and expensive to the farmers, since construction and maintenance require high investments. Here we studied the efficiency of coir geotextile with and without crop cultivation in reducing soil moisture deficiency on marginal slopes in Kerala, India. From the results it is evident that the slopes treated with geotextile and crops have the highest moisture retention capacity followed by geotextiles alone, and that the control plot has the lowest moisture retention capacity. As the poor and marginal farmers occupy the highland region, this method provides an economically viable option for income generation and food security along with slope stabilization.

Numerical Computation of Homogeneous Slope Stability

PubMed Central

Xiao, Shuangshuang; Li, Kemin; Ding, Xiaohua; Liu, Tong

2015-01-01

To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS) to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM) and particle swarm optimization algorithm (PSO) to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759) were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS). PMID:25784927

Numerical computation of homogeneous slope stability.

PubMed

Xiao, Shuangshuang; Li, Kemin; Ding, Xiaohua; Liu, Tong

2015-01-01

To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS) to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM) and particle swarm optimization algorithm (PSO) to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759) were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS).

Arctic megaslide at presumed rest

PubMed Central

Geissler, Wolfram H.; Gebhardt, A. Catalina; Gross, Felix; Wollenburg, Jutta; Jensen, Laura; Schmidt-Aursch, Mechita C.; Krastel, Sebastian; Elger, Judith; Osti, Giacomo

2016-01-01

Slope failure like in the Hinlopen/Yermak Megaslide is one of the major geohazards in a changing Arctic environment. We analysed hydroacoustic and 2D high-resolution seismic data from the apparently intact continental slope immediately north of the Hinlopen/Yermak Megaslide for signs of past and future instabilities. Our new bathymetry and seismic data show clear evidence for incipient slope instability. Minor slide deposits and an internally-deformed sedimentary layer near the base of the gas hydrate stability zone imply an incomplete failure event, most probably about 30000 years ago, contemporaneous to or shortly after the Hinlopen/Yermak Megaslide. An active gas reservoir at the base of the gas hydrate stability zone demonstrate that over-pressured fluids might have played a key role in the initiation of slope failure at the studied slope, but more importantly also for the giant HYM slope failure. To date, it is not clear, if the studied slope is fully preconditioned to fail completely in future or if it might be slowly deforming and creeping at present. We detected widespread methane seepage on the adjacent shallow shelf areas not sealed by gas hydrates. PMID:27922097

Arctic megaslide at presumed rest

NASA Astrophysics Data System (ADS)

Geissler, Wolfram H.; Gebhardt, A. Catalina; Gross, Felix; Wollenburg, Jutta; Jensen, Laura; Schmidt-Aursch, Mechita C.; Krastel, Sebastian; Elger, Judith; Osti, Giacomo

2016-12-01

Slope failure like in the Hinlopen/Yermak Megaslide is one of the major geohazards in a changing Arctic environment. We analysed hydroacoustic and 2D high-resolution seismic data from the apparently intact continental slope immediately north of the Hinlopen/Yermak Megaslide for signs of past and future instabilities. Our new bathymetry and seismic data show clear evidence for incipient slope instability. Minor slide deposits and an internally-deformed sedimentary layer near the base of the gas hydrate stability zone imply an incomplete failure event, most probably about 30000 years ago, contemporaneous to or shortly after the Hinlopen/Yermak Megaslide. An active gas reservoir at the base of the gas hydrate stability zone demonstrate that over-pressured fluids might have played a key role in the initiation of slope failure at the studied slope, but more importantly also for the giant HYM slope failure. To date, it is not clear, if the studied slope is fully preconditioned to fail completely in future or if it might be slowly deforming and creeping at present. We detected widespread methane seepage on the adjacent shallow shelf areas not sealed by gas hydrates.

A comparative analysis of hazard models for predicting debris flows in Madison County, VA

USGS Publications Warehouse

Morrissey, Meghan M.; Wieczorek, Gerald F.; Morgan, Benjamin A.

2001-01-01

During the rainstorm of June 27, 1995, roughly 330-750 mm of rain fell within a sixteen-hour period, initiating floods and over 600 debris flows in a small area (130 km2) of Madison County, Virginia. Field studies showed that the majority (70%) of these debris flows initiated with a thickness of 0.5 to 3.0 m in colluvium on slopes from 17 o to 41 o (Wieczorek et al., 2000). This paper evaluated and compared the approaches of SINMAP, LISA, and Iverson's (2000) transient response model for slope stability analysis by applying each model to the landslide data from Madison County. Of these three stability models, only Iverson's transient response model evaluated stability conditions as a function of time and depth. Iverson?s model would be the preferred method of the three models to evaluate landslide hazards on a regional scale in areas prone to rain-induced landslides as it considers both the transient and spatial response of pore pressure in its calculation of slope stability. The stability calculation used in SINMAP and LISA is similar and utilizes probability distribution functions for certain parameters. Unlike SINMAP that only considers soil cohesion, internal friction angle and rainfall-rate distributions, LISA allows the use of distributed data for all parameters, so it is the preferred model to evaluate slope stability over SINMAP. Results from all three models suggested similar soil and hydrologic properties for triggering the landslides that occurred during the 1995 storm in Madison County, Virginia. The colluvium probably had cohesion of less than 2KPa. The root-soil system is above the failure plane and consequently root strength and tree surcharge had negligible effect on slope stability. The result that the final location of the water table was near the ground surface is supported by the water budget analysis of the rainstorm conducted by Smith et al. (1996).

Hydro-mechanically coupled finite-element analysis of the stability of a fractured-rock slope using the equivalent continuum approach: a case study of planned reservoir banks in Blaubeuren, Germany

NASA Astrophysics Data System (ADS)

Song, Jie; Dong, Mei; Koltuk, Serdar; Hu, Hui; Zhang, Luqing; Azzam, Rafig

2018-05-01

Construction works associated with the building of reservoirs in mountain areas can damage the stability of adjacent valley slopes. Seepage processes caused by the filling and drawdown operations of reservoirs also affect the stability of the reservoir banks over time. The presented study investigates the stability of a fractured-rock slope subjected to seepage forces in the lower basin of a planned pumped-storage hydropower (PSH) plant in Blaubeuren, Germany. The investigation uses a hydro-mechanically coupled finite-element analyses. For this purpose, an equivalent continuum model is developed by using a representative elementary volume (REV) approach. To determine the minimum required REV size, a large number of discrete fracture networks are generated using Monte Carlo simulations. These analyses give a REV size of 28 × 28 m, which is sufficient to represent the equivalent hydraulic and mechanical properties of the investigated fractured-rock mass. The hydro-mechanically coupled analyses performed using this REV size show that the reservoir operations in the examined PSH plant have negligible effect on the adjacent valley slope.

Slope stability and bearing capacity of landfills and simple on-site test methods.

PubMed

Yamawaki, Atsushi; Doi, Yoichi; Omine, Kiyoshi

2017-07-01

This study discusses strength characteristics (slope stability, bearing capacity, etc.) of waste landfills through on-site tests that were carried out at 29 locations in 19 sites in Japan and three other countries, and proposes simple methods to test and assess the mechanical strength of landfills on site. Also, the possibility of using a landfill site was investigated by a full-scale eccentric loading test. As a result of this, landfills containing more than about 10 cm long plastics or other fibrous materials were found to be resilient and hard to yield. An on-site full scale test proved that no differential settlement occurs. The repose angle test proposed as a simple on-site test method has been confirmed to be a good indicator for slope stability assessment. The repose angle test suggested that landfills which have high, near-saturation water content have considerably poorer slope stability. The results of our repose angle test and the impact acceleration test were related to the internal friction angle and the cohesion, respectively. In addition to this, it was found that the air pore volume ratio measured by an on-site air pore volume ratio test is likely to be related to various strength parameters.

A case study on dune response to infragravity waves

NASA Astrophysics Data System (ADS)

Li, Wenshan; Wang, Hui; Li, Huan; Wu, Shuangquan; Li, Cheng

2017-08-01

A series of numerical simulations were conducted using the process-based model XBeach to investigate dune response under normal and getting rid of infragravity wave conditions with different slopes. Erosion volume upside the dune toe and dune top recession are set as indicators for dune vulnerability as well as defence capacity for its front-beach. Results show that both dune erosion volume and dune top recession decrease with gentler dune slopes. Of all the simulation cases, dune with a face slope of 1/1 lost most sand and supplied most sand for lower-bed. The presence of infragravity waves is validated to be crucial to dune vulnerability. The dune erosion volume is shown to decrease by 44.5%∼61.5% and the dune top recession decreased by 0%∼45.5% correspondingly, in the case that infragravity motion is not taken into account during simulation for different dune slopes.

Scale dependence of the diversity–stability relationship in a temperate grassland

PubMed Central

Zhang, Yunhai; He, Nianpeng; Loreau, Michel; Pan, Qingmin; Han, Xingguo

2018-01-01

A positive relationship between biodiversity and ecosystem stability has been reported in many ecosystems; however, it has yet to be determined whether and how spatial scale affects this relationship. Here, for the first time, we assessed the effects of alpha, beta and gamma diversity on ecosystem stability and the scale dependence of the slope of the diversity–stability relationship.By employing a long-term (33 years) dataset from a temperate grassland, northern China, we calculated the all possible spatial scales with the complete combination from the basic 1-m2 plots.Species richness was positively associated with ecosystem stability through species asynchrony and overyielding at all spatial scales (1, 2, 3, 4 and 5 m2). Both alpha and beta diversity were positively associated with gamma stability.Moreover, the slope of the diversity–area relationship was significantly higher than that of the stability–area relationship, resulting in a decline of the slope of the diversity–stability relationship with increasing area.Synthesis. With the positive species diversity effect on ecosystem stability from small to large spatial scales, our findings demonstrate the need to maintain a high biodiversity and biotic heterogeneity as insurance against the risks incurred by ecosystems in the face of global environmental changes. PMID:29725139

Local dynamic stability of lower extremity joints in lower limb amputees during slope walking.

PubMed

Chen, Jin-Ling; Gu, Dong-Yun

2013-01-01

Lower limb amputees have a higher fall risk during slope walking compared with non-amputees. However, studies on amputees' slope walking were not well addressed. The aim of this study was to identify the difference of slope walking between amputees and non-amputees. Lyapunov exponents λS was used to estimate the local dynamic stability of 7 transtibial amputees' and 7 controls' lower extremity joint kinematics during uphill and downhill walking. Compared with the controls, amputees exhibited significantly lower λS in hip (P=0.04) and ankle (P=0.01) joints of the sound limb, and hip joints (P=0.01) of the prosthetic limb during uphill walking, while they exhibited significantly lower λS in knee (P=0.02) and ankle (P=0.03) joints of the sound limb, and hip joints (P=0.03) of the prosthetic limb during downhill walking. Compared with amputees level walking, they exhibited significantly lower λS in ankle joints of the sound limb during both uphill (P=0.01) and downhill walking (P=0.01). We hypothesized that the better local dynamic stability of amputees was caused by compensation strategy during slope walking.

Effects of heel base size, walking speed, and slope angle on center of pressure trajectory and plantar pressure when wearing high-heeled shoes.

PubMed

Luximon, Yan; Cong, Yan; Luximon, Ameersing; Zhang, Ming

2015-06-01

High-heeled shoes are associated with instability and a high risk of fall, fracture, and ankle sprain. This study investigated the effects of heel base size (HBS) on walking stability under different walking speeds and slope angles. The trajectory of the center of pressure (COP), maximal peak pressure, pressure time integral, contact area, and perceived stability were analyzed. The results revealed that a small HBS increased the COP deviations, shifting the COP more medially at the beginning of the gait cycle. The slope angle mainly affected the COP in the anteroposterior direction. An increased slope angle shifted the COP posterior and caused greater pressure and a larger contact area in the midfoot and rearfoot regions, which can provide more support. Subjective measures on perceived stability were consistent with objective measures. The results suggested that high-heeled shoes with a small HBS did not provide stable plantar support, particularly on a small slope angle. The changes in the COP and pressure pattern caused by a small HBS might increase joint torque and muscle activity and induce lower limb problems. Copyright © 2015 Elsevier B.V. All rights reserved.

Aggregate stability, root length and root thickness influenced by a mycorrhizal inoculum? - Results from a three-year eco-engineering field experiment on an alpine slope.

NASA Astrophysics Data System (ADS)

Bast, Alexander; Wilcke, Wolfgang; Lüscher, Peter; Graf, Frank; Gärtner, Holger

2014-05-01

In mountain environments many slopes are covered by coarse grained, glacial-, periglacial- or/and denudation-derived substrate. These slopes show a high geomorphic activity and are susceptible for erosional processes, shallow landslides or debris flows, which can result in a high socio-economic hazard potential. This is especially true for steep slopes, lacking a protecting vegetation cover. Regarding hazard prevention, eco-engineering gained in importance because related techniques provide a sustainable measure to protect erosion-prone hillslopes. The idea of using plants for sustainable erosion control and protection against shallow landslides, demands some essential requirements, as e.g., a stable seedbed providing appropriate water and nutrient supply. However, degraded alpine slopes are often unstable and the coarse-grained material shows a low retention capacity of water and nutrients. Extreme conditions like this hamper a fast and sustainable development of a protecting vegetation cover even if pioneer plants are used to stabilize the slopes. Thus, the question arises what needs to be done to give planted saplings within eco-engineering projects maximum support developing their above- and belowground structures to promote slope stabilization. Laboratory experiments using potted plants have shown a positive impact of mycorrhizal fungi inoculation plant development and soil structure, i.e. the formation of (stable) aggregates within several months. Soil aggregate stability is an integrating parameter, reflecting several aspects of the plant-soil system and for this also an indicator of soil development and soil stability. Because of this and based on the promising laboratory results, we intended to apply this approach in a field-experiment We established (i) mycorrhizal and (ii) non-mycorrhizal treated eco-engineered research plots on a field experimental scale, covering a total area of approx. 1000 m2 on an ENE exposed slope (coarse morainic and denudation-derived substrate; inclination ~40 - 45 °; elevation 1220 - 1360 m a.s.l.) located in the Eastern Swiss Alps, where many environmental parameters can be seen as homogeneous. Soil aggregate stability, the formation of water stable aggregates and the fine-root development was quantified at the end of three consecutively vegetation periods. Our results show, that an impact of the mycorrhizal inoculum on aggregate stability was not traceable after one vegetation period, which contradicts our expectations and former laboratory experiments. At the mycorrhizal inoculated site, fine roots showed indeed a lower root length density compared to the non-mycorrhizal treated site, but the proportion of roots with thicker diameters tended to be higher. At the end of the third vegetation period this pattern changed. Aggregate stability is then highest at the inoculated site and root length density increased showing the highest values as well. The tendency to thicker root diameters at the mycorrhizal treated site can be confirmed. Our findings show that studies on a field experimental scale are inevitable. Laboratory experiments and field studies complement each other, and lead to a better understanding, having regard to a successful application of sustainable eco-engineering measures on erosion-prone slopes in alpine environments.

Arctic Submarine Slope Stability

NASA Astrophysics Data System (ADS)

Winkelmann, D.; Geissler, W.

2010-12-01

Submarine landsliding represents aside submarine earthquakes major natural hazard to coastal and sea-floor infrastructure as well as to coastal communities due to their ability to generate large-scale tsunamis with their socio-economic consequences. The investigation of submarine landslides, their conditions and trigger mechanisms, recurrence rates and potential impact remains an important task for the evaluation of risks in coastal management and offshore industrial activities. In the light of a changing globe with warming oceans and rising sea-level accompanied by increasing human population along coasts and enhanced near- and offshore activities, slope stability issues gain more importance than ever before. The Arctic exhibits the most rapid and drastic changes and is predicted to change even faster. Aside rising air temperatures, enhanced inflow of less cooled Atlantic water into the Arctic Ocean reduces sea-ice cover and warms the surroundings. Slope stability is challenged considering large areas of permafrost and hydrates. The Hinlopen/Yermak Megaslide (HYM) north of Svalbard is the first and so far only reported large-scale submarine landslide in the Arctic Ocean. The HYM exhibits the highest headwalls that have been found on siliciclastic margins. With more than 10.000 square kilometer areal extent and app. 2.400 cubic kilometer of involved sedimentary material, it is one of the largest exposed submarine slides worldwide. Geometry and age put this slide in a special position in discussing submarine slope stability on glaciated continental margins. The HYM occurred 30 ka ago, when the global sea-level dropped by app. 50 m within less than one millennium due to rapid onset of global glaciation. It probably caused a tsunami with circum-Arctic impact and wave heights exceeding 130 meters. The HYM affected the slope stability field in its neighbourhood by removal of support. Post-megaslide slope instability as expressed in creeping and smaller-scaled slides are the consequence. Its geometrical configuration and timing is different from submarine slides on other glaciated continental margins. Thus, it raises the question whether slope stability within the Arctic Ocean is governed by processes specific to this environment. The extraordinary thick slabs (up to 1600 m) that were moved translationally during sliding rise the question on the nature of the weak layers associated with this process. Especially theories involving higher pore pressure are being challenged by this observation, because either extreme pore pressures or alternative explanations (e.g. mineralogical and/or textural) can be considered. To assess the actual submarine slope stability and failure potential in the Arctic Ocean, we propose to drill and recover weak layer material of the HYM from the adjacent intact strata by deep drilling under the framework of Integrated Ocean Drilling Program. This is the only method to recover weak layer material from the HYM, because the strata are too thick. We further propose to drill into the adjacent deforming slope to identify material properties of the layers acting as detachment and monitor the deformation.

Direct observations of the Antarctic Slope Current transport at 113°E

NASA Astrophysics Data System (ADS)

Peña-Molino, B.; McCartney, M. S.; Rintoul, S. R.

2016-10-01

The Antarctic Slope Current (ASC), defined here as the region of westward flow along the continental slope off Antarctica, forms the southern limb of the subpolar gyres. It regulates the exchange of water across the shelf break and provides a path for interbasin westward transport. Despite its significance, the ASC remains largely unobserved around most of the Antarctic continent. Here we present direct velocity observations from a 17 month current meter moored array deployed across the continental slope between the 1000 and the 4200 m isobaths, in the southeastern Indian Ocean near 113°E. The observed time-mean flow consists of a surface-intensified jet associated with the Antarctic Slope Front (ASF) and a broader bottom-intensified westward flow that extends out to approximately the 4000 m isobath and is strongest along the upper slope. The time-mean transport of the ASC is -29.2 Sv. Fluctuations in the transport are large, typically exceeding the mean by a factor of 2. They are mainly due to changes in the northward extent of the current over the lower slope. However, seasonal changes in the wind also drive variations in the transport of the ASF and the flow in the upper slope. Both mean and variability are largely barotropic, thus invisible to traditional geostrophic methods.

Gold deposits of the southern Piedmont

USGS Publications Warehouse

Pardee, J.T.; Park, C.F.

1948-01-01

along the southeast front of the .:Appalachian Mountains from the Great Falls of the Potomac River to east-central Alabama, in the gently sloping region known as the Piedmont. The field work was done during parts of 1934 and 1935, on funds allotted by the Public Works Administration.

Perception of object motion in three-dimensional space induced by cast shadows.

PubMed

Katsuyama, Narumi; Usui, Nobuo; Nose, Izuru; Taira, Masato

2011-01-01

Cast shadows can be salient depth cues in three-dimensional (3D) vision. Using a motion illusion in which a ball is perceived to roll in depth on the bottom or to flow in the front plane depending on the slope of the trajectory of its cast shadow, we investigated cortical mechanisms underlying 3D vision based on cast shadows using fMRI techniques. When modified versions of the original illusion, in which the slope of the shadow trajectory (shadow slope) was changed in 5 steps from the same one as the ball trajectory to the horizontal, were presented to participants, their perceived ball trajectory shifted gradually from rolling on the bottom to floating in the front plane as the change of the shadow slope. This observation suggests that the perception of the ball trajectory in this illusion is strongly affected by the motion of the cast shadow. In the fMRI study, cortical activity during observation of the movies of the illusion was investigated. We found that the bilateral posterior-occipital sulcus (POS) and right ventral precuneus showed activation related to the perception of the ball trajectory induced by the cast shadows in the illusion. Of these areas, it was suggested that the right POS may be involved in the inferring of the ball trajectory by the given spatial relation between the ball and the shadow. Our present results suggest that the posterior portion of the medial parietal cortex may be involved in 3D vision by cast shadows. Copyright © 2010 Elsevier Inc. All rights reserved.

Fine-scale variability of isopycnal salinity in the California Current System

NASA Astrophysics Data System (ADS)

Itoh, Sachihiko; Rudnick, Daniel L.

2017-09-01

This paper examines the fine-scale structure and seasonal fluctuations of the isopycnal salinity of the California Current System from 2007 to 2013 using temperature and salinity profiles obtained from a series of underwater glider surveys. The seasonal mean distributions of the spectral power of the isopycnal salinity gradient averaged over submesoscale (12-30 km) and mesoscale (30-60 km) ranges along three survey lines off Monterey Bay, Point Conception, and Dana Point were obtained from 298 transects. The mesoscale and submesoscale variance increased as coastal upwelling caused the isopycnal salinity gradient to steepen. Areas of elevated variance were clearly observed around the salinity front during the summer then spread offshore through the fall and winter. The high fine-scale variances were observed typically above 25.8 kg m-3 and decreased with depth to a minimum at around 26.3 kg m-3. The mean spectral slope of the isopycnal salinity gradient with respect to wavenumber was 0.19 ± 0.27 over the horizontal scale of 12-60 km, and 31%-35% of the spectra had significantly positive slopes. In contrast, the spectral slope over 12-30 km was mostly flat, with mean values of -0.025 ± 0.32. An increase in submesoscale variability accompanying the steepening of the spectral slope was often observed in inshore areas; e.g., off Monterey Bay in winter, where a sharp front developed between the California Current and the California Under Current, and the lower layers of the Southern California Bight, where vigorous interaction between a synoptic current and bottom topography is to be expected.

Closed-loop wavelength stabilization of an optical parametric oscillator as a front end of a high-power iodine laser chain.

PubMed

Kral, L

2007-05-01

We present a complex stabilization and control system for a commercially available optical parametric oscillator. The system is able to stabilize the oscillator's output wavelength at a narrow spectral line of atomic iodine with subpicometer precision, allowing utilization of this solid-state parametric oscillator as a front end of a high-power photodissociation laser chain formed by iodine gas amplifiers. In such setup, a precise wavelength matching between the front end and the amplifier chain is necessary due to extremely narrow spectral lines of the gaseous iodine (approximately 20 pm). The system is based on a personal computer, a heated iodine cell, and a few other low-cost components. It automatically identifies the proper peak within the iodine absorption spectrum, and then keeps the oscillator tuned to this peak with high precision and reliability. The use of the solid-state oscillator as the front end allows us to use the whole iodine laser system as a pump laser for the optical parametric chirped pulse amplification, as it enables precise time synchronization with a signal Ti:sapphire laser.

Erosional development of bedrock spur and gully topography in the Valles Marineris, Mars

NASA Technical Reports Server (NTRS)

Patton, Peter C.

1990-01-01

Gully networks separated by resistant bedrock spurs are a common erosional feature along the escarpments that border the Valles Marineris. The resistant spur topography is best developed where the base of the slope is truncated by linear scarps interpreted as fault scarps. Regional variations in slope morphology imply that spur and gully topography undergoes a systematic progressive degradation through time associated with the erosional destruction of the basal fault scarps. The comparative morphometry of the divide networks indicates that the density of the spur networks and the number of first-order unbranched spurs decreases as the basal slope break becomes more sinuous. Abstraction of the spurs occurs through regolith storage in adjacent gullies at the slope base and the most degraded slope forms are entirely buried in talus. The basal fault scarps apparently control regolith transport by allowing debris to drain from the slope. As these basal scarps decay the slope base becomes increasingly sinuous and the slopes become transport limited. Dry mass-wasting may be the most important process acting on these slopes where a continually lowered base level is required to maintain the spur topography. In contrast to the Martian slopes, range front fault escarpments in the western U.S. show no systematic trend in spur network geometry as they are eroded. These weathering limited slopes are controlled by the more efficient removal of regolith through fluvial processes which rapidly create quasi-equilibrium drainage networks.

Evolution of strain localization in variable-width three-dimensional unsaturated laboratory-scale cut slopes

USGS Publications Warehouse

Morse, Michael S.; Lu, Ning; Wayllace, Alexandra; Godt, Jonathan W.

2017-01-01

To experimentally validate a recently developed theory for predicting the stability of cut slopes under unsaturated conditions, the authors measured increasing strain localization in unsaturated slope cuts prior to abrupt failure. Cut slope width and moisture content were controlled and varied in a laboratory, and a sliding door that extended the height of the free face of the slope was lowered until the cut slope failed. A particle image velocimetry tool was used to quantify soil displacement in the x-y">x-y (horizontal) and x-z">x-z (vertical) planes, and strain was calculated from the displacement. Areas of maximum strain localization prior to failure were shown to coincide with the location of the eventual failure plane. Experimental failure heights agreed with the recently developed stability theory for unsaturated cut slopes (within 14.3% relative error) for a range of saturation and cut slope widths. A theoretical threshold for sidewall influence on cut slope failures was also proposed to quantify the relationship between normalized sidewall width and critical height. The proposed relationship was consistent with the cut slope experiment results, and is intended for consideration in future geotechnical experiment design. The experimental data of evolution of strain localization presented herein provide a physical basis from which future numerical models of strain localization can be validated.

Stability of submarine slopes in the northern South China Sea: a numerical approach

NASA Astrophysics Data System (ADS)

Zhang, Liang; Luan, Xiwu

2013-01-01

Submarine landslides occur frequently on most continental margins. They are effective mechanisms of sediment transfer but also a geological hazard to seafloor installations. In this paper, submarine slope stability is evaluated using a 2D limit equilibrium method. Considerations of slope, sediment, and triggering force on the factor of safety (FOS) were calculated in drained and undrained ( Φ=0) cases. Results show that submarine slopes are stable when the slope is <16° under static conditions and without a weak interlayer. With a weak interlayer, slopes are stable at <18° in the drained case and at <9° in the undrained case. Earthquake loading can drastically reduce the shear strength of sediment with increased pore water pressure. The slope became unstable at >13° with earthquake peak ground acceleration (PGA) of 0.5 g; whereas with a weak layer, a PGA of 0.2 g could trigger instability at slopes >10°, and >3° for PGA of 0.5 g. The northern slope of the South China Sea is geomorphologically stable under static conditions. However, because of the possibility of high PGA at the eastern margin of the South China Sea, submarine slides are likely on the Taiwan Bank slope and eastern part of the Dongsha slope. Therefore, submarine slides recognized in seismic profiles on the Taiwan Bank slope would be triggered by an earthquake, the most important factor for triggering submarine slides on the northern slope of the South China Sea. Considering the distribution of PGA, we consider the northern slope of the South China Sea to be stable, excluding the Taiwan Bank slope, which is tectonically active.

Remote Performance Monitoring of a Thermoplastic Composite Bridge at Camp Mackall, NC

DTIC Science & Technology

2011-11-01

level, flow, creep, and force for slope stability, subsidence, seismicity studies, structural restoration, or site assessment applications. • Mining ...monitors mine ventilation, slope stability, convergence, and equipment performance. • Machinery testing- provides temperature, pressure, RPM, veloci...Contact an Applications Engineer for help in deter- mining the best antenna for your application. • 21831 0 dBd, ’l.t Wave Dipole Whip Antenna

Proceedings, Seminar on Probabilistic Methods in Geotechnical Engineering

NASA Astrophysics Data System (ADS)

Hynes-Griffin, M. E.; Buege, L. L.

1983-09-01

Contents: Applications of Probabilistic Methods in Geotechnical Engineering; Probabilistic Seismic and Geotechnical Evaluation at a Dam Site; Probabilistic Slope Stability Methodology; Probability of Liquefaction in a 3-D Soil Deposit; Probabilistic Design of Flood Levees; Probabilistic and Statistical Methods for Determining Rock Mass Deformability Beneath Foundations: An Overview; Simple Statistical Methodology for Evaluating Rock Mechanics Exploration Data; New Developments in Statistical Techniques for Analyzing Rock Slope Stability.

Engineering geologic conditions at the sinkhole entrance to Logan Cave, Benton County, Arkansas

USGS Publications Warehouse

Schulz, William H.; McKenna, Jonathan P.

2004-01-01

Logan Cave, located in Benton County, Arkansas, is inhabited by several endangered and threatened species. The cave and surrounding area was designated a National Wildlife Refuge under the control of the U.S. Fish and Wildlife Service (USFWS) in 1989. Cave researchers access the cave through a steep-sided sinkhole entrance, which also is one of the two access points used by endangered bats. There is evidence of instability of one of the entrance slopes that has raised concerns that the entrance could close if slope failure was to occur. At the request of USFWS, we performed an engineering geologic investigation of the sinkhole to evaluate stability of this slope, which is comprised of soil, and other mechanisms of sediment transport into the cave entrance. The investigation included engineering geologic mapping, sampling and laboratory testing of subsurface geologic materials, and slope-stability analysis. We found that the sinkhole slope that extends into the entrance of the cave is comprised of sandy and gravelly soil to the depths explored (6.4 meters). This soil likely was deposited as alluvium within a previous, larger sinkhole. Based on properties of the alluvium, geometry of the slope, and results of finite-element slope-stability analyses, we conclude that the slope is marginally stable. Future failures of the slope probably would be relatively thin and small, thus several would be required to completely close the cave entrance. However, sediment is accumulating within the cave entrance due to foot traffic of those accessing the cave, surface-water erosion and transport, and shallow slope failures from the other sinkhole slopes. We conclude that the entrance will be closed by sediment in the future, similar to another entrance that we identified that completely closed in the past. Several measures could be taken to reduce the potential for closure of the cave entrance, including periodic sediment removal, installation of materials that reduce erosion by foot traffic and surface water, construction of a sediment-retention wall, and excavation of the soil slope. Any measures taken must be carefully planned and executed so that they have no impact on organisms within the cave.

Effect of DEM resolution on rainfall-triggered landslide modeling within a triangulated network-based model. A case study in the Luquillo Forest, Puerto Rico

NASA Astrophysics Data System (ADS)

Arnone, E.; Dialynas, Y. G.; Noto, L. V.; Bras, R. L.

2013-12-01

Catchment slope distribution is one of the topographic characteristics that significantly control rainfall-triggered landslide modeling, in both direct and indirect ways. Slope directly determines the soil volume associated with instability. Indirectly slope also affects the subsurface lateral redistribution of soil moisture across the basin, which in turn determines the water pore pressure conditions that impact slope stability. In this study, we investigate the influence of DEM resolution on slope stability and the slope stability analysis by using a distributed eco-hydrological and landslide model, the tRIBS-VEGGIE (Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator - VEGetation Generator for Interactive Evolution). The model implements a triangulated irregular network to describe the topography, and it is capable of evaluating vegetation dynamics and predicting shallow landslides triggered by rainfall. The impact of DEM resolution on the landslide prediction was studied using five TINs derived from five grid DEMs at different resolutions, i.e. 10, 20, 30, 50 and 70 m respectively. The analysis was carried out on the Mameyes Basin, located in the Luquillo Experimental Forest in Puerto Rico, where previous landslide analyses have been carried out. Results showed that the use of the irregular mesh reduced the loss of accuracy in the derived slope distribution when coarser resolutions were used. The impact of the different resolutions on soil moisture patterns was important only when the lateral redistribution was considerable, depending on hydrological properties and rainfall forcing. In some cases, the use of different DEM resolutions did not significantly affect tRIBS-VEGGIE landslide output, in terms of landslide locations, and values of slope and soil moisture at failure.

Widespread gas hydrate instability on the upper U.S. Beaufort margin

USGS Publications Warehouse

Phrampus, Benjamin J.; Hornbach, Matthew J.; Ruppel, Carolyn D.; Hart, Patrick E.

2014-01-01

The most climate-sensitive methane hydrate deposits occur on upper continental slopes at depths close to the minimum pressure and maximum temperature for gas hydrate stability. At these water depths, small perturbations in intermediate ocean water temperatures can lead to gas hydrate dissociation. The Arctic Ocean has experienced more dramatic warming than lower latitudes, but observational data have not been used to study the interplay between upper slope gas hydrates and warming ocean waters. Here we use (a) legacy seismic data that constrain upper slope gas hydrate distributions on the U.S. Beaufort Sea margin, (b) Alaskan North Slope borehole data and offshore thermal gradients determined from gas hydrate stability zone thickness to infer regional heat flow, and (c) 1088 direct measurements to characterize multidecadal intermediate ocean warming in the U.S. Beaufort Sea. Combining these data with a three-dimensional thermal model shows that the observed gas hydrate stability zone is too deep by 100 to 250 m. The disparity can be partially attributed to several processes, but the most important is the reequilibration (thinning) of gas hydrates in response to significant (~0.5°C at 2σ certainty) warming of intermediate ocean temperatures over 39 years in a depth range that brackets the upper slope extent of the gas hydrate stability zone. Even in the absence of additional ocean warming, 0.44 to 2.2 Gt of methane could be released from reequilibrating gas hydrates into the sediments underlying an area of ~5–7.5 × 103 km2 on the U.S. Beaufort Sea upper slope during the next century.

Long-term Stabilization of Disturbed Slopes Resulting from Construction Operations

DOT National Transportation Integrated Search

2018-01-01

Highway construction disturbs soil, which must be stabilized to prevent migration of soil particles into water bodies. Stabilization is enforced by law, regulation, and a permit system. Stabilization is most efficiently attained by reestablishment of...

Assessing deep-seated landslide susceptibility using 3-D groundwater and slope-stability analyses, southwestern Seattle, Washington

USGS Publications Warehouse

Brien, Dianne L.; Reid, Mark E.

2008-01-01

In Seattle, Washington, deep-seated landslides on bluffs along Puget Sound have historically caused extensive damage to land and structures. These large failures are controlled by three-dimensional (3-D) variations in strength and pore-water pressures. We assess the slope stability of part of southwestern Seattle using a 3-D limit-equilibrium analysis coupled with a 3-D groundwater flow model. Our analyses use a high-resolution digital elevation model (DEM) combined with assignment of strength and hydraulic properties based on geologic units. The hydrogeology of the Seattle area consists of a layer of permeable glacial outwash sand that overlies less permeable glacial lacustrine silty clay. Using a 3-D groundwater model, MODFLOW-2000, we simulate a water table above the less permeable units and calibrate the model to observed conditions. The simulated pore-pressure distribution is then used in a 3-D slope-stability analysis, SCOOPS, to quantify the stability of the coastal bluffs. For wet winter conditions, our analyses predict that the least stable areas are steep hillslopes above Puget Sound, where pore pressures are elevated in the outwash sand. Groundwater flow converges in coastal reentrants, resulting in elevated pore pressures and destabilization of slopes. Regions predicted to be least stable include the areas in or adjacent to three mapped historically active deep-seated landslides. The results of our 3-D analyses differ significantly from a slope map or results from one-dimensional (1-D) analyses.

Tree-root control of shallow landslides

NASA Astrophysics Data System (ADS)

Cohen, Denis; Schwarz, Massimiliano

2017-08-01

Tree roots have long been recognized to increase slope stability by reinforcing the strength of soils. Slope stability models usually include the effects of roots by adding an apparent cohesion to the soil to simulate root strength. No model includes the combined effects of root distribution heterogeneity, stress-strain behavior of root reinforcement, or root strength in compression. Recent field observations, however, indicate that shallow landslide triggering mechanisms are characterized by differential deformation that indicates localized activation of zones in tension, compression, and shear in the soil. Here we describe a new model for slope stability that specifically considers these effects. The model is a strain-step discrete element model that reproduces the self-organized redistribution of forces on a slope during rainfall-triggered shallow landslides. We use a conceptual sigmoidal-shaped hillslope with a clearing in its center to explore the effects of tree size, spacing, weak zones, maximum root-size diameter, and different root strength configurations. Simulation results indicate that tree roots can stabilize slopes that would otherwise fail without them and, in general, higher root density with higher root reinforcement results in a more stable slope. The variation in root stiffness with diameter can, in some cases, invert this relationship. Root tension provides more resistance to failure than root compression but roots with both tension and compression offer the best resistance to failure. Lateral (slope-parallel) tension can be important in cases when the magnitude of this force is comparable to the slope-perpendicular tensile force. In this case, lateral forces can bring to failure tree-covered areas with high root reinforcement. Slope failure occurs when downslope soil compression reaches the soil maximum strength. When this occurs depends on the amount of root tension upslope in both the slope-perpendicular and slope-parallel directions. Roots in tension can prevent failure by reducing soil compressive forces downslope. When root reinforcement is limited, a crack parallel to the slope forms near the top of the hillslope. Simulations with roots that fail across this crack always resulted in a landslide. Slopes that did not form a crack could either fail or remain stable, depending on root reinforcement. Tree spacing is important for the location of weak zones but tree location on the slope (with respect to where a crack opens) is as important. Finally, for the specific cases tested here, intermediate-sized roots (5 to 20 mm in diameter) appear to contribute most to root reinforcement. Our results show more complex behaviors than can be obtained with the traditional slope-uniform, apparent-cohesion approach. A full understanding of the mechanisms of shallow landslide triggering requires a complete re-evaluation of this traditional approach that cannot predict where and how forces are mobilized and distributed in roots and soils, and how these control shallow landslides shape, size, location, and timing.

Straightforward and accurate technique for post-coupler stabilization in drift tube linac structures

NASA Astrophysics Data System (ADS)

Khalvati, Mohammad Reza; Ramberger, Suitbert

2016-04-01

The axial electric field of Alvarez drift tube linacs (DTLs) is known to be susceptible to variations due to static and dynamic effects like manufacturing tolerances and beam loading. Post-couplers are used to stabilize the accelerating fields of DTLs against tuning errors. Tilt sensitivity and its slope have been introduced as measures for the stability right from the invention of post-couplers but since then the actual stabilization has mostly been done by tedious iteration. In the present article, the local tilt-sensitivity slope TSn' is established as the principal measure for stabilization instead of tilt sensitivity or some visual slope, and its significance is developed on the basis of an equivalent-circuit diagram of the DTL. Experimental and 3D simulation results are used to analyze its behavior and to define a technique for stabilization that allows finding the best post-coupler settings with just four tilt-sensitivity measurements. CERN's Linac4 DTL Tank 2 and Tank 3 have been stabilized successfully using this technique. The final tilt-sensitivity error has been reduced from ±100 %/MHz down to ±3 %/MHz for Tank 2 and down to ±1 %/MHz for Tank 3. Finally, an accurate procedure for tuning the structure using slug tuners is discussed.

Assessment of Submarine Slope Stability on the Continental Margin off SW Taiwan

NASA Astrophysics Data System (ADS)

Hsu, Huai-Houh; Dong, Jia-Jyun; Cheng, Win-Bin; Su, Chih-Chieh

2017-04-01

The abundant gas hydrate reservoirs are distributed in the southwest (SW) off Taiwan. To explore this new energy, geological methods were systematically used and mainly emphasized on the storage potential evaluation. On the other hand, the correlation between gas hydrate dissociation and submarine slope stability is also an important issue. In this study, three submarine profiles on the active and passive continental margin were selected and assessed their slope stabilities by considering two influence factors (seismic forces and number of sedimentary layers). The gravity corers obtained from these three sites (Xiaoliuqiu, Yuan-An Ridge, and Pointer Ridge) to conduct soil laboratory tests. The physical property tests and isotropically consolidated undrained (CIU) triaxial tests were carried out to establish reference properties and shear strength parameters. Before the stability analysis is performed, it is also necessary to construct the seabed profile. For each submarine profile, data from P-waves and from S-waves generated by P-S conversion on reflection from airgun shots recorded along one line of ocean bottom seismometers were used to construct 2-D velocity sections. The seabed strata could be simplified to be only one sedimentary layer or to be multilayer in accordance with the velocity structure profile. Results show the safety factors (FS) of stability analysis are obviously different in considering the number of sedimentary layers, especially for a very thin layer of sediments on a steep slope. The simplified strata condition which treated all seabed strata as only one sedimentary layer might result in the FS lower than 1 and the slope was in an unstable state. On the contrary, the FS could be higher than 10 in a multilayer condition.

Enhanced stability of steep channel beds to mass failure and debris flow initiation

NASA Astrophysics Data System (ADS)

Prancevic, J.; Lamb, M. P.; Ayoub, F.; Venditti, J. G.

2015-12-01

Debris flows dominate bedrock erosion and sediment transport in very steep mountain channels, and are often initiated from failure of channel-bed alluvium during storms. While several theoretical models exist to predict mass failures, few have been tested because observations of in-channel bed failures are extremely limited. To fill this gap in our understanding, we performed laboratory flume experiments to identify the conditions necessary to initiate bed failures in non-cohesive sediment of different sizes (D = 0.7 mm to 15 mm) on steep channel-bed slopes (S = 0.45 to 0.93) and in the presence of water flow. In beds composed of sand, failures occurred under sub-saturated conditions on steep bed slopes (S > 0.5) and under super-saturated conditions at lower slopes. In beds of gravel, however, failures occurred only under super-saturated conditions at all tested slopes, even those approaching the dry angle of repose. Consistent with theoretical models, mass failures under super-saturated conditions initiated along a failure plane approximately one grain-diameter below the bed surface, whereas the failure plane was located near the base of the bed under sub-saturated conditions. However, all experimental beds were more stable than predicted by 1-D infinite-slope stability models. In partially saturated sand, enhanced stability appears to result from suction stress. Enhanced stability in gravel may result from turbulent energy losses in pores or increased granular friction for failures that are shallow with respect to grain size. These grain-size dependent effects are not currently included in stability models for non-cohesive sediment, and they may help to explain better the timing and location of debris flow occurrence.

Submarine slope failures in the Beaufort Sea; Influence of gas hydrate decomposition

NASA Astrophysics Data System (ADS)

Grozic, J. L.; Dallimore, S.

2012-12-01

The continental shelf of the Beaufort Sea is composed of complex of marine and non-marine sequences of clay, silt, and sand. In many areas of the shelf these sediments contain occurrences of ice-bonded permafrost and associated pressure and temperature conditions that are conducive to the occurrence of methane gas hydrates. This complex environment is undergoing dramatic warming, where changes in sea level, ocean bottom temperatures, and geothermal regimes are inducing permafrost thawing and gas hydrate decomposition. Decomposition is inferred to be occurring at the base and top of the gas hydrate stability zone, which will cause sediment weakening and the generation of excess water and free gas. In such settings, the overlying permafrost cap may act as a permeability barrier, which could result in significant excess pore pressures and reduction in sediment stability. The shelf to slope transition is thought to be an area of extensive regional instability with acoustic records indicating there is upwards of 500 km of slumps and glides extending over the entire Beaufort margin. Some of these slide regions are coincident with up-dip limit of the permafrost gas hydrate stability zone. In this paper, a two dimensional model of the Beaufort shelf was constructed to examine the influence of gas hydrate decomposition on slope stability. The model relies on available data on the Beaufort sediments generated from offshore hydrocarbon exploration in the 1980s and 90s, as well as knowledge available from multidisciplinary marine research programs conducted in the outer shelf area. The slope stability model investigates the influence of marine transgression and ocean bottom warming by coupling soil deformation with hydrate dissociation during undrained conditions. By combining mechanical and thermal loading of the sediment, a more accurate indication of slope stability was obtained. The stability analysis results indicate a relatively low factor of safety for the Beaufort sediments without the presence of permafrost and gas hydrate, owing to the relative slope steepness compared to other submarine failures. Including the effects of the permafrost and gas hydrate in the sediments can result in an increase of the factor of safety under static conditions. However, modeling of the temporal effects of transgression of the Beaufort Shelf (considering change in pressure and temperature), indicates that, for a reasonable assumption of between 5-35% hydrate content, the factor of safety reduces to below unity and failure occurs.

Measuring and Modeling Root Distribution and Root Reinforcement in Forested Slopes for Slope Stability Calculations

NASA Astrophysics Data System (ADS)

Cohen, D.; Giadrossich, F.; Schwarz, M.; Vergani, C.

