Slope evolution at the Calvert Cliffs, Maryland -- measuring the change from eroding bluffs to stable slopes

USGS Publications Warehouse

Herzog, Martha; Larsen, Curtis E.; McRae, Michele

2002-01-01

Despite a long history of geomorphic studies, it is difficult to ascertain the time required for slopes to change from near vertical exposures to relatively stable slopes due to inadequate age control. Actively eroding coastal bluffs along the western shore of the Chesapeake Bay provide a key for understanding the centennial-scale development of stable slopes from eroding bluff faces. The Calvert Cliffs are composed of sandy silts, silty sands, and clayey silts of Miocene-age. Active wave erosion at the bluff toes encourages rapid sloughing from bluff faces and maintains slope angles of 70-80 degrees and relatively constant bluff-retreat rates. Naturally stabilized slopes are preserved as a fossil bluff line inland from a prograding cuspate foreland at Cove Point. The foreland is migrating southward at a rate of ca. 1.5 m/yr. As it moves south, it progressively protects bluffs from wave action as new beaches are deposited at their toes. Wave erosion is reinitiated at the northern end of the complex as the landform passes. An incremental record of slope change is preserved along the fossil bluff line. 14C dating of swales between beach ridges shows the complex to span 1700 years of progressive migration history. We hypothesized that slopes would change from steep, eroding faces to low-angle slopes covered with vegetation and sought to document the rate of change. Our team measured slope angles at intervals along the fossil bluff line and dated profiles by interpolating 14C ages of adjacent beach ridges. There was no progressive decrease in slope with age. All slopes along the fossil bluff line were 30-40 degrees with a mean of 35 degrees. Constancy in slope angle suggests that steep, actively eroding bluffs were quickly changed to stable slopes by landslides and slumping once they were protected. Given the accuracy of our age control, we conclude that the time required to attain a stable slope under natural processes is less than one century. This indicates that

The shifting nature of vegetation controls on peak snowpack with varying slope and aspect

NASA Astrophysics Data System (ADS)

Biederman, J. A.; Harpold, A. A.; Broxton, P. D.; Brooks, P. D.

2012-12-01

The controls on peak seasonal snowpack are known to shift between forested and open environments as well as with slope and aspect. Peak snowpack is predicted well by interception models under uniformly dense canopy, while topography, wind and radiation are strong predictors in open areas. However, many basins have complex mosaics of forest canopy and small gaps, where snowpack controls involve complex interactions among climate, topography and forest structure. In this presentation we use a new fully distributed tree-scale model to investigate vegetation controls on snowpack for a range of slope and aspect, and we evaluate the energy balance in forest canopy and gap environments. The model is informed by airborne LiDAR and ground-based observations of climate, vegetation and snowpack. It represents interception, snow distribution by wind, latent and sensible heat fluxes, and radiative fluxes above and below the canopy at a grid scale of 1 m square on an hourly time step. First, the model is minimally calibrated using continuous records of snow depth and snow water equivalent (SWE). Next, the model is evaluated using distributed observations at peak accumulation. Finally, the domain is synthetically altered to introduce ranges of slope and aspect. Northerly aspects accumulate greater peak SWE than southerly aspects (e.g. 275 mm vs. 250 mm at a slope of 28 %) but show lower spatial variability (e. g. CV = 0.14 vs. CV = 0.17 at slope of 28 %). On northerly aspects, most of the snowpack remains shaded by vegetation, whereas on southerly aspects the northern portions of gaps and southern forest edges receive direct insolation during late winter. This difference in net radiation makes peak SWE in forest gaps and adjacent forest edges more sensitive to topography than SWE in areas under dense canopy. Tree-scale modeling of snow dynamics over synthetic terrain offers extensive possibilities to test interactions among vegetation and topographic controls.

Estimating Slope and Level Change in N = 1 Designs

ERIC Educational Resources Information Center

Solanas, Antonio; Manolov, Rumen; Onghena, Patrick

2010-01-01

The current study proposes a new procedure for separately estimating slope change and level change between two adjacent phases in single-case designs. The procedure eliminates baseline trend from the whole data series before assessing treatment effectiveness. The steps necessary to obtain the estimates are presented in detail, explained, and…

Review of science issues, deployment strategy, and status for the ARM north slope of Alaska-Adjacent Arctic Ocean climate research site

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

Stamnes, K.; Ellingson, R.G.; Curry, J.A.

1999-01-01

Recent climate modeling results point to the Arctic as a region that is particularly sensitive to global climate change. The Arctic warming predicted by the models to result from the expected doubling of atmospheric carbon dioxide is two to three times the predicted mean global warming, and considerably greater than the warming predicted for the Antarctic. The North Slope of Alaska-Adjacent Arctic Ocean (NSA-AAO) Cloud and Radiation Testbed (CART) site of the Atmospheric Radiation Measurement (ARM) Program is designed to collect data on temperature-ice-albedo and water vapor-cloud-radiation feedbacks, which are believed to be important to the predicted enhanced warming inmore » the Arctic. The most important scientific issues of Arctic, as well as global, significance to be addressed at the NSA-AAO CART site are discussed, and a brief overview of the current approach toward, and status of, site development is provided. ARM radiometric and remote sensing instrumentation is already deployed and taking data in the perennial Arctic ice pack as part of the SHEBA (Surface Heat Budget of the Arctic ocean) experiment. In parallel with ARM`s participation in SHEBA, the NSA-AAO facility near Barrow was formally dedicated on 1 July 1997 and began routine data collection early in 1998. This schedule permits the US Department of Energy`s ARM Program, NASA`s Arctic Cloud program, and the SHEBA program (funded primarily by the National Science Foundation and the Office of Naval Research) to be mutually supportive. In addition, location of the NSA-AAO Barrow facility on National Oceanic and Atmospheric Administration land immediately adjacent to its Climate Monitoring and Diagnostic Laboratory Barrow Observatory includes NOAA in this major interagency Arctic collaboration.« less

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.

Minimizing Alteration of Posterior Tibial Slope During Opening Wedge High Tibial Osteotomy: a Protocol with Experimental Validation in Paired Cadaveric Knees

PubMed Central

Westermann, Robert W; DeBerardino, Thomas; Amendola, Annunziato

2014-01-01

Introduction The High Tibial Osteotomy (HTO) is a reliable procedure in addressing uni- compartmental arthritis with associated coronal deformities. With osteotomy of the proximal tibia, there is a risk of altering the tibial slope in the sagittal plane. Surgical techniques continue to evolve with trends towards procedure reproducibility and simplification. We evaluated a modification of the Arthrex iBalance technique in 18 paired cadaveric knees with the goals of maintaining sagittal slope, increasing procedure efficiency, and decreasing use of intraoperative fluoroscopy. Methods Nine paired cadaveric knees (18 legs) underwent iBalance medial opening wedge high tibial osteotomies. In each pair, the right knee underwent an HTO using the modified technique, while all left knees underwent the traditional technique. Independent observers evaluated postoperative factors including tibial slope, placement of hinge pin, and implant placement. Specimens were then dissected to evaluate for any gross muscle, nerve or vessel injury. Results Changes to posterior tibial slope were similar using each technique. The change in slope in traditional iBalance technique was -0.3° ±2.3° and change in tibial slope using the modified iBalance technique was -0.4° ±2.3° (p=0.29). Furthermore, we detected no differences in posterior tibial slope between preoperative and postoperative specimens (p=0.74 traditional, p=0.75 modified). No differences in implant placement were detected between traditional and modified techniques. (p=0.85). No intraoperative iatrogenic complications (i.e. lateral cortex fracture, blood vessel or nerve injury) were observed in either group after gross dissection. Discussion & Conclusions Alterations in posterior tibial slope are associated with HTOs. Both traditional and modified iBalance techniques appear reliable in coronal plane corrections without changing posterior tibial slope. The present modification of the Arthrex iBalance technique may increase the

The Volpe Center GPS Adjacent Band Compatibility Program Plan : GPS Adjacent Band Compatibility Workshop, Volpe Center, Cambridge MA

DOT National Transportation Integrated Search

2014-09-18

Approach to DOT GPS Adjacent Band Compatibility Assessment. Identify forums and provide public outreach to make sure the progress and work are as open and transparent as possible. Develop an implementation plan that incorporates aspects from the DOT ...