2016-12-01

Roots provide mechanical anchorage and reinforcement of soils on slopes. Roots also modify soil hydrological properties (soil moisture content, pore-water pressure, preferential flow paths) via subsurface flow path associated with root architecture, root density, and root-size distribution. Interactions of root-soil mechanical and hydrological processes are an important control of shallow landslide initiation during rainfall events and slope stability. Knowledge of root-distribution and root strength are key components to estimate slope stability in vegetated slopes and for the management of protection forest in steep mountainous area. We present data that show the importance of measuring root strength directly in the field and present methods for these measurements. These data indicate that the tensile force mobilized in roots depends on root elongation (a function of soil displacement), root size, and on whether roots break in tension of slip out of the soil. Measurements indicate that large lateral roots that cross tension cracks at the scarp are important for slope stability calculations owing to their large tensional resistance. These roots are often overlooked and when included, their strength is overestimated because extrapolated from measurements on small roots. We present planned field experiments that will measure directly the force held by roots of different sizes during the triggering of a shallow landslide by rainfall. These field data are then used in a model of root reinforcement based on fiber-bundle concepts that span different spacial scales, from a single root to the stand scale, and different time scales, from timber harvest to root decay. This model computes the strength of root bundles in tension and in compression and their effect on soil strength. Up-scaled to the stand the model yields the distribution of root reinforcement as a function of tree density, distance from tree, tree species and age with the objective of providing quantitative estimates of tree root reinforcement for best management practice of protection forests.

Spatial and temporal characteristics of elevated temperatures in municipal solid waste landfills.

PubMed

Jafari, Navid H; Stark, Timothy D; Thalhamer, Todd

2017-01-01

Elevated temperatures in waste containment facilities can pose health, environmental, and safety risks because they generate toxic gases, pressures, leachate, and heat. In particular, MSW landfills undergo changes in behavior that typically follow a progression of indicators, e.g., elevated temperatures, changes in gas composition, elevated gas pressures, increased leachate migration, slope movement, and unusual and rapid surface settlement. This paper presents two MSW landfill case studies that show the spatial and time-lapse movements of these indicators and identify four zones that illustrate the transition of normal MSW decomposition to the region of elevated temperatures. The spatial zones are gas front, temperature front, and smoldering front. The gas wellhead temperature and the ratio of CH 4 to CO 2 are used to delineate the boundaries between normal MSW decomposition, gas front, and temperature front. The ratio of CH 4 to CO 2 and carbon monoxide concentrations along with settlement strain rates and subsurface temperatures are used to delineate the smoldering front. In addition, downhole temperatures can be used to estimate the rate of movement of elevated temperatures, which is important for isolating and containing the elevated temperature in a timely manner. Copyright © 2016 Elsevier Ltd. All rights reserved.

Standing stability enhancement with an intelligent powered transfemoral prosthesis.

PubMed

Lawson, Brian Edward; Varol, Huseyin Atakan; Goldfarb, Michael

2011-09-01

The authors have developed a ground-adaptive standing controller for a powered knee and ankle prosthesis which is intended to enhance the standing stability of transfemoral amputees. The finite-state-based controller includes a ground-searching phase, a slope estimation phase, and a joint impedance modulation phase, which together enable the prosthesis to quickly conform to the ground and provide stabilizing assistance to the user. In order to assess the efficacy of the ground-adaptive standing controller, the control approach was implemented on a powered knee and ankle prosthesis, and experimental data were collected on an amputee subject for a variety of standing conditions. Results indicate that the controller can estimate the ground slope within ±1° over a range of ±15°, and that it can provide appropriate joint impedances for standing on slopes within this range.

Reaction fronts of the autocatalytic hydrogenase reaction

NASA Astrophysics Data System (ADS)

Gyevi-Nagy, László; Lantos, Emese; Gehér-Herczegh, Tünde; Tóth, Ágota; Bagyinka, Csaba; Horváth, Dezső

2018-04-01

We have built a model to describe the hydrogenase catalyzed, autocatalytic, reversible hydrogen oxidation reaction where one of the enzyme forms is the autocatalyst. The model not only reproduces the experimentally observed front properties, but also explains the found hydrogen ion dependence. Furthermore, by linear stability analysis, two different front types are found in good agreement with the experiments.

Curved fronts in the Belousov-Zhabotinskii reaction-diffusion systems in R2

NASA Astrophysics Data System (ADS)

Niu, Hong-Tao; Wang, Zhi-Cheng; Bu, Zhen-Hui

2018-05-01

In this paper we consider a diffusion system with the Belousov-Zhabotinskii (BZ for short) chemical reaction. Following Brazhnik and Tyson [4] and Pérez-Muñuzuri et al. [45], who predicted V-shaped fronts theoretically and discovered V-shaped fronts by experiments respectively, we give a rigorous mathematical proof of their results. We establish the existence of V-shaped traveling fronts in R2 by constructing a proper supersolution and a subsolution. Furthermore, we establish the stability of the V-shaped front in R2.

Temporal pattern of soil matric suction in the unsaturated soil slope under different forest cover

NASA Astrophysics Data System (ADS)

Hayati, Elyas; Abdi, Ehsan; Mohseni Saravi, Mohsen; Nieber, John; Majnounian, Baris; Chirico, Giovanni

2017-04-01

In the vadose zone, usually, soils experience high matric suction during dry periods which results in a significant additional soil strength component (i.e., apparent cohesion) and thus plays a crucial role in the stability of unsaturated soil slopes. But, in the wet periods, when rain-water infiltrates into the soil, the matric suction of the soil dissipates partially or completely. It is a well-understood concept that vegetation can modify the hillslope hydrology and subsequent stability conditions by increasing soil matric suction through both interception of rainfall and depletion of soil water content via transpiration. Anthropogenic pressures, particularly clear-cutting and deforestation, affect many hydro-geomorphological processes including catchment and hillslope hydrology and stability. However, quantifying the changes in soil hydrologic conditions and the resulted stability of slopes due to these degrading activities remained an unresolved problem. To address this gap, a continuous measurement of soil water dynamics has been conducted at two adjacent hillslopes (one forested hillslope and one degraded hillslope) using PR2/6 profile probe for a 9-month period of time to demonstrate the forest cover-specific influence on the hillslope hydrology and stability during different seasons. The results have been then presented in terms of estimated soil matric suction to facilitate analyzing the resulted stability states due to the changes in soil water balance with time in the two studied hillslopes. The data were tested to check whether there are any differences between the forested and degraded hillslopes in terms of soil matric suction and augmented soil cohesion during different seasons. Finally, the response of soil hydrologic condition and the resulted slope stability for the 9-month period were analyzed and discussed for the different hillslopes.

Design and Application of a Field Sensing System for Ground Anchors in Slopes

PubMed Central

Choi, Se Woon; Lee, Jihoon; Kim, Jong Moon; Park, Hyo Seon

2013-01-01

In a ground anchor system, cables or tendons connected to a bearing plate are used for stabilization of slopes. Then, the stability of a slope is dependent on maintaining the tension levels in the cables. So far, no research on a strain-based field sensing system for ground anchors has been reported. Therefore, in this study, a practical monitoring system for long-term sensing of tension levels in tendons for anchor-reinforced slopes is proposed. The system for anchor-reinforced slopes is composed of: (1) load cells based on vibrating wire strain gauges (VWSGs), (2) wireless sensor nodes which receive and process the signals from load cells and then transmit the result to a master node through local area communication, (3) master nodes which transmit the data sent from sensor nodes to the server through mobile communication, and (4) a server located at the base station. The system was applied to field sensing of ground anchors in the 62 m-long and 26 m-high slope at the side of the highway. Based on the long-term monitoring, the safety of the anchor-reinforced slope can be secured by the timely applications of re-tensioning processes in tendons. PMID:23507820

Dynamic stabilization of Rayleigh-Taylor instability in an ablation front

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piriz, A. R.; Di Lucchio, L.; Rodriguez Prieto, G.

2011-01-15

Dynamic stabilization of Rayleigh-Taylor instability in an ablation front is studied by considering a modulation in the acceleration that consists of sequences of Dirac deltas. This allows obtaining explicit analytical expressions for the instability growth rate as well as for the boundaries of the stability region. As a general rule, it is found that it is possible to stabilize all wave numbers above a certain minimum value k{sub m}, but the requirements in the modulation amplitude and frequency become more exigent with smaller k{sub m}. The essential role of compressibility is phenomenologically addressed in order to find the constraint itmore » imposes on the stability region. The results for some different wave forms of the acceleration modulation are also presented.« less

The modelling influence of water content to mechanical parameter of soil in analysis of slope stability

NASA Astrophysics Data System (ADS)

Gusman, M.; Nazki, A.; Putra, R. R.

2018-04-01

One of the parameters in slope stability analysis is the shear strength of the soil. Changes in soil shear strength characteristics lead to a decrease in safety factors on the slopes. This study aims to see the effect of increased moisture content on soil mechanical parameters. The case study study was conducted on the slopes of Sitinjau Lauik Kota Padang. The research method was done by laboratory analysis and simple liniear regression analysis and multiple. Based on the test soil results show that the increase in soil water content causes a decrease in cohesion values and internal shear angle. The relationship of moisture content to cohesion is described in equation Y = 55.713-0,6X with R2 = 0.842. While the relationship of water content to shear angle in soil is described in the equation Y = 38.878-0.258X with R2 = 0.915. From several simulations of soil water level improvement, calculation of safety factor (SF) of slope. The calculation results show that the increase of groundwater content is very significant affect the safety factor (SF) slope. SF slope values are in safe condition when moisture content is 50% and when it reaches maximum water content 73.74% slope safety factor value potentially for landslide.

Structural Stabilities of β-Ti Alloys Studied Using a New Mo Equivalent Derived from [ β/( α + β)] Phase-Boundary Slopes

NASA Astrophysics Data System (ADS)

Wang, Qing; Dong, Chuang; Liaw, Peter K.

2015-08-01

Structural stabilities of β-Ti alloys are generally investigated by an empirical Mo equivalent, which quantifies the stability contribution of each alloying element, M, in comparison to that of the major β-Ti stabilizer, Mo. In the present work, a new Mo equivalent (Moeq)Q is proposed, which uses the slopes of the boundary lines between the β and ( α + β) phase zones in binary Ti-M phase diagrams. This (Moeq)Q reflects a simple fact that the β-Ti stability is enhanced, when the β phase zone is enlarged by a β-Ti stabilizer. It is expressed as (Moeq)Q = 1.0 Mo + 0.74 V + 1.01 W + 0.23 Nb + 0.30 Ta + 1.23 Fe + 1.10 Cr + 1.09 Cu + 1.67 Ni + 1.81 Co + 1.42 Mn + 0.38 Sn + 0.34 Zr + 0.99 Si - 0.57 Al (at. pct), where the equivalent coefficient of each element is the slope ratio of the [ β/( α + β)] boundary line of the binary Ti-M phase diagram to that of the Ti-Mo. This (Moeq)Q is shown to reliably characterize the critical stability limit of multi-component β-Ti alloys with low Young's moduli, where the critical lower limit for β stabilization is (Moeq)Q = 6.25 at. pct or 11.8 wt pct Mo.

Implications of flume slope on discharge estimates from 0.762-meter H flumes used in edge-of-field monitoring

USGS Publications Warehouse

Komiskey, Matthew J.; Stuntebeck, Todd D.; Cox, Amanda L.; Frame, Dennis R.

2013-01-01

The effects of longitudinal slope on the estimation of discharge in a 0.762-meter (m) (depth at flume entrance) H flume were tested under controlled conditions with slopes from −8 to +8 percent and discharges from 1.2 to 323 liters per second. Compared to the stage-discharge rating for a longitudinal flume slope of zero, computed discharges were negatively biased (maximum −31 percent) when the flume was sloped downward from the front (entrance) to the back (exit), and positively biased (maximum 44 percent) when the flume was sloped upward. Biases increased with greater flume slopes and with lower discharges. A linear empirical relation was developed to compute a corrected reference stage for a 0.762-m H flume using measured stage and flume slope. The reference stage was then used to determine a corrected discharge from the stage-discharge rating. A dimensionally homogeneous correction equation also was developed, which could theoretically be used for all standard H-flume sizes. Use of the corrected discharge computation method for a sloped H flume was determined to have errors ranging from −2.2 to 4.6 percent compared to the H-flume measured discharge at a level position. These results emphasize the importance of the measurement of and the correction for flume slope during an edge-of-field study if the most accurate discharge estimates are desired.

The role of Soil Water Retention Curve in slope stability analysis in unsaturated and heterogeneous soils.

NASA Astrophysics Data System (ADS)

Antinoro, Chiara; Arnone, Elisa; Noto, Leonardo V.

2015-04-01

The mechanisms of rainwater infiltration causing slope instability had been analyzed and reviewed in many scientific works. Rainwater infiltration into unsaturated soil increases the degree of saturation, hence affecting the shear strength properties and thus the probability of slope failure. It has been widely proved that the shear strength properties change with the soil water suction in unsaturated soils; therefore, the accuracy to predict the relationship between soil water content and soil water suction, parameterized by the soil-water characteristic curve, has significant effects on the slope stability analysis. The aim of this study is to investigate how the characterization of SWRC of differently structured unsaturated soils affects the slope stability on a simple infinite slope. In particular, the unimodal and bimodal distributions of the soil pore size were compared. Samples of 40 soils, highly different in terms of structure and texture, were collected and used to calibrate two bimodal SWRCs, i.e. Ross and Smettem (1993) and Dexter et al., (2008). The traditional unimodal van Genuchten (1980) model was also applied for comparison. Slope stability analysis was conducted in terms of Factor of Safety (FS) by applying the infinite slope model for unsaturated soils. In the used formulation, the contribution of the suction effect is tuned by a parameter 'chi' in a rate proportional to the saturation conditions. Different parameterizations of this term were also compared and analyzed. Results indicated that all three SWRC models showed good overall performance in fitting the sperimental SWRCs. Both the RS and DE models described adequately the water retention data for soils with a bimodal behavior confirmed from the analysis of pore size distribution, but the best performance was obtained by DE model confirmed. In terms of FS, the tree models showed very similar results as soil moisture approached to the saturated condition; however, within the residual zone, the DE model denoted an anomalous behavior depending on the used formulation for the 'chi' parameter, with decreasing FS as soil moisture decreases.

Pressure-Dependent Friction on Granular Slopes Close to Avalanche.

PubMed

Crassous, Jérôme; Humeau, Antoine; Boury, Samuel; Casas, Jérôme

2017-08-04

We investigate the sliding of objects on an inclined granular surface close to the avalanche threshold. Our experiments show that the stability is driven by the surface deformations. Heavy objects generate footprintlike deformations which stabilize the objects on the slopes. Light objects do not disturb the sandy surfaces and are also stable. For intermediate weights, the deformations of the surface generate a sliding of the objects. The solid friction coefficient does not follow the Amontons-Coulomb laws, but is found minimal for a characteristic pressure. Applications to the locomotion of devices and animals on sandy slopes as a function of their mass are proposed.

Pressure-Dependent Friction on Granular Slopes Close to Avalanche

NASA Astrophysics Data System (ADS)

Crassous, Jérôme; Humeau, Antoine; Boury, Samuel; Casas, Jérôme

2017-08-01

We investigate the sliding of objects on an inclined granular surface close to the avalanche threshold. Our experiments show that the stability is driven by the surface deformations. Heavy objects generate footprintlike deformations which stabilize the objects on the slopes. Light objects do not disturb the sandy surfaces and are also stable. For intermediate weights, the deformations of the surface generate a sliding of the objects. The solid friction coefficient does not follow the Amontons-Coulomb laws, but is found minimal for a characteristic pressure. Applications to the locomotion of devices and animals on sandy slopes as a function of their mass are proposed.

Reinforcing mechanism of anchors in slopes: a numerical comparison of results of LEM and FEM

NASA Astrophysics Data System (ADS)

Cai, Fei; Ugai, Keizo

2003-06-01

This paper reports the limitation of the conventional Bishop's simplified method to calculate the safety factor of slopes stabilized with anchors, and proposes a new approach to considering the reinforcing effect of anchors on the safety factor. The reinforcing effect of anchors can be explained using an additional shearing resistance on the slip surface. A three-dimensional shear strength reduction finite element method (SSRFEM), where soil-anchor interactions were simulated by three-dimensional zero-thickness elasto-plastic interface elements, was used to calculate the safety factor of slopes stabilized with anchors to verify the reinforcing mechanism of anchors. The results of SSRFEM were compared with those of the conventional and proposed approaches for Bishop's simplified method for various orientations, positions, and spacings of anchors, and shear strengths of soil-grouted body interfaces. For the safety factor, the proposed approach compared better with SSRFEM than the conventional approach. The additional shearing resistance can explain the influence of the orientation, position, and spacing of anchors, and the shear strength of soil-grouted body interfaces on the safety factor of slopes stabilized with anchors.

Aspect-dependent soil saturation and insight into debris-flow initiation during extreme rainfall in the Colorado Front Range

USGS Publications Warehouse

Ebel, Brian A.; Rengers, Francis K.; Tucker, Gregory E.

2015-01-01

Hydrologic processes during extreme rainfall events are poorly characterized because of the rarity of measurements. Improved understanding of hydrologic controls on natural hazards is needed because of the potential for substantial risk during extreme precipitation events. We present field measurements of the degree of soil saturation and estimates of available soil-water storage during the September 2013 Colorado extreme rainfall event at burned (wildfire in 2010) and unburned hillslopes with north- and south-facing slope aspects. Soil saturation was more strongly correlated with slope aspect than with recent fire history; south-facing hillslopes became fully saturated while north-facing hillslopes did not. Our results suggest multiple explanations for why aspect-dependent hydrologic controls favor saturation development on south-facing slopes, causing reductions in effective stress and triggering of slope failures during extreme rainfall. Aspect-dependent hydrologic behavior may result from (1) a larger gravel and stone fraction, and hence lower soil-water storage capacity, on south-facing slopes, and (2) lower weathered-bedrock permeability on south-facing slopes, because of lower tree density and associated deep roots penetrating bedrock as well as less intense weathering, inhibiting soil drainage.

GIS-based seismic shaking slope vulnerability map of Sicily (Central Mediterranean)

NASA Astrophysics Data System (ADS)

Nigro, Fabrizio; Arisco, Giuseppe; Perricone, Marcella; Renda, Pietro; Favara, Rocco

2010-05-01

Earthquakes often represent very dangerouses natural events in terms of human life and economic losses and their damage effects are amplified by the synchronous occurrence of seismically-induced ground-shaking failures in wide regions around the seismogenic source. In fact, the shaking associated with big earthquakes triggers extensive landsliding, sometimes at distances of more than 100 km from the epicenter. The active tectonics and the geomorphic/morphodinamic pattern of the regions affected by earthquakes contribute to the slopes instability tendency. In fact, earthquake-induced groun-motion loading determines inertial forces activation within slopes that, combined with the intrinsic pre-existing static forces, reduces the slope stability towards its failure. Basically, under zero-shear stress reversals conditions, a catastrophic failure will take place if the earthquake-induced shear displacement exceeds the critical level of undrained shear strength to a value equal to the gravitational shear stress. However, seismic stability analyses carried out for various infinite slopes by using the existing Newmark-like methods reveal that estimated permanent displacements smaller than the critical value should also be regarded as dangerous for the post-earthquake slope safety, in terms of human activities use. Earthquake-induced (often high-speed) landslides are among the most destructive phenomena related to slopes failure during earthquakes. In fact, damage from earthquake-induced landslides (and other ground-failures), sometimes exceeds the buildings/infrastructures damage directly related to ground-shaking for fault breaking. For this matter, several hearthquakes-related slope failures methods have been developed, for the evaluation of the combined hazard types represented by seismically ground-motion landslides. The methodologies of analysis of the engineering seismic risk related to the slopes instability processes is often achieved through the evaluation of the permanent displacement potentially induced by an seismic scenario. Such methodologies found on the consideration that the conditions of seismic stability and the post-seismic functionality of engineering structures are tightly related to the entity of the permanent deformations that an earthquake can induce. Regarding the existing simplified procedures among slope stability models, Newmark's model is often used to derive indications about slope instabilities due to earthquakes. In this way, we have evaluated the seismically-induced landslides hazard in Sicily (Central Mediterranean) using the Newmark-like model. In order to determine the map distribution of the seismic ground-acceleration from an earthquake scenario, the attenuation-law of Sabetta & Pugliese has been used, analyzing some seismic recordings occurred in Italy. Also, by evaluating permanent displacements, the correlation of Ambraseys & Menu has been assumed. The seismic shaking slope vulnerability map of Sicily has been carried out using GIS application, also considering max seismic ground-acceleration peak distribution (in terms of exceedance probability for fixed time), slope acclivity, cohesion/angle of internal friction of outcropping rocks, allowing the zoning of the unstable slopes under seismic forces.

On the Stability of the Detonation Wave Front in the High Explosive Liquid Mixture Tetranitromethane/Nitrobenzene

NASA Astrophysics Data System (ADS)

Fedorov, A. V.; Mikhaylov, A. L.; Men'Shikh, A. V.; Nazarov, D. V.; Finyushin, S. A.; Davydov, V. A.

2010-10-01

We performed experimental studies on the stability of the detonation wave front in mixtures of the liquids tetranitromethane (TNM) and nitrobenzene (NB). Tetranitromethane is an oxygen-rich explosive and nitrobenzene was used as a solvent or dilutant. (NB is not classed as an explosive but as an explosive would be oxygen poor and fuel rich.) The primary diagnostic was a laser velocimetry method with high temporal resolution. Data obtained were compared with the detonation parameters of the TNM/NB mixtures. In previous experimental work [1,2] it was shown that the detonation wave front in liquid explosives may be either smooth or rough. Rough detonation fronts have been reported in nitromethane, as well as nitromethane mixed with a solvent. Smooth detonation fronts have been reported in tetranitromethane. Previously, we conducted studies on the structure of the detonation wave front in liquid explosives containing tetranitromethane [3-5]. Smooth, stable fronts were recorded in pure tetranitromethane and in a 46/54 mixture of tetranitromethane and nitromethane. A pulsating, unstable detonation wave front was recorded in a 74/26 mixture of tetranitromethane and nitrobenzene. The goal of the present work is to extend our research on the structure of the detonation wave front in mixtures of tetranitromethane diluted with less energetic nitrobenzene. To this end, the following TNM/NB mixtures were studied: 95/5, 90/10, 85/15, 80/20, 74/26, and 50/50.

The Influence of Upward Groundwater between Joints on the Stability and the Behavior of Dip Slope Failures

NASA Astrophysics Data System (ADS)

Weng, C. H.; Lin, M. L.; Hsieh, P. C.

2016-12-01

In recent years, landslides have attracted much attention in the engineering field in Taiwan. As previous studies, landslides are induced by earthquakes, rainfall, and groundwater. That groundwater flows into upper layer through vertical joints, upward groundwater, erodes the slope and reduces its stability. Nevertheless, in the literature, the impact of upward groundwater to the location of sliding surface and the behaviors of dip slope failure has not be investigated. In this study, physical model tests with water flow inclinometers are used to investigate the kinematics of dip slope failures under various conditions and to identify the failure modes of specimens (Fig. 1). Besides, the mechanics of one landslide case owing to upward groundwater is studied by numerical simulation. In the physical tests, the effects of upward groundwater on slope stability are investigated with different angles of inclinometers, different position of joints on specimens and different locations of upward seepage. The test results suggest that the upward water pressure becomes lower when the number of joints increases. As the water pressure increases to 3.8 times the weight of one block of the specimen, the block will slide. Another, when the specimen is covered by one granular content layer (see Fig. 2), the failure surface tends to develop at the granular content layer, and its kinematics is similar to debris slide; when the clay seam is below of the specimen, the translational slide occurs along the bottom of the blocks. Moreover, one dip slope case, Taiwan's National Highway No. 3 landslide event, are studied by numerical simulation. According to the results, some points are concluded: water pressure makes tension cracks on the top of the vertical joints on weathered sandstones; with anchor attenuation, the sandstone moves downslope, which makes the shear strain of the slope toe region increases (see Fig. 3). If friction angle of the slope decreases, the slide surface occurs along the weak surface, and it develops to the toe of the slope.

Rock Slope Design Criteria

DOT National Transportation Integrated Search

2010-06-01

Based on the stratigraphy and the type of slope stability problems, the flat lying, Paleozoic age, sedimentary : rocks of Ohio were divided into three design units: 1) competent rock design unit consisting of sandstones, limestones, : and siltstones ...

Slope efficiency over 30% single-frequency ytterbium-doped fiber laser based on Sagnac loop mirror filter.

PubMed

Yin, Mojuan; Huang, Shenghong; Lu, Baole; Chen, Haowei; Ren, Zhaoyu; Bai, Jintao

2013-09-20

A high-slope-efficiency single-frequency (SF) ytterbium-doped fiber laser, based on a Sagnac loop mirror filter (LMF), was demonstrated. It combined a simple linear cavity with a Sagnac LMF that acted as a narrow-bandwidth filter to select the longitudinal modes. And we introduced a polarization controller to restrain the spatial hole burning effect in the linear cavity. The system could operate at a stable SF oscillating at 1064 nm with the obtained maximum output power of 32 mW. The slope efficiency was found to be primarily dependent on the reflectivity of the fiber Bragg grating. The slope efficiency of multi-longitudinal modes was higher than 45%, and the highest slope efficiency of the single longitudinal mode we achieved was 33.8%. The power stability and spectrum stability were <2% and <0.1%, respectively, and the signal-to-noise ratio measured was around 60 dB.

Seismically induced rock slope failures resulting from topographic amplification of strong ground motions: The case of Pacoima Canyon, California

USGS Publications Warehouse

Sepulveda, S.A.; Murphy, W.; Jibson, R.W.; Petley, D.N.

2005-01-01

The 1994 Northridge earthquake (Mw = 6.7) triggered extensive rock slope failures in Pacoima Canyon, immediately north of Los Angeles, California. Pacoima Canyon is a narrow and steep canyon incised in gneissic and granitic rocks. Peak accelerations of nearly 1.6 g were recorded at a ridge that forms the left abutment of Pacoima Dam; peak accelerations at the bottom of the canyon were less than 0.5 g, suggesting the occurrence of topographic amplification. Topographic effects have been previously suggested to explain similarly high ground motions at the site during the 1971 (Mw = 6.7) San Fernando earthquake. Furthermore, high landslide concentrations observed in the area have been attributed to unusually strong ground motions rather than higher susceptibility to sliding compared with nearby zones. We conducted field investigations and slope stability back-analyses to confirm the impact of topographic amplification on the triggering of landslides during the 1994 earthquake. Our results suggest that the observed extensive rock sliding and falling would have not been possible under unamplified seismic conditions, which would have generated a significantly lower number of areas affected by landslides. In contrast, modelling slope stability using amplified ground shaking predicts slope failure distributions matching what occurred in 1994. This observation confirms a significant role for topographic amplification on the triggering of landslides at the site, and emphasises the need to select carefully the inputs for seismic slope stability analyses. ?? 2005 Elsevier B.V. All rights reserved.

Landslides geotechnical analysis. Qualitative assessment by valuation factors

NASA Astrophysics Data System (ADS)

Cuanalo Oscar, Sc D.; Oliva Aldo, Sc D.; Polanco Gabriel, M. E.

2012-04-01

In general, a landslide can cause a disaster when it is combined a number of factors such as an extreme event related to a geological phenomenon, vulnerable elements exposed in a specific geographic area, and the probability of loss and damage evaluated in terms of lives and economic assets, in a certain period of time. This paper presents the qualitative evaluation of slope stability through of Valuation Factors, obtained from the characterization of the determinants and triggers factors that influence the instability; for the first the morphology and topography, geology, soil mechanics, hydrogeology and vegetation to the second, the rain, earthquakes, erosion and scour, human activity, and ultimately dependent factors of the stability analysis, and its influence ranges which greatly facilitate the selection of construction processes best suited to improve the behavior of a slope or hillside. The Valuation Factors are a set of parameters for assessing the influence of conditioning and triggering factors that influence the stability of slopes and hillsides. The characteristics of each factor must be properly categorized to involve its effect on behavior; a way to do this is by assigning a weighted value range indicating its effect on the stability of a slope. It is proposed to use Valuation Factors with weighted values between 0 and 1 (arbitrarily selected but common sense and logic), the first corresponds to no or minimal effect on stability (no effect or very little influence) and the second, the greatest impact on it (has a significant influence). The meddle effects are evaluated with intermediate values.

Determination of wave speed and wave separation in the arteries.

PubMed

Khir, A W; O'Brien, A; Gibbs, J S; Parker, K H

2001-09-01

Considering waves in the arteries as infinitesimal wave fronts rather than sinusoidal wavetrains, the change in pressure across the wave front, dP, is related to the change in velocity, dU, that it induces by the "water hammer" equation, dP=+/-rhocdU, where rho is the density of blood and c is the local wave speed. When only unidirectional waves are present, this relationship corresponds to a straight line when P is plotted against U with slope rhoc. When both forward and backward waves are present, the PU-loop is no longer linear. Measurements in latex tubes and systemic and pulmonary arteries exhibit a linear range during early systole and this provides a way of determining the local wave speed from the slope of the linear portion of the loop. Once the wave speed is known, it is also possible to separate the measured P and U into their forward and backward components. In cases where reflected waves are prominent, this separation of waves can help clarify the pattern of waves in the arteries throughout the cardiac cycle.

Slope streaks on Mars: A new “wet” mechanism

NASA Astrophysics Data System (ADS)

Kreslavsky, Mikhail A.; Head, James W.

2009-06-01

Slope steaks are one of the most intriguing modern phenomena observed on Mars. They have been mostly interpreted as some specific type of granular flow. We propose another mechanism for slope streak formation on Mars. It involves natural seasonal formation of a modest amount of highly concentrated chloride brines within a seasonal thermal skin, and runaway propagation of percolation fronts. Given the current state of knowledge of temperature regimes and the composition and structure of the surface layer in the slope streak regions, this mechanism is consistent with the observational constraints; it requires an assumption that a significant part of the observed chlorine to be in form of calcium and ferric chloride, and a small part of the observed hydrogen to be in form of water ice. This "wet" mechanism has a number of appealing advantages in comparison to the widely accepted "dry" granular flow mechanism. Potential tests for the "wet" mechanism include better modeling of the temperature regime and observations of the seasonality of streak formation.

A model for predicting embankment slope failures in clay-rich soils; A Louisiana example

NASA Astrophysics Data System (ADS)

Burns, S. F.

2015-12-01

A model for predicting embankment slope failures in clay-rich soils; A Louisiana example It is well known that smectite-rich soils significantly reduce the stability of slopes. The question is how much smectite in the soil causes slope failures. A study of over 100 sites in north and south Louisiana, USA, compared slopes that failed during a major El Nino winter (heavy rainfall) in 1982-1983 to similar slopes that did not fail. Soils in the slopes were tested for per cent clay, liquid limits, plasticity indices and semi-quantitative clay mineralogy. Slopes with the High Risk for failure (85-90% chance of failure in 8-15 years after construction) contained soils with a liquid limit > 54%, a plasticity index over 29%, and clay contents > 47%. Slopes with an Intermediate Risk (55-50% chance of failure in 8-15 years) contained soils with a liquid limit between 36-54%, plasticity index between 16-19%, and clay content between 32-47%. Slopes with a Low Risk chance of failure (< 5% chance of failure in 8-15 years after construction) contained soils with a liquid limit < 36%, a plasticity index < 16%, and a clay content < 32%. These data show that if one is constructing embankments and one wants to prevent slope failure of the 3:1 slopes, check the above soil characteristics before construction. If the soils fall into the Low Risk classification, construct the embankment normally. If the soils fall into the High Risk classification, one will need to use lime stabilization or heat treatments to prevent failures. Soils in the Intermediate Risk class will have to be evaluated on a case by case basis.

Effects of variable regolith depth, hydraulic properties, and rainfall on debris-flow initiation during the September 2013 northern Colorado Front Range rainstorm

NASA Astrophysics Data System (ADS)

Baum, R. L.; Coe, J. A.; Kean, J. W.; Jones, E. S.; Godt, J.

2015-12-01

Heavy rainfall during 9 - 13 September 2013 induced about 1100 debris flows in the foothills and mountains of the northern Colorado Front Range. Weathered bedrock was partially exposed in the basal surfaces of many of the shallow source areas at depths ranging from 0.2 to 5 m. Typical values of saturated hydraulic conductivity of soils and regolith units mapped in the source areas range from about 10-4 - 10-6 m/s, with a median value of 2.8 x 10-5 m/s based on number of source areas in each map unit. Rainfall intensities varied spatially and temporally, from 0 to 2.5 x 10-5 m/s (90 mm/hour), with two periods of relatively heavy rainfall on September 12 - 13. The distribution of debris flows appears to correlate with total storm rainfall, and reported times of greatest landslide activity coincide with times of heaviest rainfall. Process-based models of rainfall infiltration and slope stability (TRIGRS) representing the observed ranges of regolith depth, hydraulic conductivity, and rainfall intensity, provide additional insights about the timing and distribution of debris flows from this storm. For example, small debris flows from shallower source areas (<2 m) occurred late on September 11 and in the early morning of September 12, whereas large debris flows from deeper (3 - 5 m) source areas in the western part of the affected area occurred late on September 12. Timing of these flows can be understood in terms of the time required for pore pressure rise depending on regolith depth and rainfall intensity. The variable hydraulic properties combined with variable regolith depth and slope angles account for much of the observed range in timing in areas of similar rainfall intensity and duration. Modeling indicates that the greatest and most rapid pore pressure rise likely occurred in areas of highest rainfall intensity and amount. This is consistent with the largest numbers of debris flows occurring on steep canyon walls in areas of high total storm rainfall.

Evaluating a slope-stability model for shallow rain-induced landslides using gage and satellite data

USGS Publications Warehouse

Yatheendradas, S.; Kirschbaum, D.; Baum, Rex L.; Godt, Jonathan W.

2014-01-01

Improving prediction of landslide early warning systems requires accurate estimation of the conditions that trigger slope failures. This study tested a slope-stability model for shallow rainfall-induced landslides by utilizing rainfall information from gauge and satellite records. We used the TRIGRS model (Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis) for simulating the evolution of the factor of safety due to rainfall infiltration. Using a spatial subset of a well-characterized digital landscape from an earlier study, we considered shallow failure on a slope adjoining an urban transportation roadway near the Seattle area in Washington, USA.We ran the TRIGRS model using high-quality rain gage and satellite-based rainfall data from the Tropical Rainfall Measuring Mission (TRMM). Preliminary results with parameterized soil depth values suggest that the steeper slope values in this spatial domain have factor of safety values that are extremely close to the failure limit within an extremely narrow range of values, providing multiple false alarms. When the soil depths were constrained using a back analysis procedure to ensure that slopes were stable under initial condtions, the model accurately predicted the timing and location of the landslide observation without false alarms over time for gage rain data. The TRMM satellite rainfall data did not show adequately retreived rainfall peak magnitudes and accumulation over the study period, and as a result failed to predict the landslide event. These preliminary results indicate that more accurate and higher-resolution rain data (e.g., the upcoming Global Precipitation Measurement (GPM) mission) are required to provide accurate and reliable landslide predictions in ungaged basins.

Constraints on mechanisms for the growth of gully alcoves in Gasa crater, Mars, from two-dimensional stability assessments of rock slopes

USGS Publications Warehouse

Okubo, C.H.; Tornabene, L.L.; Lanza, N.L.

2011-01-01

The value of slope stability analyses for gaining insight into the geologic conditions that would facilitate the growth of gully alcoves on Mars is demonstrated in Gasa crater. Two-dimensional limit equilibrium methods are used in conjunction with high-resolution topography derived from stereo High Resolution Imaging Science Experiment (HiRISE) imagery. These analyses reveal three conditions that may produce observed alcove morphologies through slope failure: (1) a ca >10m thick surface layer that is either saturated with H2O ground ice or contains no groundwater/ice at all, above a zone of melting H2O ice or groundwater and under dynamic loading (i.e., seismicity), (2) a 1-10m thick surface layer that is saturated with either melting H2O ice or groundwater and under dynamic loading, or (3) a >100m thick surface layer that is saturated with either melting H2O ice or groundwater and under static loading. This finding of three plausible scenarios for slope failure demonstrates how the triggering mechanisms and characteristics of future alcove growth would be affected by prevailing environmental conditions. HiRISE images also reveal normal faults and other fractures tangential to the crowns of some gully alcoves that are interpreted to be the result of slope instability, which may facilitate future slope movement. Stability analyses show that the most failure-prone slopes in this area are found in alcoves that are adjacent to crown fractures. Accordingly, crown fractures appear to be a useful indicator of those alcoves that should be monitored for future landslide activity. ?? 2010.

Spatial and temporal analyses for multiscale monitoring of landslides: Examples from Northern Ireland

NASA Astrophysics Data System (ADS)

Bell, Andrew; McKinley, Jennifer; Hughes, David

2013-04-01

Landslides in the form of debris flows, large scale rotational features and composite mudflows impact transport corridors cutting off local communities and in some instances result in loss of life. This study presents landslide monitoring methods used for predicting and characterising landslide activity along transport corridors. A variety of approaches are discussed: desk based risk assessment of slopes using Geographical Information Systems (GIS); Aerial LiDAR surveys and Terrestrial LiDAR monitoring and field instrumentation of selected sites. A GIS based case study is discussed which provides risk assessment for the potential of slope stability issues. Layers incorporated within the system include Digital Elevation Model (DEM), slope, aspect, solid and drift geology and groundwater conditions. Additional datasets include consequence of failure. These are combined within a risk model, presented as likelihoods of failure. This integrated spatial approach for slope risk assessment provides the user with a preliminary risk assessment of sites. An innovative "Flexviewer" web-based server interface allows users to view data without needing advanced GIS techniques to gather information about selected areas. On a macro landscape scale, Aerial LiDAR (ALS) surveys are used for the characterisation of landslides from the surrounding terrain. DEMs are generated along with terrain derivatives: slope, curvature and various measures of terrain roughness. Spatial analysis of terrain morphological parameters allow characterisation of slope stability issues and are used to predict areas of potential failure or recently failure terrain. On a local scale ground monitoring approaches are employed for the monitoring of changes in selected slopes using ALS and risk assessment approaches. Results are shown from on-going bimonthly Terrestrial LiDAR (TLS) monitoring of the slope within a site specific geodectically referenced network. This has allowed a classification of changes in the slopes with DEMs of difference showing areas of recent movement, erosion and deposition. In addition, changes in the structure of the slope characterised by DEM of difference and morphological parameters in the form of roughness, slope and curvature measures are progressively linked to failures indicated from temporal DEM monitoring. Preliminary results are presented for a case site at Straidkilly Point, Glenarm, Co. Antrim, Northern Ireland, illustrating multiple approaches to the spatial and temporal monitoring of landslides. These indicate how spatial morphological approaches and risk assessment frameworks coupled with TLS monitoring and field instrumentation enable characterisation and prediction of potential areas of slope stability issues. On site weather instrumentation and piezometers document changes in pore water pressures resulting in site-specific information with geotechnical observations parameterised within the temporal LiDAR monitoring. This provides a multifaceted approach to the characterisation and analysis of slope stability issues. The presented methodology of multiscale datasets and surveying approaches utilising spatial parameters and risk index mapping enables a more comprehensive and effective prediction of landslides resulting in effective characterisation and remediation strategies.

Evans functions and bifurcations of nonlinear waves of some nonlinear reaction diffusion equations

NASA Astrophysics Data System (ADS)

Zhang, Linghai

2017-10-01

The main purposes of this paper are to accomplish the existence, stability, instability and bifurcation of the nonlinear waves of the nonlinear system of reaction diffusion equations ut =uxx + α [ βH (u - θ) - u ] - w, wt = ε (u - γw) and to establish the existence, stability, instability and bifurcation of the nonlinear waves of the nonlinear scalar reaction diffusion equation ut =uxx + α [ βH (u - θ) - u ], under different conditions on the model constants. To establish the bifurcation for the system, we will study the existence and instability of a standing pulse solution if 0 < 2 (1 + αγ) θ < αβγ; the existence and stability of two standing wave fronts if 2 (1 + αγ) θ = αβγ and γ2 ε > 1; the existence and instability of two standing wave fronts if 2 (1 + αγ) θ = αβγ and 0 <γ2 ε < 1; the existence and instability of an upside down standing pulse solution if 0 < (1 + αγ) θ < αβγ < 2 (1 + αγ) θ. To establish the bifurcation for the scalar equation, we will study the existence and stability of a traveling wave front as well as the existence and instability of a standing pulse solution if 0 < 2 θ < β; the existence and stability of two standing wave fronts if 2 θ = β; the existence and stability of a traveling wave front as well as the existence and instability of an upside down standing pulse solution if 0 < θ < β < 2 θ. By the way, we will also study the existence and stability of a traveling wave back of the nonlinear scalar reaction diffusion equation ut =uxx + α [ βH (u - θ) - u ] -w0, where w0 = α (β - 2 θ) > 0 is a positive constant, if 0 < 2 θ < β. To achieve the main goals, we will make complete use of the special structures of the model equations and we will construct Evans functions and apply them to study the eigenvalues and eigenfunctions of several eigenvalue problems associated with several linear differential operators. It turns out that a complex number λ0 is an eigenvalue of the linear differential operator, if and only if λ0 is a zero of the Evans function. The stability, instability and bifurcations of the nonlinear waves follow from the zeros of the Evans functions. A very important motivation to study the existence, stability, instability and bifurcations of the nonlinear waves is to study the existence and stability/instability of infinitely many fast/slow multiple traveling pulse solutions of the nonlinear system of reaction diffusion equations. The existence and stability of infinitely many fast multiple traveling pulse solutions are of great interests in mathematical neuroscience.

Permeability test and slope stability analysis of municipal solid waste in Jiangcungou Landfill, Shaanxi, China.

PubMed

Yang, Rong; Xu, Zengguang; Chai, Junrui; Qin, Yuan; Li, Yanlong

2016-07-01

With the rapid increase of city waste, landfills have become a major method to deals with municipal solid waste. Thus, the safety of landfills has become a valuable research topic. In this paper, Jiangcungou Landfill, located in Shaanxi, China, was investigated and its slope stability was analyzed. Laboratory tests were used to obtain permeability coefficients of municipal solid waste. Based on the results, the distribution of leachate and stability in the landfill was computed and analyzed. These results showed: the range of permeability coefficient was from 1.0 × 10(-7) cm sec(-1) to 6.0 × 10(-3) cm sec(-1) on basis of laboratory test and some parameters of similar landfills. Owing to the existence of intermediate cover layers in the landfill, the perched water level appeared in the landfill with heavy rain. Moreover, the waste was filled with leachate in the top layer, and the range of leachate level was from 2 m to 5 m in depth under the waste surface in other layers. The closer it gets to the surface of landfill, the higher the perched water level of leachate. It is indicated that the minimum safety factors were 1.516 and 0.958 for winter and summer, respectively. Additionally, the slope failure may occur in summer. The research of seepage and stability in landfills may provide a less costly way to reduce accidents. Landslides often occur in the Jiangcungou Landfill because of the high leachate level. Some measures should be implemented to reduce the leachate level. This paper investigated seepage and slope stability of landfills by numerical methods. These results may provide the basis for increasing stability of landfills.

Aggregate Stability and Erodibility of Purple Soil on Sloping Farmland as affected by different Soil Thickness

NASA Astrophysics Data System (ADS)

Huang, Xinjun; Zhang, Qingwen; Chen, Shanghong; Dong, Yuequn; Xiao, Meijia; Hamed, Lamy Mamdoh Mohamed

2017-04-01

Soil thickness is basic limiting condition for purple soil, not only due to its effect on crop production, but also its effect on soil structure. Steady-state of soil thickness will be achieved over time, as result the soil aggregate which the key factor of soil erodibility can be enhanced as well. However, the effect of soil thickness on aggregates stability and the characteristics of soil erodibility in sloping land have not yet fully understood.A field survey was conducted in hilly area of Sichuan region located in southeast China to study the relationship between soil aggregate stability and soil erodibility on sloping farmland under different four thickness (100cm, 80cm, 60cm, 30cm) of purple soil. Based on two different sieving methods (Dry and Wet sieving), we analyzed soil aggregate stability and its effect on soil erodibility within depth of 0-30cm soil layers. The results indicated that: Water stable aggregate on sloping farmland was ranged between 37.9% to 58.6%, where it increased with increasing the soil thickness. Moreover, fractal dimension calculated from dry-sieving and wet-sieving was 2.06-2.49 and 2.70-2.85 respectively, where it decreased with decreasing the soil thickness. The overall soil erodibility was 0.05-1.00 and a negative significant correlation was found between soil aggregate stability and erodibility(P<0.01). Moreover, farmland with thick soil profile tended to be high in soil erodibility within the top soil layer (0-30cm). The results reveal that soil thickness can affect soil aggregate stability as well as erodibility. As soil thickness increased, the top soil became more stable and less erodible. Keywords：purple soil; soil thickness; soil aggregate；soil erodibility

Role of gas hydrates in slope failure on frontal ridge of northern Cascadia margin

NASA Astrophysics Data System (ADS)

Yelisetti, Subbarao; Spence, George D.; Riedel, Michael

2014-10-01

Several slope failures are observed near the deformation front on the frontal ridges of the northern Cascadia accretionary margin off Vancouver Island. The cause for these events is not clear, although several lines of evidence indicate a possible connection between the occurrence of gas hydrate and submarine landslide features. The presence of gas hydrate is indicated by a prominent bottom-simulating reflector (BSR), at a depth of ˜265-275 m beneath the seafloor (mbsf), as interpreted from vertical-incidence and wide-angle seismic data beneath the ridge crests of the frontal ridges. For one slide, informally called Slipstream Slide, the velocity structure inferred from tomography analyses shows anomalous high velocities values of about 2.0 km s-1 at shallow depths of 100 mbsf. The estimated depth of the glide plane (100 ± 10 m) closely matches the depth of these shallow high velocities. In contrast, at a frontal ridge slide just to the northwest (informally called Orca Slide), the glide plane occurs at the same depth as the current BSR. Our new results indicate that the glide plane of the Slipstream slope failure is associated with the contrast between sediments strengthened by gas hydrate and overlying sediments where little or no hydrate is present. In contrast, the glide plane of Orca Slide is between sediment strengthened by hydrate underlain by sediments beneath the gas hydrate stability zone, possibly containing free gas. Additionally, a set of margin perpendicular normal faults are imaged from seafloor down to BSR depth at both frontal ridges. As inferred from the multibeam bathymetry, the estimated volume of the material lost during the slope failure at Slipstream Slide is about 0.33 km3, and ˜0.24 km3 of this volume is present as debris material on the ocean basin floor. The 20 per cent difference is likely due to more widely distributed fine sediments not easily detectable as bathymetric anomalies. These volume estimates on the Cascadia margin are approaching the mass failure volume for other slides that have generated large tsunamis-for example 1-3 km3 for a 1998 Papua New Guinea slide.

Progress on applications of high temperature superconducting microwave filters

NASA Astrophysics Data System (ADS)

Chunguang, Li; Xu, Wang; Jia, Wang; Liang, Sun; Yusheng, He

2017-07-01

In the past two decades, various kinds of high performance high temperature superconducting (HTS) filters have been constructed and the HTS filters and their front-end subsystems have been successfully applied in many fields. The HTS filters with small insertion loss, narrow bandwidth, flat in-band group delay, deep out-of-band rejection, and steep skirt slope are reviewed. Novel HTS filter design technologies, including those in high power handling filters, multiband filters and frequency tunable filters, are reviewed, as well as the all-HTS integrated front-end receivers. The successful applications to various civilian fields, such as mobile communication, radar, deep space detection, and satellite technology, are also reviewed.

Transient response in granular quasi-two-dimensional bounded heap flow.

PubMed

Xiao, Hongyi; Ottino, Julio M; Lueptow, Richard M; Umbanhowar, Paul B

2017-10-01

We study the transition between steady flows of noncohesive granular materials in quasi-two-dimensional bounded heaps by suddenly changing the feed rate. In both experiments and simulations, the primary feature of the transition is a wedge of flowing particles that propagates downstream over the rising free surface with a wedge front velocity inversely proportional to the square root of time. An additional longer duration transient process continues after the wedge front reaches the downstream wall. The entire transition is well modeled as a moving boundary problem with a diffusionlike equation derived from local mass balance and a local relation between the flux and the surface slope.

Road embankment and slope stabilization.

DOT National Transportation Integrated Search

2010-07-31

This report and the accompanying software are part of efforts to improve the characterization and analysis of pilestabilized : slopes using one or two rows of driven piles. A combination of the limit equilibrium analysis and strain : wedge (SW) model...

Rock Slope Design Criteria : Executive Summary Report

DOT National Transportation Integrated Search

2010-06-01

Based on the stratigraphy and the type of slope stability problems, the flat lying, Paleozoic age, sedimentary rocks of Ohio were divided into three design units: 1) competent rock design unit consisting of sandstones, limestones, and siltstones that...

Experimental test of theory for the stability of partially saturated vertical cut slopes

USGS Publications Warehouse

Morse, Michael M.; Lu, N.; Wayllace, Alexandra; Godt, Jonathan W.; Take, W.A.

2014-01-01

This paper extends Culmann's vertical-cut analysis to unsaturated soils. To test the extended theory, unsaturated sand was compacted to a uniform porosity and moisture content in a laboratory apparatus. A sliding door that extended the height of the free face of the slope was lowered until the vertical cut failed. Digital images of the slope cross section and upper surface were acquired concurrently. A recently developed particle image velocimetry (PIV) tool was used to quantify soil displacement. The PIV analysis showed strain localization at varying distances from the sliding door prior to failure. The areas of localized strain were coincident with the location of the slope crest after failure. Shear-strength and soil-water-characteristic parameters of the sand were independently tested for use in extended analyses of the vertical-cut stability and of the failure plane angle. Experimental failure heights were within 22.3% of the heights predicted using the extended theory.

Influence of the Geometry Alteration of the Landslide Slope on its Stability: A Case Study in the Carnian Alps (Italy)

NASA Astrophysics Data System (ADS)

Zabuski, Lesław; Bossi, Giulia; Marcato, Gianluca

2017-12-01

The paper presents the principles of the slope reprofiling and proves the effectiveness of this stabilization measure. The case study of two adjacent landslides in the National Road 52 "Carnica" in the Tagliamento River valley, the Carnian Alps (46°23'49″N, 12°42'51″E) are the example allowing for illustration of this approach. The phenomena have been studied for more than a decade, making it possible to carry out a detailed geological and geomorphological reconstruction. That was done on the basis of a large amount of monitoring data collected during that period. Since the landslides are threatening an important road, countermeasure works to ameliorate the stability conditions of the slides need to be designed. The paper focuses on the creation of a numerical model consistent with monitoring data and capable of reconstructing the dynamics of both landslides. Two cross-sections, one for each landslide, were selected for the analysis. The geometry of the slip surface was determined on the basis of control points, such as slip surface readings from inclinometers, and geomorphological evidence for the contour. The FLAC2D code was used to evaluate the current stability of these landslides and to determine the effectiveness of changing the slope geometry by removing material from the upper part of the slope and putting it to the lowest part as reinforcement.

An investigation of landslides in Bukit Aman and Puncak Setiawangsa, Kuala Lumpur, Malaysia

NASA Astrophysics Data System (ADS)

Ismail, Nurul Iffah; Yaacob, Wan Zuhairi Wan

2018-04-01

Landslides occur almost every year in Malaysia, especially during rainy season. Massive landslides can cause extensive damage and fatalities. An investigation has been carried out on two (2) landslides in Kuala Lumpur at two (2) different geological formations known as Kenny Hill and Hawthornden Schist. Kuala Lumpur, located at the southwest part of Peninsular Malaysia is covered by flat and hilly terrain. In the tropical region such as Kuala Lumpur most of the landslides were associated with residual soils. The purposes of the present study are therefore to examine the engineering properties of residual soil as input for slope stability analysis, to develop models of slope stability of failed soil slopes at Bukit Aman and adjacent slopes of Puncak Setiawangsa, to identify the causal factor contributing to the landslides and to recommend suitable rectification works. A well-established computer program `SLOPE/W' developed by GEOSLOPE was deployed by adopting a limit equilibrium method (LEM) to determine the factor of safety (FOS) for the slopes. Based on the results, the FOS were less than 1.5 signify the inherently unstable slopes. In regard to the investigation, the failure at Bukit Aman can be classified as a shallow failure while in the case of the adjacent slopes of Puncak Setiawangsa, a catastrophic landslide could happen if the slopes strengthening structures, "pre-stress ground anchors" lose their holding capacity. The landslides in these study areas may be attributed to a combination of several factors such as steep slope, lack of drainage system, erosion and lack of ground anchors maintenance.

Zonation of Landslide-Prone Using Microseismic Method and Slope Analysis in Margoyoso, Magelang

NASA Astrophysics Data System (ADS)

Aditya, Muchamad Reza; Fauqi Romadlon, Arriqo’; Agra Medika, Reymon; Alfontius, Yosua; Delva Jannet, Zukhruf; Hartantyo, Eddy

2018-04-01

Margoyoso Village, Salaman Sub-district, Magelang Regency, Central Java is one of the villages that were included in landslide prone areas. The steep slopes and land use in this village were quite apprehensive. There were fractures with 5 cm in width and a length of 50 m. Moreover, these fractures appeared in the home residents. Although the local government has established a disaster response organization, this village is still not getting adequate information about the landslide prone areas. Based on the description before, we conducted research with geophysical methods and geotechnical analysis to minimize the danger of landslides. The geophysical method used in this research was microseismic method and geotechnical analysis. The microseismic measurement and slope stability analysis at Margoyoso village was a step in analysing the landslide-prone zone boundary. The results of this research indicated that landslide potential areas had a low peak ground acceleration values with a range from 36 gal to 46 gal. Measurement of slope stability indicated that a slope angle values between 55°-78° are a potential landslide slope because the soil in this village has very loose properties so it is very easy to move.

Identification, characteristics and seasonal evolution of surface thermal fronts in the Argentinean Continental Shelf

NASA Astrophysics Data System (ADS)

Rivas, Andrés L.; Pisoni, Juan Pablo

2010-01-01

The location and seasonal variability of surface thermal fronts along the Argentinean Continental Shelf (38-55°S) were studied using 18 years (1985-2002) of sea surface temperature (SST) satellite data. Monthly SST gradients were calculated and a threshold was used to identify frontal pixels. Frontal areas were classified into 4 zones according to their seasonal evolution and the main forcings leading to the front's formation were identified for each group. The shelf break front was easily detected due to the large number of frontal pixels in the region and its high mean gradient values. This front showed a marked annual cycle and relatively constant position associated to the bottom slope; it tended to be located where the core of the Malvinas current is closest to the shelf. Tidal fronts also showed a strong annual cycle, being detected in three well-defined regions during spring and summer. Along the coasts of Tierra del Fuego and Santa Cruz, the combination of strong tidal mixing and low-salinity coastal plumes led to semi-annual seasonal cycles of frontal intensity and persistence that showed a relative maximum in winter. A similar behavior (semi-annual) was found at the coast off the Buenos Aires Province. There, the coastal dilution and the bathymetric gradient generated near-coastal fronts that changed direction seasonally. In the northern mid-shelf, a front linked to the intrusion of warm waters formed in the San Matías Gulf was identified during the winter.

Modern Instrumentation of a Historical Landslide to Understand Dynamic Processes Governing Slope Movement in a Hostile Environment.

NASA Astrophysics Data System (ADS)

Johnson, K. A.

2017-12-01

The Milepost 6.2 Landslide on Many Glacier Road in Glacier National Park, Montana, has been moving since construction of the roadway in the early 1900's. Movement of the slide has a direct impact on Park operations and requires regrading and reconstruction of the road on a nearly annual basis. Prior attempts to stabilize the slope were not effective. Despite the history of this slide, very little quality data was available to delineate the depth and shape of the slide or the groundwater pressures that influence slope stability due to only seasonal data collection and a hostile winter environment. Landslide dynamics are further complicated where the toe of the slide becomes submerged seasonally by Lake Sherburne. In addition, due to irrigation use the lake levels fluctuate rapidly with seasonal rise and drops commonly greater than 30 feet in elevation. Five Shape Accelerometer Array inclinometers (SAAs) were installed to depths between 60 and 200 feet, along with 10 vibrating wire piezometers, one tipping bucket rain gauge, and onsite data acquisition system with a real-time satellite communication link enabling year-round data collection. Measurements of groundwater pressures and slide dynamics were used to develop a well constrained 2-D dynamic model of slide movement. Movement is controlled by clayey zones in glacial till deposits that mantle the valley slopes, along with water pressures from groundwater in the slope and fluctuating lake levels at the toe of the slope. The SAAs document slide plane locations and rates of slide movement as it changes through the year in response to the dynamic hydrologic setting. SAAs document sliding of over 3 feet and continue to operate and generate additional data. The data collected enabled the design of an extensive horizontal drain system to lower the groundwater pressures and stabilize the slope. Continuous year-round monitoring allowed comparison of slope movement in response to changes in lake elevation and precipitation events.

Extreme Events in the tropics - Hurricane Manuel and La Pintada Landslide

NASA Astrophysics Data System (ADS)

Ramirez-Herrera, M. T.; Gaidzik, K.

2016-12-01

Extreme events in regions of humid-warm tropical climate are repeatedly causing loss of life and economic devastation. Deadly landslides are commonly triggered by extreme storms. Many of them originate on mountain slopes along river systems in areas often populated, increasing the risk to human settlements, theirs activities, and the local envrionment. Frequently hit by hurricanes and tropical cyclones the mountainous areas of Guerrero in southern Mexico are particularly prone to landslide hazard. On 16 September 2013 a huge landslide caused 71 fatalities and destroyed a large part of the La Pintada village. The landslide initiated after extreme rainfall caused by Hurricane Manuel. We performed a post-landslide field survey, applied remote sensing techniques using LIDAR DEM and images, digital models derived from Structure from Motion (SfM), satellite images, orthophotomaps, eyewitness accounts, geotechnical laboratory tests of slope material, and slope stability analysis to examine physical characteristics and processes that influenced the failure of La Pintada landslide. Our results indicate that anomalous precipitation producing oversaturation of soil was the direct factor that initiated the deep-sited La Pintada landslide, in an area where big landslides have occurred in the past. We hypothesized that climate change has contributed to the short recurrence period of extreme meteorological events that trigger great landslides in this tropical area. The lack of high and dense vegetation on La Pintada slope, resulting in increased soil erosion, acted as a preparatory causal factor for landsliding, making the slope more prone to mass wasting. It is likely that human activity (including deforestation activities) also contributed to the decrease of slope stability by cutting the toe of the slope to build houses. Seismic activity, even if did not contribute directly to the initiation of the La Pintada landslide, might have promoted the decrease in slope stability in this tectonically active region.

Stability and instability of axisymmetric droplets in thermocapillary-driven thin films

NASA Astrophysics Data System (ADS)

Nicolaou, Zachary G.

2018-03-01

The stability of compactly supported, axisymmetric droplet states is considered for driven thin viscous films evolving on two-dimensional surfaces. Stability is assessed using Lyapunov energy methods afforded by the Cahn-Hilliard variational form of the governing equation. For general driving forces, a criterion on the gradient of profiles at the boundary of their support (their contact slope) is shown to be a necessary condition for stability. Additional necessary and sufficient conditions for stability are established for a specific driving force corresponding to a thermocapillary-driven film. It is found that only droplets of sufficiently short height that satisfy the contact slope criterion are stable. This destabilization of droplets with increasing height is characterized as a saddle-node bifurcation between a branch of tall, unstable droplets and a branch of short, stable droplets.

Dealing with unquantifiable uncertainties in landslide modelling for urban risk reduction in developing countries

NASA Astrophysics Data System (ADS)

Almeida, Susana; Holcombe, Liz; Pianosi, Francesca; Wagener, Thorsten

2016-04-01

Landslides have many negative economic and societal impacts, including the potential for significant loss of life and damage to infrastructure. Slope stability assessment can be used to guide decisions about the management of landslide risk, but its usefulness can be challenged by high levels of uncertainty in predicting landslide occurrence. Prediction uncertainty may be associated with the choice of model that is used to assess slope stability, the quality of the available input data, or a lack of knowledge of how future climatic and socio-economic changes may affect future landslide risk. While some of these uncertainties can be characterised by relatively well-defined probability distributions, for other uncertainties, such as those linked to climate change, no probability distribution is available to characterise them. This latter type of uncertainty, often referred to as deep uncertainty, means that robust policies need to be developed that are expected to perform acceptably well over a wide range of future conditions. In our study the impact of deep uncertainty on slope stability predictions is assessed in a quantitative and structured manner using Global Sensitivity Analysis (GSA) and the Combined Hydrology and Stability Model (CHASM). In particular, we use several GSA methods including the Method of Morris, Regional Sensitivity Analysis and Classification and Regression Trees (CART), as well as advanced visualization tools, to assess the combination of conditions that may lead to slope failure. Our example application is a slope in the Caribbean, an area that is naturally susceptible to landslides due to a combination of high rainfall rates during the hurricane season, steep slopes, and highly weathered residual soils. Rapid unplanned urbanisation and changing climate may further exacerbate landslide risk in the future. Our example shows how we can gain useful information in the presence of deep uncertainty by combining physically based models with GSA in a scenario discovery framework.

Seasonal Effects on the Relationships Between Soil Water Content, Pore Water Pressure and Shear Strength and Their Implications for Slope Stability

NASA Astrophysics Data System (ADS)

Hughes, P. N.

2015-12-01

A soil's shear resistance is mainly dependent upon the magnitude of effective stress. For small to medium height slopes (up to 10m) in clay soils the total stress acting along potential failure planes will be low, therefore the magnitude of effective stress (and hence soil shear strength) will be dominated by the pore-water pressure. The stability of slopes on this scale through periods of increased precipitation is improved by the generation of negative pore pressures (soil suctions) during preceding, warmer, drier periods. These negative pore water pressures increase the effective stress within the soil and cause a corresponding increase in shearing resistance. The relationships between soil water content and pore water pressure (soil water retention curves) are known to be hysteretic, but for the purposes of the majority of slope stability assessments in partially saturated clay soils, these are assumed to be consistent with time. Similarly, the relationship between shear strength and water content is assumed to be consistent over time. This research presents a laboratory study in which specimens of compacted Glacial Till (typical of engineered slopes within the UK) were subjected to repeated cycles of wetting and drying to simulate seasonal cycles. At predetermined water contents, measurements of soil suction were made using tensiometer and dewpoint potentiometer methods. The undrained shear strength of the specimens was then measured using triaxial strength testing equipment. Results indicate that repeated wetting and drying cycles caused a change in the soil water retention behaviour. A reduction in undrained shear strength at corresponding water contents along the wetting and drying paths was also observed. The mechanism for the change in the relationship is believed to be a deterioration in the soil physical structure due to shrink/swell induced micro-cracking. The non-stationarity of these relationships has implications for slope stability assessment.

Deciphering the record of short-term base-level changes in Gilbert-type deltas

NASA Astrophysics Data System (ADS)

Gobo, Katarina; Ghinassi, Massimiliano; Nemec, Wojciech

2016-04-01

The geometrical relationship of fluvial topset to subaqueous foreset in a Gilbert-type delta may be 'sigmoidal' (transitional) or 'oblique' (erosional), which is generally attributed - respectively - to a rise or fall of the delta shoreline's time-distance trajectory and considered to reflect base-level changes. However, since every episode of a base-level fall forces the fluvial distributary system to cut down, the delta-brink sigmoidal signature of a preceding base-level rise tends to be removed. The geometrical record of short-term base-level changes in a Gilbert-type delta thus tends to be obliterated by fluvial erosion. The issue addressed in this presentation is whether the fully-preserved foreset to bottomset deposits may serve as a key for deciphering the base-level history of an ancient Gilbert-type delta. Outcrop studies of Plio-Pleistocene Gilbert-type deltas at the southern margin of the Corinth Rift, Greece, reveal a genetic relationship between the delta-brink morphodynamics controlled by base level behaviour and the processes of subaqueous sediment dispersal on the delta slope and in its foot zone. The component facies are deposits of turbidity currents (whether slope-derived brief surges or longer-duration hyperpycnal flows), cohesionless debrisflows and loose-gravel debrisfalls. The development of sigmoidal delta-brink architecture appears to be accompanied by deposition of a debrite-dominated facies assemblage (DFA) of delta foreset beds, thought to form when the aggrading delta front tends to store sediment and undergoes discrete gravitational collapses. Development of oblique delta-brink architecture is accompanied by deposition of a turbidite-dominated facies assemblage (TFA) of foreset beds, which is thought to form when the delta-front accommodation decreases and the sediment carried by hyperpycnal effluent largely bypasses the front. The alternation of TFA and DFA facies assemblages in delta foreset is thus attributed to changes in delta-front accommodation driven by short-term base-level changes, with some accompanying inevitable 'noise' in the facies record due to the system autogenic variability and regional climatic fluctuations. Comparison of delta coeval foreset and toeset/bottomset deposits in a delta shows further a reverse pattern of reciprocal changes in facies assemblages, with the TFA assemblage of foreset deposits passing downdip into a DFA assemblage of delta-foot deposits, and the DFA assemblage of foreset deposits passing downdip into a TFA assemblage. This reverse reciprocal alternation of TFA and DFA facies assemblages is attributed to the delta-slope own morphodynamics. When the delta slope is dominated by deposition of debrisflows, only the most diluted turbulent flows and chute bypassing turbidity currents are reaching the delta-foot zone. When the delta slope is dominated by turbiditic sedimentation, larger chutes and gullies form - triggering and conveying debrisflows to the foot zone. These case studies as a whole shed a new light on the varying pattern of subaqueous sediment dispersal processes in an evolving Gilbert-type deltaic system and point to an the attractive possibility of the recognition of a 'hidden' record of base-level changes on the basis of detailed facies analysis.

A stability theorem for energy-balance climate models

NASA Technical Reports Server (NTRS)

Cahalan, R. F.; North, G. R.

1979-01-01

The paper treats the stability of steady-state solutions of some simple, latitude-dependent, energy-balance climate models. For north-south symmetric solutions of models with an ice-cap-type albedo feedback, and for the sum of horizontal transport and infrared radiation given by a linear operator, it is possible to prove a 'slope stability' theorem, i.e., if the local slope of the steady-state iceline latitude versus solar constant curve is positive (negative) the steady-state solution is stable (unstable). Certain rather weak restrictions on the albedo function and on the heat transport are required for the proof, and their physical basis is discussed.

The preparation of new perfluoro ether fluids exhibiting excellent thermal-oxidative stabilities

NASA Technical Reports Server (NTRS)

Jones, William R., Jr.; Bierschenk, Thomas R.; Juhlke, Timothy J.; Kawa, Hajima; Lagow, Richard J.

1988-01-01

A series of low molecular weight perfluoroalkyl ethers (PFAEs) were synthesized by direct fluorination. Viscosity-temperature properties and oxidation stabilities were determined. Viscosity-temperature correlations indicated that increases in branching and increases in the size of the branching substituent caused a deterioration in viscometric properties (i.e., an increase in ASTM slope). In addition, increasing the ratio of carbon to oxygen in these compounds also increased the ASTM slope. Preliminary oxidation stability measurements indicated that highly branched PFAE fluids (i.e., those containing quaternary carbons) may be less stable than either those containing a single trifluoromethyl pendant group or those containing no branching at all.

The preparation of new perfluoroether fluids exhibiting excellent thermal-oxidative stabilities

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Bierschenk, T. R.; Juhlke, T. J.; Kawa, H.; Lagow, R. J.

1986-01-01

A series of low molecular weight perfluoroalkylethers (PFAE) were synthesized by direct fluorination. Viscosity-temperature properties and oxidation stabilities were determined. Viscosity-temperature correlations indicated that increases in branching and increases in the size of the branching substituent caused a deterioration in viscometric properties (i.e., an increase in ASTM slope). In addition, increasing the ratio of carbon to oxygen in these compounds also increased the ASTM slope. Preliminary oxidation stability tests indicated that highly branched PFAE fluids. (i.e., those containing quaternary carbons) may be less stable than either those containing a single trifluoromethyl pendant group or those containing no branching at all.

A coupled distributed hydrological-stability analysis on a terraced slope of Valtellina (northern Italy)

NASA Astrophysics Data System (ADS)

Camera, C.; Apuani, T.; Masetti, M.

2013-02-01

The aim of this work was to understand and reproduce the hydrological dynamics of a slope, which was terraced using dry-stone retaining walls and its response to these processes in terms of stability at the slope scale. The slope studied is located in Valtellina (northern Italy), near the village of Tresenda, and in the last 30 yr has experienced several soil slip/debris flow events. In 1983 alone, such events caused the death of 18 people. Direct observation of the events of 1983 enabled the principal triggering cause of these events to be recognized in the formation of an overpressure at the base of a dry-stone wall, which caused its failure. To perform the analyses it is necessary to include the presence of dry-stone walls, considering the importance they have in influencing hydrological and geotechnical processes at the slope scale. This requires a very high resolution DEM (1 m × 1 m because the walls are from 0.60 m to 1.0 m wide) that has been appositely derived. A hydrogeological raster-based model, which takes into account both the unsaturated and saturated flux components, was applied. This was able to identify preferential infiltration zones and was rather precise in the prediction of maximum groundwater levels, providing valid input for the distributed stability analysis. Results of the hydrogeological model were used for the successive stability analysis. Sections of terrace were identified from the downslope base of a retaining wall to the top of the next downslope retaining wall. Within each section a global method of equilibrium was applied to determine its safety factor. The stability model showed a general tendency to overestimate the amount of unstable areas. An investigation of the causes of this unexpected behavior was, therefore, also performed in order to progressively improve the reliability of the model.

Multi-Objective Sliding Mode Control on Vehicle Cornering Stability with Variable Gear Ratio Actuator-Based Active Front Steering Systems.

PubMed

Ma, Xinbo; Wong, Pak Kin; Zhao, Jing; Xie, Zhengchao

2016-12-28

Active front steering (AFS) is an emerging technology to improve the vehicle cornering stability by introducing an additional small steering angle to the driver's input. This paper proposes an AFS system with a variable gear ratio steering (VGRS) actuator which is controlled by using the sliding mode control (SMC) strategy to improve the cornering stability of vehicles. In the design of an AFS system, different sensors are considered to measure the vehicle state, and the mechanism of the AFS system is also modelled in detail. Moreover, in order to improve the cornering stability of vehicles, two dependent objectives, namely sideslip angle and yaw rate, are considered together in the design of SMC strategy. By evaluating the cornering performance, Sine with Dwell and accident avoidance tests are conducted, and the simulation results indicate that the proposed SMC strategy is capable of improving the cornering stability of vehicles in practice.

Corrosion evaluation of mechanically stabilized earth walls.

DOT National Transportation Integrated Search

2005-09-01

Numerous reinforced walls and slopes have been built over the past four decades in Kentucky, the United States, as well as worldwide. Tensile elements used in constructing low-cost reinforcing walls and slopes consist of metal polymer strips or grids...

Production and evaluation of sugar cane fiber geotextiles : report 2 : field testing.

DOT National Transportation Integrated Search

1997-03-01

Prior research involved the production and laboratory testing of sugar cane fiber geotextiles for soil erosion control. Comparative preliminary studies were conducted on test slopes to determine slope stability, in horticulture plots to determine gra...

Probabilistic analysis algorithm for UA slope software program.

DOT National Transportation Integrated Search

2013-12-01

A reliability-based computational algorithm for using a single row and equally spaced drilled shafts to : stabilize an unstable slope has been developed in this research. The Monte-Carlo simulation (MCS) : technique was used in the previously develop...

Cold Front Driven Flows Through Multiple Inlets of Lake Pontchartrain Estuary

NASA Astrophysics Data System (ADS)

Huang, Wei; Li, Chunyan

2017-11-01

With in situ observations using acoustic Doppler current profilers (ADCPs) and numerical experiments using the Finite Volume Coastal Ocean Model (FVCOM), this study investigates atmospheric cold front induced exchange of water between Lake Pontchartrain Estuary and coastal ocean through multiple inlets. Results show that the subtidal hydrodynamic response is highly correlated with meteorological parameters. Northerly and westerly winds tend to push water out of Lake Pontchartrain, while south and east winds tend to produce currents flowing into it. For most cases, the subtidal water level is inversely correlated with the east wind, with the correlation coefficient being ˜0.8. The most important finding of this work is that, contrary to intuition, the cold front induced remote wind effect has the greatest contribution to the overall water level variation, while the local wind stress determines the surface slope inside the estuary. It is found that wind driven flow is roughly quasi steady state: the surface slope in the north-south direction is determined by the north-south wind stress, explaining ˜83% of the variability but less so in the east-west direction (˜43%). In other words, the north-south local wind stress determines the water level gradient in that direction in the estuary while the overall water level change is pretty much controlled by the open boundary which is the "remote wind effect," a regional response that can be illustrated only by a numerical model for a much larger area encompassing the estuary.

A lidar, GIS and basic spatial statistic application for the study of ravine and palaeo-ravine evolution in the upper Vipava valley, SW Slovenia

NASA Astrophysics Data System (ADS)

Popit, Tomislav; Rožič, Boštjan; Šmuc, Andrej; Kokalj, Žiga; Verbovšek, Timotej; Košir, Adrijan

2014-01-01

The analysis of high resolution airborne lidar topography represents an essential tool for the geomorphological investigation of surface features. Here we present a detailed lidar-based geomorphological analysis of the ravines cut into the slopes of the upper Vipava valley, NW Slovenia. The NE slopes are defined by an Oligocene thrust-front of Mesozoic carbonates overthrusted on Tertiary flysch and covered by numerous fan-shaped Quaternary gravity flows, deposited in palaeo-ravines cut into the flysch base rock. In contrast, the opposite SW slopes are composed solely of flysch. The large dextral-slip Vipava fault extending in the NW-SE direction is present in the central part of the valley. Our research revealed that although the ravines on both slopes of the Vipava valley are lithologically and tectonically controlled, significant statistical differences in their directions exist. Thus, ravines on opposite slopes are not solely related to the Vipava fault system deformation, but instead reflect a more complex tectonic setting. We believe that the ravines are controlled by second-order faults and fault zones that connect the Vipava fault with adjacent faults. On the SW slopes, these include connecting faults between the Vipava and the southwestern Raša fault, with the ravines on the NE slopes formed in fault zones connecting the Vipava and northeastern Predjama faults.

103. Catalog HHistory 1, C.C.C., 58 Landscaping, Negative No. 870 ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

103. Catalog H-History 1, C.C.C., 58 Landscaping, Negative No. 870 10 ca. 1936 PROPAGATION AND PLANTING. ROOTED PLANTS TRANSPLANTED FROM HOT BEDS TO CANS TO SHADED BEDS IN PREPARATION FOR PLANTING ON ROAD SLOPES. NURSERY AT NORTH ENTRANCE. - Skyline Drive, From Front Royal, VA to Rockfish Gap, VA , Luray, Page County, VA

Stability of infinite slopes under transient partially saturated seepage conditions

NASA Astrophysics Data System (ADS)

Godt, Jonathan W.; ŞEner-Kaya, BaşAk; Lu, Ning; Baum, Rex L.

2012-05-01

Prediction of the location and timing of rainfall-induced shallow landslides is desired by organizations responsible for hazard management and warnings. However, hydrologic and mechanical processes in the vadose zone complicate such predictions. Infiltrating rainfall must typically pass through an unsaturated layer before reaching the irregular and usually discontinuous shallow water table. This process is dynamic and a function of precipitation intensity and duration, the initial moisture conditions and hydrologic properties of the hillside materials, and the geometry, stratigraphy, and vegetation of the hillslope. As a result, pore water pressures, volumetric water content, effective stress, and thus the propensity for landsliding vary over seasonal and shorter time scales. We apply a general framework for assessing the stability of infinite slopes under transient variably saturated conditions. The framework includes profiles of pressure head and volumetric water content combined with a general effective stress for slope stability analysis. The general effective stress, or suction stress, provides a means for rigorous quantification of stress changes due to rainfall and infiltration and thus the analysis of slope stability over the range of volumetric water contents and pressure heads relevant to shallow landslide initiation. We present results using an analytical solution for transient infiltration for a range of soil texture and hydrological properties typical of landslide-prone hillslopes and show the effect of these properties on the timing and depth of slope failure. We follow by analyzing field-monitoring data acquired prior to shallow landslide failure of a hillside near Seattle, Washington, and show that the timing of the slide was predictable using measured pressure head and volumetric water content and show how the approach can be used in a forward manner using a numerical model for transient infiltration.

Linking slope stability and climate change: the Nordfjord region, western Norway, case study

NASA Astrophysics Data System (ADS)

Vasskog, K.; Waldmann, N.; Ariztegui, D.; Simpson, G.; Støren, E.; Chapron, E.; Nesje, A.

2009-12-01

Valleys, lakes and fjords are spectacular features of the Norwegian landscape and their sedimentary record recall past climatic, environmental and glacio-isostatic changes since the late glacial. A high resolution multi-proxy study is being performed on three lakes in western Norway combining different geophysical methods and sediment coring with the aim of reconstructing paleoclimate and to investigate how the frequency of hazardous events in this area has changed through time. A very high resolution reflection seismic profiling revealed a series of mass-wasting deposits. These events, which have also been studied in radiocarbon-dated cores, suggest a changing impact of slope instability on lake sedimentation since the late glacial. A specially tailored physically-based mathematical model allowed a numerical simulation of one of these mass wasting events and related tsunami, which occurred during a devastating rock avalanche in 1936 killing 74 persons. The outcome has been further validated against historical, marine and terrestrial information, providing a model that can be applied to comparable basins at various temporal and geographical scales. Detailed sedimentological and geochemical studies of selected cores allows characterizing the sedimentary record and to disentangle each mass wasting event. This combination of seismic, sedimentary and geophysical data permits to extend the record of mass wasting events beyond historical times. The geophysical and coring data retrieved from these lakes is a unique trace of paleo-slope stability generated by isostatic rebound and climate change, thus providing a continuous archive of slope stability beyond the historical record. The results of this study provide valuable information about the impact of climate change on slope stability and source-to-sink processes.

Debris flow runup on vertical barriers and adverse slopes

USGS Publications Warehouse

Iverson, Richard M.; George, David L.; Logan, Matthew

2016-01-01

Runup of debris flows against obstacles in their paths is a complex process that involves profound flow deceleration and redirection. We investigate the dynamics and predictability of runup by comparing results from large-scale laboratory experiments, four simple analytical models, and a depth-integrated numerical model (D-Claw). The experiments and numerical simulations reveal the important influence of unsteady, multidimensional flow on runup, and the analytical models highlight key aspects of the underlying physics. Runup against a vertical barrier normal to the flow path is dominated by rapid development of a shock, or jump in flow height, associated with abrupt deceleration of the flow front. By contrast, runup on sloping obstacles is initially dominated by a smooth flux of mass and momentum from the flow body to the flow front, which precedes shock development and commonly increases the runup height. D-Claw simulations that account for the emergence of shocks show that predicted runup heights vary systematically with the adverse slope angle and also with the Froude number and degree of liquefaction (or effective basal friction) of incoming flows. They additionally clarify the strengths and limitations of simplified analytical models. Numerical simulations based on a priori knowledge of the evolving dynamics of incoming flows yield quite accurate runup predictions. Less predictive accuracy is attained in ab initio simulations that compute runup based solely on knowledge of static debris properties in a distant debris flow source area. Nevertheless, the paucity of inputs required in ab initio simulations enhances their prospective value in runup forecasting.

Analytical determination of the effect of structural elasticity on landing stability of a version of the Viking Lander

NASA Technical Reports Server (NTRS)

Laurenson, R. M.

1972-01-01

A limited analytical investigation was conducted to assess the effects of structural elasticity on the landing stability of a version of the Viking Lander. Two landing conditions and two lander mass and inertia distributions were considered. The results of this investigation show that the stability-critical surface slopes were lower for an uphill landing than for a downhill landing. In addition, the heavy footpad mass with its corresponding inertia distribution resulted in lower stability-critical ground slopes than were obtained for the light footpad mass and its corresponding inertia distribution. Structural elasticity was observed to have a large effect on the downhill landing stability of the light footpad mass configuration but had a negligible effect on the stability of the other configuration examined. Because of the limited nature of this study, care must be exercised in drawing conclusions from these results relative to the overall stability characteristics of the Viking Lander.

Influence of magnetic cohesion on the stability of granular slopes.

PubMed

Taylor, K; King, P J; Swift, Michael R

2008-09-01

We use a molecular dynamics model to simulate the formation and evolution of a granular pile in two dimensions in order to gain a better understanding of the role of magnetic interactions in avalanche dynamics. We find that the angle of repose increases only slowly with magnetic field; the increase in angle is small even for intergrain cohesive forces many times stronger than gravity. The magnetic forces within the bulk of the pile partially cancel as a result of the anisotropic nature of the dipole-dipole interaction between grains. However, we show that this cancellation effect is not sufficiently strong to explain the discrepancy between the angle of repose in wet systems and magnetically cohesive systems. In our simulations we observe shearing deep within the pile, and we argue that it is this motion that prevents the angle of repose from increasing dramatically. We also investigate different implementations of friction with the front and back walls of the container, and conclude that the nature of the friction dramatically affects the influence of magnetic cohesion on the angle of repose.

Illustrations of the importance of mass wasting in the evolution of continental margins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pratson, L.; Ryan, W.; Twichell, D.

1990-05-01

Side-looking sonar imagery and swath bathymetry from a variety of contemporary continental slopes all display erosional scars and debris aprons, illustrating the importance of mass wasting in the evolution of continental margins. The continental slopes examined include slopes fed directly from the fronts of ice sheets, slopes adjacent to continental shelves that were the sites of glacial outwash, slopes supplied exclusively by fluvial drainage, slopes at carbonate platforms, and slopes on accretionary prisms. Examples are drawn from the Atlantic Ocean, the Gulf of Mexico, and the Mediterranean Sea in both passive and active continental margin settings. The sonar imagery andmore » bathymetry used in this study indicate that continental slopes in different tectonic and climatic environments show similar forms of mass wasting. However, in some cases the dominant mode of erosion and/or the overall degree of mass wasting appears to be distinct to particular sedimentary environments. Timing of both recent and older exhumed erosional surfaces identified in the imagery and in seismic reflection profiles is obtained by ground truth observations using submersibles, towed camera sleds, drilling, and coring. These observations suggest that eustatic fluctuations common to all the margins examined do not explain the range in magnitude and areal density of the observed mass wasting. More localized factors such as lithology, diagenesis, pore fluid conditions, sediment supply rates, and seismic ground motion appear to have a major influence in the evolution of erosional scars and their corresponding unconformities.« less

Performance Test of the Next Generation X-Ray Beam Position Monitor System for The APS Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, B.; Lee, S.; Westferro, F.

The Advanced Photon Source is developing its next major upgrade (APS-U) based on the multi-bend achromat lattice. Improved beam stability is critical for the upgrade and will require keeping short-time beam angle change below 0.25 µrad and long-term angle drift below 0.6 µrad. A reliable white x-ray beam diagnostic system in the front end will be a key part of the planned beam stabilization system. This system includes an x-ray beam position monitor (XBPM) based on x-ray fluorescence (XRF) from two specially designed GlidCop A-15 absorbers, a second XBPM using XRF photons from the Exit Mask, and two white beammore » intensity monitors using XRF from the photon shutter and Compton-scattered photons from the front end beryllium window or a retractable diamond film in windowless front ends. We present orbit stability data for the first XBPM used in the feedback control during user operations, as well as test data from the second XBPM and the intensity monitors. They demonstrate that the XBPM system meets APS-U beam stability requirements.« less

A New Methodology for Open Pit Slope Design in Karst-Prone Ground Conditions Based on Integrated Stochastic-Limit Equilibrium Analysis

NASA Astrophysics Data System (ADS)

Zhang, Ke; Cao, Ping; Ma, Guowei; Fan, Wenchen; Meng, Jingjing; Li, Kaihui

2016-07-01

Using the Chengmenshan Copper Mine as a case study, a new methodology for open pit slope design in karst-prone ground conditions is presented based on integrated stochastic-limit equilibrium analysis. The numerical modeling and optimization design procedure contain a collection of drill core data, karst cave stochastic model generation, SLIDE simulation and bisection method optimization. Borehole investigations are performed, and the statistical result shows that the length of the karst cave fits a negative exponential distribution model, but the length of carbonatite does not exactly follow any standard distribution. The inverse transform method and acceptance-rejection method are used to reproduce the length of the karst cave and carbonatite, respectively. A code for karst cave stochastic model generation, named KCSMG, is developed. The stability of the rock slope with the karst cave stochastic model is analyzed by combining the KCSMG code and the SLIDE program. This approach is then applied to study the effect of the karst cave on the stability of the open pit slope, and a procedure to optimize the open pit slope angle is presented.

The stabilization of unstable detonation waves for the mixture of nitromethane/methanol

NASA Astrophysics Data System (ADS)

Utkin, A. V.; Koldunov, S. A.; Mochalova, V. M.; Torunov, S. I.; Lapin, S. M.

2015-11-01

Using a laser interferometer VISAR the measurements of the particle velocity profiles in detonation waves for nitromethane/methanol mixtures with additions of a sensitizer diethylenetriamine were conducted. It is shown that the detonation front in a mixture of nitromethane/methanol is unstable and sensitizer is an effective method for the flow stabilization. If the diluent concentration is less than 10%, the detonation front is stabilized by adding of 1% diethylenetriamine. At higher concentrations of methanol, the sensitizer does not reject instability, but the amplitude of oscillations decreases in several times. An increase of the limit concentration of methanol at the addition of diethylenetriamine to the mixture was found.

Putting weathering into a landscape context: Variations in exhumation rates across the Colorado Front Range

NASA Astrophysics Data System (ADS)

Anderson, Suzanne P.; Foster, Melissa A.; Anderson, Scott W.; Dühnforth, Miriam; Anderson, Robert S.

2015-04-01

Erosion rates are expected vary with lithology, climate, and topographic slope, yet assembling these variations for an entire landscape is rarely done. The Front Range of the southern Rocky Mountains in Colorado, USA, exhibits contrasts in all three parameters. The range comprises ~2300 m in relief from the Plains to the crags of the Continental Divide. Its abrupt mountain front coincides closely with the boundary between marine sedimentary rocks to the east and Proterozoic crystalline rocks (primarily granodiorite and gneiss) to the west. Mean annual temperature declines and mean annual precipitation increases with elevation, from ~11° C/490 mm at the western edge of the Plains to -3.7° C/930 mm on Niwot Ridge near the range crest. The range contains regions of low relief with rolling topography, in which slopes rarely exceed 20° , as well as deeply incised glacial valleys and fluvial canyons lined by steep slopes (>25° ). Cosmogenic 10Be based erosion rates vary by a factor of ~5 within crystalline rock across the range. The lowest rates (5-10 mm/ka) are found on low relief summit tors in the alpine, where temperatures are low and precipitation is high. Slightly higher erosion rates (20-30 mm/ka) are found in low relief crystalline rock areas with montane forest cover. Taken together, these rates suggest that on low slopes, rock-weathering rates (which place a fundamental limit on erosion rates) are lower in cold alpine settings. Over the 40-150 ka averaging time of 10Be erosion rates, lower rates are found where periglacial/tundra conditions have prevailed, while moderate rates occur where conditions have varied from periglacial/tundra in the past to frigid regime/montane forest in the Holocene. Higher basin-averaged erosion rates of 40-60 mm/ka are reported for 'canyon edge' basins (Dethier et al., 2014, Geology), which are small, steep basins responding to fluvial bedrock incision that formed the canyons in the late Cenozoic. Are higher erosion rates in canyon-edge basins evidence that topographic slope affects weathering rates? We argue that it is more likely that these high erosion rates reflect faster weathering in areas with thinner soil cover. A recent major storm unleashed landslides and debris flows from ~10% of these canyon-edge basins. On average, the volume of material evacuated in these basins was equivalent to ~300 years of soil production by weathering at these rates, approximately the recurrence interval of the storm. The conceptual model that emerges is that agents that cut into rock (bedrock rivers, glaciers) set the pace for exhumation. Adjoining hillslopes erode at a pace set by weathering in the prevailing climate/vegetation regime, conditioned by the ability of sediment transport processes to limit soil thickness on the slopes.

Wind modulation of upwelling at the shelf-break front off Patagonia: Observational evidence

NASA Astrophysics Data System (ADS)

Carranza, M. M.; Gille, S. T.; Piola, A. R.; Charo, M.; Romero, S. I.