Geologic Assessment of Undiscovered, Technically Recoverable Coalbed-Gas Resources in Cretaceous and Tertiary Rocks, North Slope and Adjacent State Waters, Alaska

USGS Publications Warehouse

Roberts, Stephen B.

2008-01-01

The purpose of the U.S. Geological Survey's (USGS) National Oil and Gas Assessment is to develop geology-based hypotheses regarding the potential for additions to oil and gas reserves in priority areas of the United States, focusing on the distribution, quantity, and availability of oil and natural gas resources. The USGS has completed an assessment of the undiscovered, technically recoverable coalbed-gas resources in Cretaceous and Tertiary rocks underlying the North Slope and adjacent State waters of Alaska (USGS Northern Alaska Province 5001). The province is a priority Energy Policy and Conservation Act (EPCA) province for the National Assessment because of its potential for oil and gas resources. The assessment of this province is based on geologic principles and uses the total petroleum system concept. The geologic elements of a total petroleum system include hydrocarbon source rocks (source rock maturation, hydrocarbon generation and migration), reservoir rocks (stratigraphy, sedimentology, petrophysical properties), and hydrocarbon traps (trap formation and timing). In the Northern Alaska Province, the USGS used this geologic framework to define one composite coalbed gas total petroleum system and three coalbed gas assessment units within the petroleum system, and quantitatively estimated the undiscovered coalbed-gas resources within each assessment unit.

Ride-on lawnmowers warnings: slope measurements and safety-by-separation.

PubMed

Karnes, Edward W; Leonard, S David; Lenorovitz, David R

2012-01-01

Various single-rider open vehicles, such as lawnmowers, are susceptible to overturning on slopes that are too steep for them. Warnings have included separation from the vehicles and avoiding slopes that are too steep. A recommended maximum slope is commonly 15 degrees. However, many individuals cannot evaluate slopes just by sight. Some mower manufacturers have warned about too steep slopes and have provided slope gauges for users to determine the slopes in natural settings. This article evaluated the usefulness of such gauges for users who might be expected to need to evaluate slopes and the efficacy of a separation procedure for avoiding injuries. It was concluded that neither of these were likely to be successful and suggestions are made for alternative approaches.

Variability of adjacency effects in sky reflectance measurements.

PubMed

Groetsch, Philipp M M; Gege, Peter; Simis, Stefan G H; Eleveld, Marieke A; Peters, Steef W M

2017-09-01

Sky reflectance R sky (λ) is used to correct in situ reflectance measurements in the remote detection of water color. We analyzed the directional and spectral variability in R sky (λ) due to adjacency effects against an atmospheric radiance model. The analysis is based on one year of semi-continuous R sky (λ) observations that were recorded in two azimuth directions. Adjacency effects contributed to R sky (λ) dependence on season and viewing angle and predominantly in the near-infrared (NIR). For our test area, adjacency effects spectrally resembled a generic vegetation spectrum. The adjacency effect was weakly dependent on the magnitude of Rayleigh- and aerosol-scattered radiance. The reflectance differed between viewing directions 5.4±6.3% for adjacency effects and 21.0±19.8% for Rayleigh- and aerosol-scattered R sky (λ) in the NIR. Under which conditions in situ water reflectance observations require dedicated correction for adjacency effects is discussed. We provide an open source implementation of our method to aid identification of such conditions.

Slope/Shelf Circulation and Cross-Slope/Shelf Transport Out of a Bay Driven by Eddies from the Open Ocean

DTIC Science & Technology

2009-09-01

channel. More recently, they examined the role of eddies in the overturning circulation of the Southern Ocean using the hemispheric HIM with realistic... meridional velocity with intervals of 0.1 · 10−3ms−1 159 PV equation to study the bay-scale circulations : d dt ( f + ζ H0 − f0h0 H 20 ) = F, (4.30) where...2009-18 DOCTORAL DISSERTATION by Yu Zhang September 2009 Slope/shelf Circulation and Cross-slope/shelf Transport Out of a Bay Driven by Eddies from

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.

Permeability changes induced by microfissure closure and opening in tectonized materials. Effect on slope pore pressure regime.

NASA Astrophysics Data System (ADS)

De la Fuente, Maria; Vaunat, Jean; Pedone, Giuseppe; Cotecchia, Federica; Sollecito, Francesca; Casini, Francesca

2015-04-01

Tectonized clays are complex materials characterized by several levels of structures that may evolve during load and wetting/drying processes. Some microstructural patterns, as microfissures, have a particular influence on the value of permeability which is one of the main factors controlling pore pressure regime in slopes. In this work, the pore pressure regime measured in a real slope of tectonized clay in Southern Italy is analyzed by a numerical model that considers changes in permeability induced by microfissure closure and opening during the wetting and drying processes resulting from climatic actions. Permeability model accounts for the changes in Pore Size Distribution observed by Microscopy Intrusion Porosimetry. MIP tests are performed on representative samples of ground in initial conditions ("in situ" conditions) and final conditions (deformed sample after applying a wetting path that aims to reproduce the saturation of the soil under heavy rains). The resulting measurements allow for the characterization at microstructural level of the soil, identifying the distribution of dominant families pores in the sample and its evolution under external actions. Moreover, comparison of pore size density functions allows defining a microstructural parameter that depends on void ratio and degree of saturation and controls the variation of permeability. Model has been implemented in a thermo-hydro-mechanical code provided with a special boundary condition for climatic actions. Tool is used to analyze pore pressure measurements obtained in the tectonized clay slope. Results are analyzed at the light of the effect that permeability changes during wetting and drying have on the pore pressure regime.

30 CFR 77.1911 - Ventilation of slopes and shafts.

Code of Federal Regulations, 2010 CFR

2010-07-01

... or air contamination from any other source; (4) Equipped with an automatic signal device designed to... be examined before each shift and the quantity of air in the slope or shaft measured daily by a... connected to the slope or shaft opening with fireproof air ducts; (3) Designed to permit the reversal of the...

Transfer of lipid molecules and polycyclic aromatic hydrocarbons to open marine waters by dense water cascading events

NASA Astrophysics Data System (ADS)

Salvadó, Joan A.; Grimalt, Joan O.; López, Jordi F.; Palanques, Albert; Heussner, Serge; Pasqual, Catalina; Sanchez-Vidal, Anna; Canals, Miquel

2017-12-01

Settling particles were collected by a set of moored sediment traps deployed during one year in the western Gulf of Lion along Cap de Creus and Lacaze-Duthiers submarine canyons and on the adjacent southern open slope. These traps collected particles during periods of pelagic settling and also during events of deep water flushing by dense shelf water cascading (DSWC). Analyses of lipid biomarkers (n-alkanes, n-alkan-1-ols, sterols and C37-C38 alkenones) and polycyclic aromatic hydrocarbons (PAHs) showed much higher transfer of terrestrial lipids and PAHs to open deep waters during DSWC than in the absence of cascading. The area of highest lateral fluxes was mostly located at 1000 m depth but also at 1500 m depth and extended along the canyons and to the adjacent slope. Higher fluxes were observed near the bottom (30 m above bottom; mab) than at intermediate waters (500 mab) which is consistent with the formation and sinking of dense water over the continental shelf, and its transport through the canyons towards the continental slope and deep basin. DSWC involved the highest settling fluxes of terrestrial lipids and PAHs ever described in marine continental slopes and the pelagic domain, as illustrated by peak values of C23-C33 odd carbon numbered alkanes (405 ng m-2 d-1), C22-C32 even carbon numbered alkan-1-ols (850 ng m-2 d-1), β-sitosterol+sitostanol (4800 ng m-2 d-1) and PAHs (55 μg m-2 d-1). The algal lipids also showed higher transfer to deep waters during DSWC but to a lower extent than the terrigenous compounds. However, the C37-C38 alkenones constituted an exception and their settling fluxes were not influenced by DSWC. The lack of influence of the DSWC on the C37-C38 alkenone settling is consistent with absence of haptophyte algal inputs from the continental shelf and reinforces the reliability of these molecules for palaeothermometry and palaeoproductivity measurements in pelagic systems.