2017-03-01

The South-Atlantic Patagonian shelf is the largest chlorophyll-a (Chl-a) hot spot in Southern Ocean color images. While a persistent 1500 km long band of high Chl-a along the shelf-break front (SBF) is indicative of upwelling, the mechanisms that drive it are not entirely known. Along-front wind oscillations can enhance upwelling and provide a nutrient pumping mechanism at shelf-break fronts of western boundary currents. Here we assess wind-induced upwelling at the SBF off Patagonia from daily satellite Chl-a and winds, historical hydrographic observations, cross-shelf Chl-a fluorescence transects from two cruises, and in situ winds and water column structure from a mooring site. Satellite Chl-a composites segregated by along-front wind direction indicate that surface Chl-a is enhanced at the SBF with southerly winds and suppressed with northerly winds. Northerly winds also result in enhanced Chl-a further offshore (˜25-50 km). Synoptic transects as well as mean hydrographic sections segregated by along-front winds show isopycnals tilted upward for southerly winds. Spring observations from the mooring also suggest that southerly winds destratify the water column and northerly winds restratify, in agreement with Ekman transport interacting with the front. Moreover, changes in water column temperature lag along-front wind forcing by 2-4 days. Our results suggest that oscillations in along-front winds, on timescales typical of atmospheric storms (2-10 days), can significantly modulate the upwelling and Chl-a concentrations at the SBF off Patagonia, revealing the importance of wind-induced upwelling for shelf-slope exchange at shelf-break fronts of western boundary currents.

Polarization and wavelength diversities of Gulf Stream fronts imaged by AIRSAR

NASA Technical Reports Server (NTRS)

Lee, J. S.; Jansen, R. W.; Marmorino, G. O.; Chubb, S. R.

1995-01-01

During the 1990 Gulf Stream Experiment, NASA/JPL AIRSAR imaged the north edge of the Gulf Stream near the coast of Virginia. Simultaneous in-situ measurements of currents, temperatures, salinities, etc. were made for several crossings of the north edge by the R/V Cape Henlopen. Measurements identified two fronts with shearing and converging flows. The polarimetric SAR images from the fronts showed two bright linear features. One of them corresponds to the temperature front, which separated the warm Gulf Stream water to the south from a cool, freshwater filament to the north. The other line, located about 8 km north of the temperature front, is believed to correspond to the velocity front between the filament and the slope water. At these fronts, wave-current interactions produced narrow bands of steep and breaking waves manifesting higher radar returns in polarimetric SAR images. In general, our AIRSAR imagery shows that the signal-to-clutter ratio of radar cross sections for the temperature front is higher than that of the velocity front. In this paper, we study the polarization and wavelength diversities of radar response of these two fronts using the P-, L-, and C-Band Polarimetric SAR data. The north-south flight path of the AIRSAR crossed the temperature front several times and provided valuable data for analysis. Three individual passes are investigated. We found that for the temperature front, the cross-pol (HV) responses are much higher than co-pol responses (VV and HH), and that P-Band HV has the highest signal to clutter ratio. For the velocity front, the ratio is the strongest in P-Band VV, and it is indistinguishable for all polarizations in C-Band. The radar cross sections for all three polarization (HH, HV, and VV) and for all three bands are modelled using an ocean wave model and a composite Bragg scattering model. In our initial investigations, the theoretical model agrees qualitatively with the AIRSAR observations.

Reducing the risk of the collapse of the soil by macro system modeling the slopes stability of the quarries

NASA Astrophysics Data System (ADS)

Klimova, E. V.; Semeykin, A. Yu

2018-01-01

The urgent task of modern production is to reduce the risks of man-made disasters and, as a consequence, preserve the life and health of workers, material properties and natural environment. In the mining industry, one of the reasons for the high level of injuries and accidents is the collapse of the soil. Macro system modelling of slopes stability of the quarries is based on the compliance with the conditions of physical and mathematical correctness of the application of the model of a continuous medium. This type of modelling allows to choose the safe parameters of the slopes of the quarries and to reduce the risk of collapse of the soil.

Rainfall-induced landslides in Puerto Rico: An overview

USGS Publications Warehouse

Pando, M.A.; Ruiz, M.E.; Larsen, M.C.

2005-01-01

Rainfall-induced landslides are common in Puerto Rico (PR). The presence of steep slopes in mountainous terrain, coupled with weathered soils and intense rainfall, leads to severe slope-stability problems throughout the island. Episodic triggering events such as hurricanes and earthquakes further exacerbate these problems. All physiographic provinces of the island have experienced landslides. The stability of natural and man-made slopes is a serious concern for government authorities and the civil engineering community in Puerto Rico. This paper presents an overview of the rainfall induced landslide problem in PR, a summary of literature published on this subject, and proposes a rainfall intensity landslide threshold based on landslide events data from 1959 to 2003. This threshold can be used as part of a potential landslide warning system.

Use of MSE technology to stabilize highway embankments and slopes in Oklahoma.

DOT National Transportation Integrated Search

2009-09-30

Departments of transportation across the U.S., including ODOT, are invariably faced with a persistent problem of landslides and slope failures along highways. Repairs and maintenance work associated with these failures cost these agencies millions of...

Does mycorrhizal inoculation improve plant survival, aggregate stability, and fine root development on a coarse-grained soil in an alpine eco-engineering field experiment?

NASA Astrophysics Data System (ADS)

Bast, A.; Wilcke, W.; Graf, F.; Lüscher, P.; Gärtner, H.

2016-08-01

Steep vegetation-free talus slopes in high mountain environments are prone to superficial slope failures and surface erosion. Eco-engineering measures can reduce slope instabilities and thus contribute to risk mitigation. In a field experiment, we established mycorrhizal and nonmycorrhizal research plots and determined their biophysical contribution to small-scale soil fixation. Mycorrhizal inoculation impact on plant survival, aggregate stability, and fine root development was analyzed. Here we present plant survival (ntotal = 1248) and soil core (ntotal = 108) analyses of three consecutive years in the Swiss Alps. Soil cores were assayed for their aggregate stability coefficient (ASC), root length density (RLD), and mean root diameter (MRD). Inoculation improved plant survival significantly, but it delayed aggregate stabilization relative to the noninoculated site. Higher aggregate stability occurred only after three growing seasons. Then also RLD tended to be higher and MRD increased significantly at the mycorrhizal treated site. There was a positive correlation between RLD, ASC, and roots <0.5 mm, which had the strongest impact on soil aggregation. Our results revealed a temporal offset between inoculation effects tested in laboratory and field experiments. Consequently, we recommend to establish an intermediate to long-term field experimental monitoring before transferring laboratory results to the field.

Static Longitudinal Stability of a Rocket Vehicle Having a Rear-Facing Step Ahead of the Stabilizing Fins

NASA Technical Reports Server (NTRS)

Keynton, Robert J.

1961-01-01

Tests were conducted at Mach numbers of 3.96 and 4.65 in the Langley Unitary Plan wind tunnel to determine the static longitudinal stability characteristics of a fin-stabilized rocket-vehicle configuration which had a rearward facing step located upstream of the fins. Two fin sizes and planforms, a delta and a clipped delta, were tested. The angle of attack was varied from 6 deg to -6 deg and the Reynolds number based on model 6 length was about 10 x 10. The configuration with the larger fins (clipped delta) had a center of pressure slightly rearward of and an initial normal-force-curve slope slightly higher than that of the configuration with the smaller fins (delta) as would be expected. Calculations of the stability parameters gave a slightly lower initial slope of the normal-force curve than measured data, probably because of boundary-layer separation ahead of the step. The calculated center of pressure agreed well with the measured data. Measured and calculated increments in the initial slope of the normal-force curve and in the center of pressure, due to changing fins, were in excellent agreement indicating that separated flow downstream of the step did not influence flow over the fins. This result was consistent with data from schlieren photographs.

Convection induced by thermal gradients on thin reaction fronts

NASA Astrophysics Data System (ADS)

Ruelas Paredes, David R. A.; Vasquez, Desiderio A.

2017-09-01

We present a thin front model for the propagation of chemical reaction fronts in liquids inside a Hele-Shaw cell or porous media. In this model we take into account density gradients due to thermal and compositional changes across a thin interface. The front separating reacted from unreacted fluids evolves following an eikonal relation between the normal speed and the curvature. We carry out a linear stability analysis of convectionless flat fronts confined in a two-dimensional rectangular domain. We find that all fronts are stable to perturbations of short wavelength, but they become unstable for some wavelengths depending on the values of compositional and thermal gradients. If the effects of these gradients oppose each other, we observe a range of wavelengths that make the flat front unstable. Numerical solutions of the nonlinear model show curved fronts of steady shape with convection propagating faster than flat fronts. Exothermic fronts increase the temperature of the fluid as they propagate through the domain. This increment in temperature decreases with increasing speed.

Comprehensive evaluation of high-steep slope stability and optimal high-steep slope design by 3D physical modeling

NASA Astrophysics Data System (ADS)

Lai, Xing-ping; Shan, Peng-fei; Cai, Mei-feng; Ren, Fen-hua; Tan, Wen-hui

2015-01-01

High-steep slope stability and its optimal excavation design in Shuichang open pit iron mine were analyzed based on a large 3D physical simulation technique. An optimal excavation scheme with a relatively steeper slope angle was successfully implemented at the northwest wall between Nos. 4 and 5 exploration lines of Shuichang Iron Mine, taking into account the 3D scale effect. The physico-mechanical properties of rock materials were obtained by laboratory tests conducted on sample cores from exploration drilling directly from the iron mine. A porous rock-like composite material was formed for the model, and the mechanical parameters of the material were assessed experimentally; specifically, the effect of water on the sample was quantitatively determined. We adopted an experimental setup using stiff modular applied static loading to carry out a visual excavation of the slope at a random depth. The setup was equipped with acoustic emission (AE) sensors, and the experiments were monitored by crack optical acquirement, ground penetrating radar, and close-field photogrammetry to investigate the mechanisms of rock-mass destabilization in the high-steep slope. For the complex study area, the model results indicated a clear correlation between the model's destabilization resulting from slope excavation and the collected monitoring information. During the model simulation, the overall angle of the slope increased by 1-6 degrees in different sections. Dramatically, the modeled excavation scheme saved over 80 million tons of rock from extraction, generating enormous economic and ecological benefits.

Mapping basin-wide subaquatic slope failure susceptibility as a tool to assess regional seismic and tsunami hazards

NASA Astrophysics Data System (ADS)

Strasser, Michael; Hilbe, Michael; Anselmetti, Flavio S.

2010-05-01

With increasing awareness of oceanic geohazards, submarine landslides are gaining wide attention because of their catastrophic impacts on both offshore infrastructures (e.g. pipelines, cables and platforms) and coastal areas (e.g. landslide-induced tsunamis). They also are of great interest because they can be directly related to primary trigger mechanisms including earthquakes, rapid sedimentation, gas release, glacial and tidal loading, wave action, or clathrate dissociation, many of which represent potential geohazards themselves. In active tectonic environments, for instance, subaquatic landslide deposits can be used to make inferences regarding the hazard derived from seismic activity. Enormous scientific and economic efforts are thus being undertaken to better determine and quantify causes and effects of natural hazards related to subaquatic landslides. In order to achieve this fundamental goal, the detailed study of past events, the assessment of their recurrence intervals and the quantitative reconstruction of magnitudes and intensities of both causal and subsequent processes and impacts are key requirements. Here we present data and results from a study using fjord-type Lake Lucerne in central Switzerland as a "model ocean" to test a new concept for the assessment of regional seismic and tsunami hazard by basin-wide mapping of critical slope stability conditions for subaquatic landslide initiation. Previously acquired high-resolution bathymetry and reflection seismic data as well as sedimentological and in situ geotechnical data, provide a comprehensive data base to investigate subaquatic landslides and related geohazards. Available data are implemented into a basin-wide slope model. In a Geographic Information System (GIS)-framework, a pseudo-static limit equilibrium infinite slope stability equation is solved for each model point representing reconstructed slope conditions at different times in the past, during which earthquake-triggered landslides occurred. Comparison of reconstructed critical stability conditions with the known distribution of landslide deposits reveals minimum and maximum threshold conditions for slopes that failed or remained stable, respectively. The resulting correlations reveal good agreements and suggest that the slope stability model generally succeeds in reproducing past events. The basin-wide mapping of subaquatic slope failure susceptibility through time thus can also be considered as a promising paleoseismologic tool that allows quantification of past earthquake ground shaking intensities. Furthermore, it can be used to assess the present-day slope failure susceptibility allowing for identification of location and estimation of size of future, potentially tsunamigenic subaquatic landslides. The new approach presented in our comprehensive lake study and resulting conceptual ideas can be vital to improve our understanding of larger marine slope instabilities and related seismic and oceanic geohazards along formerly glaciated ocean margins and closed basins worldwide.

Multipurpose bedrock surficial, and environmental geologic maps, New River valley, southwest Virginia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schultz, A.; Collins, T.

1994-03-01

Multipurpose bedrock, surficial, and environmental geologic maps have recently been completed for portions of the Valley and Ridge province of southwest VA. The maps, at both 1:100,000 and 1:24,000 scales, show generalized and detailed bedrock geology grouped by lithology and environmental hazard associations. Also shown are a variety of alluvial, colluvial, debris flow, and landslide deposits, as well as karst features. Multidisciplinary research topics addressed during the mapping included slope evolution and geomorphology, drainage history and terrace distribution, ancient large-scale landsliding, and sinkhole development. The maps have been used by land-use planners and engineering firms in an evaluation of Appalachianmore » paleoseismicity and to assess potential groundwater contamination and subsidence in karst areas. The maps are being used for environmental hazard assessment and site selection of a proposed large electric powerline that crosses the Jefferson National Forest. Also, the maps are proving useful in planning for a public access interpretive geologic enter focused on large-scale slope failures. Some of the largest known landslides in eastern North America took place within the map area. Field comparisons and detailed structure mapping of similar features along the Front Range of the Colorado Rockies indicate that the landslides were probably emplaced during a single catastrophic event of short duration. Although the giles County seismic zone is nearby, stability analyses of slopes in the map area have shown that failure need not have been initiated by a seismic event. Several distinct colluvial units mapped within the area of landslides document a period of extensive weathering that postdates slide emplacement. Radiocarbon dates from landslide sag ponds indicate a minimum age of 9,860 B.P. for emplacement of some of the landslides. These results indicate that pre-slide colluvial and debris flow deposits are at least Pleistocene in age.« less

Sedimentary Fabrics of Stratified Slope Deposits at a Site near Hoover's Camp, Shenandoah National Park, Virginia

USGS Publications Warehouse

Smoot, Joseph P.

2004-01-01

An outcrop of stratified slope deposits in Shenandoah National Park is described in detail. The Pleistocene age deposits are comprised of a mixture of clay to cobbles defining a series of offlapping wedges. Elongate clasts are oriented parallel to wedge boundaries except at the toe of the wedge, where they are oriented nearly vertical. The wedges represent sedimentation by freeze-thaw of ground ice. Thin layers of pebbly sand separate matrix-rich wedge deposits, which represent sheetfloods during periods of thaw. Thicker sand layers and lenses of clay are placed upslope of coarse-grained wedge fronts. This association represents ponding of water around the solifluction lobe topography during warm periods. Stratified slope deposits at an outcrop at a higher elevation lack the sandy sheetflood and pond deposits, whereas sheetflood fabrics dominate deposits at a lower elevation. These variations are attributed to differences in temperature at the different elevations.

Purpose-driven public sector reform: the need for within-government capacity build for the management of slope stability in communities in the Caribbean.

PubMed

Anderson, Malcolm; Holcombe, Liz

2006-01-01

This article stresses the importance of within-government capacity build as the optimal approach to minimizing landslide risk to the most vulnerable communities in the developing world. Landslide risk is an integrated issue that demands strong managerial leadership and multidisciplinary inclusion to develop structures that deliver sustainable improvements in the reduction of risk. The tension between projects demanding international technical and financial intervention and those capable of "within-country" solutions are examined. More particularly, the challenges of developing a management methodology capable of energizing inter-ministry collaboration to achieve community-level action is examined in the context of a recently established program of slope stability management in St. Lucia. The program, Management of Slope Stability in Communities (MoSSaiC), is shown to have successfully fostered not only extensive technical collaboration within government but also to have energized local communities in the shared mission of capacity build through their direct involvement in the management process.

Landslide and slope stability evaluation in the historical town of Kruja, Albania

NASA Astrophysics Data System (ADS)

Muceku, Y.; Korini, O.

2014-03-01

This paper describes landslides and slope stability evaluation in the urban area of Kruja, Albania. Kruja is a historical and heritage center, due to the existence of many important cultural monuments, including "Skanderbeg" castle and Bazaar square, etc. The urban area of Kruja has been affected by landslide effects, in the past and also the present. From this phenomenon many engineering objects such as buildings, roads, etc., are damaged and demolished. From engineering geological mapping at scale 1:5000 it is observed that many active landslides have dramatically increased in activity since the 1980s. The landslide types found in the studied area are earthslides, debris flow, as well as rockfall and rock rolling. Also, from field works and laboratory analysis, the slope stability of the whole urban area has been determined; for this purpose the studied zone is divided into stable and unstable areas, which helps to better understand mass movement activity as one of the most harmful hazards of geodynamic phenomena.

Landslides and slope stability evaluation in the historical town of Kruja, Albania

NASA Astrophysics Data System (ADS)

Muceku, Y.; Korini, O.

2013-07-01

This paper describes the landslides and slope stability evaluation in the urban area of Kruja town, Albania. Kruja is a~historical and heritage center, due to the existence of many important cultural monuments including Skanderbeg castle and Bazaar square etc. The urban area of Kruja town has been affected from the Landslides effects, in the past and also present. From this phenomenon many engineering objects such as buildings, roads etc. are damaged and demolished. From the engineering geological mapping at scale 1 : 5000 it is observed that many active landslides have dramatically increased in activity after 1980s. The landslide types found in the studied area are earth slides, debris flow, as well as rock fall and rock rolling. Also, from field works and laboratory analysis, the slope stability of whole urban areas has been determined; for this purpose the studied zone is divided into the stable and unstable areas, which helps to better understand the mass movement's activity as one of the most harmful hazards of the geodynamics' phenomena.

Purpose-Driven Public Sector Reform: The Need for Within-Government Capacity Build for the Management of Slope Stability in Communities in the Caribbean

NASA Astrophysics Data System (ADS)

Anderson, Malcolm; Holcombe, Liz

2006-01-01

This article stresses the importance of within-government capacity build as the optimal approach to minimizing landslide risk to the most vulnerable communities in the developing world. Landslide risk is an integrated issue that demands strong managerial leadership and multidisciplinary inclusion to develop structures that deliver sustainable improvements in the reduction of risk. The tension between projects demanding international technical and financial intervention and those capable of “within-country” solutions are examined. More particularly, the challenges of developing a management methodology capable of energizing inter-ministry collaboration to achieve community-level action is examined in the context of a recently established program of slope stability management in St. Lucia. The program, Management of Slope Stability in Communities (MoSSaiC), is shown to have successfully fostered not only extensive technical collaboration within government but also to have energized local communities in the shared mission of capacity build through their direct involvement in the management process.

Pipe crawler with stabilizing midsection

DOEpatents

Zollinger, W.T.; Treanor, R.C.

1994-12-27

A pipe crawler is described having a midsection that provides the stability and flexibility to allow the pipe crawler to negotiate curved and uneven segments of piping while traveling through piping systems. The pipe crawler comprises a front leg assembly, a rear leg assembly, a midsection with a gimbal at each end for connecting the midsection to the front and rear leg assemblies in a flexible manner, and an air cylinder for changing the distance between the front and rear leg assemblies. The pipe crawler moves in ''inch worm'' fashion with the front and rear leg assemblies alternating between an extended and a retracted position as the air cylinder moves the retracted leg assembly forward. The midsection has a plurality of legs extending radially for holding the midsection within a maximum displacement from the piping axis so that the gimbals are not pivoted to extreme angles where they might lock up or seize. When the midsection is displaced sufficiently, its legs with wheels on each end engage the interior surface of the piping and prevent further displacement. Using two gimbals divides the angle between the planes defined by the front and rear leg assemblies which also helps to prevent excessive gimbal pivoting. 5 figures.

Pipe crawler with stabilizing midsection

DOEpatents

Zollinger, William T.; Treanor, Richard C.

1994-01-01

A pipe crawler having a midsection that provides the stability and flexibty to allow the pipe crawler to negotiate curved and uneven segments of piping while traveling through piping systems. The pipe crawler comprises a front leg assembly, a rear leg assembly, a midsection with a gimbal at each end for connecting the midsection to the front and rear leg assemblies in a flexible manner, and an air cylinder for changing the distance between the front and rear leg assemblies. The pipe crawler moves in "inch worm" fashion with the front and rear leg assemblies alternating between an extended and a retracted position as the air cylinder moves the retracted leg assembly forward. The midsection has a plurality of legs extending radially for holding the midsection within a maximum displacement from the piping axis so that the gimbals are not pivoted to extreme angles where they might lock up or seize. When the midsection is displaced sufficiently, its legs with wheels on each end engage the interior surface of the piping and prevent further displacement. Using two gimbals divides the angle between the planes defined by the front and rear leg assemblies which also helps to prevent excessive gimbal pivoting.

Pipe crawler with stabilizing midsection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zollinger, W.T.; Treanor, R.C.

1993-09-20

This invention is comprised of a pipe crawler having a midsection that provides the stability and flexibility to allow the pipe crawler to negotiate curved and uneven segments of piping while traveling through piping systems. The pipe crawler comprises a front leg assembly, a rear leg assembly, a midsection with a gimbal at each end for connecting the midsection to the front and rear leg assemblies in a flexible manner, and an air cylinder for changing the distance between the front and rear leg assemblies. The pipe crawler moves in ``inch worm`` fashion with the front and rear leg assembliesmore » alternating between an extended and a retracted position as the air cylinder moves the retracted leg assembly forward. The midsection has a plurality of legs extending radially for holding the midsection within a maximum displacement from the piping axis so that the gimbals are not pivoted to extreme angles where they might lock up or seize. When the midsection is displaced sufficiently, its legs with wheels on each end engage the interior surface of the piping and prevent further displacement. Using two gimbals divides the angle between the planes defined by the front and rear leg assemblies which also helps to prevent excessive gimbal pivoting.« less

Pipe crawler with stabilizing midsection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zollinger, W.T.; Treanor, R.C.

1994-12-27

A pipe crawler is described having a midsection that provides the stability and flexibility to allow the pipe crawler to negotiate curved and uneven segments of piping while traveling through piping systems. The pipe crawler comprises a front leg assembly, a rear leg assembly, a midsection with a gimbal at each end for connecting the midsection to the front and rear leg assemblies in a flexible manner, and an air cylinder for changing the distance between the front and rear leg assemblies. The pipe crawler moves in ''inch worm'' fashion with the front and rear leg assemblies alternating between anmore » extended and a retracted position as the air cylinder moves the retracted leg assembly forward. The midsection has a plurality of legs extending radially for holding the midsection within a maximum displacement from the piping axis so that the gimbals are not pivoted to extreme angles where they might lock up or seize. When the midsection is displaced sufficiently, its legs with wheels on each end engage the interior surface of the piping and prevent further displacement. Using two gimbals divides the angle between the planes defined by the front and rear leg assemblies which also helps to prevent excessive gimbal pivoting. 5 figures.« less

Application of interleaving models for the description of intrusive layering at the fronts of deep polar water in the Eurasian Basin (Arctic)

NASA Astrophysics Data System (ADS)

Kuzmina, N. P.; Zhurbas, N. V.; Emelianov, M. V.; Pyzhevich, M. L.

2014-09-01

Interleaving models of pure thermohaline and baroclinic frontal zones are applied to describe intrusions at the fronts found in the upper part of the Deep Polar Water (DPW) when the stratification was absolutely stable. It is assumed that differential mixing is the main mechanism of the intrusion formation. Important parameters of the interleaving such as the growth rate, vertical scale, and slope of the most unstable modes relative to the horizontal plane are calculated. It was found that the interleaving model for a pure thermohaline front satisfactory describes the important intrusion parameters observed at the frontal zone. In the case of a baroclinic front, satisfactory agreement over all the interleaving parameters is observed between the model calculations and observations provided that the vertical momentum diffusivity significantly exceeds the corresponding coefficient of mass diffusivity. Under specific (reasonable) constraints of the vertical momentum diffusivity, the most unstable mode has a vertical scale approximately two-three times smaller than the vertical scale of the observed intrusions. A thorough discussion of the results is presented.

Influence of an electric field on the buoyancy-driven instabilities.

PubMed

Zadrazil, Ales; Sevcíková, Hana

2005-11-01

The influence of dc electric fields (EFs) on the development of buoyancy-driven instabilities of reaction fronts is investigated experimentally in a modified Hele-Shaw cell for the arsenous acid-iodate system. Assessment of effects of external EFs is made both visually and through dispersion curves. It is shown that density fingering, observed on ascending fronts, is suppressed by the EF if the front propagates towards the positive electrode and is enhanced when the front propagates towards the negative electrode. The stabilizing (destabilizing) effects include slower (faster) development of fingers and the decrease (increase) in their numbers. The descending front, stable under no EF conditions, remains stable when an EF is applied with the positive electrode facing the approaching front. When the descending front faces the negative electrode, the tiny fingerlike structure develops after quite a long time.

Using a Remotely Piloted Aircraft System (RPAS) to analyze the stability of a natural rock slope

NASA Astrophysics Data System (ADS)

Salvini, Riccardo; Esposito, Giuseppe; Mastrorocco, Giovanni; Seddaiu, Marcello

2016-04-01

This paper describes the application of a rotary wing RPAS for monitoring the stability of a natural rock slope in the municipality of Vecchiano (Pisa, Italy). The slope under investigation is approximately oriented NNW-SSE and has a length of about 320 m; elevation ranges from about 7 to 80 m a.s.l.. The hill consists of stratified limestone, somewhere densely fractured, with dip direction predominantly oriented in a normal way respect to the slope. Fracture traces are present in variable lengths, from decimetre to metre, and penetrate inward the rock versant with thickness difficult to estimate, often exceeding one meter in depth. The intersection between different fracture systems and the slope surface generates rocky blocks and wedges of variable size that may be subject to phenomena of gravitational instability (with reference to the variation of hydraulic and dynamic conditions). Geometrical and structural info about the rock mass, necessary to perform the analysis of the slope stability, were obtained in this work from geo-referenced 3D point clouds acquired using photogrammetric and laser scanning techniques. In particular, a terrestrial laser scanning was carried out from two different point of view using a Leica Scanstation2. The laser survey created many shadows in the data due to the presence of vegetation in the lower parts of the slope and limiting the feasibility of geo-structural survey. To overcome such a limitation, we utilized a rotary wing Aibotix Aibot X6 RPAS geared with a Nikon D3200 camera. The drone flights were executed in manual modality and the images were acquired, according to the characteristics of the outcrops, under different acquisition angles. Furthermore, photos were captured very close to the versant (a few meters), allowing to produce a dense 3D point cloud (about 80 Ma points) by the image processing. A topographic survey was carried out in order to guarantee the necessary spatial accuracy to the process of images exterior orientation. The coordinates of GCPs were calculated through the post-processing of data collected by using two GPS receivers, operating in static modality, and a Total Station. The photogrammetric processing of image blocks allowed us to create the 3D point cloud, DTM, orthophoto, and 3D textured model with high level of cartographic detail. Discontinuities were deterministically characterized in terms of attitude, persistence, and spacing. Moreover, the main discontinuity sets were identified through a density analysis of attitudes in stereographic projection. In addition, the size and shape of potentially unstable blocks identified along the rock slope were measured. Finally, using additional data from traditional engineering-geological surveys executed in accessible outcrops, the kinematic and dynamic stability analysis of the rocky slope was performed. Results from this step have indicated the deterministic safety factors of rock blocks and wedges, and will be used by local Authorities to plan the protection works for safety guarantee. Results from this application show the great advantage of modern RPAS that can be successfully applied for the analysis of sub-vertical rocky slopes, especially in areas either difficult to access with traditional techniques or masked by the presence of vegetation. KEY WORDS: 3D point cloud, RPAS photogrammetry, Terrestrial laser scanning, Rock slope, Fracture mapping, Stability analysis

The effect of chestnut coppice forests abandon on slope stability: a case study

NASA Astrophysics Data System (ADS)

Vergani, Chiara; Bassanelli, Chiara; Rossi, Lorenzo; Chiaradia, Enrico Antonio; Battista Bischetti, Gian

2013-04-01

Sweet chestnut has been fundamental for Italian mountainous economies for many centuries. This kind of forest was traditionally managed by coppicing in shortly rotation (15-20 years) to rapidly produce wood biomass until half of XX century. In the last decades these forests were in large part abandoned due to change in economy which made coppiced forest management unprofitable, especially in steeper slopes and where forest viability is scarce. As a consequence most of them are over aged and very dense, leading to an observed increasing in localized slope instability, primary because of the uprooting of stools (Vogt et al., 2006). In this work the effect of the abandon of chestnut coppice on slope stability was analyzed, focusing on shallow landslides triggering. The mechanical contribution to soil shear strength of differently managed chestnut stand was estimated and compared in terms of additional root cohesion. The study area is located in the Valcuvia Valley (Lombardy Prealps - Northern Italy) at an elevation about 600 m a.s.l., where two different stands, one managed and the other abandoned (over 40 year aged), were chosen. The two sampling stands are on cohesionless slopes (quaternary moraine deposits) and are homogeneous with regard to the substrate, exposure and elevation. Slope steepness influences heavily forestry practices and steeper stands are more frequently abandoned than stands on gentler terrain: in fact in the abandoned coppice the slope was higher (35 degrees against 13 in the managed stand) and no stands completely homogeneous can be found. In each site the main characteristics of the stand were surveyed and a trench in each stand was excavated to analyze root diameter and number distribution with depth; root specimens were also collected for the tensile force determination through laboratory tensile tests. Root distribution and force were then used to estimate root cohesion values through a Fiber Boundle Model (Pollen and Simon, 2005). Results, as expected, show that management didn't affect root mechanical properties, whereas root distribution within the soil profile did. In terms of additional root cohesion, values are higher in the managed stand, and lower in the abandoned one, at least in the first 50 cm of soil. In the abandoned stand, in fact, roots reach deeper layers of soil (100 cm) than the managed one (50 cm), mainly because of an unexpected greater soil depth. To assess the implication of such results in terms of slope stability, a simple infinite slope model was applied to the two conditions. The results showed that the abandoned stand is prone to instability also with a low level of saturation. On the contrary, by applying the additional root cohesion profile obtained in the managed stand to the steeper slopes, stability should be guaranteed, except in the case of total saturation. In conclusion, although more investigations are required especially to extend the number of stands, coppicing practice seem to be fundamental to prevent shallow landsliding in sweet chestnut forests over cohesionless slopes.

Landslide prediction using combined deterministic and probabilistic methods in hilly area of Mt. Medvednica in Zagreb City, Croatia

NASA Astrophysics Data System (ADS)

Wang, Chunxiang; Watanabe, Naoki; Marui, Hideaki

2013-04-01

The hilly slopes of Mt. Medvednica are stretched in the northwestern part of Zagreb City, Croatia, and extend to approximately 180km2. In this area, landslides, e.g. Kostanjek landslide and Črešnjevec landslide, have brought damage to many houses, roads, farmlands, grassland and etc. Therefore, it is necessary to predict the potential landslides and to enhance landslide inventory for hazard mitigation and security management of local society in this area. We combined deterministic method and probabilistic method to assess potential landslides including their locations, size and sliding surfaces. Firstly, this study area is divided into several slope units that have similar topographic and geological characteristics using the hydrology analysis tool in ArcGIS. Then, a GIS-based modified three-dimensional Hovland's method for slope stability analysis system is developed to identify the sliding surface and corresponding three-dimensional safety factor for each slope unit. Each sliding surface is assumed to be the lower part of each ellipsoid. The direction of inclination of the ellipsoid is considered to be the same as the main dip direction of the slope unit. The center point of the ellipsoid is randomly set to the center point of a grid cell in the slope unit. The minimum three-dimensional safety factor and corresponding critical sliding surface are also obtained for each slope unit. Thirdly, since a single value of safety factor is insufficient to evaluate the slope stability of a slope unit, the ratio of the number of calculation cases in which the three-dimensional safety factor values less than 1.0 to the total number of trial calculation is defined as the failure probability of the slope unit. If the failure probability is more than 80%, the slope unit is distinguished as 'unstable' from other slope units and the landslide hazard can be mapped for the whole study area.

Slope stability analysis using limit equilibrium method in nonlinear criterion.

PubMed

Lin, Hang; Zhong, Wenwen; Xiong, Wei; Tang, Wenyu

2014-01-01

In slope stability analysis, the limit equilibrium method is usually used to calculate the safety factor of slope based on Mohr-Coulomb criterion. However, Mohr-Coulomb criterion is restricted to the description of rock mass. To overcome its shortcomings, this paper combined Hoek-Brown criterion and limit equilibrium method and proposed an equation for calculating the safety factor of slope with limit equilibrium method in Hoek-Brown criterion through equivalent cohesive strength and the friction angle. Moreover, this paper investigates the impact of Hoek-Brown parameters on the safety factor of slope, which reveals that there is linear relation between equivalent cohesive strength and weakening factor D. However, there are nonlinear relations between equivalent cohesive strength and Geological Strength Index (GSI), the uniaxial compressive strength of intact rock σ ci , and the parameter of intact rock m i . There is nonlinear relation between the friction angle and all Hoek-Brown parameters. With the increase of D, the safety factor of slope F decreases linearly; with the increase of GSI, F increases nonlinearly; when σ ci is relatively small, the relation between F and σ ci is nonlinear, but when σ ci is relatively large, the relation is linear; with the increase of m i , F decreases first and then increases.

Slope Stability Analysis Using Limit Equilibrium Method in Nonlinear Criterion

PubMed Central

Lin, Hang; Zhong, Wenwen; Xiong, Wei; Tang, Wenyu

2014-01-01

In slope stability analysis, the limit equilibrium method is usually used to calculate the safety factor of slope based on Mohr-Coulomb criterion. However, Mohr-Coulomb criterion is restricted to the description of rock mass. To overcome its shortcomings, this paper combined Hoek-Brown criterion and limit equilibrium method and proposed an equation for calculating the safety factor of slope with limit equilibrium method in Hoek-Brown criterion through equivalent cohesive strength and the friction angle. Moreover, this paper investigates the impact of Hoek-Brown parameters on the safety factor of slope, which reveals that there is linear relation between equivalent cohesive strength and weakening factor D. However, there are nonlinear relations between equivalent cohesive strength and Geological Strength Index (GSI), the uniaxial compressive strength of intact rock σ ci, and the parameter of intact rock m i. There is nonlinear relation between the friction angle and all Hoek-Brown parameters. With the increase of D, the safety factor of slope F decreases linearly; with the increase of GSI, F increases nonlinearly; when σ ci is relatively small, the relation between F and σ ci is nonlinear, but when σ ci is relatively large, the relation is linear; with the increase of m i, F decreases first and then increases. PMID:25147838

Opportunity's First Dip into Victoria Crater

NASA Technical Reports Server (NTRS)

2007-01-01

NASA's Mars Exploration Rover Opportunity entered Victoria Crater during the rover's 1,291st Martian day, or sol, (Sept. 11, 2007). The rover team commanded Opportunity to drive just far enough into the crater to get all six wheels onto the inner slope, and then to back out again and assess how much the wheels slipped on the slope. The driving commands for the day included a precaution for the rover to stop driving if the wheels were slipping more than 40 percent. Slippage exceeded that amount on the last step of the drive, so Opportunity stopped with its front pair of wheels still inside the crater. The rover team planned to assess results of the drive, then start Opportunity on an extended exploration inside the crater.

This wide-angle view taken by Opportunity's front hazard-identification camera at the end of the day's driving shows the wheel tracks created by the short dip into the crater. The left half of the image looks across an alcove informally named 'Duck Bay' toward a promontory called 'Cape Verde' clockwise around the crater wall. The right half of the image looks across the main body of the crater, which is 800 meters (half a mile) in diameter.

A dual slope charge sampling analog front-end for a wireless neural recording system.

PubMed

Lee, Seung Bae; Lee, Byunghun; Gosselin, Benoit; Ghovanloo, Maysam

2014-01-01

This paper presents a novel dual slope charge sampling (DSCS) analog front-end (AFE) architecture, which amplifies neural signals by taking advantage of the charge sampling concept for analog signal conditioning, such as amplification and filtering. The presented DSCS-AFE achieves amplification, filtering, and sampling in a simultaneous fashion, while consuming very small amount of power. The output of the DSCS-AFE produces a pulse width modulated (PWM) signal that is proportional to the input voltage amplitude. A circular shift register (CSR) utilizes time division multiplexing (TDM) of the PWM pulses to create a pseudo-digital TDM-PWM signal that can feed a wireless transmitter. The 8-channel system-on-a-chip was fabricated in a 0.35-μm CMOS process, occupying 2.4 × 2.1 mm(2) and consuming 255 μW from a 1.8V supply. Measured input-referred noise for the entire system, including the FPGA in order to recover PWM signal is 6.50 μV(rms) in the 288 Hz~10 kHz range. For each channel, sampling rate is 31.25 kHz, and power consumption is 31.8 μW.

A Dual Slope Charge Sampling Analog Front-End for a Wireless Neural Recording System

PubMed Central

Lee, Seung Bae; Lee, Byunghun; Gosselin, Benoit

2015-01-01

This paper presents a novel dual slope charge sampling (DSCS) analog front-end (AFE) architecture, which amplifies neural signals by taking advantage of the charge sampling concept for analog signal conditioning, such as amplification and filtering. The presented DSCS-AFE achieves amplification, filtering, and sampling in a simultaneous fashion, while consuming very small amount of power. The output of the DSCS-AFE produces a pulse width modulated (PWM) signal that is proportional to the input voltage amplitude. A circular shift register (CSR) utilizes time division multiplexing (TDM) of the PWM pulses to create a pseudo-digital TDM-PWM signal that can feed a wireless transmitter. The 8-channel system-on-a-chip was fabricated in a 0.35-µm CMOS process, occupying 2.4 × 2.1 mm2 and consuming 255 µW from a 1.8V supply. Measured input-referred noise for the entire system, including the FPGA in order to recover PWM signal is 6.50 µVrms in the 288 Hz~10 kHz range. For each channel, sampling rate is 31.25 kHz, and power consumption is 31.8 µW. PMID:25570655

MOD silver metallization for photovoltaics

NASA Technical Reports Server (NTRS)

Vest, G. M.; Vest, R. W.

1984-01-01

Photovoltaic cells require back side metallization and a collector grid system on the front surface. Both front and back surface metallizations should have good adhesion, low contact resistance, low sheet resistance, long term stability, and their deposition methods should not degrade the n-p junction. Advantages and disadvantages of different deposition methods are discussed.

Non-contact online thickness measurement system for metal films based on eddy current sensing with distance tracking technique.

PubMed

Li, Wei; Wang, Hongbo; Feng, Zhihua

2016-04-01

This paper proposes an online, non-contact metal film thickness measurement system based on eddy current sensing. The slope of the lift-off curve (LOC) is used for characterizing target thickness. Theoretical derivation was conducted to prove that the slope is independent of the lift-off variation. In practice, the measurement has some immunity to the lift-off, but not perfect. The slope of LOC is still affected at some extent by the lift-off. Hence, a height tracking system was also proposed, which could stabilize the distance between the sensor and the target and significantly reduce the lift-off effect. The height tracking system contains a specially designed probe, which could vibrate rapidly to obtain a fast measurement speed, and its height can be adjusted up and down continuously to stabilize the lift-off. The sensor coil in the thickness measurement system was also used as the height sensor in the height tracking system. Several experiments were conducted to test the system performances under static and dynamic conditions. This measurement system demonstrated significant advantages, such as simple and clear conversion between the slope of LOC and target thickness, high resolution and stability, and minimized effect of lift-off variation.

[Impact of land use type on stability and organic carbon of soil aggregates in Jinyun Mountain].

PubMed

Li, Jian-Lin; Jiang, Chang-Sheng; Hao, Qing-Ju

2014-12-01

Soil aggregates have the important effect on soil fertility, soil quality and the sustainable utilization of soil, and they are the mass bases of water and fertilizer retention ability of soil and the supply or release of soil nutrients. In this paper, in order to study the impact of land use type on stability and organic carbon of soil aggregates in Jinyun Mountain, we separated four land use types of soil, which are woodland, abandoned land, orchard and sloping farmland by wet sieving method, then we got the proportion of large macroaggregates (> 2 mm), small macroaggregates (0.25-2 mm), microaggregates (53 μm-0.25 mm) and silt + clay (< 53 μm) and measured the content of organic carbon in each aggregate fraction in soil depth of 0-60 cm and calculated the total content of organic carbon of all aggregates fraction in each soil. The results showed that reclamation of woodland will lead to fragmentation of macroaggregates and deterioration of soil structure, and the proportion of macroaggrgates (> 0.25 mm) were 44.62% and 32.28% respectively in the soils of orchard and sloping farmland, which reduced 38.58% (P < 0.05) and 91.52% (P < 0.05) compared with woodland. While after changing the sloping farmland to abandoned land, which lead to the conversion of soil fraction from silt + clay to large macroaggregates and small macroaggregates, so it will improve the soil structure. MWD (mean weight diameter) and GMD (geometric mean diameter) are important indicators of evaluating the stability of soil aggregates. We found the MWD and GWD in soil depth of 0-60 cm in orchards and sloping farmland were significantly lower than those in woodland (P < 0.05), while after changing the sloping farmland to abandoned land, the MWD and GWD increased significantly (P < 0.05), which indicated that reclamation of woodland will lead to the decrease of stability of soil aggregates, and they will be separated more easily by water. However, after changing the sloping farmland to abandoned land will enhance the stability of soil aggregates, and improve the ability of soil to resist external damage. The organic carbon content in each soil aggregate of four land use types decreased with the increase of soil depth. In soil depth of 0-60 cm, the storage of organic carbon of large macroaggregates in each soil are in orders of woodland (14.98 Mg x hm(-2)) > abandoned land (8.71 Mg x hm(-2)) > orchard (5.82 Mg x hm(-2)) > sloping farmland (2.13 Mg x hm(-2)), and abandoned land (35.61 Mg x hm(-2)) > woodland (20.38 Mg x hm-(-2)) > orchard (13.83 Mg x hm(-2)) > sloping farmland (6.77 Mg x hm(-2)) in small macroaggregates, and abandoned land (22.44 Mg x hm(-2)) > woodland (10.20 Mg x hm(-2)) > orchard (6.80 Mg x hm(-2)) > sloping farmland (5. 60 Mg x hm(-2)) in microaggregates, and abandoned land (22.21 Mg x hm(-2)) > woodland (17.01 Mg x hm(-2)) > orchard (16.70 Mg x hm(-2)) > sloping farmland (9.85 Mg x hm(-2)) in silt and clay fraction. Storage of organic carbon in each aggregate in the soils of woodland and abandoned land were higher than those in the soils of orchard and sloping farmland, which indicated that reclamation of woodland will lead to a loss of organic carbon in each soil aggregate fraction, while after changing the sloping farmland to abandoned land will contribute to restore and sequestrate the soil organic carbon. In addition, it showed that most organic carbon accumulated in small macroaggregate in soils of woodland and abandoned land, while they are in silt and clay in soils of orchard and sloping farmland, indicating that organic carbon in larger aggregates is unstable and is easier to convert during the land use change.

Stability of a Shock-Decelerated Ablation Front

DTIC Science & Technology

2009-01-01

the target through the ablation front. Our experiments on the Nike laser at the Naval Research Laboratory (NRL) are aimed at obtaining...separated from the CH foil by a 100-120 μm wide vacuum gap. The front side of the plastic foil is irradiated by 37 overlapping beams of the Nike ...krypton fluoride laser ( 248=Lλ nm) [19]. The Nike laser produces a very uniform irradiation with a time-averaged rms non-uniformity ɘ.3% in a central

Influence of wheelchair front caster wheel on reverse directional stability.

PubMed

Guo, Songfeng; Cooper, Rory A; Corfman, Tom; Ding, Dan; Grindle, Garrett

2003-01-01

The purpose of this research was to study directional stability during reversing of rear-wheel drive, electric powered wheelchairs (EPW) under different initial front caster orientations. Specifically, the weight distribution differences caused by certain initial caster orientations were examined as a possible mechanism for causing directional instability that could lead to accidents. Directional stability was quantified by measuring the drive direction error of the EPW by a motion analysis system. The ground reaction forces were collected to determine the load on the front casters, as well as back-emf data to attain the speed of the motors. The drive direction error was found to be different for various initial caster orientations. Drive direction error was greatest when both casters were oriented 90 degrees to the left or right, and least when both casters were oriented forward. The results show that drive direction error corresponds to the loading difference on the casters. The data indicates that loading differences may cause asymmetric drag on the casters, which in turn causes unbalanced torque load on the motors. This leads to a difference in motor speed and drive direction error.

The effect of plate position and size on tibial slope in high tibial osteotomy: a cadaveric study.

PubMed

Rubino, L Joseph; Schoderbek, Robert J; Golish, S Raymond; Baumfeld, Joshua; Miller, Mark D

2008-01-01

Opening wedge high tibial osteotomies are performed for degenerative changes and varus. Opening wedge osteotomies can change proximal tibial slope in the sagittal plane, possibly imparting stability in the ACL-deficient knee. The aim of this study was to assess the effect of plate position and size on change in tibial slope. Eight cadaveric knees underwent opening wedge high tibial osteotomy with Puddu plates of each different size. Plates were placed anterior, central, and posterior for each size used. Lateral radiographs were obtained. Tibial slope was measured and compared with baseline slope. Tibial slope was affected by plate position (P < 0.05) and size (P < 0.001). Smaller, posterior plates had less effect on tibial slope. However, anterior and central plates increased tibial slope over all plate sizes (P < 0.05). This study found that tibial slope increases with opening wedge high tibial osteotomy. Larger corrections and anterior placement of the plate are associated with larger increases in slope.

INFILTRATION ON MOUNTAIN SLOPES: A COMPARISON OF THREE ENVIRONMENTS. (R825157)

EPA Science Inventory

Water is well established as a major driver of the geomorphic change that eventually reduces mountains to lower relief landscapes. Nonetheless, within the altitudinal limits of continuous vegetation in humid climates, water is also an essential factor in slope stability. In th...

The dependence of sea surface slope on atmospheric stability and swell conditions

NASA Technical Reports Server (NTRS)

Hwang, Paul A.; Shemdin, Omar H.

1988-01-01

A tower-mounted optical device is used to measure the two-orthogonal components of the sea surface slope. The results indicate that an unstable stratification at the air-sea interface tends to enhance the surface roughness. The presence of a long ocean swell system steers the primary direction of shortwave propagation away from wind direction, and may increase or reduce the mean square slope of the sea surface.

A 0.18 μm biosensor front-end based on 1/f noise, distortion cancelation and chopper stabilization techniques.

PubMed

Balasubramanian, Viswanathan; Ruedi, Pierre-Francois; Temiz, Yuksel; Ferretti, Anna; Guiducci, Carlotta; Enz

2013-10-01

This paper presents a novel sensor front-end circuit that addresses the issues of 1/f noise and distortion in a unique way by using canceling techniques. The proposed front-end is a fully differential transimpedance amplifier (TIA) targeted for current mode electrochemical biosensing applications. In this paper, we discuss the architecture of this canceling based front-end and the optimization methods followed for achieving low noise, low distortion performance at minimum current consumption are presented. To validate the employed canceling based front-end, it has been realized in a 0.18 μm CMOS process and the characterization results are presented. The front-end has also been tested as part of a complete wireless sensing system and the cyclic voltammetry (CV) test results from electrochemical sensors are provided. Overall current consumption in the front-end is 50 μA while operating on a 1.8 V supply.

Multiple calibrator measurements improve accuracy and stability estimates of automated assays.

PubMed

Akbas, Neval; Budd, Jeffrey R; Klee, George G

2016-01-01

The effects of combining multiple calibrations on assay accuracy (bias) and measurement of calibration stability were investigated for total triiodothyronine (TT3), vitamin B12 and luteinizing hormone (LH) using Beckman Coulter's Access 2 analyzer. Three calibration procedures (CC1, CC2 and CC3) combined 12, 34 and 56 calibrator measurements over 1, 2, and 3 days. Bias was calculated between target values and average measured value over 3 consecutive days after calibration. Using regression analysis of calibrator measurements versus measurement date, calibration stability was determined as the maximum number of days before a calibrator measurement exceeded 5% tolerance limits. Competitive assays (TT3, vitamin B12) had positive time regression slopes, while sandwich assay (LH) had a negative slope. Bias values for TT3 were -2.49%, 1.49%, and -0.50% using CC1, CC2 and CC3 respectively, with calibrator stability of 32, 20, and 30 days. Bias values for vitamin B12 were 2.44%, 0.91%, and -0.50%, with calibrator stability of 4, 9, and 12 days. Bias values for LH were 2.26%, 1.44% and -0.29% with calibrator stability of >43, 39 and 36 days. Measured stability was more consistent across calibration procedures using percent change rather than difference from target: 26 days for TT3, 12 days for B12 and 31 days for LH. Averaging over multiple calibrations produced smaller bias, consistent with improved accuracy. Time regression slopes in percent change were unaffected by number of calibration measurements but calibrator stability measured from the target value was highly affected by the calibrator value at time zero.

Methods for assessing the stability of slopes during earthquakes-A retrospective

USGS Publications Warehouse

Jibson, R.W.

2011-01-01

During the twentieth century, several methods to assess the stability of slopes during earthquakes were developed. Pseudostatic analysis was the earliest method; it involved simply adding a permanent body force representing the earthquake shaking to a static limit-equilibrium analysis. Stress-deformation analysis, a later development, involved much more complex modeling of slopes using a mesh in which the internal stresses and strains within elements are computed based on the applied external loads, including gravity and seismic loads. Stress-deformation analysis provided the most realistic model of slope behavior, but it is very complex and requires a high density of high-quality soil-property data as well as an accurate model of soil behavior. In 1965, Newmark developed a method that effectively bridges the gap between these two types of analysis. His sliding-block model is easy to apply and provides a useful index of co-seismic slope performance. Subsequent modifications to sliding-block analysis have made it applicable to a wider range of landslide types. Sliding-block analysis provides perhaps the greatest utility of all the types of analysis. It is far easier to apply than stress-deformation analysis, and it yields much more useful information than does pseudostatic analysis. ?? 2010.

Multi-Objective Sliding Mode Control on Vehicle Cornering Stability with Variable Gear Ratio Actuator-Based Active Front Steering Systems

PubMed Central

Ma, Xinbo; Wong, Pak Kin; Zhao, Jing; Xie, Zhengchao

2016-01-01

Active front steering (AFS) is an emerging technology to improve the vehicle cornering stability by introducing an additional small steering angle to the driver’s input. This paper proposes an AFS system with a variable gear ratio steering (VGRS) actuator which is controlled by using the sliding mode control (SMC) strategy to improve the cornering stability of vehicles. In the design of an AFS system, different sensors are considered to measure the vehicle state, and the mechanism of the AFS system is also modelled in detail. Moreover, in order to improve the cornering stability of vehicles, two dependent objectives, namely sideslip angle and yaw rate, are considered together in the design of SMC strategy. By evaluating the cornering performance, Sine with Dwell and accident avoidance tests are conducted, and the simulation results indicate that the proposed SMC strategy is capable of improving the cornering stability of vehicles in practice. PMID:28036037

Fourier power spectrum characteristics of face photographs: attractiveness perception depends on low-level image properties.

PubMed

Menzel, Claudia; Hayn-Leichsenring, Gregor U; Langner, Oliver; Wiese, Holger; Redies, Christoph

2015-01-01

We investigated whether low-level processed image properties that are shared by natural scenes and artworks - but not veridical face photographs - affect the perception of facial attractiveness and age. Specifically, we considered the slope of the radially averaged Fourier power spectrum in a log-log plot. This slope is a measure of the distribution of special frequency power in an image. Images of natural scenes and artworks possess - compared to face images - a relatively shallow slope (i.e., increased high spatial frequency power). Since aesthetic perception might be based on the efficient processing of images with natural scene statistics, we assumed that the perception of facial attractiveness might also be affected by these properties. We calculated Fourier slope and other beauty-associated measurements in face images and correlated them with ratings of attractiveness and age of the depicted persons (Study 1). We found that Fourier slope - in contrast to the other tested image properties - did not predict attractiveness ratings when we controlled for age. In Study 2A, we overlaid face images with random-phase patterns with different statistics. Patterns with a slope similar to those in natural scenes and artworks resulted in lower attractiveness and higher age ratings. In Studies 2B and 2C, we directly manipulated the Fourier slope of face images and found that images with shallower slopes were rated as more attractive. Additionally, attractiveness of unaltered faces was affected by the Fourier slope of a random-phase background (Study 3). Faces in front of backgrounds with statistics similar to natural scenes and faces were rated as more attractive. We conclude that facial attractiveness ratings are affected by specific image properties. An explanation might be the efficient coding hypothesis.

Fourier Power Spectrum Characteristics of Face Photographs: Attractiveness Perception Depends on Low-Level Image Properties

PubMed Central

Langner, Oliver; Wiese, Holger; Redies, Christoph

2015-01-01

We investigated whether low-level processed image properties that are shared by natural scenes and artworks – but not veridical face photographs – affect the perception of facial attractiveness and age. Specifically, we considered the slope of the radially averaged Fourier power spectrum in a log-log plot. This slope is a measure of the distribution of special frequency power in an image. Images of natural scenes and artworks possess – compared to face images – a relatively shallow slope (i.e., increased high spatial frequency power). Since aesthetic perception might be based on the efficient processing of images with natural scene statistics, we assumed that the perception of facial attractiveness might also be affected by these properties. We calculated Fourier slope and other beauty-associated measurements in face images and correlated them with ratings of attractiveness and age of the depicted persons (Study 1). We found that Fourier slope – in contrast to the other tested image properties – did not predict attractiveness ratings when we controlled for age. In Study 2A, we overlaid face images with random-phase patterns with different statistics. Patterns with a slope similar to those in natural scenes and artworks resulted in lower attractiveness and higher age ratings. In Studies 2B and 2C, we directly manipulated the Fourier slope of face images and found that images with shallower slopes were rated as more attractive. Additionally, attractiveness of unaltered faces was affected by the Fourier slope of a random-phase background (Study 3). Faces in front of backgrounds with statistics similar to natural scenes and faces were rated as more attractive. We conclude that facial attractiveness ratings are affected by specific image properties. An explanation might be the efficient coding hypothesis. PMID:25835539

Iterative wave-front reconstruction in the Fourier domain.

PubMed

Bond, Charlotte Z; Correia, Carlos M; Sauvage, Jean-François; Neichel, Benoit; Fusco, Thierry

2017-05-15

The use of Fourier methods in wave-front reconstruction can significantly reduce the computation time for large telescopes with a high number of degrees of freedom. However, Fourier algorithms for discrete data require a rectangular data set which conform to specific boundary requirements, whereas wave-front sensor data is typically defined over a circular domain (the telescope pupil). Here we present an iterative Gerchberg routine modified for the purposes of discrete wave-front reconstruction which adapts the measurement data (wave-front sensor slopes) for Fourier analysis, fulfilling the requirements of the fast Fourier transform (FFT) and providing accurate reconstruction. The routine is used in the adaptation step only and can be coupled to any other Wiener-like or least-squares method. We compare simulations using this method with previous Fourier methods and show an increase in performance in terms of Strehl ratio and a reduction in noise propagation for a 40×40 SPHERE-like adaptive optics system. For closed loop operation with minimal iterations the Gerchberg method provides an improvement in Strehl, from 95.4% to 96.9% in K-band. This corresponds to ~ 40 nm improvement in rms, and avoids the high spatial frequency errors present in other methods, providing an increase in contrast towards the edge of the correctable band.

Modern sediment characteristics and accumulation rates from the delta front to prodelta of the Yellow River (Huanghe)

NASA Astrophysics Data System (ADS)

Zhou, Liangyong; Liu, Jian; Saito, Yoshiki; Gao, Maosheng; Diao, Shaobo; Qiu, Jiandong; Pei, Shaofeng

2016-08-01

Since 1976, the main channel of the Yellow River (Huanghe) has been on the east side of the delta complex, and the river has prograded a broad new delta lobe in Laizhou Bay of the Bohai Sea. In 2012, extensive bathymetric and high-resolution seismic profiles were conducted and sediment cores were collected off the new delta lobe. This study examined delta sedimentation and morphology along a profile across the modern subaqueous Yellow River delta and into Laizhou Bay, by analyzing sediment radionuclides (137Cs, 210Pb and 7Be), sedimentary structure, grain-size composition, organic carbon content, and morphological changes between 1976 and 2012. The change in the bathymetric profile, longitudinal to the river's course, reveals subaqueous delta progradation during this period. The subbottom boundary between the new delta lobe sediment and the older seafloor sediment (before the 1976 course shift) was identified in terms of lithology and radionuclide distributions, and recognized as a downlap surface in the seismic record. The accumulation rate of the new delta lobe sediment is estimated to be 5-18.6 cm year-1 on the delta front slope, 2 cm year-1 at the toe of the slope, and 1-2 cm year-1 in the shelf areas of Laizhou Bay. Sediment facies also change offshore, from alternations of gray and brown sediment in the proximal area to gray bioturbated fine sediment in the distal area. Based on 7Be distribution, the shorter-term deposition rate was at least 20 cm year-1 in the delta front.

Variability of slope current positioning from space: Application to the Northern Current in the North Western Mediterranean Sea

NASA Astrophysics Data System (ADS)

Bouffard, Jerome; Marmain, Julien; Bosse, Anthony; Petrenko, Anne; Forget, Philippe; Doglioli, Andrea; Testor, Pierre; Mortier, Laurent

The space-time variability of slope currents plays a key role on the across-shore transport of natural and anthropogenic elements. It is therefore of critical importance to monitor the front positioning associated with these hydrodynamical features in a synoptic way, in particular along densely populated coasts such as the littoral zone of the Mediterranean Sea. Our paper proposes to address this issue by developing a new multi-satellite altimetric-based approach aiming at monitoring the long-term behaviour of the Northern Current, from 2002 to 2012. Our method is assessed by direct comparisons with observations from glider transects of the current, coastal HF radar and a moored current-meter. Despite important limitations due to the current altimetric sampling and a lower accuracy in the 50 km coastal band, we demonstrate the ability of our new method to characterize the variability of the front positioning from intra-seasonal to annual scales. We particularly focus the analysis on the Gulf of Lion, where the distance between the mean geostrophic flow and the coast allows a good detection of high frequency signals associated with slope current intrusions over the continental shelf. We show that such abrupt events generally occur in autumn and are forced by heterogeneous, strong and rapidly evolving south-easterly wind events. This work is based on an original exploitation of the existing along-track altimetry data and paves the way for new applications within the prospect of the next satellite generation whose technology is more suitable for coastal studies.

Reactive composite compositions and mat barriers

DOEpatents

Langton, Christine A.; Narasimhan, Rajendran; Karraker, David G.

2001-01-01

A hazardous material storage area has a reactive multi-layer composite mat which lines an opening into which a reactive backfill and hazardous material are placed. A water-inhibiting cap may cover the hazardous material storage area. The reactive multi-layer composite mat has a backing onto which is placed an active layer which will neutralize or stabilize hazardous waste and a fronting layer so that the active layer is between the fronting and backing layers. The reactive backfill has a reactive agent which can stabilize or neutralize hazardous material and inhibit the movement of the hazardous material through the hazardous material storage area.

14 CFR 29.177 - Static directional stability.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Static directional stability. 29.177... Static directional stability. (a) The directional controls must operate in such a manner that the sense... versus directional control position curve may have a negative slope within a small range of angles around...

14 CFR 27.173 - Static longitudinal stability.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Static longitudinal stability. 27.173... longitudinal stability. (a) The longitudinal control must be designed so that a rearward movement of the... the maneuvers specified in § 27.175(a) through (d), the slope of the control position versus airspeed...

14 CFR 29.173 - Static longitudinal stability.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Static longitudinal stability. 29.173... Static longitudinal stability. (a) The longitudinal control must be designed so that a rearward movement... constant during the maneuvers specified in § 29.175(a) through (d), the slope of the control position...

14 CFR 27.177 - Static directional stability.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Static directional stability. 27.177... directional stability. (a) The directional controls must operate in such a manner that the sense and direction... sideslip angle versus directional control position curve may have a negative slope within a small range of...

Microfocusing options for the inelastic X-ray scattering beamline at sector 3 of the Advanced Photon Source.

PubMed

Alsmadi, A M; Alatas, A; Zhao, J Y; Hu, M Y; Yan, L; Alp, E E

2014-05-01

Synchrotron radiation from third-generation high-brilliance storage rings is an ideal source for X-ray microbeams. The aim of this paper is to describe a microfocusing scheme that combines both a toroidal mirror and Kirkpatrick-Baez (KB) mirrors for upgrading the existing optical system for inelastic X-ray scattering experiments at sector 3 of the Advanced Photon Source. SHADOW ray-tracing simulations without considering slope errors of both the toroidal mirror and KB mirrors show that this combination can provide a beam size of 4.5 µm (H) × 0.6 µm (V) (FWHM) at the end of the existing D-station (66 m from the source) with use of full beam transmission of up to 59%, and a beam size of 3.7 µm (H) × 0.46 µm (V) (FWHM) at the front-end of the proposed E-station (68 m from the source) with a transmission of up to 52%. A beam size of about 5 µm (H) × 1 µm (V) can be obtained, which is close to the ideal case, by using high-quality mirrors (with slope errors of less than 0.5 µrad r.m.s.). Considering the slope errors of the existing toroidal and KB mirrors (5 and 2.9 µrad r.m.s., respectively), the beam size grows to about 13.5 µm (H) × 6.3 µm (V) at the end of the D-station and to 12.0 µm (H) × 6.0 µm (V) at the front-end of the proposed E-station. The simulations presented here are compared with the experimental measurements that are significantly larger than the theoretical values even when slope error is included in the simulations. This is because of the experimental set-up that could not yet be optimized.

Challenges in Modeling Debris-Flow Initiation during the Exceptional September 2013 Northern Colorado Front Range Rainstorm

NASA Astrophysics Data System (ADS)

Baum, R. L.; Coe, J. A.; Godt, J.; Kean, J. W.

2014-12-01

Heavy rainfall during 9 - 13 September 2013 induced about 1100 debris flows in the foothills and mountains of the northern Colorado Front Range. Eye-witness accounts and fire-department records put the times of greatest landslide activity during the times of heaviest rainfall on September 12 - 13. Antecedent soil moisture was relatively low, particularly at elevations below 2250 m where many of the debris flows occurred, based on 45 - 125 mm of summer precipitation and absence of rainfall for about 2 weeks before the storm. Mapping from post-event imagery and field observations indicated that most debris flows initiated as small, shallow landslides. These landslides typically formed in colluvium that consisted of angular clasts in a sandy or silty matrix, depending on the nature of the parent bedrock. Weathered bedrock was partially exposed in the basal surfaces of many of the shallow source areas at depths ranging from 0.2 to 5 m, and source areas commonly occupied less than 500 m2. Although 49% of the source areas occurred in swales and 3 % in channels, where convergent flow might have contributed to pore-pressure build up during the rainfall, 48% of the source areas occurred on open slopes. Upslope contributing areas of most landslides (58%) were small (< 1000 m2) and 78% of the slides occurred on south-facing slopes (90°≤ aspect ≤270°). These observations pose challenges for modeling initiation of the debris flows. Effects of variable soil depth and properties, vegetation, and rainfall must be examined to explain the dominance of debris flows on south-facing slopes. Accounting for the small sizes and mixed swale and open-slope settings of source areas demands new approaches for resolving soil-depth and physical-properties variability. The low-moisture initial conditions require consideration of unsaturated zone effects. Ongoing fieldwork and computational modeling are aimed at addressing these challenges related to initiation of the September 2013 debris flows.

Combustor oscillating pressure stabilization and method

DOEpatents

Gemmen, R.S.; Richards, G.A.; Yip, M.T.J.; Robey, E.H.; Cully, S.R.; Addis, R.E.

1998-08-11

High dynamic pressure oscillations in hydrocarbon-fueled combustors typically occur when the transport time of the fuel to the flame front is at some fraction of the acoustic period. These oscillations are reduced to acceptably lower levels by restructuring or repositioning the flame front in the combustor to increase the transport time. A pilot flame front located upstream of the oscillating flame and pulsed at a selected frequency and duration effectively restructures and repositions the oscillating flame in the combustor to alter the oscillation-causing transport time. 7 figs.

Roots and the stability of forested slopes

Treesearch

R. R. Ziemer

1981-01-01

Abstract - Root decay after timber cutting can lead to slope failure. In situ measurements of soil with tree roots showed that soil strength increased linearly as root biomass increased. Forests clear-felled 3 years earlier contained about one-third of the root biomass of old-growth forests. Nearly all of the roots

Landslide susceptibility mapping using downscaled AMSR-E soil moisture: A case study from Cleveland Corral, California, US

USDA-ARS?s Scientific Manuscript database

As soil moisture increases, slope stability decreases. Remotely sensed soil moisture data can provide routine updates of slope conditions necessary for landslide predictions. For regional scale landslide investigations, only remote sensing methods have the spatial and temporal resolution required to...

Design and verification for front mirror-body structure of on-axis three mirror anastigmatic space camera

NASA Astrophysics Data System (ADS)

Wang, Xiaoyong; Guo, Chongling; Hu, Yongli; He, Hongyan

2017-11-01

The primary and secondary mirrors of onaxis three mirror anastigmatic (TMA) space camera are connected and supported by its front mirror-body structure, which affects both imaging performance and stability of the camera. In this paper, the carbon fiber reinforced plastics (CFRP) thin-walled cylinder and titanium alloy connecting rod have been used for the front mirror-body opto-mechanical structure of the long-focus on-axis and TMA space camera optical system. The front mirror-body component structure has then been optimized by finite element analysis (FEA) computing. Each performance of the front mirror-body structure has been tested by mechanics and vacuum experiments in order to verify the validity of such structure engineering design.

SLOPE STABILITY EVALUATION AND EQUIPMENT SETBACK DISTANCES FOR BURIAL GROUND EXCAVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

MCSHANE DS

2010-03-25

After 1970 Transuranic (TRU) and suspect TRU waste was buried in the ground with the intention that at some later date the waste would be retrieved and processed into a configuration for long term storage. To retrieve this waste the soil must be removed (excavated). Sloping the bank of the excavation is the method used to keep the excavation from collapsing and to provide protection for workers retrieving the waste. The purpose of this paper is to document the minimum distance (setback) that equipment must stay from the edge of the excavation to maintain a stable slope. This evaluation examinesmore » the equipment setback distance by dividing the equipment into two categories, (1) equipment used for excavation and (2) equipment used for retrieval. The section on excavation equipment will also discuss techniques used for excavation including the process of benching. Calculations 122633-C-004, 'Slope Stability Analysis' (Attachment A), and 300013-C-001, 'Crane Stability Analysis' (Attachment B), have been prepared to support this evaluation. As shown in the calculations the soil has the following properties: Unit weight 110 pounds per cubic foot; and Friction Angle (natural angle of repose) 38{sup o} or 1.28 horizontal to 1 vertical. Setback distances are measured from the top edge of the slope to the wheels/tracks of the vehicles and heavy equipment being utilized. The computer program utilized in the calculation uses the center of the wheel or track load for the analysis and this difference is accounted for in this evaluation.« less

Can sea level rise cause large submarine landslides on continental slopes?

NASA Astrophysics Data System (ADS)

Urlaub, Morelia

2014-05-01

Submarine landslides are one of the volumetrically most important sediment transport processes at continental margins. Moreover, these landslides are a major geohazard as they can cause damaging tsunamis and destroy seabed infrastructure. Due to their inaccessibility our understanding of what causes these landslides is limited and based on hypotheses that are difficult to test. Some of the largest submarine landslides, such as the Storegga Slide off Norway, occurred during times of eustatic sea level rise. It has been suggested that this global sea level rise was implicated in triggering of the landslides by causing an increase in excess pore pressure in the subseafloor. However, in a homogeneous slope a change in the thickness of the overlying water mass is not expected to affect its stability, as only the hydrostatic pressure component will change, whereas pore pressures in excess of hydrostatic will remain unaltered. Whether sufficiently rapid sea level rise, aided by rather impermeable sediment and complex layering, could cause excess pore pressures that may destabilise a continental slope is more difficult to answer and has not yet been tested. I use Finite Element Modelling to explore and quantify the direct effect of changes in the thickness of the overlying water mass on the stability of a generic sediment column with different stratigraphic conditions and hydro-mechanical properties. The results show that the direct effect of sea level rise on continental slope stability is minimal. Nevertheless, sea level rise may foster other processes, such as lithospheric stress changes resulting in increased seismicity, that could potentially cause large submarine landslides on continental slopes.

Integrated patch and slot array antenna for terahertz quantum cascade lasers at 4.7 THz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonzon, C., E-mail: bonzonc@phys.ethz.ch; Benea Chelmus, I. C.; Ohtani, K.

2014-04-21

Our work presents a slot and a patch array antenna at the front facet of a 4.7 THz quantum cascade laser as extractor, decreasing the facet reflectivity down to 2.6%. The resulting output power increases by a factor 2 and the slope efficiency by a factor 4. The simulated and the measured far-fields are in good agreement.

Integrating soils and geomorphology in mountains - An example from the Front Range of Colorado

USGS Publications Warehouse

Birkeland, P.W.; Shroba, R.R.; Burns, S.F.; Price, A.B.; Tonkin, P.J.

2003-01-01

Soil distribution in high mountains reflects the impact of several soil-forming factors. Soil geomorphologists use key pedological properties to estimate ages of Quaternary deposits of various depositional environments, estimate long-term stability and instability of landscapes, and make inferences on past climatic change. Once the influence of the soil-forming factors is known, soils can be used to help interpret some aspects of landscape evolution that otherwise might go undetected. The Front Range of Colorado rises from the plains of the Colorado Piedmont at about 1700 m past a widespread, dissected Tertiary erosion surface between 2300 and 2800 m up to an alpine Continental Divide at 3600 to over 4000 m. Pleistocene valley glaciers reached the western edge of the erosion surface. Parent rocks are broadly uniform (granitic and gneissic). Climate varies from 46 cm mean annual precipitation (MAP) and 11 ??C mean annual temperature (MAT) in the plains to 102 cm and -4 ??C, respectively, near the range crest. Vegetation follows climate with grassland in the plains, forest in the mountains, and tundra above 3450 m. Soils reflect the bioclimatic transect from plains to divide: A/Bw or Bt/Bk or K (grassland) to A/E/Bw or Bt/C (forest) to A/Bw/C (tundra). Corresponding soil pH values decrease from 8 to less than 5 with increasing elevation. The pedogenic clay minerals dominant in each major vegetation zone are: smectite (grassland), vermiculite (forest), and 1.0-1.8 nm mixed-layer clays (tundra). Within the lower forested zone, the topographic factor (aspect) results in more leached, colder soils, with relatively thin O horizons, well-expressed E horizons and Bt horizons (Alfisols) on N-facing slopes, whereas soils with thicker A horizons, less developed or no E horizons, and Bw or Bt horizons (Mollisols) are more common on S-facing slopes. The topographic factor in the tundra results in soil patterns as a consequence of wind-redistributed snow and the amount of time it lingers on the landscape. An important parent material factor is airborne dust, which results in fine-grained surface horizons and, if infiltrated, contributes to clay accumulation in some Bt horizons. The time factor is evaluated by soil chronosequence studies of Quaternary deposits in tundra, upper forest, and plains grassland. Few soils in the study area are >10,000 years old in the tundra, >100,000 years old in the forest, and >2 million years old in the grassland. Stages of granite weathering vary with distance from the Continental Divide and the best developed is grus near the sedimentary/granitic rock contact just west of the mountain front. Grus takes a minimum of 100,000 years to form. Some of the relations indicated by the soil map patterns are: (1) parts of the erosion surface have been stable for 100,000 years or more; (2) development of grus near the mountain front could be due in part to pre-Pennsylvanian weathering; (3) a few soil properties reflect Quaternary paleoclimate; and (4) a correlation between soil development in the canyons and stream incision rates. ?? 2003 Elsevier Science B.V. All rights reserved.

Dual-tracer method to estimate coral reef response to a plume of chemically modified seawater

NASA Astrophysics Data System (ADS)

Maclaren, J. K.; Caldeira, K.

2013-12-01

We present a new method, based on measurement of seawater samples, to estimate the response of a reef ecosystem to a plume of an additive (for example, a nutrient or other chemical). In the natural environment, where there may be natural variability in concentrations, it can be difficult to distinguish between changes in concentrations that would occur naturally and changes in concentrations that result from a chemical addition. Furthermore, in the unconfined natural environment, chemically modified water can mix with waters that have not been modified, making it difficult to distinguish between effects of dilution and effects of chemical fluxes or transformations. We present a dual-tracer method that extracts signals from observations that may be affected by both natural variability and dilution. In this dual-tracer method, a substance (in our example case, alkalinity) is added to the water in known proportion to a passive conservative tracer (in our example case, Rhodamine WT dye). The resulting plume of seawater is allowed to flow over the study site. Two transects are drawn across the plume at the front and back of the study site. If, in our example, alkalinity is plotted as a function of dye concentration for the front transect, the slope of the resulting mixing line is the ratio of alkalinity to dye in the added fluid. If a similar mixing line is measured and calculated for the back transect, the slope of this mixing line will indicate the amount of added alkalinity that remains in the water flowing out of the study site per unit of added dye. The ratio of the front and back slopes indicates the fraction of added alkalinity that was taken up by the reef. The method is demonstrated in an experiment performed on One Tree Reef (Queensland, Australia) aimed at showing that ocean acidification is already affecting coral reef growth. In an effort to chemically reverse some of the changes to seawater chemistry that have occurred over the past 200 years, we added sodium hydroxide to increase alkalinity in the plume and controlled for dilution with Rhodamine WT dye. Preliminary data will be presented and analyzed using the approach described above.

Crustal structure and tectonic deformation of the southern Ecuadorian margin

NASA Astrophysics Data System (ADS)

Calahorrano, Alcinoe; Collot, Jean-Yves; Sage, Françoise; Ranero, César R.

2010-05-01

Multichannel seismic lines acquired during the SISTEUR cruise (2000) provide new constraints on the structure and deformation of the subduction zone at the southern Ecuadorian margin, from the deformation front to the continental shelf of the Gulf of Guayaquil. The pre-stack depth migrated images allows to characterise the main structures of the downgoing and overriding plates and to map the margin stratigraphy in order to propose a chronology of the deformation, by means of integrating commercial well data and industry seismic lines located in the gulf area. The 100-km-long seismic lines show the oceanic Nazca plate underthrusting the South American plate, as well as the subduction channel and inter-plate contact from the deformation front to about 90 km landward and ~20 km depth. Based on seismic structure we identify four upper-plate units, consisting of basement and overlaying sedimentary sequences A, B and C. The sedimentary cover varies along the margin, being few hundreds of meters thick in the lower and middle slope, and ~2-3 km thick in the upper slope. Exceptionally, a ~10-km -thick basin, here named Banco Peru basin, is located on the upper slope at the southernmost part of the gulf. This basin seems to be the first evidence of the Gulf of Guayaquil opening resulting from the NE escaping of the North Andean Block. Below the continental shelf, thick sedimentary basins of ~6 to 8 km occupy most of the gulf area. Tectonic deformation across most of the upper-plate is dominated by extensional regime, locally disturbed by diapirism. Compression evidences are restricted to the deformation front and surrounding areas. Well data calibrating the seismic profiles indicate that an important portion of the total thickness of the sedimentary coverage of the overriding plate are Miocene or older. The data indicate the extensional deformation resulting from the NE motion of the North Andean Block and the opening of the Gulf of Guayaquil, evolves progressively in age from the southern edge of the gulf near Banco Peru, where main subsidence seems to be Miocene or older, toward the northern limit, where high subsidence rates are early Pleistocene.

Fine-grained linings of leveed channels facilitate runout of granular flows

USGS Publications Warehouse

Kokelaar, B.P.; Graham, R. L.; Gray, J.M.N.T.; Vallance, James W.

2014-01-01

Catastrophic dense granular flows, such as occur in rock avalanches, debris flows and pyroclastic flows, move as fully shearing mixtures that have approximately 60 vol.% solids and tend to segregate to form coarse-grained fronts and leveed channels. Levees restrict spreading of unconfined flows and form as coarse particles that become concentrated in the top of the flow are transported to the front and then advect to the sides in the flow head. Channels from which most material has drained away down slope are commonly lined with fine-grained deposit, widely thought to remain from the tail of the waning flow. We show how segregation in experimental dense flows of carborundum or sand (300–425 μm) mixed with spherical fine ballotini (150–250 μm), on rough slopes of 27–29°, produces fine-grained channel linings that are deposited with the levees, into which they grade laterally. Maximum runout distance is attained with mixtures containing 30–40% sand, just sufficient to segregate and form levees that are adequately robust to restrict the spreading attributable to the low-friction fines. Resin impregnation and serial sectioning of deliberately arrested experimental flows shows how fines-lined levees form from the flow head; the flows create their own stable ‘conduit’ entirely from the front, which in a geophysical context can play an important mechanistic role in facilitating runout. The flow self-organization ensures that low-friction fines at the base of the segregated channel flow shear over fine-grained substrate in the channel, thus reducing frictional energy losses. We propose that in pyroclastic flows and debris flows, which have considerable mobility attributable to pore-fluid pressures, such fine-grained flow-contact zones form similarly and not only reduce frictional energy losses but also reduce flow–substrate permeability so as to enhance pore-fluid pressure retention. Thus the granular flow self-organization that produces fine-grained channel linings can be an important factor in facilitating long runout of catastrophic geophysical flows on the low slopes (few degrees) of depositional fans and aprons around mountains and volcanoes.

Fine-grained linings of leveed channels facilitate runout of granular flows

NASA Astrophysics Data System (ADS)

Kokelaar, B. P.; Graham, R. L.; Gray, J. M. N. T.; Vallance, J. W.

2014-01-01

Catastrophic dense granular flows, such as occur in rock avalanches, debris flows and pyroclastic flows, move as fully shearing mixtures that have approximately 60 vol.% solids and tend to segregate to form coarse-grained fronts and leveed channels. Levees restrict spreading of unconfined flows and form as coarse particles that become concentrated in the top of the flow are transported to the front and then advect to the sides in the flow head. Channels from which most material has drained away down slope are commonly lined with fine-grained deposit, widely thought to remain from the tail of the waning flow. We show how segregation in experimental dense flows of carborundum or sand (300-425 μm) mixed with spherical fine ballotini (150-250 μm), on rough slopes of 27-29°, produces fine-grained channel linings that are deposited with the levees, into which they grade laterally. Maximum runout distance is attained with mixtures containing 30-40% sand, just sufficient to segregate and form levees that are adequately robust to restrict the spreading attributable to the low-friction fines. Resin impregnation and serial sectioning of deliberately arrested experimental flows shows how fines-lined levees form from the flow head; the flows create their own stable ‘conduit’ entirely from the front, which in a geophysical context can play an important mechanistic role in facilitating runout. The flow self-organization ensures that low-friction fines at the base of the segregated channel flow shear over fine-grained substrate in the channel, thus reducing frictional energy losses. We propose that in pyroclastic flows and debris flows, which have considerable mobility attributable to pore-fluid pressures, such fine-grained flow-contact zones form similarly and not only reduce frictional energy losses but also reduce flow-substrate permeability so as to enhance pore-fluid pressure retention. Thus the granular flow self-organization that produces fine-grained channel linings can be an important factor in facilitating long runout of catastrophic geophysical flows on the low slopes (few degrees) of depositional fans and aprons around mountains and volcanoes.

On ice rifts and the stability of non-Newtonian extensional flows on a sphere

NASA Astrophysics Data System (ADS)

Sayag, Roiy

2017-11-01

Rifts that form at the fronts of floating ice shelves that spread into the ocean can trigger major calving events in the ice. The deformation of ice can be modeled as a thin viscous film driven by buoyancy. The front of such a viscous film that propagates over a flat surface with no-slip basal conditions is known to have stable axisymmetric solutions. In contrast, when the fluid propagates under free-slip conditions at the substrate, the front can become unstable to small perturbations if the fluid is sufficiently strain-rate softening. Consequently, the front will develop tongues with a characteristic wavelength that coarsens over time, a pattern that is reminiscent of ice rifts. Here we investigate the stability of a spherical sheet of power-law fluids under free-slip basal conditions. The fluid is discharged at constant flux and axisymmetrically with respect to the pole, and propagates towards the equator. The propagating front in such a situation may become unstable due to its failure to sustain large extensional forces, resulting in the formation of rifts. This study has implications to understanding the cause of patterns that are observed on shells of floating ice in a range of planetary objects, and whether open rifts that sustain life were feasible in snowball earth. Israel Science Foundation 1368/16.

Role of slope stability in cumulative impact assessment of hydropower development: North Cascades, Washington

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, R.R.; Staub, W.P.

1993-08-01

Two environmental assessments considered the potential cumulative environmental impacts resulting from the development of eight proposed hydropower projects in the Nooksack River Basin and 11 proposed projects in the Skagit River Basin, North Cascades, Washington, respectively. While not identified as a target resource, slope stability and the alteration of sediment supply to creeks and river mainstems significantly affect other resources. The slope stability assessment emphasized the potential for cumulative impacts under disturbed conditions (e.g., road construction and timber harvesting) and a landslide-induced pipeline rupture scenario. In the case of small-scale slides, the sluicing action of ruptured pipeline water on themore » fresh landslide scarp was found to be capable of eroding significantly more material than the original landslide. For large-scale landslides, sluiced material was found to be a small increment of the original landslide. These results predicted that hypothetical accidental pipeline rupture by small-scale landslides may result in potential cumulative impacts for 12 of the 19 projects with pending license applications in both river basins. 5 refs., 2 tabs.« less

Implications of climate change on landslide hazard in Central Italy.

PubMed

Alvioli, Massimiliano; Melillo, Massimo; Guzzetti, Fausto; Rossi, Mauro; Palazzi, Elisa; von Hardenberg, Jost; Brunetti, Maria Teresa; Peruccacci, Silvia

2018-07-15

The relation between climate change and its potential effects on the stability of slopes remains an open issue. For rainfall induced landslides, the point consists in determining the effects of the projected changes in the duration and amounts of rainfall that can initiate slope failures. We investigated the relationship between fine-scale climate projections obtained by downscaling and the expected modifications in landslide occurrence in Central Italy. We used rainfall measurements taken by 56 rain gauges in the 9-year period 2003-2011, and the RainFARM technique to generate downscaled synthetic rainfall fields from regional climate model projections for the 14-year calibration period 2002-2015, and for the 40-year projection period 2010-2049. Using a specific algorithm, we extracted a number of rainfall events, i.e. rainfall periods separated by dry periods of no or negligible amount of rain, from the measured and the synthetic rainfall series. Then, we used the selected rainfall events to forcethe Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Model TRIGRS v. 2.1. We analyzed the results in terms of variations (or lack of variations) in the rainfall thresholds for the possible initiation of landslides, in the probability distribution of landslide size (area), and in landslide hazard. Results showed that the downscaled rainfall fields obtained by RainFARM can be used to single out rainfall events, and to force the slope stability model. Results further showed that while the rainfall thresholds for landslide occurrence are expected to change in future scenarios, the probability distribution of landslide areas are not. We infer that landslide hazard in the study area is expected to change in response to the projected variations in the rainfall conditions. We expect our results to contribute to regional investigations of the expected impact of projected climate variations on slope stability conditions and on landslide hazards. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Sensitivity analysis and calibration of a dynamic physically based slope stability model

NASA Astrophysics Data System (ADS)

Zieher, Thomas; Rutzinger, Martin; Schneider-Muntau, Barbara; Perzl, Frank; Leidinger, David; Formayer, Herbert; Geitner, Clemens

2017-06-01

Physically based modelling of slope stability on a catchment scale is still a challenging task. When applying a physically based model on such a scale (1 : 10 000 to 1 : 50 000), parameters with a high impact on the model result should be calibrated to account for (i) the spatial variability of parameter values, (ii) shortcomings of the selected model, (iii) uncertainties of laboratory tests and field measurements or (iv) parameters that cannot be derived experimentally or measured in the field (e.g. calibration constants). While systematic parameter calibration is a common task in hydrological modelling, this is rarely done using physically based slope stability models. In the present study a dynamic, physically based, coupled hydrological-geomechanical slope stability model is calibrated based on a limited number of laboratory tests and a detailed multitemporal shallow landslide inventory covering two landslide-triggering rainfall events in the Laternser valley, Vorarlberg (Austria). Sensitive parameters are identified based on a local one-at-a-time sensitivity analysis. These parameters (hydraulic conductivity, specific storage, angle of internal friction for effective stress, cohesion for effective stress) are systematically sampled and calibrated for a landslide-triggering rainfall event in August 2005. The identified model ensemble, including 25 behavioural model runs with the highest portion of correctly predicted landslides and non-landslides, is then validated with another landslide-triggering rainfall event in May 1999. The identified model ensemble correctly predicts the location and the supposed triggering timing of 73.0 % of the observed landslides triggered in August 2005 and 91.5 % of the observed landslides triggered in May 1999. Results of the model ensemble driven with raised precipitation input reveal a slight increase in areas potentially affected by slope failure. At the same time, the peak run-off increases more markedly, suggesting that precipitation intensities during the investigated landslide-triggering rainfall events were already close to or above the soil's infiltration capacity.

Geomorphology and Sediment Stability of a Segment of the U.S. Continental Slope off New Jersey.

PubMed

Robb, J M; Hampson, J C; Twichell, D C

1981-02-27

The morphology of complex deposits of Pleistocene sediments covering the upper continental slope between Lindenkohl Canyon and South Toms Canyon results from both depositional and erosional processes. Small slump or slide features were detected primarily on the flanks of canyons or valleys and were observed to occur only within Pleistocene-aged sediments. Eocene to Miocene sediments are exposed over much of the mid- and lower slope in this area.

Landslide assessment of Newell Creek Canyon, Oregon City, Oregon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Growney, L.; Burris, L.; Garletts, D.

1993-04-01

A study has been conducted in Newell Creek Canyon near Oregon City, Oregon, T3S, T2S, R2E. A landslide inventory has located 53 landslides in the 2.8 km[sup 2] area. The landslides range in area from approximately 15,000m[sup 2] to 10m[sup 2]. Past slides cover an approximate 7% of the canyon area. Landslide processes include: slump, slump-translational, slump-earthflow and earthflow. Hard, impermeable clay-rich layers in the Troutdale Formation form the failure planes for most of the slides. Slopes composed of Troutdale material may seem to be stable, but when cuts and fills are produced, slope failure is common because of themore » perched water tables and impermeable failure planes. Good examples of cut and fill failures are present on Highway 213 which passes through Newell Creek Canyon. Almost every cut and fill has failed since the road construction began. The latest failure is in the fill located at mile-post 2.1. From data gathered, a slope stability risk map was generated. Stability risk ratings are divided into three groups: high, moderate and low. High risk of slope instability is designated to all landslides mapped in the slide inventory. Moderate risk is designated to slopes in the Troutdale Formation greater than 8[degree]. Low risk is designated to slopes in the Troutdale Formation less than 8[degree].« less

Coupled Growth in Hypermonotectics

NASA Technical Reports Server (NTRS)

Andrews, J. Barry; Coriell, Sam R.