Architecture and sedimentary processes on the mid-Norwegian continental slope: A 2.7 Myr record from extensive seismic evidence

NASA Astrophysics Data System (ADS)

Montelli, A.; Dowdeswell, J. A.; Ottesen, D.; Johansen, S. E.

2018-07-01

Quaternary architectural evolution and sedimentary processes on the mid-Norwegian continental slope are investigated using margin-wide three- and two-dimensional seismic datasets. Of ∼100,000 km3 sediments delivered to the mid-Norwegian shelf and slope over the Quaternary, ∼75,000 km3 comprise the slope succession. The structural high of the Vøring Plateau, characterised by initially low (∼1-2°) slope gradients and reduced accommodation space, exerted a strong control over the long-term architectural evolution of the margin. Slope sediment fluxes were higher on the Vøring Plateau area, increasing up to ∼32 km3 ka-1 during the middle Pleistocene, when fast-flowing ice streams advanced to the palaeo-shelf edge. Resulted in a more rapid slope progradation on the Vøring Plateau, these rates of sediment delivery are high compared to the maximum of ∼7 km3 ka-1 in the adjacent sectors of the slope, characterised by steeper slope (∼3-5°), more available accommodation space and smaller or no palaeo-ice streams on the adjacent shelves. In addition to the broad-scale architectural evolution, identification of more than 300 buried slope landforms provides an unprecedented level of detailed, process-based palaeoenvironmental reconstruction. Channels dominate the Early Pleistocene record (∼2.7-0.8 Ma), during which glacimarine sedimentation on the slope was influenced by dense bottom-water flow and turbidity currents. Morphologic signature of glacigenic debris-flows appear within the Middle-Late Pleistocene (∼0.8-0 Ma) succession. Their abundance increases towards Late Pleistocene, marking a decreasing role for channelized turbidity currents and dense water flows. This broad-scale palaeo-environmental shift coincides with the intensification of Northern Hemispheric glaciations, highlighting first-order climate control on the sedimentary processes in high-latitude continental slopes.

Performance evaluation of setback buildings with open ground storey on plain and sloping ground under earthquake loadings and mitigation of failure

NASA Astrophysics Data System (ADS)

Ghosh, Rahul; Debbarma, Rama

2017-06-01

Setback structures are highly vulnerable during earthquakes due to its vertical geometrical and mass irregularity, but the vulnerability becomes higher if the structures also have stiffness irregularity in elevation. The risk factor of such structure may increase, if the structure rests on sloping ground. In this paper, an attempt has been made to evaluate the seismic performance of setback structures resting on plain ground as well as in the slope of a hill, with soft storey configuration. The analysis has been performed in three individual methods, equivalent static force method, response spectrum method and time history method and extreme responses have been recorded for open ground storeyed setback building. To mitigate this soft storey effect and the extreme responses, three individual mitigation techniques have been adopted and the best solution among these three techniques is presented.

Blasting methods for heterogeneous rocks in hillside open-pit mines with high and steep slopes

NASA Astrophysics Data System (ADS)

Chen, Y. J.; Chang, Z. G.; Chao, X. H.; Zhao, J. F.

2017-06-01

In the arid desert areas in Xinjiang, most limestone quarries are hillside open-pit mines (OPMs) where the limestone is hard, heterogeneous, and fractured, and can be easily broken into large blocks by blasting. This study tried to find effective technical methods for blasting heterogeneous rocks in such quarries based on an investigation into existing problems encountered in actual mining at Hongshun Limestone Quarry in Xinjiang. This study provided blasting schemes for hillside OPMs with different heights and slopes. These schemes involve the use of vertical deep holes, oblique shallow holes, and downslope hole-by-hole sublevel or simultaneous detonation techniques. In each bench, the detonations of holes in a detonation unit occur at intervals of 25-50 milliseconds. The research findings can offer technical guidance on how to blast heterogeneous rocks in hillside limestone quarries.

Recurring slope lineae in equatorial regions of Mars

USGS Publications Warehouse

McEwen, Alfred S.; Dundas, Colin M.; Mattson, Sarah S.; Toigo, Anthony D.; Ojha, Lujendra; Wray, James J.; Chojnacki, Matthew; Byrne, Shane; Murchie, Scott L.; Thomas, Nicolas

2014-01-01

The presence of liquid water is a requirement of habitability on a planet. Possible indicators of liquid surface water on Mars include intermittent flow-like features observed on sloping terrains. These recurring slope lineae are narrow, dark markings on steep slopes that appear and incrementally lengthen during warm seasons on low-albedo surfaces. The lineae fade in cooler seasons and recur over multiple Mars years. Recurring slope lineae were initially reported to appear and lengthen at mid-latitudes in the late southern spring and summer and are more common on equator-facing slopes where and when the peak surface temperatures are higher. Here we report extensive activity of recurring slope lineae in equatorial regions of Mars, particularly in the deep canyons of Valles Marineris, from analysis of data acquired by the Mars Reconnaissance Orbiter. We observe the lineae to be most active in seasons when the slopes often face the sun. Expected peak temperatures suggest that activity may not depend solely on temperature. Although the origin of the recurring slope lineae remains an open question, our observations are consistent with intermittent flow of briny water. Such an origin suggests surprisingly abundant liquid water in some near-surface equatorial regions of Mars.

A critical review of the glaciomarine model for Irish sea deglaciation: evidence from southern Britain, the Celtic shelf and adjacent continental slope

NASA Astrophysics Data System (ADS)

Scourse, J. D.; Furze, M. F. A.

2001-07-01

In support of their glaciomarine model for the deglaciation of the Irish Sea basin, Eyles and McCabe cited the occurrence of distal glaciomarine mud drapes onshore in the Isles of Scilly and North Devon, and of arctic beach-face gravels and sands around the shores of the Celtic Sea. Glacial and sea-level data from the southern part of the Irish Sea in the terminal zone of the ice stream and the adjacent continental slope are reviewed here to test this aspect of the model. The suggestion that the glacial sequences of both the Isles of Scilly and Fremington in North Devon are glaciomarine mud drapes is rejected. An actively calving tidewater margin only occurred early in the deglacial sequence close to the terminal zone in the south-central Celtic Sea. Relative sea-levels were lower, and therefore glacio-isostatic depression less, than envisaged in the glaciomarine model. Geochronological, sedimentological and biostratigraphical data indicate that the raised beach sequences around the shores of the Celtic Sea and English Channel were deposited at, or during regression soon after, interglacial eustatic highstands. Evidence for ice-rafting at a time of high relative sea-levels is restricted to a phase(s) earlier than the Late Devensian. These data indicate that the raised beach sequences have no bearing on the style of Irish Sea deglaciation.

Carbonate platform, slope, and basinal deposits of Upper Oligocene, Kalimantan, Indonesia

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

Armin, R.A.; Cutler, W.G.; Mahadi, S.

1987-05-01

Upper Oligocene platform carbonates (Berai Formation) occur extensively on the Barito shelf in southeastern Kalimantan (Borneo) and are flanked northward by coeval slope and basinal deposits (Bongan Formation) which accumulated in the southwestern part of the Kutei basin. Isolated carbonate buildups equivalent to the Berai Formation also occur within the Kutei basin and were probably deposited on basement highs. The distribution of these facies is fairly well constrained by the study of outcrops, wells, and seismic profiles. The Berai Formation consists of diverse limestone types with a wide range of textures and with dominant skeletal components of large foraminifera, redmore » algae, and corals. Deposition of the Berai Formation occurred in moderate- and high-energy shallow-marine conditions. Slope and basin facies occur in extensional basins adjacent to the shelfal carbonates and peripheral to isolated carbonate buildups. Slope deposits consist of hemipelagic claystone, debris-flow conglomerate, calciturbidite, and volcaniclastic intervals. syndepositional downslope transport of slope deposits was an important process, as indicated by intervals containing redeposited debris flows, intraformational truncation surfaces, slide blocks, and associated shear planes. Recurrent movement on basin-margin faults and local volcanism probably perpetuated instability of slope deposits. Basinal deposits consist of calcareous claystone with intercalated thin, distal calciturbidite and volcaniclastic beds.« less

Effects of wind velocity and slope on fire behavior

Treesearch

D.R. Weise; G.S. Biging

1994-01-01

Effects of wind velocity and slope on fire spread rate and flame length were examined. Fuel beds of vertical sticks (13.97 cm x 0.455 cm x 0.1 10 cm) and coarse excelsior were burned in an open-topped tilting wind tunnel. Mean fuel moisture content of sticks and excelsior was 11% and 12%, respectively. Mean surface area to volume ratio was 23 cm-! Five slopes (negative...