2001-01-01

The overall objective of this project is to obtain a fundamental understanding of the physics controlling solidification processes in immiscible alloy systems. The investigation involves both experimentation and the development of a model describing solidification in monotectic systems. The experimental segment was designed to first demonstrate that it is possible to obtain interface stability and steady state coupled growth in hypermonotectic alloys through microgravity processing. Microgravity results obtained to date have verified this possibility. Future flights will permit experimental determination of the limits of interface stability and the influence of alloy composition and growth rate on microstructure. The objectives of the modeling segment of the investigation include prediction of the limits of interface stability, modeling of convective flow due to residual acceleration, and the influence of surface tension driven flows at the solidification interface. The study of solidification processes in immiscible alloy systems is hindered by the inherent convective flow that occurs on Earth and by the possibility of sedimentation of the higher density immiscible liquid phase. It has been shown that processing using a high thermal gradient and a low growth rate can lead to a stable macroscopically planar growth front even in hypermonotectic alloys. Processing under these growth conditions can avoid constitutional supercooling and prevent the formation of the minor immiscible liquid phase in advance of the solidification front. However, the solute depleted boundary layer that forms in advance of the solidification front is almost always less dense than the liquid away from the solidification front. As a result, convective instability is expected. Ground based testing has indicated that convection is a major problem in these alloy systems and leads to gross compositional variations along the sample and difficulties maintaining interface stability. Sustained low gravity processing conditions are necessary in order to minimize these problems and obtain solidification conditions which approach steady state.

Physical and mathematical modeling of transient infiltration through shallow layered pyroclastic deposits

NASA Astrophysics Data System (ADS)

Damiano, Emilia; Greco, Roberto; Guida, Andrea; Olivares, Lucio; Picarelli, Luciano

2017-04-01

Layered pyroclastic deposits covering steep slopes, characteristic of large mountainous areas of Campania (southern Italy), are often affected by shallow landslides triggered by heavy rainfall events. In fact, the equilibrium of such deposits is usually guaranteed by the contribution to soil shear strength offered by soil suction, which decreases during wetting. As the return period of the triggering events has been in many cases not extreme, other factors concur to establish triggering conditions. In this respect, heterogeneities, strongly affecting transient infiltration, may in some cases play a crucial role. In this study, the effect of the presence of soil layers, characterized by markedly different hydraulic properties, on the rainwater infiltration process is investigated. In fact, the pyroclastic covers of Campania, being the result of the deposition of materials originated by several eruptions of the nearby volcanic complexes, usually consist of alternating layers of ashes (silty sands) and pumices (gravel with sand). The presence of coarse-textured pumices between finer ashes strongly affects the infiltration process. In fact, the pumices, which are characterized by saturated hydraulic conductivity larger than ashes, are capable of retaining less water than ashes in unsaturated conditions, so that their unsaturated hydraulic conductivity is usually very small. Hence, depending on the water potential distribution throughout the cover at the onset of rainfall, pumices may act as a barrier to the propagation of the wet front (the so-called capillary barrier effect), or, approaching saturation, let the water pass through them very quickly. Such a complex behavior has been studied by means of a series of infiltration experiments carried out in an instrumented flume in the Geotechnical Laboratory of the University of Campania (http://www.dicdea.unina2.it/it/dipartimento/laboratori/laboratorio-di-geotecnica). Starting from different initial moisture conditions, small scale physical models of layered slopes, with various geometry and inclination, have been subjected to rainfalls of various intensities. During the infiltration processes and the following water redistribution phases, soil moisture and matric potential have been measured at various locations by means of TDR probes and tensiometers, respectively. The interpretation of the experimental results has been aided by a 2D mathematical model based on the integration of Richards' equation with the finite differences method. The obtained results indicate that a layer of dry pumices may induce lateral redistribution of water through the overlying ashes. In steep sloping deposits, this may favor the establishment of downslope directed subsurface runoff, which drains part of the infiltrating water towards the toe of the slope. In real slopes, depending on local morphology, such a downslope flow may have a beneficial effect on slope stability, as some water is drained out of the slope, or may even contribute to the establishment of triggering conditions, as it can result in flow concentration leading to local failure.

Stress resistance strategy in an arid land shrub: interactions between developmental instability and fractal dimention

USGS Publications Warehouse

Escos, J.; Alados, C.L.; Pugnaire, F. I.; Puigdefábregas, J.; Emlen, J.

2000-01-01

This paper investigates allocation of energy to mechanisms that generate and preserve architectural forms (i.e. developmental stability, complexity of branching patterns) and productivity (growth and reproduction) in response to environmental disturbances (i.e. grazing and resource availability). The statistical error in translational symmetry was used to detect random intra-individual variability during development. This can be thought of as a measure of developmental instability caused by stress. Additionally, we use changes in fractal complexity and shoot distribution of branch structures as an alternate indicator of stress. These methods were applied to Anthyllis cytisoides L., a semi-arid environment shrub, to ascertain the effect of grazing and slope exposure on developmental traits in a 2×2 factorial design. The results show that A. cytisoidesmaintains developmental stability at the expense of productivity. Anthyllis cytisoides was developmentally more stable when grazed and when on south-facing, as opposed to north-facing slopes. On the contrary, shoot length, leaf area, fractal dimension and reproductive-to-vegetative allocation ratio were larger in north- than in south-facing slopes. As a consequence, under extreme xeric conditions, shrub mortality increased in north-facing slopes, especially when not grazed. The removal of transpiring area and the reduction of plant competition favoured developmental stability and survival in grazed plants. Differences between grazed and ungrazed plants were most evident in more mesic (north-facing) areas.

Side slope stability of articulated-frame logging tractors

Treesearch

H.G. Gibson; K.C. Elliott; S.P.E. Persson

1971-01-01

Many log or pulpwood transporting machines have hinged or articulated frames for steering. The articulated frame offers advantages for these machines, but the design introduces some problems in stability. We formulated and analyzed a mathematical model simulating stability of a 4-wheel-drive, articulated frame logging tractor (wheeled skidder) at static or low constant...

Implication of Groundwater Resources Utilization in Mountainous Region for Slopeland Disaster Prevention

NASA Astrophysics Data System (ADS)

Huang, Chi-Chao; Hsu, Shih-Meng; Lo, Hung-Chieh

2016-04-01

In recent years, groundwater resources from mountainous regions have been considered as an alternative water resource in Taiwan. According to previous research outcomes (Hsu, 2011), such a groundwater resource is capable of providing stable and high quality water resources. Additionally, another advantage of using the water resources is attributed to the contribution of slopeland disaster prevention. While pumping groundwater as water resources in hilly areas (e.g., at landslide-prone sites), pore-water pressures can be dropped, which can result in stabilizing landslide-prone slopes. However, the benefit to slope stability by using groundwater resources needs to be quantified. The purpose of this study is to investigate groundwater potential of a deep-seated landslide site first, and then to evaluate variations of slope stability by changing well pumping rate conditions. In this paper, the Baolong landslide site located at the Jiasian district of Kaohsiung city in Southern Taiwan has been selected as a case study. Hydrogeological investigation for the landslide site was conducted to clarify the complexity of field characteristics and to establish a precise conceptual model for simulation. The investigation content includes surficial geology investigation, borehole drilling (6 drilling boreholes and 350 meters drilling length in total), 45 m pumping well construction, borehole hydrogeological tests (borehole televiewer, caliper, borehole electrical logging, sonic logging, flowmeter measurement, pumping test, and double packer test), and laboratory tests from rock core samples (physical properties test of soil and rocks, triaxial permeability test of soil, porosity determination test using helium, and gas permeability test). Based on the aforementioned investigation results, a hydrogeological conceptual model for the Baolong landslide site was constructed, and a 2D slope stability model coupled with transient seepage flow model was used for numerical simulation to determine changes of slope stability by means of different well pumping rate conditions. The simulation results show that a positive relationship between the pumping rate and drawdown of well exists. In addition, the positive relationship was found between the pumping rate and the increase of safety factor for both shallow and deep sliding surfaces. If the constant pumping rate reached up to 180 L/min with the decline of groundwater level by 10.6 m, the safety factors of shallow and deep sliding surfaces are raised up to 11.87% and 15.72%, respectively. The amount of pumped water can provide daily water demand for approximately 997 people. This demonstrates the groundwater resource at this area is productive. Meanwhile, the benefit to slope stabilization by pumping groundwater is proved. Therefore, this study can provide the solution for ensuring both the safety of slopeland environment and the supply of water resources in mountainous areas. Such a win-win idea is a good mitigation measure for meeting the aim of territorial and resource sustainability.

Stabilization process of human population: a descriptive approach.

PubMed

Kayani, A K; Krotki, K J

1981-01-01

An attempt is made to inquire into the process of stabilization of a human population. The same age distribution distorted by past variations in fertility is subjected to several fixed schedules of fertility. The schedules are different from each other monotonically over a narrow range. The primary concern is with the process, almost year by year, through which the populations become stable. There is particular interest in the differential impact in the same original age distribution of the narrowly different fixed fertility schedules. The exercise is prepared in 3 stages: general background of the process of stabilization; methodology and data used; and analysis and discussion of the stabilization process. Among the several approaches through which the analysis of stable population is possible, 2 are popular: the integral equation and the projection matrix. In this presentation the interest is in evaluating the effects of fertility on the stabilization process of a population. Therefore, only 1 initial age distribution and only 1 life table but a variety of narrowly different schedules of fertility have been used. Specifically, the U.S. 1963 female population is treated as the initial population. The process of stabilization is viewed in the light of the changes in the slopes between 2 successive age groups of an age distribution. A high fertility schedule with the given initial age distribution and mortality level overcomes the oscillations more quickly than the low fertility schedule. Simulation confirms the intuitively expected positive relationship between the mean of the slope and the level of fertility. The variance of the slope distribution is an indicator of the aging of the distribution.

A Hybrid FEM-ANN Approach for Slope Instability Prediction

NASA Astrophysics Data System (ADS)

Verma, A. K.; Singh, T. N.; Chauhan, Nikhil Kumar; Sarkar, K.

2016-09-01

Assessment of slope stability is one of the most critical aspects for the life of a slope. In any slope vulnerability appraisal, Factor Of Safety (FOS) is the widely accepted index to understand, how close or far a slope from the failure. In this work, an attempt has been made to simulate a road cut slope in a landslide prone area in Rudrapryag, Uttarakhand, India which lies near Himalayan geodynamic mountain belt. A combination of Finite Element Method (FEM) and Artificial Neural Network (ANN) has been adopted to predict FOS of the slope. In ANN, a three layer, feed- forward back-propagation neural network with one input layer and one hidden layer with three neurons and one output layer has been considered and trained using datasets generated from numerical analysis of the slope and validated with new set of field slope data. Mean absolute percentage error estimated as 1.04 with coefficient of correlation between the FOS of FEM and ANN as 0.973, which indicates that the system is very vigorous and fast to predict FOS for any slope.

You Don't Need Richards'... A New General 1-D Vadose Zone Solution Method that is Reliable

NASA Astrophysics Data System (ADS)

Ogden, F. L.; Lai, W.; Zhu, J.; Steinke, R. C.; Talbot, C. A.

2015-12-01

Hydrologic modelers and mathematicians have strived to improve 1-D Richards' equation (RE) solution reliability for predicting vadose zone fluxes. Despite advances in computing power and the numerical solution of partial differential equations since Richards first published the RE in 1931, the solution remains unreliable. That is to say that there is no guarantee that for a particular set of soil constitutive relations, moisture profile conditions, or forcing input that a numerical RE solver will converge to an answer. This risk of non-convergence renders prohibitive the use of RE solvers in hydrological models that need perhaps millions of infiltration solutions. In lieu of using unreliable numerical RE solutions, researchers have developed a wide array of approximate solutions that more-or-less mimic the behavior of the RE, with some notable deficiencies such as parameter insensitivity or divergence over time. The improved Talbot-Ogden (T-O) finite water-content scheme was shown by Ogden et al. (2015) to be an extremely good approximation of the 1-D RE solution, with a difference in cumulative infiltration of only 0.2 percent over an 8 month simulation comparing the improved T-O scheme with a RE numerical solver. The reason is that the newly-derived fundamental flow equation that underpins the improved T-O method is equivalent to the RE minus a term that is equal to the diffusive flux divided by the slope of the wetting front. Because the diffusive flux has zero mean, this term is not important in calculating the mean flux. The wetting front slope is near infinite (sharp) in coarser soils that produce more significant hydrological interactions between surface and ground waters, which also makes this missing term 1) disappear in the limit, and, 2) create stability challenges for the numerical solution of RE. The improved T-O method is a replacement for the 1-D RE in soils that can be simulated as homogeneous layers, where the user is willing to neglect the effects of soil water diffusivity. This presentation emphasizes the transformative nature of the improved T-O finite water-content solution, and highlights the benefits of the methods' reliability in high-resolution large watershed simulations in the high performance computing environment, and discusses coupling of the soil matrix and non-Darcian macropores.

Comparison of two landslide susceptibility assessments in the Champagne-Ardenne region (France)

NASA Astrophysics Data System (ADS)

Den Eeckhaut, M. Van; Marre, A.; Poesen, J.

2010-02-01

The vineyards of the Montagne de Reims are mostly planted on steep south-oriented cuesta fronts receiving a maximum of sun radiation. Due to the location of the vineyards on steep hillslopes, the viticultural activity is threatened by slope failures. This study attempts to better understand the spatial patterns of landslide susceptibility in the Champagne-Ardenne region by comparing a heuristic (qualitative) and a statistical (quantitative) model in a 1120 km² study area. The heuristic landslide susceptibility model was adopted from the Bureau de Recherches Géologiques et Minières, the GEGEAA - Reims University and the Comité Interprofessionnel du Vin de Champagne. In this model, expert knowledge of the region was used to assign weights to all slope classes and lithologies present in the area, but the final susceptibility map was never evaluated with the location of mapped landslides. For the statistical landslide susceptibility assessment, logistic regression was applied to a dataset of 291 'old' (Holocene) landslides. The robustness of the logistic regression model was evaluated and ROC curves were used for model calibration and validation. With regard to the variables assumed to be important environmental factors controlling landslides, the two models are in agreement. They both indicate that present and future landslides are mainly controlled by slope gradient and lithology. However, the comparison of the two landslide susceptibility maps through (1) an evaluation with the location of mapped 'old' landslides and through (2) a temporal validation with spatial data of 'recent' (1960-1999; n = 48) and 'very recent' (2000-2008; n = 46) landslides showed a better prediction capacity for the statistical model produced in this study compared to the heuristic model. In total, the statistically-derived landslide susceptibility map succeeded in correctly classifying 81.0% of the 'old' and 91.6% of the 'recent' and 'very recent' landslides. On the susceptibility map derived from the heuristic model, on the other hand, only 54.6% of the 'old' and 64.0% of the 'recent' and 'very recent' landslides were correctly classified as unstable. Hence, the landslide susceptibility map obtained from logistic regression is a better tool for regional landslide susceptibility analysis in the study area of the Montagne de Reims. The accurate classification of zones with very high and high susceptibility allows delineating zones where viticulturists should be informed and where implementation of precaution measures is needed to secure slope stability.

Infiltration on mountain slopes: a comparison of three environments.

Treesearch

Carol P. Harden*; P. Delmas Scruggs

2003-01-01

Water is well established as a major driver of the geomorphic change that eventually reduces mountains to lower relief landscapes. Nonetheless, within the altitudinal limits of continuous vegetation in humid climates, water is also an essential factor in slope stability. In this paper, we present results from field experiments to determine infiltration rates at...

Rockfall hazard and risk assessment: an example from a high promontory at the historical site of Monemvasia, Greece

NASA Astrophysics Data System (ADS)

Saroglou, H.; Marinos, V.; Marinos, P.; Tsiambaos, G.

2012-06-01

The paper presents the kinematics of rock instability of a high limestone promontory, where the Monemvasia historical site is situated, in Peloponnese in Southern Greece. The instability phenomena poses a significant threat to the town located at the base of the slope. Rockfall episodes occurred in the past due to the relaxation of the high cliff, whereas significant undermining of the castle frontiers has been observed at the slope crest. The predominant types of instability are of planar, wedge and toppling failure of medium to large blocks. In order to investigate the existing stability conditions and decide upon the protection measures, stability and rockfall analyses were carried out for numerous slope sections under different loading conditions and protection measures were suggested. A rock-fall risk rating system is proposed, which is based on morphological and structural criteria of the rock mass and on vulnerability and consequences. The rating system is applied for individual sections along the slope and a risk map was produced, which depicted areas having different degree of risk against rockfall occurrences.

Physical and geotechnical properties and assessment of sediment stability on the continental slope and basin of the Bransfield Basin (Antarctica Peninsula)

USGS Publications Warehouse

Casas, D.; Ercilla, G.; Estrada, F.; Alonso, B.; Baraza, J.; Lee, H.; Kayen, R.; Chiocci, F.

2004-01-01

Our investigation is centred on the continental slope of the Antarctic Peninsula and adjacent basin. Type of sediments, sedimentary stratigraphy, and physical and geotechnical characterization of the sediments have been integrated. Four different types of sediments have been defined: diamictons, silty and muddy turbidites, muddy, silty and muddy matrix embedded clast contourites. There is a close correspondence between the physical properties (density, magnetic susceptibility and p-wave velocity) and the texture and/or fabric as laminations and stratification. From a quantitative point of view, only a few statistical correlations between textural and physical properties have been found. Within the geotechnical properties, only water content is most influenced by texture. This slope, with a maximum gradient observed (20??), is stable, according to the stability under gravitational loading concepts, and the maximum stable slope that would range from 22?? to 29??. Nevertheless, different instability features have been observed. Volcanic activity, bottom currents, glacial loading-unloading or earthquakes can be considered as potential mechanisms to induce instability in this area. Copyright ?? Taylor & Francis Inc.

Smooth seaward-dipping horizons - An important factor in sea-floor stability?

USGS Publications Warehouse

McGregor, B.A.

1981-01-01

Mass movement has influenced in varying degrees the morphology of the United States east coast continental margin seaward of the Baltimore Canyon trough as revealed by detailed geophysical studies using high-resolution 3.5-kHz, and seismic reflection data. Each of three areas studied is along the slope within a distance of 225 km, and is seaward of a nonglaciated shelf but near major land drainage systems. Thick sequences of material believed to be Pleistocene were deposited on the slope in all three areas. Sediment failure in the form of large block movement involving block thicknesses of more than 100 m, however, has taken place in only two of the areas. A factor common to the two areas where failure took place, but absent in the area where no failure took place, is smooth seaward-dipping sub-bottom horizons. Whatever the triggering mechanism, a smooth slip surface that has a seward slope may contribute to mass movement by reducing the internal friction. This may be one of several factors that should be considered in assessing slope stability. ?? 1981.

Design guidelines for horizontal drains used for slope stabilization.

DOT National Transportation Integrated Search

2013-03-01

The presence of water is one of the most critical factors contributing to the instability of hillslopes. A common : solution to stabilize hillslopes is installation of horizontal drains to decrease the elevation of the water table : surface. Lowering...

Anchorage strength and slope stability of a landfill liner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villard, P.; Gourc, J.P.; Feki, N.

1997-11-01

In order to determine reliable dimensions of an anchorage system and satisfactory operation of the watertight liner in a waste landfill, it is essential to make an accurate assessment of the tensions acting on the geosynthetics on the top of the slope. Experimental and theoretical studies have been carried out in parallel. The former concern a full-scale experiment undertaken in Montreuil sur Barse on a waste storage site with instrumented slope. The latter concern anchorage tests performed on a scale model for different anchorage geometries.

Stability and predictors of change in salivary cortisol measures over six years: MESA.

PubMed

Wang, Xu; Sánchez, Brisa N; Golden, Sherita Hill; Shrager, Sandi; Kirschbaum, Clemens; Karlamangla, Arun S; Seeman, Teresa E; Roux, Ana V Diez

2014-11-01

A major challenge in characterizing features of the daily cortisol curve is variability in features over time. Few studies have examined the stability of daily features of the cortisol curve over long periods or the predictors of long term changes. Repeated salivary cortisol measures on 580 adults from the MESA Stress study were used to examine the stability of various features of the daily cortisol curve (wakeup value, the cortisol awakening response (CAR), the early and late decline slope and the area under the curve (AUC)), over short periods (several days) and long periods (approximately 6-years) and to investigate the association of demographic factors with the changes. Intraclass correlation coefficients (ICCs) were used to estimate the short and long term stability. Piecewise linear mixed models were used to assess factors associated with changes in features over time. For most features, short term stability (ICCs: 0.17-0.74) was higher than long term stability (ICCs: 0.05-0.42), and long term stability was highest when several days were averaged for each time point. The decline over the day showed the highest long term stability: when several days for each wave were averaged the stability of the daily decline slope across 6 years was similar (or higher) than the stability across short periods. AUC had high stability over short periods (ICCs: 0.65-0.74) but much lower stability across long periods (ICC: 0.05). All features of daily cortisol curve investigated changed significantly over the approximately 6 year follow-up period. The wakeup cortisol became higher; the CAR became smaller; both the early and late decline became flatter; and the AUC became larger. Hispanics experienced significantly larger increases in the wakeup value; and African-Americans and Hispanics showed less flattening over time of the early decline slope than Non-Hispanic Whites. Our findings have implications for characterization of features in studies linking cortisol to health outcomes. The presence of variability over time suggests opportunities for future investigation of the predictors of changes over time as well as the links between these changes and health outcomes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Measurement of Posterior Tibial Slope Using Magnetic Resonance Imaging.

PubMed

Karimi, Elham; Norouzian, Mohsen; Birjandinejad, Ali; Zandi, Reza; Makhmalbaf, Hadi

2017-11-01

Posterior tibial slope (PTS) is an important factor in the knee joint biomechanics and one of the bone features, which affects knee joint stability. Posterior tibial slope has impact on flexion gap, knee joint stability and posterior femoral rollback that are related to wide range of knee motion. During high tibial osteotomy and total knee arthroplasty (TKA) surgery, proper retaining the mechanical and anatomical axis is important. The aim of this study was to evaluate the value of posterior tibial slope in medial and lateral compartments of tibial plateau and to assess the relationship among the slope with age, gender and other variables of tibial plateau surface. This descriptive study was conducted on 132 healthy knees (80 males and 52 females) with a mean age of 38.26±11.45 (20-60 years) at Imam Reza hospital in Mashhad, Iran. All patients, selected and enrolled for MRI in this study, were admitted for knee pain with uncertain clinical history. According to initial physical knee examinations the study subjects were reported healthy. The mean posterior tibial slope was 7.78± 2.48 degrees in the medial compartment and 6.85± 2.24 degrees in lateral compartment. No significant correlation was found between age and gender with posterior tibial slope ( P ≥0.05), but there was significant relationship among PTS with mediolateral width, plateau area and medial plateau. Comparison of different studies revealed that the PTS value in our study is different from other communities, which can be associated with genetic and racial factors. The results of our study are useful to PTS reconstruction in surgeries.

Prediction for potential landslide zones using seismic amplitude in Liwan gas field, northern South China Sea

NASA Astrophysics Data System (ADS)

Li, Xishuang; Liu, Baohua; Liu, Lejun; Zheng, Jiewen; Zhou, Songwang; Zhou, Qingjie

2017-12-01

The Liwan (Lw) gas field located in the northern slope of the South China Sea (SCS) is extremely complex for its sea-floor topograghy, which is a huge challenge for the safety of subsea facilities. It is economically impractical to obtain parameters for risk assessment of slope stability through a large amount of sampling over the whole field. The linkage between soil shear strength and seabed peak amplitude derived from 2D/3D seismic data is helpful for understanding the regional slope-instability risk. In this paper, the relationships among seabed peak, acoustic impedance and shear strength of shallow soil in the study area were discussed based on statistical analysis results. We obtained a similar relationship to that obtained in other deep-water areas. There is a positive correlation between seabed peak amplitude and acoustic impedance and an exponential relationship between acoustic impedance and shear strength of sediment. The acoustic impedance is the key factor linking the seismic amplitude and shear strength. Infinite slope stability analysis results indicate the areas have a high potential of shallow landslide on slopes exceeding 15° when the thickness of loose sediments exceeds 8 m in the Lw gas field. Our prediction shows that they are mainly located in the heads and walls of submarine canyons.

Cold fronts and reservoir limnology: an integrated approach towards the ecological dynamics of freshwater ecosystems.

PubMed

Tundisi, J G; Matsumura-Tundisi, T; Pereira, K C; Luzia, A P; Passerini, M D; Chiba, W A C; Morais, M A; Sebastien, N Y

2010-10-01

In this paper the authors discuss the effects of cold fronts on the dynamics of freshwater ecosystems of southeast South America. Cold fronts originating from the Antarctic show a monthly frequency that promotes turbulence and vertical mixing in reservoirs with a consequence to homogenize nutrient distribution, dissolved oxygen and temperature. Weak thermoclines and the athelomixis process immediately before, during and after the passage of cold fronts interfere with phytoplankton succession in reservoirs. Cyanobacteria blooms in eutrophic reservoirs are frequently connected with periods of stratification and stability of the water column. Cold fronts in the Amazon and Pantanal lakes may produce fish killings during the process of "friagem" associated mixing events. Further studies will try to implement a model to predict the impact of cold fronts and prepare management procedures in order to cope with cyanobacteria blooms during warm and stable water column periods. Changes in water quality of reservoirs are expected during circulation periods caused by cold fronts.

Reply: Comparison of slope instability screening tools following a large storm event and application to forest management and policy

NASA Astrophysics Data System (ADS)

Whittaker, Kara A.; McShane, Dan

2013-02-01

A large storm event in southwest Washington State triggered over 2500 landslides and provided an opportunity to assess two slope stability screening tools. The statistical analysis conducted demonstrated that both screening tools are effective at predicting where landslides were likely to take place (Whittaker and McShane, 2012). Here we reply to two discussions of this article related to the development of the slope stability screening tools and the accuracy and scale of the spatial data used. Neither of the discussions address our statistical analysis or results. We provide greater detail on our sampling criteria and also elaborate on the policy and management implications of our findings and how they complement those of a separate investigation of landslides resulting from the same storm. The conclusions made in Whittaker and McShane (2012) stand as originally published unless future analysis indicates otherwise.

Roller bearing geometry design

NASA Technical Reports Server (NTRS)

Savage, M.; Pinkston, B. H. W.

1976-01-01

A theory of kinematic stabilization of rolling cylinders is extended and applied to the design of cylindrical roller bearings. The kinematic stabilization mechanism puts a reverse skew into the rolling elements by changing the roller taper. Twelve basic bearing modification designs are identified amd modeled. Four have single transverse convex curvature in their rollers while eight have rollers which have compound transverse curvature made up of a central cylindrical band surrounded by symmetric bands with slope and transverse curvature. The bearing designs are modeled for restoring torque per unit axial displacement, contact stress capacity, and contact area including dynamic loading, misalignment sensitivity and roller proportion. Design programs are available which size the single transverse curvature roller designs for a series of roller slopes and load separations and which design the compound roller bearings for a series of slopes and transverse radii of curvature. The compound rollers are proportioned to have equal contact stresses and minimum size. Design examples are also given.

Landslides induced by heavy rainfall in July 2012 in Northern Kyushu District, Japan and the influence of long term rainfall increase comparing with the slope destabilization due to strong seismic shaking

NASA Astrophysics Data System (ADS)

Kubota, Tetsuya; Shinohara, Yoshinori; Aditian, Aril

2013-04-01

1. Objective We had a deluge in July 2012 in the northern Kyushu district with intense rainfall of 800mm and 108mm/hr. This intensity yielded countless traces of debris flow and landslides, slope failures that induced tremendous damage and causalities in the area. Hence, several field investigations and reconnaissance tasks were conducted to delve into this sediment-related disaster. The various results and the information obtained through this investigation were reported, mentioning the damage, the meteorological condition, geologic-geomorphologic features and hydraulic characteristics of the debris flows, vegetation effects, and the influence of the climate change. Increase in rainfall that may be induced by the global climate change is obvious in Kyushu district, Japan, according to the analysis of rain data observed in various locations including mountainside points that are not influenced by local warming due to urbanization. On this point of view, we are intrigued to elucidate the response of landslide to this increase in rainfall. Hence, its long term impact on this landslide disaster is also analyzed comparing with the slope destabilization due to strong seismic shaking. 2. Method and target areas Field investigation on landslides slopes, slope failures and torrents where debris flows occurred are conducted to obtain the geologic data, geo-structure, vegetation feature, soil samples and topographic data i.e. cross sections, then soil shear tests and soil permeability tests are also conducted. The rainfall data at the nearest rain observatory were obtained from the database of Japan meteorological agency. The long term impact on the slope stability at some slopes in the area is analyzed by the finite element method (FEM) combined with rain infiltration and seepage analysis with the long term rainfall fluctuation data, obtaining factor of safety ( Fs) on real landslide slopes. The results are compared with the destabilized influence on the slopes due to the soil strength reduction by seismic shaking. The target areas are located in northern Kyushu district, western Japan where they often have severe landslide disasters. The geology in research areas consists of Paleozoic and Mesozoic rocks (mainly schist, slate) and Quaternary volcanic sediment such as Aso volcano body. The vegetation consists of mainly Japanese cypress, cedar or bamboo. 3. Result and consideration Consequently, the long term rainfall increase in the region such as increment of approximately 20 mm/hr for rain intensity Ri in 36 years is confirmed statistically using Kendall's rank correlation, and it is found that its impact on slope stability is considerable and critical in other cases. In the sample landslide slopes, even the increase in rain of duration for only 10 years has impact to a certain extent on their stabilities in terms of Fs. The Fs calculated with rains in previous decade is higher than 1.0 that corresponds to stable state, whereas the Fs with present rains is lower than 1.0 such as 0.99 which means unstable state. Extremely heavy rainfall with this impact is generally cause extreme ground water pressure in the slope. It is also obvious that the extreme ground water content rendered even small landslides liquefied to be source of destructive debris flows. In this disaster, especially in the Aso volcanic region, tremendous number of debris flow occurred and even the talus cone slopes which are usually stable collapsed to flow down. However, the influence of the long term rainfall increase on the slopes (such as 1% decrease in Fs) is not relatively small compared with the destabilization of the slopes due to the reduction of soil strength by seismic shaking (8~9 % reduction in Fs after seismic shaking of even 490gal). 4. Conclusion In the disaster in July 2012, many landslides and debris flows originated from landslides induced by concentrated underground water supplied by the heavy rainfall occurred. The increase of rainfall due to climate change with the increasing rate such as 20 mm/hr surely has impact on almost landslide slopes in aspects of slope stability, although the influence of the long term rainfall increase on the slopes is relatively small compared with the destabilization of the slopes due to the reduction of soil strength by seismic shakings. Therefore, with this rain increase rate, it is possible for many forest slopes or natural slopes to become unstable and cause landslide disasters especially after potential strong earthquake in the near future.

Actuation stability test of the LISA pathfinder inertial sensor front-end electronics

NASA Astrophysics Data System (ADS)

Mance, Davor; Gan, Li; Weber, Bill; Weber, Franz; Zweifel, Peter

In order to limit the residual stray forces on the inertial sensor test mass in LISA pathfinder, √ it is required that the fluctuation of the test mass actuation voltage is within 2ppm/ Hz. The actuation voltage stability test on the flight hardware of the inertial sensor front-end electronics (IS FEE) is presented in this paper. This test is completed during the inertial sensor integration at EADS Astrium Friedrichshafen, Germany. The standard measurement method using voltmeter is not sufficient for verification, since the instrument low frequency √ fluctuation is higher than the 2ppm/ Hz requirement. In this test, by using the differential measurement method and the lock-in amplifier, the actuation stability performance is verified and the quality of the IS FEE hardware is confirmed by the test results.

A rill erosion-vegetation modeling approach for the evaluation of slope reclamation success in water-limited environments

NASA Astrophysics Data System (ADS)

Moreno de las Heras, Mariano; Diaz Sierra, Ruben; Nicolau, Jose M.; Zavala, Miguel A.

2013-04-01

Slope reclamation from surface mining and road construction usually shows important constraints in water-limited environments. Soil erosion is perceived as a critical process, especially when rill formation occurs, as rills can condition the spatial distribution and availability of soil moisture for plant growth, hence affecting vegetation development. On the other hand, encouraging early vegetation establishment is essential to reduce the risk of degradation in these man-made systems. This work describes a modeling approach focused on stability analysis of water-limited reclaimed slopes, where interactive relationships between rill erosion and vegetation regulate ecosystem stability. Our framework reproduces two main groups of trends along the temporal evolution of reclaimed slopes: successful trends, characterized by widespread vegetation development and the effective control of rill erosion processes; and gullying trends, characterized by the progressive loss of vegetation and a sharp logistic increase in erosion rates. Furthermore, this analytical approach allows the determination of threshold values for both vegetation cover and rill erosion that drive the system's stability, facilitating the identification of critical situations that require specific human intervention (e.g. revegetation or, in very problematic cases, revegetation combined with rill network destruction) to ensure the long-term sustainability of the restored ecosystem. We apply our threshold analysis framework in Mediterranean-dry reclaimed slopes derived form surface coal mining (the Teruel coalfield in central-east Spain), obtaining a good field-based performance. Therefore, we believe that this model is a valuable contribution for the management of water-limited reclaimed systems, as it can play an important role in decision-making during ecosystem restoration and provides a tool for the assessment of restoration success in severely disturbed landscapes.

Testing the suitability of some endemic and exotic species for eco-engineering applications to control slope processes

NASA Astrophysics Data System (ADS)

Cammeraat, L. H.; van Beek, L. P. H.

2009-04-01

Eco-engineering is a growing, but still under rated field at the interface of landscape ecology and civil engineering. Although the principles are already known for a long period, the attention for green remediation techniques is increasing, especially in slope stabilizing projects as well as in soil erosion protection. This study discusses tests carried out on the effectiveness of plants to stabilize steep slopes. Four different treatments were compared: A naturally vegetated terrace slope (Brachyopodum retusem grass dominated), a slope completely stripped from vegetation, a slope planted with Arrundo donax (Spanish cane) and a slope with vetiver grass (Vetiver zizanioides), the last one being an often successfully applied, but exotic tropical species for erosion and slope protection. The tests were carried out in double, on unarmored steep bench terrace slopes (30-60° slope angle) on homogeneous marl in E Spain (Rio Serpis Basin). Vegetation was planted in summer and irrigated during the first summer period. Precipitation and soil temperature were measured and runoff and erosion was measured at the installed ‘Gerlach troughs'. Soil physical properties were determined such as bulk density and shear strength. The uprooting resistance of the vetiver grass was also determined as well as root density, root depth and other root parameters. Above ground plant characteristic such as plant height and base diameter were also measured. Results showed that within one year the bare slope was completely covered again with natural Brachiopodum grass dominated vegetation and that the planted vetiver and Spanish cane vegetation seemed to develop successfully. However, investigations showed that especially the roots of the vetiver grasses were not as well and deeply developed as could be expected from literature, although their surface cover and above ground biomass were good. All tested species worked well with respect to retaining soil material under overland flow conditions including the vetiver grass slopes. In the second spring after the start of the experiment however, a large rainfall event occurred and one of the test slopes planted with vetiver grass, slumped downwards over a slide plane at 30-40 cm depth, whereas the other vetiver slope remained in position. The other test slopes did not show any downward movement or erosion phenomena. The disappointing effectiveness of vetiver might be attributed to 1) hot and dry summer conditions when root growth is reduced or stops, to 2) low winter temperature conditions, which also hampers biomass production or creating frost damage, 3) the relative dense subsoil, which is difficult to penetrate by roots. Although Spanish cane showed good effectiveness, it spreads very fast and uncontrolled to other places, and is then difficult to remove. The conclusion can be made that despite the wide application of vetiver, also in the Mediterranean, it is not suitable for Mediterranean areas with either too dry conditions or that are too cold in winter. Spanish cane is also not suitable for its uncontrolled expansion. The remaining conclusion is that endemic species that are adapted to the local conditions are more favorable for application in eco-engineering applications, given that the species selected have potential for capturing sediment and increasing infiltration under overland flow conditions, or have well developed deep root systems that increase slope stability.

Growth rates of the buoyancy-driven instability of an autocatalytic reaction front in a narrow cell

PubMed

Bockmann; Muller

2000-09-18

Experimental studies were performed on the buoyancy-driven instability of an autocatalytic reaction front in a quasi-2D cell. The unstable density stratification at an ascending front leads to convection that results in a fingerlike front deformation. The growth rates of the spatial modes of the instability are determined at the initial stage. A stabilization is found at higher wave numbers, while the system is unstable against low wave number perturbations. Whereas comparison with a reported model governed by Hele-Shaw flow fails, a two-dimensional Navier-Stokes model yields more satisfactory results. Still, present deviations suggest the presence of an additional mechanism that suppresses the growth.

New classification of landslide-inducing anthropogenic activities

NASA Astrophysics Data System (ADS)

Michoud, C.; Jaboyedoff, M.; Derron, M.-H.; Nadim, F.; Leroi, E.

2012-04-01

Although landslides are usually considered typical examples of natural hazards, they can be influenced by human activities. Many examples can be found in the literature about slope instabilities induced by anthropogenic activities, ranging from small superficial landslides to rock avalanches. Research on this topic is of primary importance for understanding and mitigation of landslide risk. Indeed, slope stabilities influenced by human actions contribute significantly to the risk level because, by definition, they are located where elements at risk and people are present. Within the framework of the European project SafeLand "Living with Landslide Risk in Europe", the authors analyzed the landslides induced by anthropogenic factors in Europe and elsewhere (SafeLand deliverable D1.6). During the bibliographical research, it appeared that a complete and illustrated classification on human activities influencing slope stabilities does not yet exist. Therefore, a new classification was introduced by Michoud et al. (2011) about anthropogenic activities affecting slope stability conditions. This classification takes into account conceptual processes leading to landslides (Terzaghi, 1950; Jaboyedoff and Derron, 2005) and the distinction between destabilization factors and triggering factors (Vaunat et al., 1994; Leroueil et al., 1996). The classification was tested and improved through fifty-eight well-documented case studies, even lots of large landslides, such as Elm, Aberfan, Namsos and Rissa landslides, etc. Furthermore, the boundary between natural and "anthropogenic" landslide triggers (e.g. water run-off modified by new land-uses, creating landslides some km farther), and the time during which changes and reactions are to be considered as direct consequences of human activities were highlighted. Finally, anthropogenic influences can also be positive and examples of (non-voluntary) positive human impacts on slope stability are presented. Jaboyedoff, M. and Derron, M.-H. 2005. Integrated risk assessment process for landslides. In: Landslide risk management, Hungr, O., Fell, R., Couture, R. and Eberhardt, E. (eds.): 776 p. Leroueil, S., Locat, J., Vaunat, J., Picarelli, L. Lee, H. and Faure, R. 1996. Geotechnical characterization of slope movements, Landslides, Senneset (ed.), 53-73. Michoud, C., Jaboyedoff, M., Derron, M.-H., Nadim, F. and Leroi, E. 2011. Classification of landslide-inducing anthropogenic activities, 5th Canadian Conference on Geotechnique and Natural Hazards, Kelowna, Canada, 10 p. Terzaghi, K. 1950. Mechanism of Landslides, The Geological Society of America, Engineering Geology (Berkley) Volume, 83-123. Vaunat, J., Leroueil, S. and Faure, R. 1994. Slope movements: a geotechnical perspective. Proc. 7th Int. Congress of Int. Association of Engineering Geology, Oliveira (ed.), 1637-1646.

Using Controlled Landslide Initiation Experiments to Test Limit-Equilibrium Analyses of Slope Stability

NASA Astrophysics Data System (ADS)

Reid, M. E.; Iverson, R. M.; Brien, D. L.; Iverson, N. R.; Lahusen, R. G.; Logan, M.

2004-12-01

Most studies of landslide initiation employ limit equilibrium analyses of slope stability. Owing to a lack of detailed data, however, few studies have tested limit-equilibrium predictions against physical measurements of slope failure. We have conducted a series of field-scale, highly controlled landslide initiation experiments at the USGS debris-flow flume in Oregon; these experiments provide exceptional data to test limit equilibrium methods. In each of seven experiments, we attempted to induce failure in a 0.65m thick, 2m wide, 6m3 prism of loamy sand placed behind a retaining wall in the 31° sloping flume. We systematically investigated triggering of sliding by groundwater injection, by prolonged moderate-intensity sprinkling, and by bursts of high intensity sprinkling. We also used vibratory compaction to control soil porosity and thereby investigate differences in failure behavior of dense and loose soils. About 50 sensors were monitored at 20 Hz during the experiments, including nests of tiltmeters buried at 7 cm spacing to define subsurface failure geometry, and nests of tensiometers and pore-pressure sensors to define evolving pore-pressure fields. In addition, we performed ancillary laboratory tests to measure soil porosity, shear strength, hydraulic conductivity, and compressibility. In loose soils (porosity of 0.52 to 0.55), abrupt failure typically occurred along the flume bed after substantial soil deformation. In denser soils (porosity of 0.41 to 0.44), gradual failure occurred within the soil prism. All failure surfaces had a maximum length to depth ratio of about 7. In even denser soil (porosity of 0.39), we could not induce failure by sprinkling. The internal friction angle of the soils varied from 28° to 40° with decreasing porosity. We analyzed stability at failure, given the observed pore-pressure conditions just prior to large movement, using a 1-D infinite-slope method and a more complete 2-D Janbu method. Each method provides a static Factor of Safety (FS), and in theory failure occurs when FS ≤ 1. Using the 1-D analysis, all experiments having failure had FS well below 1 (typically 0.5-0.8). Using the 2-D analysis for these same conditions, FS was less than but closer to 1 (typically 0.8-0.9). For the experiment with no failure, the 2-D FS was, reassuringly, > 1. These results indicate that the 2-D Janbu analysis is more accurate than the 1-D infinite-slope method for computing limit-equilibrium slope stability in shallow slides with limited areal extent.

Numerical experiments based on a coupled physical-biochemical ocean model to study the Kuroshio-induced nutrient supply on the shelf-slope region off the southwestern coast of Japan

NASA Astrophysics Data System (ADS)

Kuroda, Hiroshi; Takasuka, Akinori; Hirota, Yuichi; Kodama, Taketoshi; Ichikawa, Tadafumi; Takahashi, Daisuke; Aoki, Kazuhiro; Setou, Takashi

2018-03-01

We developed a triply nested 1/50° ocean model coupled with a NPZD-type lower trophic level ecosystem model and used it to conduct numerical experiments to identify the major processes that supply nutrients on the shelf-slope region north of the Kuroshio. Tosa Bay, an open-type bay facing the Kuroshio, was selected for our experiment. Comparisons of numerical simulations using different grid sizes revealed that a grid size no larger than 1/50° was essential to reproduce a time-independent density structure related to the Kuroshio jet that uplifted nitrate from subsurface waters into the euphotic zone north of the Kuroshio front. The monthly mean budget of nitrate within the euphotic zone on the shelf showed that primary production was nearly balanced by physical advection and the biochemical supply of nitrate via mechanisms such as remineralization of detritus. Eddy advection of nitrate based on Reynolds decomposition, attributable primarily to submesoscale variations, had both positive and negative values within the bay, the indication being that eddy advection functioned regionally to supply or remove nitrate. Lagrangian particle-tracking experiments were performed to examine the major pathways of the nitrate used for primary production in Tosa Bay during the summer, when subsurface maxima of primary production typically appeared. The experiments revealed that when the Kuroshio took a stable nearshore path, nitrate was frequently uplifted around the Kuroshio front and horizontally transported along the front and into the bay via the counterclockwise circulation within the bay; it was sometimes further uplifted onto the shelf.

Front-Eddy Influence on Water Column Properties, Phytoplankton Community Structure, and Cross-Shelf Exchange of Diatom Taxa in the Shelf-Slope Area off Concepción (˜36-37°S)

NASA Astrophysics Data System (ADS)

Morales, Carmen E.; Anabalón, Valeria; Bento, Joaquim P.; Hormazabal, Samuel; Cornejo, Marcela; Correa-Ramírez, Marco A.; Silva, Nelson

2017-11-01

In eastern boundary current systems (EBCSs), submesoscale to mesocale variability contributes to cross-shore exchanges of water properties, nutrients, and plankton. Data from a short-term summer survey and satellite time series (January-February 2014) were used to characterize submesoscale variability in oceanographic conditions and phytoplankton distribution across the coastal upwelling and coastal transition zones north of Punta Lavapié, and to explore cross-shelf exchanges of diatom taxa. A thermohaline front (FRN-1) flanked by a mesoscale anticyclonic intrathermocline eddy (ITE-1), or mode-water eddy, persisted during the time series and the survey was undertaken during a wind relaxation event. At the survey time, ITE-1 contributed to an onshore intrusion of warm oceanic waters (southern section) and an offshore advection of cold coastal waters (northern section), with the latter forming a cold, high chlorophyll-a filament. In situ phytoplankton and diatom biomasses were highest at the surface in FRN-1 and at the subsurface in ITE-1, whereas values in the coastal zone were lower and dominated by smaller cells. Diatom species typical of the coastal zone and species dominant in oceanic waters were both found in the FRN-1 and ITE-1 interaction area, suggesting that this mixture was the result of both offshore and onshore advection. Overall, front-eddy interactions in EBCSs could enhance cross-shelf exchanges of coastal and oceanic plankton, as well as sustain phytoplankton growth in the slope area through localized upward injections of nutrients in the frontal zone, combined with ITE-induced advection and vertical nutrient inputs to the surface layer.