The Q-Slope Method for Rock Slope Engineering

NASA Astrophysics Data System (ADS)

Bar, Neil; Barton, Nick

2017-12-01

Q-slope is an empirical rock slope engineering method for assessing the stability of excavated rock slopes in the field. Intended for use in reinforcement-free road or railway cuttings or in opencast mines, Q-slope allows geotechnical engineers to make potential adjustments to slope angles as rock mass conditions become apparent during construction. Through case studies across Asia, Australia, Central America, and Europe, a simple correlation between Q-slope and long-term stable slopes was established. Q-slope is designed such that it suggests stable, maintenance-free bench-face slope angles of, for instance, 40°-45°, 60°-65°, and 80°-85° with respective Q-slope values of approximately 0.1, 1.0, and 10. Q-slope was developed by supplementing the Q-system which has been extensively used for characterizing rock exposures, drill-core, and tunnels under construction for the last 40 years. The Q' parameters (RQD, J n, J a, and J r) remain unchanged in Q-slope. However, a new method for applying J r/ J a ratios to both sides of potential wedges is used, with relative orientation weightings for each side. The term J w, which is now termed J wice, takes into account long-term exposure to various climatic and environmental conditions such as intense erosive rainfall and ice-wedging effects. Slope-relevant SRF categories for slope surface conditions, stress-strength ratios, and major discontinuities such as faults, weakness zones, or joint swarms have also been incorporated. This paper discusses the applicability of the Q-slope method to slopes ranging from less than 5 m to more than 250 m in height in both civil and mining engineering projects.

Gaseous polycyclic aromatic hydrocarbon concentrations are higher in urban forests than adjacent open areas during summer but not in winter--Exploratory study.

PubMed

Viippola, Viljami; Rantalainen, Anna-Lea; Yli-Pelkonen, Vesa; Tervo, Peatta; Setälä, Heikki

2016-01-01

While the potential of plants to uptake polycyclic aromatic hydrocarbons (PAHs) is widely acknowledged, empirical evidence of the effects of this process on local atmospheric PAH concentrations and human health is tenuous. We measured gaseous PAH concentrations using passive samplers in urban tree-covered areas and adjacent open, treeless areas in a near-road environment in Finland to gain information on the ability of urban vegetation to improve air quality. The ability of urban, mostly deciduous, vegetation to affect PAHs was season dependent: during summer, concentrations were significantly higher in tree-covered areas, while in the fall, concentrations in open areas exceeded those in tree-covered areas. During winter, concentrations in tree-covered areas were either lower or did not differ from those in open areas. Results of this study imply that the commonly believed notion that trees unequivocally improve air quality does not apply to PAHs studied here. Copyright © 2015 Elsevier Ltd. All rights reserved.

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.

Continuity in fire disturbance between riparian and adjacent sideslopes in the Douglas-fire forest series.

Treesearch

Richard L. Everett; Richard Schellhaas; Pete Ohlson

2000-01-01

Fire scar and stand cohort records were used to estimate the number and timing of fire disturbance events that impacted riparian and adjacent sideslope forests in the Douglas-fir series. Data were gathered from 49 stream segments on 24 separate streams on the east slope of the Washington Cascade Range. Upslope forests had more traceable disturbance events than riparian...

Inexpensive Device for Demonstrating Rock Slope Failure and Other Collapse Phenomena.

ERIC Educational Resources Information Center

Stimpson, B.

1980-01-01

Describes an inexpensive modeling technique for demonstrating large-scale displacement phenomena in rock masses, such as slope collapse and failure of underground openings. Excavation of the model material occurs through openings made in the polyurethane foam in the correct excavation sequence. (Author/SA)

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.

Hydrology of two slopes in subarctic Yukon, Canada

NASA Astrophysics Data System (ADS)

Carey, Sean K.; Woo, Ming-Ko

1999-11-01

Two subarctic forested slopes in central Wolf Creek basin, Yukon, were studied in 1996-1997 to determine the seasonal pattern of the hydrologic processes. A south-facing slope has a dense aspen forest on silty soils with seasonal frost only and a north-facing slope has open stands of black spruce and an organic layer on top of clay sediments with permafrost. Snowmelt is advanced by approximately one month on the south-facing slope due to greater radiation receipt. Meltwater infiltrates its seasonally frozen soil with low ice content, recharging the soil moisture reservoir but yielding no lateral surface or subsurface flow. Summer evaporation depletes this recharged moisture and any additional rainfall input, at the expense of surface or subsurface flow. The north-facing slope with an ice rich substrate hinders deep percolation. Snow meltwater is impounded within the organic layer to produce surface runoff in rills and gullies, and subsurface flow along pipes and within the matrix of the organic soil. During the summer, most subsurface flows are confined to the organic layer which has hydraulic conductivities orders of magnitudes larger than the underlying boulder-clay. Evaporation on the north-facing slope declines as both the frost table and the water table descend in the summer. A water balance of the two slopes demonstrates that vertical processes of infiltration and evaporation dominate moisture exchanges on the south-facing slope, whereas the retardation of deep drainage by frost and by clayey soil on the permafrost slope promotes a strong lateral flow component, principally within the organic layer. These results have the important implication that permafrost slopes and organic horizons are the principal controls on streamflow generation in subarctic catchments.

Beyond debuttressing: Mechanics of paraglacial rock slope damage during repeat glacial cycles

NASA Astrophysics Data System (ADS)

Grämiger, Lorenz M.; Moore, Jeffrey R.; Gischig, Valentin S.; Ivy-Ochs, Susan; Loew, Simon

2017-04-01

Cycles of glaciation impose mechanical stresses on underlying bedrock as glaciers advance, erode, and retreat. Fracture initiation and propagation constitute rock mass damage and act as preparatory factors for slope failures; however, the mechanics of paraglacial rock slope damage remain poorly characterized. Using conceptual numerical models closely based on the Aletsch Glacier region of Switzerland, we explore how in situ stress changes associated with fluctuating ice thickness can drive progressive rock mass failure preparing future slope instabilities. Our simulations reveal that glacial cycles as purely mechanical loading and unloading phenomena produce relatively limited new damage. However, ice fluctuations can increase the criticality of fractures in adjacent slopes, which may in turn increase the efficacy of fatigue processes. Bedrock erosion during glaciation promotes significant new damage during first deglaciation. An already weakened rock slope is more susceptible to damage from glacier loading and unloading and may fail completely. We find that damage kinematics are controlled by discontinuity geometry and the relative position of the glacier; ice advance and retreat both generate damage. We correlate model results with mapped landslides around the Great Aletsch Glacier. Our result that most damage occurs during first deglaciation agrees with the relative age of the majority of identified landslides. The kinematics and dimensions of a slope failure produced in our models are also in good agreement with characteristics of instabilities observed in the field. Our results extend simplified assumptions of glacial debuttressing, demonstrating in detail how cycles of ice loading, erosion, and unloading drive paraglacial rock slope damage.

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.

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

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).

HDMR methods to assess reliability in slope stability analyses

NASA Astrophysics Data System (ADS)

Kozubal, Janusz; Pula, Wojciech; Vessia, Giovanna

2014-05-01

Stability analyses of complex rock-soil deposits shall be tackled considering the complex structure of discontinuities within rock mass and embedded soil layers. These materials are characterized by a high variability in physical and mechanical properties. Thus, to calculate the slope safety factor in stability analyses two issues must be taken into account: 1) the uncertainties related to structural setting of the rock-slope mass and 2) the variability in mechanical properties of soils and rocks. High Dimensional Model Representation (HDMR) (Chowdhury et al. 2009; Chowdhury and Rao 2010) can be used to carry out the reliability index within complex rock-soil slopes when numerous random variables with high coefficient of variations are considered. HDMR implements the inverse reliability analysis, meaning that the unknown design parameters are sought provided that prescribed reliability index values are attained. Such approach uses implicit response functions according to the Response Surface Method (RSM). The simple RSM can be efficiently applied when less than four random variables are considered; as the number of variables increases, the efficiency in reliability index estimation decreases due to the great amount of calculations. Therefore, HDMR method is used to improve the computational accuracy. In this study, the sliding mechanism in Polish Flysch Carpathian Mountains have been studied by means of HDMR. The Southern part of Poland where Carpathian Mountains are placed is characterized by a rather complicated sedimentary pattern of flysh rocky-soil deposits that can be simplified into three main categories: (1) normal flysch, consisting of adjacent sandstone and shale beds of approximately equal thickness, (2) shale flysch, where shale beds are thicker than adjacent sandstone beds, and (3) sandstone flysch, where the opposite holds. Landslides occur in all flysch deposit types thus some configurations of possible unstable settings (within fractured rocky

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

Rock mass characterisation and stability analyses of excavated slopes

NASA Astrophysics Data System (ADS)

Zangerl, Christian; Lechner, Heidrun

2016-04-01

Excavated slopes in fractured rock masses are frequently designed for open pit mining, quarries, buildings, highways, railway lines, and canals. These slopes can reach heights of several hundreds of metres and in cases concerning open pit mines slopes larger than 1000 m are not uncommon. Given that deep-seated slope failures can cause large damage or even loss of life, the slope design needs to incorporate sufficient stability. Thus, slope design methods based on comprehensive approaches need to be applied. Excavation changes slope angle, groundwater flow, and blasting increases the degree of rock mass fracturing as well as rock mass disturbance. As such, excavation leads to considerable stress changes in the slopes. Generally, slope design rely on the concept of factor of safety (FOS), often a requirement by international or national standards. A limitation of the factor of safety is that time dependent failure processes, stress-strain relationships, and the impact of rock mass strain and displacement are not considered. Usually, there is a difficulty to estimate the strength of the rock mass, which in turn is controlled by an interaction of intact rock and discontinuity strength. In addition, knowledge about in-situ stresses for the failure criterion is essential. Thus, the estimation of the state of stress of the slope and the strength parameters of the rock mass is still challenging. Given that, large-scale in-situ testing is difficult and costly, back-calculations of case studies in similar rock types or rock mass classification systems are usually the methods of choice. Concerning back-calculations, often a detailed and standardised documentation is missing, and a direct applicability to new projects is not always given. Concerning rock mass classification systems, it is difficult to consider rock mass anisotropy and thus the empirical estimation of the strength properties possesses high uncertainty. In the framework of this study an approach based on

Structure of Infaunal Communities on the Beaufort Sea Shelf and Slope: Insights from Morphological and Environmental DNA Sequencing Approaches

NASA Astrophysics Data System (ADS)

Hardy, S. M.; Bik, H.; Walker, A.; Sharma, J.; Blanchard, A.

2016-02-01

Rapid change is occurring in the Arctic concurrently with increased human activity, yet our knowledge of the structure and function of high-Arctic sediment communities is still rudimentary. The Beaufort Sea is particularly poorly sampled, and largely unexplored at slope depths, providing little information with which to assess the impacts of petroleum exploration activities now beginning in this area. We are investigating diversity and community structure of meio- and macrobenthic infauna on the continental shelf and slope of the Beaufort Sea across a range of depths (50 to 1000 m) using traditional taxonomic and environmental DNA sequencing approaches, and comparing results to additional sites in the adjacent NE Chukchi Sea petroleum lease-sale area. The Beaufort slope is topographically complex and characterized by an east-west gradient in benthic habitat characteristics, with heavy input of terrestrial organic matter particularly in the region of the Mackenzie River delta. Warmer, saltier subsurface Atlantic water masses impact benthic communities at mid-slope depths, likely influencing turnover in community structure observed with depth. Food resources are variable across the region, with very high sediment chlorophyll concentrations at 350 m depth in some areas. Differences in nematode assemblages were detected across the Beaufort Sea shelf/slope, across depths within the Beaufort Sea, and between the Beaufort and adjacent NE Chukchi Sea. These differences were apparent in both morphological and environmental sequencing data. Macrofaunal communities showed variable community structure among transects, with high abundance and high dominance in polychaete assemblages coincident with the chlorophyll maximum. Sequencing data also revealed an abundance of protists in sediments which have been mostly ignored in studies of ecosystem dynamics in this region, and may represent an important component of the food web.

Geophysical investigation and dynamic modelling of unstable slopes: case-study of Kainama (Kyrgyzstan)

NASA Astrophysics Data System (ADS)

Danneels, G.; Bourdeau, C.; Torgoev, I.; Havenith, H.-B.

2008-10-01

The presence of massive Quaternary loess units at the eastern border of the Fergana Basin (Kyrgyzstan, Central Asia) makes this area particularly prone to the development of catastrophic loess earthflows, causing damages and injuries almost every year. Efficient disaster management requires a good understanding of the main causes of these mass movements, that is, increased groundwater pressure and seismic shaking. This paper focuses on the Kainama earthflow, mainly composed of loess, which occurred in 2004 April. Its high velocity and the long run-out zone caused the destruction of 12 houses and the death of 33 people. In summer 2005, a field survey consisting of geophysical and seismological measurements was carried out along the adjacent slope. By combination and geostatistical analysis of these data, a reliable 3-D model of the geometry and properties of the subsurface layers, as shown in the first part of the paper, was created. The analysis of the seismological data allowed us to point out a correlation between the thickness of the loess cover and the measured resonance frequencies and associated amplification potential. The second part of this paper is focused on the study of the seismic response of the slope by numerical simulations, using a 2-D finite difference code named FLAC. Modelling of the seismic amplification potential along the slope confirmed the results obtained from the seismological survey-strong amplifications at the crest and bottom of the slope where there is a thick loess cover and almost no amplification in the middle part of the slope. Furthermore, dynamic slope stability analyses were conducted to assess the influence of local amplifications and increased groundwater pressures on the slope failure. The results of the dynamic modelling, although preliminary, show that a combination of seismic and hydrologic origin (pore pressure build-up during the seismic shaking) is the most probable scenario responsible for the 2004 failure.

Influence of bedrock geology on water chemistry of slope wetlands and headwater streams in the southern Rocky Mountains

Treesearch

Monique LaPerriere Nelson; Charles C. Rhoades; Kathleen A. Dwire

2011-01-01

We characterized the water chemistry of nine slope wetlands and adjacent headwater streams in Colorado subalpine forests and compared sites in basins formed on crystalline bedrock with those formed in basins with a mixture of crystalline and sedimentary bedrock. The pH, Ca2+, Mg2+, NH4 +, acid neutralizing capacity, and electrical conductivity of wetland porewater and...

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

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

Characterization of Unstable Rock Slopes Through Passive Seismic Measurements

NASA Astrophysics Data System (ADS)

Kleinbrod, U.; Burjanek, J.; Fäh, D.

2014-12-01

Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. An analysis of ambient vibrations of unstable rock slopes might be a new alternative to the already existing methods, e.g. geotechnical displacement measurements. Systematic measurements have been performed recently in Switzerland to study the seismic response of potential rockslides concerning a broad class of slope failure mechanisms and material conditions. Small aperture seismic arrays were deployed at sites of interest for a short period of time (several hours) in order to record ambient vibrations. Each measurement setup included a reference station, which was installed on a stable part close to the instability. Recorded ground motion is highly directional in the unstable parts of the rock slope, and significantly amplified with respect to stable areas. These effects are strongest at certain frequencies, which were identified as eigenfrequencies of the unstable rock mass. In most cases the directions of maximum amplification are perpendicular to open cracks and in good agreement with the deformation directions obtained by geodetic measurements. Such unique signatures might improve our understanding of slope structure and stability. Thus we link observed vibration characteristics with available results of detailed geological characterization. This is supported by numerical modeling of seismic wave propagation in fractured media with complex topography.For example, a potential relation between eigenfrequencies and unstable rock mass volume is investigated.