Permit application modifications

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1995-11-01

This document contains the Permit Application Modifications for the Y-12 Industrial Landfill V site on the Oak Ridge Reservation. These modifications include the assessment of stability of the proposed Landfill V under static and loading conditions. Analyses performed include the general slope stability, veneer stability of the bottom liner and cover system, and a liquefaction potential assessment of the foundation soils.

Interaction between drilled shaft and mechanically stabilized earth (MSE) wall : project summary.

DOT National Transportation Integrated Search

2015-08-31

Drilled shafts are being constructed within the reinforced zone of mechanically stabilized earth (MSE) walls (Figure 1). The drilled shafts may be subjected to horizontal loads and push against the front of the wall. Distress of MSE wall panels has b...

Integrated Chassis Control of Active Front Steering and Yaw Stability Control Based on Improved Inverse Nyquist Array Method

PubMed Central

2014-01-01

An integrated chassis control (ICC) system with active front steering (AFS) and yaw stability control (YSC) is introduced in this paper. The proposed ICC algorithm uses the improved Inverse Nyquist Array (INA) method based on a 2-degree-of-freedom (DOF) planar vehicle reference model to decouple the plant dynamics under different frequency bands, and the change of velocity and cornering stiffness were considered to calculate the analytical solution in the precompensator design so that the INA based algorithm runs well and fast on the nonlinear vehicle system. The stability of the system is guaranteed by dynamic compensator together with a proposed PI feedback controller. After the response analysis of the system on frequency domain and time domain, simulations under step steering maneuver were carried out using a 2-DOF vehicle model and a 14-DOF vehicle model by Matlab/Simulink. The results show that the system is decoupled and the vehicle handling and stability performance are significantly improved by the proposed method. PMID:24782676

Integrated chassis control of active front steering and yaw stability control based on improved inverse nyquist array method.

PubMed

Zhu, Bing; Chen, Yizhou; Zhao, Jian

2014-01-01

An integrated chassis control (ICC) system with active front steering (AFS) and yaw stability control (YSC) is introduced in this paper. The proposed ICC algorithm uses the improved Inverse Nyquist Array (INA) method based on a 2-degree-of-freedom (DOF) planar vehicle reference model to decouple the plant dynamics under different frequency bands, and the change of velocity and cornering stiffness were considered to calculate the analytical solution in the precompensator design so that the INA based algorithm runs well and fast on the nonlinear vehicle system. The stability of the system is guaranteed by dynamic compensator together with a proposed PI feedback controller. After the response analysis of the system on frequency domain and time domain, simulations under step steering maneuver were carried out using a 2-DOF vehicle model and a 14-DOF vehicle model by Matlab/Simulink. The results show that the system is decoupled and the vehicle handling and stability performance are significantly improved by the proposed method.

Numerical Modeling of Infragravity Wave Runup on Steep and Mildly Sloping Natural Beaches

NASA Astrophysics Data System (ADS)

Fiedler, J. W.; Smit, P.; Brodie, K. L.; McNinch, J.; Guza, R. T.; Gallien, T.

2016-12-01

We present ongoing work which aims to validate the non-hydrostatic model SWASH for wave runup and infragravity waves generated by a range of different incident wave spectra at the offshore boundary, including the effect of finite directional spread. Flume studies of wave runup are limited to normally incident (1D) sea and infragravity waves, but natural waves are directionally spread (2D), with substantially different dynamics from 1D. For example, refractive trapping (edge waves) is only possible with 2D waves, and the bound infragravity wave response to short wave groups is highly amplified for the special case of normal incidence. Selected case studies are modeled at Agate Beach, Oregon, a low slope (1:80) beach with maximum offshore wave heights greater than 7m, and Cardiff, California, a steep (1:8) beach with maximum wave heights of 2m. Peak periods ranged between 5-20 s at both sites. On both beaches, waves were measured on a transect from approximately 10m depth to the runup, using pressure sensors, current meters, and a scanning lidar. Bulk short wave quantities, wave runup, infragravity frequency spectra and energy fluxes are compared with SWASH. On the low slope beach with energetic incident waves, the observed horizontal runup excursions reach 140m ( 100s periods). Swash front velocities reached up to several m/s, causing short waves to stack up during runup drawdown. On reversal of the infragravity phase, the stacked short waves are swept onshore with the long wave front, effectively enhancing runup by phase coupling long and short waves. Statistical variability and nonlinearity in swash generation lead to time-varying runup heights. Here, we test these observations with 2D SWASH, as well as the sensitivity of modeled runup to the parameterization of bottom friction.

Slope movements triggered by heavy rainfall, November 3–5, 1985, in Virginia and West Virginia, U.S.A.

USGS Publications Warehouse

Jacobson, Robert B.; Cron, Elizabeth D.; McGeehin, John P.

1989-01-01

Study of slope movements triggered by the storm of November 3–5, 1985, in the central Appalachian Mountains, U.S.A., has helped to define the meteorologic conditions leading to slope movements and the relative importance of land cover, bedrock, surficial geology, and geomorphology in slope movement location. This long-duration rainfall at moderate intensities triggered more than 1,000 slope movements in a 1,040-km2 study area. Most were shallow slips and slip-flows in thin colluvium and residuum on shale slopes. Locations of these failures were sensitive to land cover and slope aspect but were relatively insensitive to topographic setting. A few shallow slope movements were triggered by the same rainfall on interbedded limestone, shale, and sandstone. Several large debris slide-avalanches were triggered in sandstone regolith high on ridges in areas of the highest measured rainfall. Most of these sites were on slopes that dip 30 to 35° and lie parallel to bedding planes, presumably the sites of least stability.

Development of a GIS-based failure investigation system for highway soil slopes

NASA Astrophysics Data System (ADS)

Ramanathan, Raghav; Aydilek, Ahmet H.; Tanyu, Burak F.

2015-06-01

A framework for preparation of an early warning system was developed for Maryland, using a GIS database and a collective overlay of maps that highlight highway slopes susceptible to soil slides or slope failures in advance through spatial and statistical analysis. Data for existing soil slope failures was collected from geotechnical reports and field visits. A total of 48 slope failures were recorded and analyzed. Six factors, including event precipitation, geological formation, land cover, slope history, slope angle, and elevation were considered to affect highway soil slope stability. The observed trends indicate that precipitation and poor surface or subsurface drainage conditions are principal factors causing slope failures. 96% of the failed slopes have an open drainage section. A majority of the failed slopes lie in regions with relatively high event precipitation ( P>200 mm). 90% of the existing failures are surficial erosion type failures, and only 1 out of the 42 slope failures is deep rotational type failure. More than half of the analyzed slope failures have occurred in regions having low density land cover. 46% of failures are on slopes with slope angles between 20° and 30°. Influx of more data relating to failed slopes should give rise to more trends, and thus the developed slope management system will aid the state highway engineers in prudential budget allocation and prioritizing different remediation projects based on the literature reviewed on the principles, concepts, techniques, and methodology for slope instability evaluation (Leshchinsky et al., 2015).

Landslide susceptibility mapping along PLUS expressways in Malaysia using probabilistic based model in GIS

NASA Astrophysics Data System (ADS)

Yusof, Norbazlan M.; Pradhan, Biswajeet

2014-06-01

PLUS Berhad holds the concession for a total of 987 km of toll expressways in Malaysia, the longest of which is the North-South Expressway or NSE. Acting as the backbone' of the west coast of the peninsula, the NSE stretches from the Malaysian-Thai border in the north to the border with neighbouring Singapore in the south, linking several major cities and towns along the way. North-South Expressway in Malaysia contributes to the country economic development through trade, social and tourism sector. Presently, the highway is good in terms of its condition and connection to every state but some locations need urgent attention. Stability of slopes at these locations is of most concern as any instability can cause danger to the motorist. In this paper, two study locations have been analysed; they are Gua Tempurung (soil slope) and Jelapang (rock slope) which are obviously having two different characteristics. These locations passed through undulating terrain with steep slopes where landslides are common and the probability of slope instability due to human activities in surrounding areas is high. A combination of twelve (12) landslide conditioning factors database on slope stability such as slope degree and slope aspect were extracted from IFSAR (interoferometric synthetic aperture radar) while landuse, lithology and structural geology were constructed from interpretation of high resolution satellite data from World View II, Quickbird and Ikonos. All this information was analysed in geographic information system (GIS) environment for landslide susceptibility mapping using probabilistic based frequency ratio model. Consequently, information on the slopes such as inventories, condition assessments and maintenance records were assessed through total expressway maintenance management system or better known as TEMAN. The above mentioned system is used by PLUS as an asset management and decision support tools for maintenance activities along the highways as well as for data quality checking and integrity. In this study, TEMAN data were further analysed and subsequently integrated with landslide susceptible map for Gua Tempurung and Jelapang area in Perak.

Myosin IIA/IIB restrict adhesive and protrusive signaling to generate front-back polarity in migrating cells.

PubMed

Vicente-Manzanares, Miguel; Newell-Litwa, Karen; Bachir, Alexia I; Whitmore, Leanna A; Horwitz, Alan Rick

2011-04-18

Migratory front-back polarity emerges from the cooperative effect of myosin IIA (MIIA) and IIB (MIIB) on adhesive signaling. We demonstrate here that, during polarization, MIIA and MIIB coordinately promote localized actomyosin bundling, which generates large, stable adhesions that do not signal to Rac and thereby form the cell rear. MIIA formed dynamic actomyosin proto-bundles that mark the cell rear during spreading; it also bound to actin filament bundles associated with initial adhesion maturation in protrusions. Subsequent incorporation of MIIB stabilized the adhesions and actomyosin filaments with which it associated and formed a stable, extended rear. These adhesions did not turn over and no longer signal to Rac. Microtubules fine-tuned the polarity by positioning the front opposite the MIIA/MIIB-specified rear. Decreased Rac signaling in the vicinity of the MIIA/MIIB-stabilized proto-bundles and adhesions was accompanied by the loss of Rac guanine nucleotide exchange factor (GEFs), like βPIX and DOCK180, and by inhibited phosphorylation of key residues on adhesion proteins that recruit and activate Rac GEFs. These observations lead to a model for front-back polarity through local GEF depletion.

Radar Detected Rainfall Intensity As An Input For Shallow Landslides Slope Stability Model

NASA Astrophysics Data System (ADS)

Leoni, L.; Rossi, G.; Catani, F.; Righini, G.; Rudari, R.

2008-12-01

The term "shallow landslides" is widely used in literature to describe a slope movement of limited size that mainly develops in soils up to a maximum of a few meters. Shallow landslides are usually triggered by heavy rainfall because, as the water starts to infiltrate in the soil, the pore-water pressure increases so that the shear strength of the soil is reduced leading to slope failure. For this work we have developed a distributed hydrological-geotechnical model for the forecasting of the temporal and spatial distribution of shallow landslide to be used as a warning system for civil protection purpose. The main goal of this work is the use of radar detected rainfall intensity as the input for the hydrological simulation of the infiltration. Using the rainfall pattern detected by the radar is in fact possible to dynamically control the redistribution of groundwater pressure associated with transient infiltration of rain so as to infer the slope stability of the studied area. The model deals with both saturated and unsaturated conditions. Two pilot sites have been chosen to develop and test this model: the Armea basin (Liguria, Italy) and the Ischia Island (Campania, Italy). In recent years several severe rainstorms have occurred in both these areas. In at least two cases these have triggered numerous shallow landslides that have caused victims and damaged roads, buildings and agricultural activities. In its current stage the basic basin-scale model applied for predicting the probable location of shallow landslides involves several stand-alone components. A module for estimating the groundwater pressure head distribution according to radar detected rainfall intensity, a soil depth prediction scheme and a limit-equilibrium infinite slope stability algorithm which produces a factor of safety (FS). The additional ancillary data required have been collected during the field work. The single components are seamlessly integrated into a system that automatically publishes constantly updated FS values to a WebGIS in near-real- time so that local administrators responsible for public safety can access and download the data from the internet. This system has been running for a few months and is now being validated. Several types of problems hinder a correct validation of the system. One major obstacle was overcome when major storms triggered several tens of soil slips in December 2006 for the Armea basin and in April 2006 for Ischia. This events provided both the necessary rainfall data for the soil saturation component, which until then for previous occurred landslides was lacking, and a new landslide inventory for comparison with the FS produced by the slope stability model for the same event. The inventory was derived from a newly acquired VHR satellite image. Another important aspect of the research being performed regards the assessment of the relative importance of the different parameters involved in the limit-equilibrium infinite slope stability model. This statistical sensitivity analysis has the aim of determining which errors in the input variables slope gradient, soil depth, soil saturation, cohesion and angle of internal friction produce the largest errors in the output FS values. Preliminary results indicate the importance of topographic attributes and of soil depth.

Effects of Goal Line Feedback on Level, Slope, and Stability of Performance within Curriculum-Based Measurement.

ERIC Educational Resources Information Center

Fuchs, Lynn S.; And Others

1991-01-01

Nineteen special educators implemented Curriculum-Based Measurement with a total of 36 learning-disabled math pupils in grades 2-8 to examine the effects of goal line feedback. Results indicated comparable levels and slopes of student performance across treatment conditions, although goal line feedback was associated with greater performance…

An apparatus to measure the crosscut shearing strength of roots

Treesearch

Robert R. Ziemer

1978-01-01

Loss of tree root strength after timber cutting is a principal mechanism leading to slope failure and landslides. Measurement of root shear strength changes can be useful in evaluating effects of logging on slope stability. The simple apparatus described measures shear strength directly on roots up to 50 mm diameter. Tests on live roots showed excellent correlation...

A multidisciplinary methodological approach for slope stability assessment of an area prone to shallow landslides

NASA Astrophysics Data System (ADS)

Bordoni, Massimiliano; Meisina, Claudia; Valentino, Roberto; Bittelli, Marco; Battista Bischetti, Gian; Vercesi, Alberto; Chersich, Silvia; Giuseppina Persichillo, Maria

2016-04-01

Rainfall-induced shallow landslides are widespread slope instabilities phenomena in several hilly and mountainous contexts all over the world. Due to their high density of diffusion also in small areas, they can provoke important damages to terrains, infrastructures, buildings, and, sometimes, loss of human lives. Shallow landslides affect superficial soils of limited thickness (generally lower than 2 m), located above weathered or not bedrock levels. Their triggering mechanism is strictly linked to the hydrological response of the soils to rainfall events. Thus, it becomes fundamental a comprehensive analysis of the soil properties which can influence the susceptibility of a slope to shallow landslides. In this study, a multidisciplinary approach was followed for the characterization of the soils and the individuation of the triggering conditions in an area particularly prone to shallow failures, for slope stability assessment. This area corresponded to the hilly sector of North-Eastern Oltrepò Pavese (Lombardy Region, Northern Italy), where the density of shallow landslides is really high, reaching more than 36 landslides per km2. The soils of the study area were analyzed through a multidisciplinary characterization, which took into account for the main geotechnical, mechanical and mineralogical parameters and also for the main pedological features of the materials. This approach allowed for identifying the main features and the horizons which could influence the soil behavior in relation to the conditions that are preparatory to shallow landslides development. In a test-site slope, representative of the main geomorphological, geological and landslides distribution characteristics typical of the study area, a continuous in time monitoring of meteorological (rainfall amount, air temperature, air humidity, atmospheric pressure, net solar radiation, wind speed and direction) and hydrological (soil water content, pore water pressure) parameters was implemented. In this way, the triggering mechanism of shallow failures in the study area was identified and the effects of the different hydrological parameters on slope stability assessment through a simplified physically-based model (Lu and Godt's model) was quantified. In several slopes, representative of the main land uses (cultivated vineyards, abandoned vineyards, shrub lands, woodlands) of the study area, soil root reinforcement of the vegetation of the slopes was measured since root density and root tensile strength. This parameter was, then, integrated in the same simplified physically-based model (Lu and Godt's model), in order to improve the assessment of slope instabilities. Moreover, this analysis allowed for a better identification of the land use classes more susceptible to shallow landslides, furnishing an important tool for land planning.

Conceptual design of front ends for the advanced photon source multi-bend achromats upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaski, Y., E-mail: jaskiy@aps.anl.gov; Westferro, F., E-mail: westferr@aps.anl.gov; Lee, S. H., E-mail: shlee@aps.anl.gov

2016-07-27

The proposed Advanced Photon Source (APS) upgrade from a double-bend achromats (DBA) to multi-bend achromats (MBA) lattice with ring energy change from 7 GeV to 6 GeV and beam current from 100 mA to 200 mA poses new challenges for front ends. All front ends must be upgraded to fulfill the following requirements: 1) handle the high heat load from two insertion devices in either inline or canted configuration, 2) include a clearing magnet in the front end to deflect and dump any electrons in case the electrons escape from the storage ring during swap-out injection with the safety shuttersmore » open, 3) incorporate the next generation x-ray beam position monitors (XBPMs) into the front end to meet the new stringent beam stability requirements. This paper presents the evaluation of the existing APS front ends and standardizes the insertion device (ID) front ends into two types: one for the single beam and one for the canted beams. The conceptual design of high heat load front end (HHLFE) and canted undulator front end (CUFE) for APS MBA upgrade is presented.« less

Conceptual Design of Front Ends for the Advanced Photon Source Multi-bend Achromats Upgrade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaski, Y.; Westferro, F.; Lee, S. H.

2016-07-27

The proposed Advanced Photon Source (APS) upgrade from a double-bend achromats (DBA) to multi-bend achromats (MBA) lattice with ring energy change from 7 GeV to 6 GeV and beam current from 100 mA to 200 mA poses new challenges for front ends. All front ends must be upgraded to fulfill the following requirements: 1) handle the high heat load from two insertion devices in either inline or canted configuration, 2) include a clearing magnet in the front end to deflect and dump any electrons in case the electrons escape from the storage ring during swap-out injection with the safety shuttersmore » open, 3) incorporate the next generation x-ray beam position monitors (XBPMs) into the front end to meet the new stringent beam stability requirements. This paper presents the evaluation of the existing APS front ends and standardizes the insertion device (ID) front ends into two types: one for the single beam and one for the canted beams. The conceptual design of high heat load front end (HHLFE) and canted undulator front end (CUFE) for APS MBA upgrade is presented.« less

The dynamics of oceanic fronts. Part 1: The Gulf Stream

NASA Technical Reports Server (NTRS)

Kao, T. W.

1970-01-01

The establishment and maintenance of the mean hydrographic properties of large scale density fronts in the upper ocean is considered. The dynamics is studied by posing an initial value problem starting with a near surface discharge of buoyant water with a prescribed density deficit into an ambient stationary fluid of uniform density. The full time dependent diffusion and Navier-Stokes equations for a constant Coriolis parameter are used in this study. Scaling analysis reveals three independent length scales of the problem, namely a radius of deformation or inertial length scale, Lo, a buoyance length scale, ho, and a diffusive length scale, hv. Two basic dimensionless parameters are then formed from these length scales, the thermal (or more precisely, the densimetric) Rossby number, Ro = Lo/ho and the Ekman number, E = hv/ho. The governing equations are then suitably scaled and the resulting normalized equations are shown to depend on E alone for problems of oceanic interest. Under this scaling, the solutions are similar for all Ro. It is also shown that 1/Ro is a measure of the frontal slope. The governing equations are solved numerically and the scaling analysis is confirmed. The solution indicates that an equilibrium state is established. The front can then be rendered stationary by a barotropic current from a larger scale along-front pressure gradient. In that quasisteady state, and for small values of E, the main thermocline and the inclined isopycnics forming the front have evolved, together with the along-front jet. Conservation of potential vorticity is also obtained in the light water pool. The surface jet exhibits anticyclonic shear in the light water pool and cyclonic shear across the front.

Robot Would Climb Steep Terrain

NASA Technical Reports Server (NTRS)

Kennedy, Brett; Ganino, Anthony; Aghazarian, Hrand; Hogg, Robert; McHerny, Michael; Garrett, Michael

2007-01-01

This brief describes the steep terrain access robot (STAR) -- a walking robot that has been proposed for exploring steep terrain on remote planets. The STAR would be able to climb up or down on slopes as steep as vertical, and even beyond vertical to overhangs. Its system of walking mechanisms and controls would be to react forces and maintain stability. To enable the STAR to anchor itself in the terrain on steep slopes to maintain stability and react forces, it would be necessary to equip the tips of the walking legs with new ultrasonic/ sonic drill corers (USDCs) and to develop sensors and control algorithms to enable robust utilization of the USDCs.

Effect of Root Moisture Content and Diameter on Root Tensile Properties.

PubMed

Yang, Yuanjun; Chen, Lihua; Li, Ning; Zhang, Qiufen

2016-01-01

The stabilization of slopes by vegetation has been a topical issue for many years. Root mechanical characteristics significantly influence soil reinforcement; therefore it is necessary to research into the indicators of root tensile properties. In this study, we explored the influence of root moisture content on tensile resistance and strength with different root diameters and for different tree species. Betula platyphylla, Quercus mongolica, Pinus tabulaeformis, and Larix gmelinii, the most popular tree species used for slope stabilization in the rocky mountainous areas of northern China, were used in this study. A tensile test was conducted after root samples were grouped by diameter and moisture content. The results showedthat:1) root moisture content had a significant influence on tensile properties; 2) slightly loss of root moisture content could enhance tensile strength, but too much loss of water resulted in weaker capacity for root elongation, and consequently reduced tensile strength; 3) root diameter had a strong positive correlation with tensile resistance; and4) the roots of Betula platyphylla had the best tensile properties when both diameter and moisture content being controlled. These findings improve our understanding of root tensile properties with root size and moisture, and could be useful for slope stabilization using vegetation.

Effect of Root Moisture Content and Diameter on Root Tensile Properties

PubMed Central

Yang, Yuanjun; Chen, Lihua; Li, Ning; Zhang, Qiufen

2016-01-01

The stabilization of slopes by vegetation has been a topical issue for many years. Root mechanical characteristics significantly influence soil reinforcement; therefore it is necessary to research into the indicators of root tensile properties. In this study, we explored the influence of root moisture content on tensile resistance and strength with different root diameters and for different tree species. Betula platyphylla, Quercus mongolica, Pinus tabulaeformis, and Larix gmelinii, the most popular tree species used for slope stabilization in the rocky mountainous areas of northern China, were used in this study. A tensile test was conducted after root samples were grouped by diameter and moisture content. The results showedthat:1) root moisture content had a significant influence on tensile properties; 2) slightly loss of root moisture content could enhance tensile strength, but too much loss of water resulted in weaker capacity for root elongation, and consequently reduced tensile strength; 3) root diameter had a strong positive correlation with tensile resistance; and4) the roots of Betula platyphylla had the best tensile properties when both diameter and moisture content being controlled. These findings improve our understanding of root tensile properties with root size and moisture, and could be useful for slope stabilization using vegetation. PMID:27003872

On cup anemometer rotor aerodynamics.

PubMed

Pindado, Santiago; Pérez, Javier; Avila-Sanchez, Sergio

2012-01-01

The influence of anemometer rotor shape parameters, such as the cups' front area or their center rotation radius on the anemometer's performance was analyzed. This analysis was based on calibrations performed on two different anemometers (one based on magnet system output signal, and the other one based on an opto-electronic system output signal), tested with 21 different rotors. The results were compared to the ones resulting from classical analytical models. The results clearly showed a linear dependency of both calibration constants, the slope and the offset, on the cups' center rotation radius, the influence of the front area of the cups also being observed. The analytical model of Kondo et al. was proved to be accurate if it is based on precise data related to the aerodynamic behavior of a rotor's cup.

78 FR 52870 - Airworthiness Directives; Beechcraft Corporation Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-08-27

... the front spar cap angles and hat section structure of the vertical stabilizer. This proposed AD would require inspections of the vertical stabilizer spar angles and hat section for cracks with corrective... information identified in this proposed AD, contact Beechcraft Corporation at address: 10511 E. Central...

Groundwater monitoring of an open-pit limestone quarry: groundwater characteristics, evolution and their connections to rock slopes.

PubMed

Eang, Khy Eam; Igarashi, Toshifumi; Fujinaga, Ryota; Kondo, Megumi; Tabelin, Carlito Baltazar

2018-03-06

Groundwater flow and its geochemical evolution in mines are important not only in the study of contaminant migration but also in the effective planning of excavation. The effects of groundwater on the stability of rock slopes and other mine constructions especially in limestone quarries are crucial because calcite, the major mineral component of limestone, is moderately soluble in water. In this study, evolution of groundwater in a limestone quarry located in Chichibu city was monitored to understand the geochemical processes occurring within the rock strata of the quarry and changes in the chemistry of groundwater, which suggests zones of deformations that may affect the stability of rock slopes. There are three distinct geological formations in the quarry: limestone layer, interbedded layer of limestone and slaty greenstone, and slaty greenstone layer as basement rock. Although the hydrochemical facies of all groundwater samples were Ca-HCO 3 type water, changes in the geochemical properties of groundwater from the three geological formations were observed. In particular, significant changes in the chemical properties of several groundwater samples along the interbedded layer were observed, which could be attributed to the mixing of groundwater from the limestone and slaty greenstone layers. On the rainy day, the concentrations of Ca 2+ and HCO 3 - in the groundwater fluctuated notably, and the groundwater flowing along the interbedded layer was dominated by groundwater from the limestone layer. These suggest that groundwater along the interbedded layer may affect the stability of rock slopes.

Slope stability and rockfall assessment of volcanic tuffs using RPAS with 2-D FEM slope modelling

NASA Astrophysics Data System (ADS)

Török, Ákos; Barsi, Árpád; Bögöly, Gyula; Lovas, Tamás; Somogyi, Árpád; Görög, Péter

2018-02-01

Steep, hardly accessible cliffs of rhyolite tuff in NE Hungary are prone to rockfalls, endangering visitors of a castle. Remote sensing techniques were employed to obtain data on terrain morphology and to provide slope geometry for assessing the stability of these rock walls. A RPAS (Remotely Piloted Aircraft System) was used to collect images which were processed by Pix4D mapper (structure from motion technology) to generate a point cloud and mesh. The georeferencing was made by Global Navigation Satellite System (GNSS) with the use of seven ground control points. The obtained digital surface model (DSM) was processed (vegetation removal) and the derived digital terrain model (DTM) allowed cross sections to be drawn and a joint system to be detected. Joint and discontinuity system was also verified by field measurements. On-site tests as well as laboratory tests provided additional engineering geological data for slope modelling. Stability of cliffs was assessed by 2-D FEM (finite element method). Global analyses of cross sections show that weak intercalating tuff layers may serve as potential slip surfaces. However, at present the greatest hazard is related to planar failure along ENE-WSW joints and to wedge failure. The paper demonstrates that RPAS is a rapid and useful tool for generating a reliable terrain model of hardly accessible cliff faces. It also emphasizes the efficiency of RPAS in rockfall hazard assessment in comparison with other remote sensing techniques such as terrestrial laser scanning (TLS).

Observations of Antarctic Slope Current Transport and Dense Water Flow in the Northwestern Weddell Sea

NASA Astrophysics Data System (ADS)

Azaneu, M. V. C.; Heywood, K. J.; Queste, B. Y.; Thompson, A. F.

2016-02-01

In early 2012 the GENTOO project deployed three Seagliders in the northwest Weddell Sea, acquiring high temporal and spatial resolution measurements around Powell Basin for a period of 10 weeks. The Antarctic Slope Front and associated currents form a physical and dynamical barrier to the cross-slope exchange of properties, influencing local and global ocean dynamics. The Seaglider dataset comprises 1598 temperature and salinity profiles and is used to better understand cross-slope processes. From this dataset, 582 glider profiles with altimetric information at the east Antarctic Peninsula continental slope are used to investigate the properties and thickness of the dense bottom water spilling off the shelf. The dense water is identified mostly over the slope, between the 500 and 1000 m isobaths. The dense layer is thickest around ˜ 63.33 °S, along the 1000 m isobath, becoming thinner onshore and towards northern areas. We also evaluate with unprecedented resolution the along-stream velocity and potential vorticity fields along the 17 transects across the eastern Antarctic Peninsula shelf-break and the 4 transects that cross the South Orkney Islands plateau. Using an improved hydrodynamic flight model, we reference the geostrophic shear to the glider-derived depth-averaged currents corrected for tides. In the western Weddell Sea, the geostrophic velocities fields indicate the presence of a surprisingly weakened Antarctic Slope Current (ASC) around 63.5 °S, possibly indicative of high eddy activity in the area. ASC transport in this southernmost section is less than 0.2 Sv. In a more northerly section (˜ 63.1 °S), the ASC transport reaches 6 Sv. The transects west of the South Orkney Island indicate a northward flow, opposite to the previously assumed regime. The results also show intensified northward bottom flows close to the slope, which can be related to processes occurring in the bottom boundary layer. The potential vorticity fields are used to identify potential instability mechanisms contributing to the cross-slope exchange of water mass properties.

Effects of tibial slope changes in the stability of fixed bearing medial unicompartmental arthroplasty in anterior cruciate ligament deficient knees.

PubMed

Suero, Eduardo M; Citak, Musa; Cross, Michael B; Bosscher, Marianne R F; Ranawat, Anil S; Pearle, Andrew D

2012-08-01

Patients with anterior cruciate ligament (ACL) deficiency may have increased failure rates with UKA as a result of abnormal contact stresses and altered knee kinematics. Variations in the slope of the tibial component in UKA may alter tibiofemoral translation, and affect outcomes. This cadaveric study evaluated tibiofemoral translation during the Lachman and pivot shift tests after changing the slope of a fixed bearing unicondylar tibial component. Sectioning the ACL increased tibiofemoral translation in both the Lachman and pivot shift tests (P<0.05). Tibial slope leveling (decreasing the posterior slope) of the polyethylene insert in a UKA decreases anteroposterior tibiofemoral translation in the sagittal plane to a magnitude similar to that of the intact knee. With 8° of tibial slope leveling, anterior tibial translation during the Lachman test decreased by approximately 5mm. However, no variation in slope altered the pivot shift kinematics in the ACL deficient knees. Copyright © 2011 Elsevier B.V. All rights reserved.

Fracture and slope stability monitoring at Puigcercós landslide (Catalonia, Spain)

NASA Astrophysics Data System (ADS)

Khazaradze, Giorgi; Vasquez, Sebastian; López, Robert; Guinau, Guinau; Calvet, Jaume; Vilaplana, Joan Manuel; Blanch, Xabier; Tapia, Mar; Roig, Pere; Suriñach, Emma

2017-04-01

The village of Puigcercós ( 50 inhabitants) is located in the region of Pallars Jussà (Lleida) in Catalonia, several km south of the town of Tremp. In 1881 the entire village had to be moved from its historical location on top of the hill to its current location. This was caused by a series of landslides caused by continuing rainfall. The most important landslide occurred on January 13th 1881, which displaced more than 5 million cubic meters of sediments and rocks and created an impressive rock scar of approximately 25 m height and 150 m width. The area where the sediments were accumulated is extensive, reaching 8 hectares. During the last years, our group has chosen the site of Puigcercós to conduct pilot studies of landslides and rockfalls using multidisciplinary approach, involving Terrestrial Laser Scanner, Total Station, DGPS, seismic monitoring and geophysical techniques. The geophysical surveys of the zone of the sediment accumulation, can help determine the internal structure of the displaced sediments. The work presented here mainly concerns the deformation monitoring at the site using geodetic techniques. In July 2015, a network of 11 new geodetic points has been established and measured with GPS. The location of these points was chosen with the purpose of answering two important questions in the studies of the stability and geomorphological activity of the Puigcercós landslide: 1) As a result of combined analysis of the tape-meter, total station and GPS measurements, we hope to obtain absolute values of deformation in the upper part of the escarpment, controlling the stability of the escarpment front and the associated fractures near the coronation. For this purpose, two geodetic control points have been established at the hilltop, some 5 meters away from the escarpment itself. 2) Determine the slope stability of the depositional area, where we established nine geodetic points. As of today, these points have been measured twice, in 2015 and 2016, during 24 hour long campaigns, overlapping a midnight. Thus, obtained GPS observations cover at least 8 hours for 2 consecutive days, ensuring the millimeter level accuracy after the post-processing using GAMIT/GLOBK software from MIT. After the realization of the third campaign in the spring of 2017, we hope to give more definitive answers to the questions raised above. This work is conducted within the framework of the project CHARMA (CGL2013-40828-R), financed by the Ministry of Economy, Industry and Competitiveness of Spain. We are thankful to the students who participated in the GPS campaigns: E. Bravo, M. Galindos, Ciscu Sánchez.

Recent and future warm extreme events and high-mountain slope stability.

PubMed

Huggel, C; Salzmann, N; Allen, S; Caplan-Auerbach, J; Fischer, L; Haeberli, W; Larsen, C; Schneider, D; Wessels, R

2010-05-28

The number of large slope failures in some high-mountain regions such as the European Alps has increased during the past two to three decades. There is concern that recent climate change is driving this increase in slope failures, thus possibly further exacerbating the hazard in the future. Although the effects of a gradual temperature rise on glaciers and permafrost have been extensively studied, the impacts of short-term, unusually warm temperature increases on slope stability in high mountains remain largely unexplored. We describe several large slope failures in rock and ice in recent years in Alaska, New Zealand and the European Alps, and analyse weather patterns in the days and weeks before the failures. Although we did not find one general temperature pattern, all the failures were preceded by unusually warm periods; some happened immediately after temperatures suddenly dropped to freezing. We assessed the frequency of warm extremes in the future by analysing eight regional climate models from the recently completed European Union programme ENSEMBLES for the central Swiss Alps. The models show an increase in the higher frequency of high-temperature events for the period 2001-2050 compared with a 1951-2000 reference period. Warm events lasting 5, 10 and 30 days are projected to increase by about 1.5-4 times by 2050 and in some models by up to 10 times. Warm extremes can trigger large landslides in temperature-sensitive high mountains by enhancing the production of water by melt of snow and ice, and by rapid thaw. Although these processes reduce slope strength, they must be considered within the local geological, glaciological and topographic context of a slope.

Revegetation of Acid Rock Drainage (ARD) Producing Slope Surface Using Phosphate Microencapsulation and Artificial Soil

NASA Astrophysics Data System (ADS)

Kim, Jae Gon

2017-04-01

Oxidation of sulfides produces acid rock drainage (ARD) upon their exposure to oxidation environment by construction and mining activities. The ARD causes the acidification and metal contamination of soil, surface water and groundwater, the damage of plant, the deterioration of landscape and the reduction of slope stability. The revegetation of slope surface is one of commonly adopted strategies to reduce erosion and to increase slope stability. However, the revegetation of the ARD producing slope surface is frequently failed due to its high acidity and toxic metal content. We developed a revegetation method consisting of microencapsualtion and artificial soil in the laboratory. The revegetation method was applied on the ARD producing slope on which the revegetation using soil coverage and seeding was failed and monitored the plant growth for one year. The phosphate solution was applied on sulfide containing rock to form stable Fe-phosphate mineral on the surface of sulfide, which worked as a physical barrier to prevent contacting oxidants such as oxygen and Fe3+ ion to the sulfide surface. After the microencapsulation, two artificial soil layers were constructed. The first layer containing organic matter, dolomite powder and soil was constructed at 2 cm thickness to neutralize the rising acidic capillary water from the subsurface and to remove the dissolved oxygen from the percolating rain water. Finally, the second layer containing seeds, organic matter, nutrients and soil was constructed at 3 cm thickness on the top. After application of the method, the pH of the soil below the artificial soil layer increased and the ARD production from the rock fragments reduced. The plant growth showed an ordinary state while the plant died two month after germination for the previous revegetation trial. No soil erosion occurred from the slope during the one year field test.

Traveling wave solutions in a chain of periodically forced coupled nonlinear oscillators

NASA Astrophysics Data System (ADS)

Duanmu, M.; Whitaker, N.; Kevrekidis, P. G.; Vainchtein, A.; Rubin, J. E.

2016-06-01

Motivated by earlier studies of artificial perceptions of light called phosphenes, we analyze traveling wave solutions in a chain of periodically forced coupled nonlinear oscillators modeling this phenomenon. We examine the discrete model problem in its co-traveling frame and systematically obtain the corresponding traveling waves in one spatial dimension. Direct numerical simulations as well as linear stability analysis are employed to reveal the parameter regions where the traveling waves are stable, and these waves are, in turn, connected to the standing waves analyzed in earlier work. We also consider a two-dimensional extension of the model and demonstrate the robust evolution and stability of planar fronts. Our simulations also suggest the radial fronts tend to either annihilate or expand and flatten out, depending on the phase value inside and the parameter regime. Finally, we observe that solutions that initially feature two symmetric fronts with bulged centers evolve in qualitative agreement with experimental observations of phosphenes.

Traveling wave solutions in a chain of periodically forced coupled nonlinear oscillators

DOE PAGES

Duanmu, M.; Whitaker, N.; Kevrekidis, P. G.; ...

2016-02-27

Artificial perceptions of light called phosphenes were motivated by earlier studies. We analyze traveling wave solutions in a chain of periodically forced coupled nonlinear oscillators modeling this phenomenon. We examine the discrete model problem in its co-traveling frame and systematically obtain the corresponding traveling waves in one spatial dimension. Direct numerical simulations as well as linear stability analysis are employed to reveal the parameter regions where the traveling waves are stable, and these waves are, in turn, connected to the standing waves analyzed in earlier work. We also consider a two-dimensional extension of the model and demonstrate the robust evolutionmore » and stability of planar fronts. Moreover, our simulations also suggest the radial fronts tend to either annihilate or expand and flatten out, depending on the phase value inside and the parameter regime. Finally, we observe that solutions that initially feature two symmetric fronts with bulged centers evolve in qualitative agreement with experimental observations of phosphenes.« less

Traveling wave solutions in a chain of periodically forced coupled nonlinear oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duanmu, M.; Whitaker, N.; Kevrekidis, P. G.

Artificial perceptions of light called phosphenes were motivated by earlier studies. We analyze traveling wave solutions in a chain of periodically forced coupled nonlinear oscillators modeling this phenomenon. We examine the discrete model problem in its co-traveling frame and systematically obtain the corresponding traveling waves in one spatial dimension. Direct numerical simulations as well as linear stability analysis are employed to reveal the parameter regions where the traveling waves are stable, and these waves are, in turn, connected to the standing waves analyzed in earlier work. We also consider a two-dimensional extension of the model and demonstrate the robust evolutionmore » and stability of planar fronts. Moreover, our simulations also suggest the radial fronts tend to either annihilate or expand and flatten out, depending on the phase value inside and the parameter regime. Finally, we observe that solutions that initially feature two symmetric fronts with bulged centers evolve in qualitative agreement with experimental observations of phosphenes.« less

Landslide stability analysis on basis of LIDAR data extraction

NASA Astrophysics Data System (ADS)

Hu, Hui; Fernandez-Steeger, Tomas M.; Dong, Mei; Azzam, Rafig

2010-05-01

Currently, existing contradictory between remediation and acquisition from natural resource induces a series of divergences. With regard to open pit mining, legal regulation requires human to fill back the open pit area with water or recreate new landscape by other materials; on the other hand, human can not help excavating the mining area due to the shortage of power resource. However, to engineering geologists, one coincident problem which takes place not only in filling but also in mining operation should be paid more attention to, i.e. the slope stability analysis within these areas. There are a number of construction activities during remediation or mining process which can directly or indirectly cause slope failure. Lives can be endangered since local failure either while or after remediation; for mining process, slope failure in a bench, which carries a main haul road or is adjacent to human activity area, would be significant catastrophe to the whole mining program. The stability of an individual bench or slope is controlled by several factors, which are geological condition, morphology, climate, excavation techniques and transportation approach. The task which takes the longest time is to collect the morphological data. Consequently, it is one of the most dangerous tasks due to the time consuming in mining field. LIDAR scanning for morphological data collecting can help to skip this obstacle since advantages of LIDAR techniques as follows: • Dynamic range available on the market: from 3 m to beyond 1 km, • Ruggedly designed for demanding field applications, • Compact, easily hand-carried and deployed by a single operator. In 2009, scanning campaigns for 2 open pit quarry have been carried out. The aim for these LIDAR detections is to construct a detailed 3D quarry model and analyze the bench stability to support the filling planning. The 3D quarry surface was built up by using PolyWorks 10.1 on basis of LIDAR data. LIDAR data refining takes an important role during surface construction for further more precise analysis purpose. 3D geological model can be built based on the connection between surface model and geological data like borehole data in GOCAD. Regarding the bench stability analysis, LEM (Limit Equilibrium Method) analysis using Janbu and FEM (Finite Element Method) have been adopted during this analyzing task. A program was developed to convert GOCAD 2D section data directly into the FEM software. The meshed model is then used for stability analysis. In one quarry, 3 cross sections have been extracted on basis of LIDAR original data (original 3 cross sections). To evaluate the advantages of LIDAR data for slope analysis, the results of safety factor (SF) were compared to simplified slope models as they are used normally. The comparison showed that variations of the SF reach up to 9%. Additionally, conservative evaluation demonstrated by SF results based on simplified model is not adaptive for decision making of filling.

Measuring the iron spectral opacity in solar conditions using a double ablation front scheme

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colaitis, A.; Ducret, J. E.; Turck-Chieze, S

We propose a new method to achieve hydrodynamic conditions relevant for the investigation of the radiation transport properties of the plasma at the base of the solar convection zone. The method is designed in the framework of opacity measurements with high-power lasers and exploits the temporal and spatial stability of hydrodynamic parameters in counter-propagating Double Ablation Front (DAF) structures.

Spatial variability and its main controlling factors of the permafrost soil-moisture on the northern-slope of Bayan Har Mountains in Qinghai-Tibet Plateau

NASA Astrophysics Data System (ADS)

Cao, W.; Sheng, Y.

2017-12-01

The soil moisture movement is an important carrier of material cycle and energy flow among the various geo-spheres in the cold regions. It is very critical to protect the alpine ecology and hydrologic cycle in Qinghai-Tibet Plateau. Especially, it becomes one of the key problems to reveal the spatial-temporal variability of soil moisture movement and its main influence factors in earth system science. Thus, this research takes the north slope of Bayan Har Mountains in Qinghai-Tibet Plateau as a case study. The present study firstly investigates the change of permafrost moisture in different slope positions and depths. Based on this investigation, this article attempts to investigate the spatial variability of permafrost moisture and identifies the key influence factors in different terrain conditions. The method of classification and regression tree (CART) is adopted to identify the main controlling factors influencing the soil moisture movement. And the relationships between soil moisture and environmental factors are revealed by the use of the method of canonical correspondence analysis (CCA). The results show that: 1) the change of the soil moisture on the permafrost slope is divided into 4 stages, including the freezing stability phase, the rapid thawing phase, the thawing stability phase and the fast freezing phase; 2) this greatly enhances the horizontal flow in the freezing period due to the terrain slope and the freezing-thawing process. Vertical migration is the mainly form of the soil moisture movement. It leads to that the soil-moisture content in the up-slope is higher than that in the down-slope. On the contrary, the soil-moisture content in the up-slope is lower than that in the down-slope during the melting period; 3) the main environmental factors which affect the slope-permafrost soil-moisture are elevation, soil texture, soil temperature and vegetation coverage. But there are differences in the impact factors of the soil moisture in different freezing-thawing stages; 4) the main factors that affect the slope-permafrost soil-moisture at the shallow depth of 0-20cm are slope, elevation and vegetation coverage. And the main factors influencing the soil moisture at the middle and lower depth are complex.

Large-scale Mass Transport Deposits in the Valencia Basin (Western Mediterranean): slope instability induced by rapid sea-level drawdown?