North Slope (Wahluke Slope) expedited response action cleanup plan

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

Not Available

The purpose of this action is to mitigate any threat to public health and the environment from hazards on the North Slope and meet the expedited response action (ERA) objective of cleanup to a degree requiring no further action. The ERA may be the final remediation of the 100-I-3 Operable Unit. A No Action record of decision (ROD) may be issued after remediation completion. The US Department of Energy (DOE) currently owns or administers approximately 140 mi{sup 2} (about 90,000 acres) of land north and east of the Columbia River (referred to as the North Slope) that is part ofmore » the Hanford Site. The North Slope, also commonly known as the Wahluke Slope, was not used for plutonium production or support facilities; it was used for military air defense of the Hanford Site and vicinity. The North Slope contained seven antiaircraft gun emplacements and three Nike-Ajax missile positions. These military positions were vacated in 1960--1961 as the defense requirements at Hanford changed. They were demolished in 1974. Prior to government control in 1943, the North Slope was homesteaded. Since the initiation of this ERA in the summer of 1992, DOE signed the modified Hanford Federal Agreement and Consent Order (Tri-Party Agreement) with the Washington Department of Ecology (Ecology) and the US Environmental Protection Agency (EPA), in which a milestone was set to complete remediation activities and a draft closeout report by October 1994. Remediation activities will make the North Slope area available for future non-DOE uses. Thirty-nine sites have undergone limited characterization to determine if significant environmental hazards exist. This plan documents the results of that characterization and evaluates the potential remediation alternatives.« less

Near-bottom currents over the continental slope in the Mid-Atlantic Bight

USGS Publications Warehouse

Csanady, G.T.; Churchill, J.H.; Butman, B.

1988-01-01

From a set of 28 current meter records we have found that near-bottom currents faster than 0.2 m s-1 occur frequently over the outer continental shelf of the Mid-Atlantic Bight (bottom depth <210 m) but very rarely (<1% of the time) between bottom depths of 500 m and 2 km over the slope. The rarity of strong near-bottom flow over the middle and lower slope allows the accumulation of fine-grained sediment and organic carbon in this region. Fast near-bottom currents which do occur over the slope are invariably associated with topographic waves, although it is often superimposed inertial oscillations which increase current speed above the level of 0.2 m s-1. Episodes of intense inertial oscillations occur randomly and last typically for 10-20 days. Their energy source is unknown. Topographic wave energy exhibits a slight, but statistically significant, minimum over the mid-slope. These waves appear irregularly and vary both along isobaths and in time. The irregularity is presumably a consequence of random topographic wave generation by Gulf Stream instability. The current regime within sea-floor depressions in the slope (canyons and gullies) is distinctly different from that of the open slope; most notable is the near absence of topographic wave motion within depressions. ?? 1988.

Theoretical Prediction of the Heats of Formation, Densities and Relative Sensitivities, and/or Synthetic Approaches Toward the Synthesis of High Energy Dense Materials (HEDMs): 3,5-Dinitro-1,3,5-Oxadiazinane, Bis-Adjacent RDX, Bis-Adjacent HMX, 4,4’,6,6’-Tetranitro-1,1’-Bis(N-oxide)-5,5’,6,6’-4H,4’H-5,5’-Bisimidazo Oxadiazole, and the Open-Cage Derivative of CL-20

DTIC Science & Technology

2015-09-01

HMX , 4,4’,6,6’- Tetranitro-1,1’-Bis(N-oxide)-5,5’,6,6’-4H,4’H- 5,5’-Bisimidazo Oxadiazole, and the Open- Cage Derivative of CL-20...HEDMs): 3,5-Dinitro-1,3,5-Oxadiazinane, Bis-Adjacent RDX, Bis-Adjacent HMX , 4,4’,6,6’- Tetranitro-1,1’-Bis(N-oxide)-5,5’,6,6’-4H,4’H- 5,5’-Bisimidazo...Materials (HEDMs): 3,5-Dinitro-1,3,5-Oxadiazinane, Bis-Adjacent RDX, Bis-Adjacent HMX , 4,4’,6,6’-Tetranitro-1,1’-Bis(N-oxide)-

[Effects of slope gradient on slope runoff and sediment yield under different single rainfall conditions].

PubMed

He, Ji-Jun; Cai, Qiang-Guo; Liu, Song-Bo

2012-05-01

Based on the field observation data of runoff and sediment yield produced by single rainfall events in runoff plots, this paper analyzed the variation patterns of runoff and sediment yield on the slopes with different gradients under different single rainfall conditions. The differences in the rainfall conditions had little effects on the variation patterns of slope runoff with the gradient. Under the conditions of six different rainfall events in the study area, the variation patterns of slope runoff with the gradient were basically the same, i. e., the runoff increased with increasing gradient, but the increment of the runoff decreased slightly with increasing gradient, which was mainly determined by the infiltration flux of atmospheric precipitation. Rainfall condition played an important role on the slope sediment yield. Generally, there existed a critical slope gradient for slope erosion, but the critical gradient was not a fixed value, which varied with rainfall condition. The critical slope gradient for slope erosion increased with increasing slope gradient. When the critical slope gradient was greater, the variation of slope sediment yield with slope gradient always became larger.

Left-turn lanes at unsignalized median openings.

DOT National Transportation Integrated Search

2014-03-01

Due to the frequent presence of median openings in urban arterial settings, the requirements for the deceleration and : storage of turning vehicles (e.g. AASHTO Green Book) often exceed the available length between two adjacent : openings which leave...

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.

Effects of wind velocity and slope on flame properties

Treesearch

David R. Weise; Gregory S. Biging

1996-01-01

Abstract: The combined effects of wind velocity and percent slope on flame length and angle were measured in an open-topped, tilting wind tunnel by burning fuel beds composed of vertical birch sticks and aspen excelsior. Mean flame length ranged from 0.08 to 1.69 m; 0.25 m was the maximum observed flame length for most backing fires. Flame angle ranged from -46o to 50o...

Storm-driven delivery of sediment to the continental slope: Numerical modeling for the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Harris, C. K.; Kniskern, T. A.; Arango, H.

2016-02-01

The supply of sediment from the continental shelf to deeper waters is of critical importance for building continental margin repositories of sediment, and may also factor into episodic events on the continental slope such as turbidity currents and slope failures. While numerical sediment transport models have been developed for coastal and continental shelf areas, they have not often been used to infer sediment delivery to deeper waters. A three-dimensional coupled hydrodynamic - suspended sediment transport model for the northern Gulf of Mexico has been developed and run to evaluate the types of conditions that are associated with delivery of suspended sediment to the continental slope. Accounting for sediment delivery by riverine plumes and for sediment resuspension by energetic waves and currents, the sediment transport calculations were implemented within the Regional Ocean Modeling System (ROMS). The model domain represents the northern Gulf of Mexico shelf and slope including the Mississippi birdfoot delta and the Mississippi and DeSoto Canyons. To investigate the role of storms in driving down-slope sediment fluxes, model runs that encompassed fall, 2007 through late summer, 2008 the summer and fall of 2008 were analyzed. This time period included several winter storms, and the passage of two hurricanes (Ike and Gustav) over the study area. Preliminary results indicated that sediment delivery to the continental slope was triggered by the passage of these storm events, and focused at certain locations, such as submarine canyons. Additionally, a climatological analysis indicates that storm track influences both the wind-driven currents and wave energy on the shelf, and as such plays an important role in determining which storms trigger delivery of suspended continental shelf sediment to the adjacent slope.

Slope Streaks or RSL?

NASA Image and Video Library

2016-12-14

The image shows a region we see many slope streaks, typically dark features on slopes in the equatorial regions on Mars. They may extend for tens of meters in length and gradually fade away with time as new ones form. The most common hypothesis is that they are generated by dust avalanches that regularly occur on steep slopes exposing fresh dark materials from underneath the brighter dust. There are many types of slope streaks but one of the most recent and significant findings using HiRISE was the discovery of a new type called "recurring slope lineae," or RSL for short. Recent studies suggest that RSL may form through the flow of briny (extremely salty) liquid water that can be stable on the surface of Mars even under current climatic conditions for a limited time in summer when it is relatively warm. How can we distinguish between conventional slope streaks like the ones we see here and RSL? There are many criteria. For instance, RSL are usually smaller in size than regular slope streaks. However, one of the most important conditions is seasonal behavior, since RSL appear to be active only in summer while regular slope streaks can be active anytime of the year. This site is monitored regularly by HiRISE scientists because of the high density of slope streaks and their different sizes and orientations. If we look at a time-lapse sequence, we will see that a new slope streak has indeed formed in the period since April 2016 (and we can note how dark it is in comparison to the others indicating its freshness). However, this period corresponds mainly to the autumn season in this part of Mars, whereas we do not see any major changes in the summer season. This suggests that the feature that developed is a regular slope streak just like all the others in the area. http://photojournal.jpl.nasa.gov/catalog/PIA21272

Sedimentary processes on the Atlantic Continental Slope of the United States

USGS Publications Warehouse

Knebel, H.J.

1984-01-01

Until recently, the sedimentary processes on the United States Atlantic Continental Slope were inferred mainly from descriptive studies based on the bathymetry and on widely spaced grab samples, bottom photographs, and seismic-reflection profiles. Over the past 6 years, however, much additional information has been collected on the bottom morphology, characteristics of shallow-subbottom strata, velocity of bottom currents, and transport of suspended and bottom sediments. A review of these new data provides a much clearer understanding of the kinds and relative importance of gravitational and hydrodynamic processes that affect the surface sediments. On the rugged slope between Georges Bank and Cape Lookout, N.C., these processes include: (1) small scale mass wasting within submarine canyons and peripheral gullies; (2) density flows within some submarine valleys; (3) sand spillover near the shelf break; (4) sediment creep on the upper slope; and (5) hemipelagic sedimentation on the middle and lower slope. The area between Georges Bank and Hudson Canyon is further distinguished by the relative abundance of large-scale slump scars and deposits on the open slope, the presence of ice-rafted debris, and the transport of sand within the heads of some submarine canyons. Between Cape Lookout and southern Florida, the slope divides into two physiographic units, and the topography is smooth and featureless. On the Florida-Hatteras Slope, offshelf sand spillover and sediment winnowing, related to Gulf Stream flow and possibly to storm-driven currents, are the major processes, whereas hemipelagic sedimentation is dominant over the offshore slope along the seaward edge of the Blake Plateau north of the Blake Spur. Slumping generally is absent south of Cape Lookout, although one large slump scarp (related to uplift over salt diapirs) has been identified east of Cape Romain. Future studies concerning sedimentary processes on the Atlantic slope need to resolve: (1) the ages and

Western Ross Sea continental slope gravity currents

NASA Astrophysics Data System (ADS)

Gordon, Arnold L.; Orsi, Alejandro H.; Muench, Robin; Huber, Bruce A.; Zambianchi, Enrico; Visbeck, Martin

2009-06-01

Antarctic Bottom Water of the world ocean is derived from dense Shelf Water that is carried downslope by gravity currents at specific sites along the Antarctic margins. Data gathered by the AnSlope and CLIMA programs reveal the presence of energetic gravity currents that are formed over the western continental slope of the Ross Sea when High Salinity Shelf Water exits the shelf through Drygalski Trough. Joides Trough, immediately to the east, offers an additional escape route for less saline Shelf Water, while the Glomar Challenger Trough still farther east is a major pathway for export of the once supercooled low-salinity Ice Shelf Water that forms under the Ross Ice Shelf. The Drygalski Trough gravity currents increase in thickness from ˜100 to ˜400 m on proceeding downslope from ˜600 m (the shelf break) to 1200 m (upper slope) sea floor depth, while turning sharply to the west in response to the Coriolis force during their descent. The mean current pathway trends ˜35° downslope from isobaths. Benthic-layer current and thickness are correlated with the bottom water salinity, which exerts the primary control over the benthic-layer density. A 1-year time series of bottom-water current and hydrographic properties obtained on the slope near the 1000 m isobath indicates episodic pulses of Shelf Water export through Drygalski Trough. These cold (<-1 °C), salty (>34.75) pulses correlate with strong downslope bottom flow. Extreme examples occurred during austral summer/fall 2003, comprising concentrated High Salinity Shelf Water (-1.9 °C; 34.79) and approaching 1.5 m s -1 at descent angles as large as ˜60° relative to the isobaths. Such events were most common during November-May, consistent with a northward shift in position of the dense Shelf Water during austral summer. The coldest, saltiest bottom water was measured from mid-April to mid-May 2003. The summer/fall export of High Salinity Shelf Water observed in 2004 was less than that seen in 2003. This

Wintertime slope winds and its turbulent characteristics in the Yeongdong region of Korea

NASA Astrophysics Data System (ADS)

Jeon, H. R.; Eun, S. H.; Kim, B. G.; Lee, Y. H.

2015-12-01

The Yeongdong region has various meteorological phenomenons by virtue of complicated geographical characteristics with high Taebaek Mountains running from the north to the south and an adjacent East Sea to the east. There are few studies on the slope winds and its turbulent characteristics over the complex terrain, which are critical information in mountain climbing, hiking, paragliding, even winter sports such as alpine skiing and ski jump etc. For the understanding of diverse mountain winds in the complex terrain in Yeongdong, hot-wire anemometers (Campbell Scientific) have been installed at a couple of sites since October 2014 and several automatic weather stations at several sites around the mountainous region in Yeongdong since November 2012.WRF model simulations have been also done with an ultra-fine horizontal resolution of 300 m for 10 years. Generally, model and observation show that the dominant wind is westerly, approximately more than 75%. It is quite consistent that wind fields from both model and observation agree with each other in the valley region and at the top of the mountain, but there is a significant disagreement in wind direction specifically in the slide slope. Probably this implies model's performance with even an ultra-fine resolution is still not enough for the slide slope domain of complex terrains. Despite that, the observation clearly showed up- and down slope winds for the weak synoptic conditions carefully selected such as strong insolation and a synoptic wind less than 5m/s in the 850 hPa. The up- and down slope flows are also demonstrated in the snow-covered condition as well as grass ground. Further, planar fit transformation algorithm against the coordinate tilt has been applied to raw wind data (10Hz) of the slope site for the analysis of turbulence properties. Turbulence also increases with synoptic wind strength. Detailed analysis of mechanical turbulence and buoyance will be discussed for different surface properties (grass

29 CFR Appendix B to Subpart P of... - Sloping and Benching

Code of Federal Regulations, 2013 CFR

2013-07-01

... excavations 20 feet or less in depth made in layered soils shall have a maximum allowable slope for each layer.... Distress means that the soil is in a condition where a cave-in is imminent or is likely to occur. Distress... 24 hours that an excavation is open. (c) Requirements—(1) Soil classification. Soil and rock deposits...

29 CFR Appendix B to Subpart P of... - Sloping and Benching

Code of Federal Regulations, 2012 CFR

2012-07-01

... excavations 20 feet or less in depth made in layered soils shall have a maximum allowable slope for each layer.... Distress means that the soil is in a condition where a cave-in is imminent or is likely to occur. Distress... 24 hours that an excavation is open. (c) Requirements—(1) Soil classification. Soil and rock deposits...

29 CFR Appendix B to Subpart P of... - Sloping and Benching

Code of Federal Regulations, 2014 CFR

2014-07-01

... excavations 20 feet or less in depth made in layered soils shall have a maximum allowable slope for each layer.... Distress means that the soil is in a condition where a cave-in is imminent or is likely to occur. Distress... 24 hours that an excavation is open. (c) Requirements—(1) Soil classification. Soil and rock deposits...

29 CFR Appendix B to Subpart P of... - Sloping and Benching

Code of Federal Regulations, 2011 CFR

2011-07-01

... excavations 20 feet or less in depth made in layered soils shall have a maximum allowable slope for each layer.... Distress means that the soil is in a condition where a cave-in is imminent or is likely to occur. Distress... 24 hours that an excavation is open. (c) Requirements—(1) Soil classification. Soil and rock deposits...

29 CFR Appendix B to Subpart P of... - Sloping and Benching

Code of Federal Regulations, 2010 CFR

2010-07-01

... excavations 20 feet or less in depth made in layered soils shall have a maximum allowable slope for each layer.... Distress means that the soil is in a condition where a cave-in is imminent or is likely to occur. Distress... 24 hours that an excavation is open. (c) Requirements—(1) Soil classification. Soil and rock deposits...