NASA Astrophysics Data System (ADS)

Cameselle, Alejandra L.; Urgeles, Roger; Llopart, Jaume

2014-05-01

The Messinian Salinity Crisis (MSC) strongly affected the physiography of the Mediterranean margins at the end of the Miocene. The sharp sea-level fall gave a new configuration to the Mediterranean basin and created dramatic morphological and sedimentological changes: margins have been largely eroded whereas the deep basins accumulated thick evaporitic and detrital units. Amongst these detrital units, there are evidences on seismic reflection data for major large-scale slope failure of the Mediterranean continental margins. About 2700 km of seismic reflection profiles in the southwestern part of the Valencia Basin (Western Mediterranean) have enabled us the detailed mapping of distinctive Messinian erosional surfaces, evaporites and deep detrital deposits. The detrital deposits occur in a distinct unit that is made of chaotic, roughly-bedded or transparent seismic bodies, which have been mainly mapped in the basin domain. Locally, the seismic unit shows discontinuous high-amplitude reflections and/or an imbricate internal structure. This unit is interpreted to be formed by a series of Mass Transport Deposits (MTDs). Rapid drawdown has long been recognized as one of the most severe loadings conditions that a slope can be subjected to. Several large historical slope failures have been documented to occur due to rapid drawdown in dams, riverbanks and slopes. During drawdown, the stabilizing effect of the water on the upstream face is lost, but the pore-water pressures within the slope may remain high. The dissipation of these pore pressures in the slope is controlled by the permeability and the storage characteristics of the slope sediments. We hypothesize that the MTDs observed in our data formed under similar conditions and represent a large-scale equivalent of this phenomenon. Therefore, these MTDs can be used to put some constraints on the duration of the drawdown phase of the MSC. We have performed a series of slope stability analysis under rapid Messinian sea-level drawdown using slope geotechnical properties and pre-conditioning factors related to the geological setting of the Valencia Basin. Using several sea-level fall ratios, the variation of the safety factor with respect to successive positions of the sea-level during drawdown has been evaluated.

Does mycorrhizal inoculation benefit plant survival, plant development and small-scale soil fixation? Results from a perennial eco-engineering field experiment in the Swiss Alps.

NASA Astrophysics Data System (ADS)

Bast, Alexander; Grimm, Maria; Graf, Frank; Baumhauer, Roland; Gärtner, Holger

2015-04-01

In mountain environments superficial slope failures on coarse grained, vegetation-free slopes are common processes and entail a certain risk for humans and socio-economic structures. Eco-engineering measures can be applied to mitigate slope instabilities. In this regard, limited plant survival and growth can be supported by mycorrhizal inoculation, which was successfully tested in laboratory studies. However, related studies on a field scale are lacking. Furthermore, mycorrhizae are known to enhance soil aggregation, which is linked to soil physics such as shear strength, and hence it is a useful indicator for near-surface soil/slope stability. The overall objective of our contribution was to test whether mycorrhizal inoculation can be used to promote eco-engineering measures in steep alpine environments based on a five-year field experiment. We hypothesized that mycorrhizal inoculation (i) enhances soil aggregation, (ii) stimulate plant survival and fine root development, (iii) effects plant performance, (iv) the stimulated root development in turn influences aggregate stability, and (v) that climatic variations play a major role in fine-root development. We established mycorrhizal and non-mycorrhizal treated eco-engineered research plots (hedge layers mainly consisting of Alnus spp. and Salix spp.) on a field experimental scale. The experimental site is in the eastern Swiss Alps at an erosion-prone slope where many environmental conditions can be seen as homogeneous. Soil aggregation, fine root development and plant survival was quantified at the end of four growing seasons (2010, '11, '12, '14). Additionally, growth properties of Alnus spp. and Salix spp. were measured and their biomass estimated. Meteorological conditions, soil temperature and soil water content were recorded. (i) The introduced eco-engineering measures enhanced aggregate stability significantly. In contrast to published greenhouse and laboratory studies, mycorrhizal inoculation delayed soil aggregate stabilization relative to the non-inoculated site but resulted in a significantly higher aggregate stability compared to the control and the non-inoculated site at the end of the third growing season. (ii) Plant survival was significantly improved by the inoculation. Fine-root development was stimulated but not immediately. At the end of the third growing season, root length density tended to be higher and mean root diameter was significantly increased at the mycorrhizal treated site. (iii) Analyses on plant performance of Alnus and Salix demonstrated that the inoculated saplings achieved significantly higher survival rates. There was no treatment effect on plant growth properties except in 2010, where plant height and main stem diameter of Alnus was increased at the mycorrhizal treated site. The estimated total biomass of Alnus and Salix was higher at the mycorrhizal treated site. (iv) There was a positive correlation between root length density and aggregate stability, whereas roots < 0.5 mm were most influential on aggregate stability. (v) Interannual climatic variations seem to have a crucial influence on root development and, hence, on slope stability. There is a temporal offset of two growing seasons between inoculation effects tested in greenhouse/laboratory and the presented field experiment. However, the application of a commercial mycorrhizal inoculum in eco-engineering measures is a beneficial promoter to mitigate slope instability and surface erosion but needs to be tested at other sites. The contribution is mainly based on Bast (2014) and was funded by the Wolfermann Nägeli Stiftung Zürich and the Swiss Federal Office for Environment (BAFU No.: 09.0027.PJ/I211-3446). Bast, A. (2014): Mycorrhizal inoculation as a promoter for sustainable eco-engineering measures in steep alpine environments? Results of a three-year field experiment in the Arieschbach catchment, Fideris, eastern Swiss Alps. PhD Thesis. University of Berne: 149pp.

Root strength changes after logging in southeast Alaska

Treesearch

R. R. Ziemer; D. N. Swanston

1977-01-01

Abstract - A crucial factor in the stability of steep forested slopes is the role of plant roots in maintaining the shear strength of soil mantles. Roots add strength to the soil by vertically anchoring through the soil mass into failures in the bedrock and by laterally tying the slope together across zones of weakness or instability. Once the covering vegetation is...

Qualitative stability assessment of cut slopes along the National Highway-05 around Jhakri area, Himachal Pradesh, India

NASA Astrophysics Data System (ADS)

Kundu, Jagadish; Sarkar, Kripamoy; Tripathy, Ashutosh; Singh, T. N.

2017-12-01

Several deformation phases in tectonically active Himalayas have rendered the rock masses very complex in terms of structure, lithology and degree of metamorphism. Again, anthropogenic activities such as roads, tunnels and other civil engineering constructions have led to a state of disequilibrium which in many cases, results in failure of rock masses. National Highway-05 around Jhakri area in India is a major connecting route to the China border in the hilly terrains of the state Himachal Pradesh. It cuts through the Himalayan rocks and has a hazardous history of landslides destroying human lives and interrupting communication very frequently. As a contribution towards the mitigation process, a study has been carried out along the highway to analyse kinematic stability and qualitative estimation of rock mass condition through rock mass classification systems. The kinematic analysis shows that the rock slopes are prone to planar and wedge failure. Rock mass rating for most of the locations lies between 7 and 34, representing a poor rock mass quality (Class IV), whereas slope mass rating is more disperse and ranges from 11 to 52 for most of the slopes (Class III, IV and V).

The numerical simulation on the stability of steep rock slope by DDA

NASA Astrophysics Data System (ADS)

Zhu, Jianye; Xue, Yiguo; Tao, Yufan; Zhang, Kai; Li, Zhiqiang; Zhang, Xuedong; Yang, Ying

2017-05-01

China is a mountainous country, especially in the southwest area. Recently, the variety of geological disasters such as landslides caused by roadway excavation has become a growing concern for our society. Blindly pursuing mining interests without regard for either the environment or residents in the surrounding areas has created a dangerous situation. In recent years, frequent collapses have occurred at Zengzi Rock in Chongqing, especially after torrential rains [1]. This landslide site is a typical example of collapse caused by mine roadway excavations. To study the mechanism of mining slope stability, we conducted a numerical simulation by DDA based on Zengzi Rock in Chongqing, China. The numerical simulation analyzes the slopes under different engineering conditions and rainfall conditions. The results show that the slope has already been changed under the action of its own joints and fissures. After the excavation of the roadway and the rainfall action, this change is drastically increased and the effect is obvious. Through the result graph, we can find that the change of the displacement and stress distribution is obvious, and the simulation results can be great significance to the mining and support of similar mountain conditions.

Landslides! Engaging students in natural hazards and STEM principles through the exploration of landslide analog models

NASA Astrophysics Data System (ADS)

Gochis, E. E.; Lechner, H. N.; Brill, K. A.; Lerner, G.; Ramos, E.

2014-12-01

Graduate students at Michigan Technological University developed the "Landslides!" activity to engage middle & high school students participating in summer engineering programs in a hands-on exploration of geologic engineering and STEM (Science, Technology, Engineering and Math) principles. The inquiry-based lesson plan is aligned to Next Generation Science Standards and is appropriate for 6th-12th grade classrooms. During the activity students focus on the factors contributing to landslide development and engineering practices used to mitigate hazards of slope stability hazards. Students begin by comparing different soil types and by developing predictions of how sediment type may contribute to differences in slope stability. Working in groups, students then build tabletop hill-slope models from the various materials in order to engage in evidence-based reasoning and test their predictions by adding groundwater until each group's modeled slope fails. Lastly students elaborate on their understanding of landslides by designing 'engineering solutions' to mitigate the hazards observed in each model. Post-evaluations from students demonstrate that they enjoyed the hands-on nature of the activity and the application of engineering principles to mitigate a modeled natural hazard.

The Effects on Muscle Activation of Flatfoot during Gait According to the Velocity on an Ascending Slope.

PubMed

Lee, Chang-Ryeol; Kim, Myoung-Kwon

2014-05-01

[Purpose] This study determined the difference between flatfeet and normal feet in humans on an ascending slope using electromyography (EMG). [Subjects] This study was conducted on 30 adults having normal feet (n=15) and flatfeet (n=15), all of whom were 21 to 30 years old. [Methods] A treadmill (AC5000M, SCIFIT,) was used to analyze kinematic features during gait. These features were analyzed at slow, normal, and fast gait velocities on an ascending slope. A surface electromyogram (TeleMyo 2400T, Noraxon Co., USA) was used to measure muscle activity changes. [Results] The activities of most muscles in the subjects with flatfeet were significantly different from the muscle activities in the subjects with normal feet at different gait velocities on an ascending slope. There were significant differences in the vastus medialis and abductor hallucis muscles. [Conclusion] Because muscle activation of the vastus medialis in relation to stability of the lower extremity has a tendency to increase with an increase in gait velocity on an ascending slope, we hypothesized that higher impact transfer to the knee joints occurs in subjects with flatfeet due to the lack of a medial longitudinal arch and that the abductor halluces muscles, which provide dynamic stability to the medial longitudinal arches, do not activate well when they are needed in subjects with flatfeet.

Overpressure, Flow Focusing, Compaction and Slope Stability on the continental slope: Insights from IODP Expedition 308

NASA Astrophysics Data System (ADS)

Flemings, P. B.

2010-12-01

Integrated Ocean Drilling Program Expepedition 308 used direct measurements of pore pressure, analysis of hydromechanical properties, and geological analysis to illuminate how sedimentation, flow focusing, overpressure, and slope stability couple beneath the seafloor on the deepwater continental slope in the Gulf of Mexico. We used pore pressure penetrometers to measure severe overpressures (60% of the difference between lithostatic stress and hydrostatic pressure) that extend from the seafloor for 100’s of meters. We ran uniaxial consolidation experiments on whole core and found that although permeability is relatively high near the seafloor, the sediments are highly compressible. As a result, the coefficient of consolidation (the hydraulic diffusivity) is remarkably constant over a large range of effective stresses. This behavior accounts for the high overpressure that begins near the seafloor and extends to depth. Forward modeling suggests that flow is driven laterally along a permeable unit called the Blue Unit. Calculations suggest that soon after deposition, lateral flow lowered the effective stress and triggered the submarine landslides that we observe. Later in the evolution of this system, overpressure may have pre-conditioned the slope to failure by earthquakes. Results from IODP Expedition 308 illustrate how pore pressure and sedimentation control the large-scale form of continental margins, how submarine landslides form, and provide strategies for designing stable drilling programs.

Posterior slope of the tibial implant and the outcome of unicompartmental knee arthroplasty.

PubMed

Hernigou, Philippe; Deschamps, Gerard

2004-03-01

Laboratory studies have suggested that the sagittal displacements permitted by a knee replacement are influenced by the posterior slope of the tibial implant. The effect of the posterior slope of the tibial implant on the outcome of unicompartmental arthroplasty is not well known. The purpose of the present study was to assess the effect of the posterior slope on the long-term outcome of unicompartmental arthroplasty in knees with intact and deficient anterior cruciate ligaments. We retrospectively reviewed the results of ninety-nine unicompartmental arthroplasties after a mean duration of follow-up of sixteen years. At the time of the arthroplasty, the anterior cruciate ligament was considered to be normal in fifty knees, damaged in thirty-one, and absent in eighteen. At the most recent follow-up, we measured the posterior tibial slope and the anterior tibial translation on standing lateral radiographs. The anteroposterior stability of seventy-seven knees that had not been revised by the time of the most recent follow-up was evaluated clinically. In the group of seventy-seven knees that had not been revised by the time of the most recent follow-up, there was a significant linear relationship between anterior tibial translation (mean, 3.7 mm) and posterior tibial slope (mean, 4.3 degrees ) (p < 0.01). The mean posterior slope of the tibial implant was significantly less in the group of seventy-seven knees without loosening of the implant than it was in the group of seventeen knees with loosening of the implant (p < 0.05). Five ruptures of the anterior cruciate ligament occurred in knees in which the ligament had been considered to be normal at the time of implantation; the posterior tibial slope in these five knees was > or = 13 degrees. Clinical evaluation revealed normal or nearly normal anteroposterior stability at the time of the most recent follow-up in all sixty-six unrevised knees in which the anterior cruciate ligament had been present at the time of implantation. Of the eighteen knees in which the anterior cruciate ligament had been absent at the time of the arthroplasty, eleven still had the implant in situ at the time of the most recent follow-up; the mean posterior tibial slope in these eleven knees was <5 degrees. Seven knees in which the anterior cruciate ligament had been absent at the time of the arthroplasty were revised. In these knees, the tibial prosthesis was implanted with a posterior slope of >8 degrees. These findings suggest that >7 degrees of posterior slope of the tibial implant should be avoided, particularly if the anterior cruciate ligament is absent at the time of implantation. An intact anterior cruciate ligament, even when partly degenerated, was associated with the maintenance of normal anteroposterior stability of the knee for an average of sixteen years following unicompartmental knee arthroplasty. Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Fundamental performance of transverse wind estimator from Shack-Hartmann wave-front sensor measurements.

PubMed

Li, Zhenghan; Li, Xinyang

2018-04-30

Real time transverse wind estimation contributes to predictive correction which is used to compensate for the time delay error in the control systems of adaptive optics (AO) system. Many methods that apply Shack-Hartmann wave-front sensor to wind profile measurement have been proposed. One of the obvious problems is the lack of a fundamental benchmark to compare the various methods. In this work, we present the fundamental performance limits for transverse wind estimator from Shack-Hartmann wave-front sensor measurements using Cramér-Rao lower bound (CRLB). The bound provides insight into the nature of the transverse wind estimation, thereby suggesting how to design and improve the estimator in the different application scenario. We analyze the theoretical bound and find that factors such as slope measurement noise, wind velocity and atmospheric coherence length r 0 have important influence on the performance. Then, we introduced the non-iterative gradient-based transverse wind estimator. The source of the deterministic bias of the gradient-based transverse wind estimators is analyzed for the first time. Finally, we derived biased CRLB for the gradient-based transverse wind estimators from Shack-Hartmann wave-front sensor measurements and the bound can predict the performance of estimator more accurately.

The Influence of Plant Root Systems on Subsurface Flow: Implications for Slope Stability

EPA Science Inventory

Although research has explained how plant roots mechanically stabilize soils, in this article we explore how root systems create networks of preferential flow and thus influence water pressures in soils to trigger landslides. Root systems may alter subsurface flow: Hydrological m...

Comparison of slope stability in two Brazilian municipal landfills.

PubMed

Gharabaghi, B; Singh, M K; Inkratas, C; Fleming, I R; McBean, E

2008-01-01

The implementation of landfill gas to energy (LFGTE) projects has greatly assisted in reducing the greenhouse gases and air pollutants, leading to an improved local air quality and reduced health risks. The majority of cities in developing countries still dispose of their municipal waste in uncontrolled 'open dumps.' Municipal solid waste landfill construction practices and operating procedures in these countries pose a challenge to implementation of LFGTE projects because of concern about damage to the gas collection infrastructure (horizontal headers and vertical wells) caused by minor, relatively shallow slumps and slides within the waste mass. While major slope failures can and have occurred, such failures in most cases have been shown to involve contributory factors or triggers such as high pore pressures, weak foundation soil or failure along weak geosynthetic interfaces. Many researchers who have studied waste mechanics propose that the shear strength of municipal waste is sufficient such that major deep-seated catastrophic failures under most circumstances require such contributory factors. Obviously, evaluation of such potential major failures requires expert analysis by geotechnical specialists with detailed site-specific information regarding foundation soils, interface shearing resistances and pore pressures both within the waste and in clayey barrier layers or foundation soils. The objective of this paper is to evaluate the potential use of very simple stability analyses which can be used to study the potential for slumps and slides within the waste mass and which may represent a significant constraint on construction and development of the landfill, on reclamation and closure and on the feasibility of a LFGTE project. The stability analyses rely on site-specific but simple estimates of the unit weight of waste and the pore pressure conditions and use "generic" published shear strength envelopes for municipal waste. Application of the slope stability analysis method is presented in a case study of two Brazilian landfill sites; the Cruz das Almas Landfill in Maceio and the Muribeca Landfill in Recife. The Muribeca site has never recorded a slope failure and is much larger and better-maintained when compared to the Maceio site at which numerous minor slumps and slides have been observed. Conventional limit-equilibrium analysis was used to calculate factors of safety for stability of the landfill side slopes. Results indicate that the Muribeca site is more stable with computed factors of safety values in the range 1.6-2.4 compared with computed values ranging from 0.9 to 1.4 for the Maceio site at which slope failures have been known to occur. The results suggest that this approach may be useful as a screening-level tool when considering the feasibility of implementing LFGTE projects.

Episodic Growth of Fold-Thrust Belts: Insights from Finite Element Modelling

NASA Astrophysics Data System (ADS)

Yang, X.; Peel, F.; Sanderson, D. J.; McNeill, L. C.

2016-12-01

The sequential development of an imbricate thrust system was investigated using a set of 2D FEM models. This study provides new insights on how the style and location of thrust activity changes through cycles of thrust accretion by making refined measurements of the thrust system parameters through time and tracking these parameters through each cycle. In addition to conventional wedge parameters (i.e. surface slope, wedge width and height), the overall taper angle is used to determine how the critical taper angle is reached; a particular focus is on the region of outboard minor horizontal displacement provides insights into the forward propagation of material within, and in front of, the thrust wedge; tracking the position of the failure front (where the frontal thrust roots into the basal detachment) reveals the sequence and advancement of the imbricate thrusts. The model results show that a thrust system is generally composed of three deformation components: thrust wedge, pre-wedge and wedge front. A thrust belt involves growth that repeats episodically and cyclically. When a wedge reaches critical taper ( 10°), thrust movement within the wedge slows while the taper angle and wedge width gradually increase. In contrast, the displacement front (tracked here by the location of 0 m displacement) rapidly propagates forward along whilst the wedge height is fast growing. During this period, the wedge experiences a significant shortening after a new thrust initiates at the failure front, leading to an obvious decrease in wedge width. As soon as the critical taper is achieved, wedge interior (tracked here by the location of 50 m displacement) accelerates forward reducing the taper angle below critical. This is accompanied by a sudden increase in wedge width, slow advancement of displacement front, and slow uplift of the fold-thrust belt. The rapid movements within and in front of the wedge occur alternately. The model results also show that there is clear, although minor, activity (5-10 m displacement) in front of the thrust wedge, which distinguishes the failure front from the displacement front throughout the fold-thrust belt development. This spatial and temporal relationship may not have been previously recognized in natural systems.

DYNAMICS AND MAGNETIZATION IN GALAXY CLUSTER CORES TRACED BY X-RAY COLD FRONTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keshet, Uri; Markevitch, Maxim; Birnboim, Yuval

2010-08-10

Cold fronts (CFs)-density and temperature plasma discontinuities-are ubiquitous in cool cores of galaxy clusters, where they appear as X-ray brightness edges in the intracluster medium, nearly concentric with the cluster center. We analyze the thermodynamic profiles deprojected across core CFs found in the literature. While the pressure appears continuous across these CFs, we find that all of them require significant centripetal acceleration beneath the front. This is naturally explained by a tangential, nearly sonic bulk flow just below the CF, and a tangential shear flow involving a fair fraction of the plasma beneath the front. Such shear should generate near-equipartitionmore » magnetic fields on scales {approx}<50pc from the front and could magnetize the entire core. Such fields would explain the apparent stability of cool core CFs and the recently reported CF-radio minihalo association.« less

Feasibility of biochar application on a landfill final cover-a review on balancing ecology and shallow slope stability.

PubMed

Chen, Xun-Wen; Wong, James Tsz-Fung; Ng, Charles Wang-Wai; Wong, Ming-Hung

2016-04-01

Due to the increasing concerns on global warming, scarce land for agriculture, and contamination impacts on human health, biochar application is being considered as one of the possible measures for carbon sequestration, promoting higher crop yield and contamination remediation. Significant amount of researches focusing on these three aspects have been conducted during recent years. Biochar as a soil amendment is effective in promoting plant performance and sustainability, by enhancing nutrient bioavailability, contaminants immobilization, and microbial activities. The features of biochar in changing soil physical and biochemical properties are essential in affecting the sustainability of an ecosystem. Most studies showed positive results and considered biochar application as an effective and promising measure for above-mentioned interests. Bio-engineered man-made filled slope and landfill slope increasingly draw the attention of geologists and geotechnical engineers. With increasing number of filled slopes, sustainability, low maintenance, and stability are the major concerns. Biochar as a soil amendment changes the key factors and parameters in ecology (plant development, soil microbial community, nutrient/contaminant cycling, etc.) and slope engineering (soil weight, internal friction angle and cohesion, etc.). This paper reviews the studies on the production, physical and biochemical properties of biochar and suggests the potential areas requiring study in balancing ecology and man-made filled slope and landfill cover engineering. Biochar-amended soil should be considered as a new type of soil in terms of soil mechanics. Biochar performance depends on soil and biochar type which imposes challenges to generalize the research outcomes. Aging process and ecotoxicity studies of biochar are strongly required.

Mechanical Stability of Stratified Sediments along the upper continental Slope off Vesterålen, northern Norway - Insights from in situ CPTU Tests

NASA Astrophysics Data System (ADS)

Voelker, D.; Stegmann, S.; Kreiter, S.; L'Heureux, J. S.; Vanneste, M. W. B.; Baeten, N. J.; Knudsen, S.; Rise, L.; Longva, O.; Brendryen, J.; Haflidason, H.; Chand, S.; Mörz, T.; Kopf, A.

2015-12-01

High-resolution single channel-seismic data (3.5 kHz) reveal small-scale submarine landslide structures and superficial deformation features (e.g. tension cracks) along the gently dipping (3°) upper continental slope west of the Vesterålen Archipelago off northern Norway. Previous laboratory-based geotechnical studies attest that the slope is per sestable and that seismic events in an order of magnitude M5.7 may have triggered the slope sediments to fail. Here we present geotechnical in situ data (sedimentary strength, pore pressure), which were obtained with RV Poseidon in summer 2014 using the static CPTU system GOST. The CPTU system provided high-resolution geotechnical profiles of the uppermost sediments to a maximum penetration depth of ~ 20 m at six sites within the landslide features and beside them in undisturbed slope sediments as reference. The CPTU data reveal the occurrence of mechanically weaker zones (MWZ) by the drop of sedimentary strength. These zones are interbedded by coarser, more competent layers. The occurrence of sensitive fine-grained material may be responsible for the loss of strength in the deeper portion (appx. 12 to 18 m below seafloor). An 1D infinite pseudo-static stability analysis attests that the mechanically weaker zones (MWZ) correlate well with portions, where the Factor of Safety (FoS) ≤ 1 (meta-stable to unstable) indicates permanent deformation or failure in case additional dynamic load is induced by an earthquake. Thus, the mechanically weak layers can be considered as one important pre-condition for landslide activity. In conclusion, the integration of in situ CPTU data with geophysical data improves soil characterization and hence foster a better understanding of the pre-conditioning factors for slope instability at the upper continental slope off Vesterålen. Risk assessment for the present-day slope off Vesterålen is particularly crucial, because the opening of the region for offshore oil and gas exploration is controversially debated.

Characteristics and short-term changes of the Po Delta seafloor morphology through high-resolution bathymetric and backscatter data

NASA Astrophysics Data System (ADS)

Madricardo, Fantina; Bosman, Alessandro; Kruss, Aleksandra; Remia, Alessandro; Correggiari, Anna; Fogarin, Stefano; Romagnoli, Claudia; Moscon, Giorgia

2016-04-01

River deltas are highly dynamical and valuable environments and often undergo strong natural and human-induced actions that need constant monitoring. Whereas remote sensing observations of the sub-aerial part of the delta are very important for the assessment of the morphological changes over long time scales (years-decades), the short time-scale evolution of the submerged part of the system remains often undetermined. In particular, the shallow-water submarine pro-delta front is commonly characterized by active depositional and erosional processes. This area is crucial for the understanding of the fluvial and coastal dynamics. In this study, we applied geophysical investigations to characterize the very shallow-water area of the Po river delta in the northern Adriatic Sea. The modern Po delta is the result of increased sediment flux derived from both climate change (Little Ice Age) and human impact (deforestation and diversion and construction of artificial levees) and in recent years is suffering erosion. Here, we present the results of two high-resolution multibeam echosounder surveys carried out in June 2013 and in September 2014 on the Po river mouth and delta front in the framework of the Ritmare Project. The Po delta front, as other modern deltas, has a complicated morphology, consisting of multiple terminal distributary channels, subaqueous levee deposits, and mouth bars. The high-resolution bathymetric data show that the prodelta slope has a curved shape with an overall southward asymmetry of the submerged delta due to prevalent longshore currents. The 2013 bathymetric map highlights a number of sedimentary features, such as depositional bars, radiating in the prodelta slope with an asymmetric section, with steeper southward lee side. The new bathymetric map collected in 2014 shows impressive changes: in correspondence with the depositional lobes, we observed extensive collapse depressions with bathymetric changes of over 1 m in 15 months and widespread instability phenomena along the slope. Moreover, the acoustic backscatter intensity data and grab samples collected in the area provided information about the superficial sediment distribution during the two surveys, while the study of the water-column backscatter intensity revealed the presence of gas plume in the water-column. These results contribute to a better understanding the recent sediment dynamics and evolution of the Po Delta system.

A new parameterization of regolith formation and the response time of weathering front propagation to climate and tectonic forcing

NASA Astrophysics Data System (ADS)

Braun, Jean

2017-04-01

The thickness of the regolith remains one of the most difficult elements of the critical zone to predict or quantify. The regolith hosts a substantial proportion of the world's freshwater reservoir and its shape and physical properties control the hydrology of most river catchments, which is essential to the development and evolution of many eco-systems. The base of the regolith is controlled by the propagation of a weathering front through a range of chemical and physical processes, such as primary mineral dissolution, frost cracking or fracturing helped by topographic stress. We have recently parameterize the evolution of the weathering front under the relatively well accepted assumption that the rate of weathering front propagation, Ḃ, is directly proportional to the velocity of the fluid circulating within the regolith v, i.e. Ḃ = Fv. This approach is justified in most situations where chemical dissolution of highly soluble minerals is thought to dominate the transformation of bedrock into regolith. Under this assumption, the thickness of the regolith reaches a steady-state under the combined effects of weathering front propagation at its base and surface erosion, and the distribution of the regolith is controlled by two dimensionless numbers. The first : Ω = FKS/˙ɛ depends on the surface slope, S, and the steady-state erosion rate, ˙ɛ, through the hydraulic conductivity K and F ; the second: Γ = KS2/P depends on the surface slope and the mean precipitation rate, P . Ω controls the mean thickness of the regolith layer and needs to be larger than unity (i.e. ɛ˙ < FKS) for the regolith layer to exists. We have also shown that Ω is the ratio between the erosional response time of the system LS/ɛ˙ and the weathering response time of the system LF/K implying that where regolith is present at the Earth surface and erosional steady-state, i.e. between uplift and surface erosion, has been reached, the regolith thickness must have reached steady-state as well. On the other hand, Γ controls the shape of the regolith layer and, more precisely, whether it thickens towards the top (Γ > 1) or towards the base (Γ < 1) of topographic features. Our simple parameterization therefore explains why the regolith is thickest on top of hills in tectonically active areas, i.e. where slopes are elevated, and more uniformly distributed or even thickest near base level in tectonically quiescent areas, i.e. in anorogenic areas such as in most continental interiors. These fundamental results have now been expanded to more realistic two-dimensional numerical simulations in which drainage density is dynamically determined by the onset of surface flow, i.e. where the water table intersects the topographic surface. In this way, the length scale of water table connectivity, L, which controls the value of all of the system response times (erosional, weathering and hydraulic) is determined in a self-consistent manner which allows us to predict more accurately the range of responses of the system to tectonic and climatic changes at a variety of forcing periods.

Seasonal inorganic nitrogen release in alpine lakes on the Colorado western slope

USGS Publications Warehouse

Inyan, B.I.; Williams, M.W.; Tonnessen, K.; Turk, J.T.; Campbell, D.H.

1998-01-01

In the Rocky Mountains, the association of increases in acidic deposition with increased atmospheric loading of sulfate and direct changes in surface water chemistry has been well established. The importance, though, of increased nitrogen (N) deposition in the episodic acidification of alpine lakes and N saturation in alpine ecosystems is only beginning to be documented. In alpine areas of the Colorado Front Range, modest loadings of N in deposition have been associated with leakage of N to surface waters. On the Colorado western slope, however, no leakage of N to surface waters has been reported. A 1995 study that included early season under-ice water samples that were not available in earlier studies showed that there is, in fact, N leakage to surface waters in some western slope basins. Under-ice nitrate (NO3-) concentrations were as high as 10.5 ??q L-1, and only decreased to detection limits in September. Landscape type appears to be important in leakage of N to surface waters, which is associated with basins having steep slopes, thin soils, and large amounts of exposed bedrock. NO3- leakage compounds the existing sensitivity to episodic acidification from low acid neutralizing capacity (ANC), which is less than 40 ??eq L-1 in those basins.

Integrated satellite InSAR and slope stability modeling to support hazard assessment at the Safuna Alta glacial lake, Peru

NASA Astrophysics Data System (ADS)

Cochachin, Alejo; Frey, Holger; Huggel, Christian; Strozzi, Tazio; Büechi, Emanuel; Cui, Fanpeng; Flores, Andrés; Saito, Carlos

2017-04-01

The Safuna glacial lakes (77˚ 37' W, 08˚ 50' S) are located in the headwater of the Tayapampa catchment, in the northernmost part of the Cordillera Blanca, Peru. The upper lake, Laguna Safuna Alta at 4354 m asl has formed in the 1960s behind a terminal moraine of the retreating Pucajirca Glacier, named after the peak south of the lakes. Safuna Alta currently has a volume of 15 x 106 m3. In 2002 a rock fall of several million m3 from the proximal left lateral moraine hit the Safuna Alta lake and triggered an impact wave which overtopped the moraine dam and passed into the lower lake, Laguna Safuna Baja, which absorbed most of the outburst flood from the upper lake, but nevertheless causing loss in cattle, degradation of agricultural land downstream and damages to a hydroelectric power station in Quitaracsa gorge. Event reconstructions showed that the impact wave in the Safuna Alta lake had a runup height of 100 m or more, and weakened the moraine dam of Safuna Alta. This fact, in combination with the large lake volumes and the continued possibility for landslides from the left proximal moraine pose a considerable risk for the downstream settlements as well as the recently completed Quitaracsa hydroelectric power plant. In the framework of a project funded by the European Space Agency (ESA), the hazard situation at the Safuna Alta lake is assessed by a combination of satellite radar data analysis, field investigations, and slope stability modeling. Interferometric analyses of the Synthetic Aperture Radar (InSAR) of ALOS-1 Palsar-1, ALOS-2 Palsar-2 and Sentinel-1 data from 2016 reveal terrain displacements of 2 cm y-1 in the detachment zone of the 2002 rock avalanche. More detailed insights into the characteristics of these terrain deformations are gained by repeat surveys with differential GPS (DGPS) and tachymetric measurements. A drone flight provides the information for the generation of a high-resolution digital elevation model (DEM), which is used for the modeling of the geomechanical slope stability using the W/Slope and UDEC models. Model application, however, is limited due to data scarcity regarding geotechnical slope properties, which needed to be estimated. The combination of these data products, measurements and model results provide important information for the estimation of potential source areas for future slope collapses and involved volumes. Eventually, such information can be used for the definition of possible rock avalanche scenarios and related chain reactions in order to elaborate a hazard map for resulting lake outburst floods. At the same time, the potential for an operational slope stability monitoring system at this site will be evaluated.

14 CFR 23.175 - Demonstration of static longitudinal stability.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Demonstration of static longitudinal stability. 23.175 Section 23.175 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... must be shown as follows: (a) Climb. The stick force curve must have a stable slope at speeds between...

14 CFR 23.175 - Demonstration of static longitudinal stability.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Demonstration of static longitudinal stability. 23.175 Section 23.175 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF... must be shown as follows: (a) Climb. The stick force curve must have a stable slope at speeds between...

30 CFR 816.74 - Disposal of excess spoil: Preexisting benches.

Code of Federal Regulations, 2010 CFR

2010-07-01

... be backfilled and graded to— (1) Achieve the most moderate slope possible which does not exceed the... underdrains as necessary to control erosion, prevent water infiltration into the fill, and ensure stability..., concurrently compacted as necessary to ensure mass stability and to prevent mass movement, and graded to allow...

30 CFR 817.74 - Disposal of excess spoil: Preexisting benches.

Code of Federal Regulations, 2010 CFR

2010-07-01

... be backfilled and graded to— (1) Achieve the most moderate slope possible which does not exceed the... underdrains as necessary to control erosion, prevent water infiltration into the fill, and ensure stability..., concurrently compacted as necessary to ensure mass stability and to prevent mass movement, and graded to allow...

Experimental investigation of detonation waves instabilities in liquid high explosives

NASA Astrophysics Data System (ADS)

Sosikov, V. A.; Torunov, S. I.; Utkin, A. V.; Mochalova, V. M.; Rapota, D. Yu

2018-01-01

Experimental investigation of unstable detonation front structure in mixtures of liquid high explosives (nitromethane and FEFO—bis-(2-fluor-2.2-dinitroethyl)-formal) with inert diluents (acetone, methanol, DETA—diethylene triamine) has been carried out. Inhomogeneities have been registered by electro-optical camera NANOGATE 4BP allowing to make 4 frames with the exposure time 10 ns. According to experimental results the detonation front in nitromethane-acetone mixture is unstable. It is evident that pulsations on detonation front do not form spatial periodic structure and their dimensions differ several times. But mean longitudinal size of pulsation is about 500 μm at 20 wt% of acetone concentration. This means that the typical size of cell equals to reaction zone width. The same structure of cellular front have been registered in 70/30 FEFO-methanol mixture. Second kind of instability, failure waves, was observed in neat nitromethane at the free surface. In this case the stability loss result in turbulent flow which is clearly detected in the shots obtained. Adding small amount of DETA (0.5 wt%) results in disappearance of the failure waves and flow stabilization. The effect is caused by the fact that DETA sharply accelerates initial rate of chemical reaction because it is sensitizer for nitromethane.

Initial colonization, erosion and accretion of coral substrate

NASA Astrophysics Data System (ADS)

Davies, Peter J.; Hutchings, Patricia A.

1983-08-01

Blocks cut from Porites lutea were laid on the fore reef slope, reef flat and a lagoonal patch reef at Lizard Island, in the Northern Great Barrier Reef, and replicates removed from each environment at intervals of three months over a period of one and a half years. Variations in bioeroders and bioaccretors were noted. Microfaunas are far more numerous than macrofaunas as block colonizers; the principal borers are polychaete worms, whereas encrusters are molluscs, bryozoans, serpulids and solitary corals. The reef slope is more readily colonised by microfauna pioneer communities than are the other areas. All the environments exhibit a change from cirratulids to either sabellids or spionids (polydorids) over the length of the experiment. Accretion occurred on all blocks during the experiment, with significant differences detectable between environments; both reef slope and reef flat blocks showed weight increases of 9 10% whereas blocks from the patch reef showed increases of 15%. Annual erosion rates produced by polychaete worms are 0.694 kg m-2 year-1 (reef front), 0.843 kg m-2 year-1 (reef flat) and 1.788 kg m-2 year-1 (patch reef).

The ichthyoplankton assemblage and the environmental variables off the NW and N Iberian Peninsula coasts, in early spring

NASA Astrophysics Data System (ADS)

Rodriguez, J. M.; Gonzalez-Nuevo, G.; Gonzalez-Pola, C.; Cabal, J.

2009-05-01

Ichthyoplankton and mesozooplankton were sampled and fluorescence and physical environmental variables were measured off the NW and N Iberian Peninsula coasts, during April 2005. A total of 51 species of fish larvae, belonging to 26 families, were recorded. Sardina pilchardus, with 43.8% and 58.7% of the total fish egg and larval catches, respectively, dominated the ichthyoplankton assemblage. The study area was divided by a cross-shelf frontal structure into two hydrographic regions that coincided with the Atlantic and Cantabrian geographic regions. Ichthyoplankton abundance was higher in the Cantabrian region while larval diversity was higher in the Atlantic region. This was the main alongshore variability in the structure of the larval fish assemblage. Nevertheless, the stronger variability, related with the presence of a shelf-slope front, was found in the central-eastern Cantabrian region where two major larval fish assemblages, an "outer" and a "coastal", were distinguished. The Atlantic region, where the shelf-slope front was not found, was inhabited by a single larval fish assemblage. Canonical correspondence analysis revealed that, off the NW and N Iberian Peninsula coasts, the horizontal distribution of larval fish species in early spring may be explained by a limited number of environmental variables. Of these, the most important were the physical variables depth and sea surface temperature.

Along - Strike Analysis of Contemporary Ocean Temperature Change on the Cascadia Margin and Implications to Upper Slope Hydrate Instability

NASA Astrophysics Data System (ADS)

Phrampus, B.; Harris, R. N.; Trehu, A. M.; Embley, R. W.; Merle, S. G.

2017-12-01

Gas hydrates are found globally on continental margins and due to the large amount of sequestered carbon in hydrate reservoirs, whether these deposits are dynamic or stable has significant implications for slope stability, ocean/atmosphere carbon budget, and deep-water energy exploration. Recent studies indicate that upper slope hydrate degradation may be relatively widespread on passive margins due to recent ocean temperature warming between 0.012 and 0.033 °C/yr (e.g. Svalbard, North Alaska, and US Atlantic margin). However, the potential and breadth of warming induced hydrate instability remains contentious based on multiple observations including: 1) seep locations not consistent with locations of hydrate dissociation, 2) a lack of hydrate in regions of warming, and 3) evidence for long-lived seepage in regions associated with contemporary warming-induced hydrate dissociation. At the Cascadia margin, a recent study suggests that contemporary warming of intermediate water intersects the hydrate stability zone leading to hydrate dissociation that feeds upper slope seeps. Here, we provide a systematic analysis of along-strike variations in hydrate distribution along the Cascadia margin combined with a multivariable regression of ocean temperatures to characterize the potential of upper slope hydrate instability. Preliminary seep locations reveal upper slope seeps and observed regions of hydrate are correlated spatially between 42.5 and 48.0 °N, outside this region there is a dearth of identified upper slope hydrate and seeps. Between 44.5 and 48.0 °N a contemporary warming trend is as large as 0.006 °C/yr and is collocated with upper slope hydrate and gas seepage. This warming rate is relatively small, 2-5x smaller than warming trends identified in the Arctic where temperature induced hydrate instability remains uncertain. Additionally, we identify a region between 42.5 and 44.5 °N with collocated upper slope seepage and hydrate but no evidence of ocean warming, suggesting upper slope seepage is not driven by temperature induced hydrate instability, but maybe driven by tectonic uplift. These results highlight the absence of temperature driven seepage and slope instability on the Cascadia margin and deemphasize the impact of lower latitude warming on global hydrate dynamics and carbon budget.

A risk analysis approach for using discriminant functions to manage logging-related landslides on granitic terrain

Treesearch

Raymond M. Rice; Norman H. Pillsbury; Kurt W. Schmidt

1985-01-01

Abstract - A linear discriminant function, developed to predict debris avalanches after clearcut logging on a granitic batholith in northwestern California, was tested on data from two batholiths. The equation was inaccurate in predicting slope stability on one of them. A new equation based on slope, crown cover, and distance from a stream (retained from the original...

Slope stability problems associated with timber harvesting in mountainous regions of the western United States.

Treesearch

D.N. Swanston

1974-01-01

Natural soil-mass-movements on forested slopes in the Western United States can be divided into two major groups of closely related landslide types. These include, in order of decreasing importance and regional frequency of occurrence: (1) debris slides, debris avalanches, debris flows, and debris torrents; and (2) creep, slumps, and earth flows. Each type requires the...

Effects of tree roots on shallow landslides distribution and frequency in the European Alps using a new physically-based discrete element model

NASA Astrophysics Data System (ADS)

Cohen, Denis; Schwarz, Massimiliano

2017-04-01

Shallow landslides are hillslope processes that play a key role in shaping landscapes in forested catchments. Shallow landslides are, in some regions, the dominant regulating mechanisms by which soil is delivered from the hillslopes to steep channels and fluvial systems. Several studies have highlighted the importance of roots to better understand mechanisms of root reinforcement and their contributions to the stabilization of hillslopes. In this context, the spatio-temporal distribution of root reinforcement has a major repercussion on the dynamic of sediment transport at the catchment scale and on the availability of productive soils. Here we present a new model for shallow slope stability calculations, SOSlope, that specifically considers the effects of root reinforcement on shallow landslide initiation. The model is a strain-step discrete element model that reproduces the self-organized redistribution of forces on a slope during rainfall-triggered shallow landslides. Tree roots govern tensile and compressive force redistribution and determine the stability of the slope, the timing, location, and dimension of the failure mass. We use SOSlope to quantify the role of protection forest in several localities in the European Alps, making use of detailed field measurements of root densities and root-size distribution, and root tensile and compressive strength for three species common in the Alps (spruce, fir, and beech) to compute landslide distributions and frequency during landslide-triggering rainfall events. We show the mechanisms by which tree roots impart reinforcement to slopes and offer protection against shallow landslides.

The Influence of Preferential Flow on Pressure Propagation and Landslide Triggering of the Rocca Pitigliana Landslide

NASA Astrophysics Data System (ADS)

Shao, W.; Bogaard, T.; Bakker, M.; Berti, M.; Savenije, H. H. G.

2016-12-01

The fast pore water pressure response to rain events is an important triggering factor for slope instability. The fast pressure response may be caused by preferential flow that bypasses the soil matrix. Currently, most of the hydro-mechanical models simulate pore water pressure using a single-permeability model, which cannot quantify the effects of preferential flow on pressure propagation and landslide triggering. Previous studies showed that a model based on the linear-diffusion equation can simulate the fast pressure propagation in near-saturated landslides such as the Rocca Pitigliana landslide. In such a model, the diffusion coefficient depends on the degree of saturation, which makes it difficult to use the model for predictions. In this study, the influence of preferential flow on pressure propagation and slope stability is investigated with a 1D dual-permeability model coupled with an infinite-slope stability approach. The dual-permeability model uses two modified Darcy-Richards equations to simultaneously simulate the matrix flow and preferential flow in hillslopes. The simulated pressure head is used in an infinite-slope stability analysis to identify the influence of preferential flow on the fast pressure response and landslide triggering. The dual-permeability model simulates the height and arrival of the pressure peak reasonably well. Performance of the dual-permeability model is as good as or better than the linear-diffusion model even though the dual-permeability model is calibrated for two single pulse rain events only, while the linear-diffusion model is calibrated for each rain event separately.