Infiltration on sloping terrain and its role on runoff generation and slope stability

NASA Astrophysics Data System (ADS)

Loáiciga, Hugo A.; Johnson, J. Michael

2018-06-01

A modified Green-and-Ampt model is formulated to quantify infiltration on sloping terrain underlain by homogeneous soil wetted by surficial water application. This paper's theory for quantifying infiltration relies on the mathematical statement of the coupled partial differential equations (pdes) governing infiltration and runoff. These pdes are solved by employing an explicit finite-difference numerical method that yields the infiltration, the infiltration rate, the depth to the wetting front, the rate of runoff, and the depth of runoff everywhere on the slope during external wetting. Data inputs consist of a water application rate or the rainfall hyetograph of a storm of arbitrary duration, soil hydraulic characteristics and antecedent moisture, and the slope's hydraulic and geometric characteristics. The presented theory predicts the effect an advancing wetting front has on slope stability with respect to translational sliding. This paper's theory also develops the 1D pde governing suspended sediment transport and slope degradation caused by runoff influenced by infiltration. Three examples illustrate the application of the developed theory to calculate infiltration and runoff on a slope and their role on the stability of cohesive and cohesionless soils forming sloping terrain.

The boundary conditions for simulations of a shake-table experiment on the seismic response of 3D slope

NASA Astrophysics Data System (ADS)

Tang, Liang; Cong, Shengyi; Ling, Xianzhang; Ju, Nengpan

2017-01-01

Boundary conditions can significantly affect a slope's behavior under strong earthquakes. To evaluate the importance of boundary conditions for finite element (FE) simulations of a shake-table experiment on the slope response, a validated three-dimensional (3D) nonlinear FE model is presented, and the numerical and experimental results are compared. For that purpose, the robust graphical user-interface "SlopeSAR", based on the open-source computational platform OpenSees, is employed, which simplifies the effort-intensive pre- and post-processing phases. The mesh resolution effect is also addressed. A parametric study is performed to evaluate the influence of boundary conditions on the FE model involving the boundary extent and three types of boundary conditions at the end faces. Generally, variations in the boundary extent produce inconsistent slope deformations. For the two end faces, fixing the y-direction displacement is not appropriate to simulate the shake-table experiment, in which the end walls are rigid and rough. In addition, the influence of the length of the 3D slope's top face and the width of the slope play an important role in the difference between two types of boundary conditions at the end faces (fixing the y-direction displacement and fixing the ( y, z) direction displacement). Overall, this study highlights that the assessment of a comparison between a simulation and an experimental result should be performed with due consideration to the effect of the boundary conditions.

Magnetic resonance imaging evaluation of adjacent segments after cervical disc arthroplasty: magnet strength and its effect on image quality. Clinical article.

PubMed

Antosh, Ivan J; DeVine, John G; Carpenter, Clyde T; Woebkenberg, Brian J; Yoest, Stephen M

2010-12-01

Disc arthroplasty is an alternative to fusion following anterior discectomy when treating either cervical radiculopathy or myelopathy. Its theoretical benefits include preservation of the motion segment and the potential prevention of adjacent-segment degeneration. There is a paucity of data regarding the ability to use MR imaging to evaluate the adjacent segments. The purpose of this study was for the authors to introduce open MR imaging as an alternative method in imaging adjacent segments following cervical disc arthroplasty using a Co-Cr implant and to report their preliminary results using this technique. Postoperative cervical MR images were obtained in the first 16 patients in whom the porous coated motion (PCM-V) cervical arthroplasty system was used to treat a single level between C-3 and C-7. Imaging was performed in all 16 patients with a closed 1.5-T unit, and in the final 6 patients it was also performed with an open 0.2-T unit. All images were evaluated by an independent radiologist observer for the ability to visualize the superior endplate, disc space, and inferior endplate at the superior and inferior adjacent levels. Utilizing the 1.5-T magnet to assess the superior adjacent level, the superior endplate, disc space, and inferior endplate could each be visualized less than 50% of the time on sagittal T1- and sagittal and axial T2-weighted images. Similarly, the inferior adjacent level structures were adequately visualized less than 50% of the time, with the exception of slightly improved visualization of the inferior endplate on T1-weighted images (56%). Axial images allowed worse visualization than sagittal images at both the superior and inferior adjacent levels. Utilizing the 0.2-T magnet to assess the superior and inferior adjacent levels, the superior endplate, disc space, and inferior endplate were adequately visualized in 100% of images. Based on the results of this case series, it appears that the strength of the magnet affects the artifact

Forecasting slope failures from space-based synthetic aperture radar (SAR) measurements

NASA Astrophysics Data System (ADS)

Wasowski, J.; Bovenga, F.; Nutricato, R.; Nitti, D. O.; Chiaradia, M. T.; Tijani, K.; Morea, A.

2017-12-01

New space-borne radar sensors enable multi-scale monitoring of potentially unstable slopes thanks to wide-area coverage (tens of thousands km2), regular long-term image acquisition schedule with increasing re-visit frequency (weekly to daily), and high measurement precision (mm). In particular, the recent radar satellite missions e.g., COSMO-SkyMed (CSK), Sentinel-1 (S-1) and improved multi-temporal interferometry (MTI) processing techniques allow timely delivery of information on slow ground surface displacements. Here we use two case study examples to show that it is possible to capture pre-failure slope strains through long-term MTI-based monitoring. The first case is a retrospective investigation of a huge 500ML m3 landslide, which occurred in Sept. 2016 in a large, active open-cast coal mine in central Europe. We processed over 100 S-1 images acquired since Fall 2014. The MTI results showed that the slope that failed had been unstable at least since 2014. Importantly, we detected consistent displacement trends and trend changes, which can be used for slope failure forecasting. Specifically, we documented significant acceleration in slope surface displacement in the two months preceding the catastrophic failure. The second case of retrospectively captured pre-failure slope strains regards our earlier study of a small 50 m long landslide, which occurred on Jan. 2014 and caused the derailment of a train on the railway line connecting NW Italy to France. We processed 56 CSK images acquired from Fall 2008 to Spring 2014. The MTI results revealed pre-failure displacements of the engineering structures on the slope subsequently affected by the 2014 slide. The analysis of the MTI time series further showed that the displacements had been occurring since 2009. This information could have been used to forewarn the railway authority about the slope instability hazard. The above examples indicate that more frequent and consistent image acquisitions by the new radar

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

Pelvic incidence-lumbar lordosis mismatch predisposes to adjacent segment disease after lumbar spinal fusion.

PubMed

Rothenfluh, Dominique A; Mueller, Daniel A; Rothenfluh, Esin; Min, Kan

2015-06-01

Several risk factors and causes of adjacent segment disease have been debated; however, no quantitative relationship to spino-pelvic parameters has been established so far. A retrospective case-control study was carried out to investigate spino-pelvic alignment in patients with adjacent segment disease compared to a control group. 45 patients (ASDis) were identified that underwent revision surgery for adjacent segment disease after on average 49 months (7-125), 39 patients were selected as control group (CTRL) similar in the distribution of the matching variables, such as age, gender, preoperative degenerative changes, and numbers of segments fused with a mean follow-up of 84 months (61-142) (total n = 84). Several radiographic parameters were measured on pre- and postoperative radiographs, including lumbar lordosis measured (LL), sacral slope, pelvic incidence (PI), and tilt. Significant differences between ASDis and CTRL groups on preoperative radiographs were seen for PI (60.9 ± 10.0° vs. 51.7 ± 10.4°, p = 0.001) and LL (48.1 ± 12.5° vs. 53.8 ± 10.8°, p = 0.012). Pelvic incidence was put into relation to lumbar lordosis by calculating the difference between pelvic incidence and lumbar lordosis (∆PILL = PI-LL, ASDis 12.5 ± 16.7° vs. CTRL 3.4 ± 12.1°, p = 0.001). A cutoff value of 9.8° was determined by logistic regression and ROC analysis and patients classified into a type A (∆PILL <10°) and a type B (∆PILL ≥10°) alignment according to pelvic incidence-lumbar lordosis mismatch. In type A spino-pelvic alignment, 25.5 % of patients underwent revision surgery for adjacent segment disease, whereas 78.3 % of patients classified as type B alignment had revision surgery. Classification of patients into type A and B alignments yields a sensitivity for predicting adjacent segment disease of 71 %, a specificity of 81 % and an odds ratio of 10.6. In degenerative disease of the lumbar spine a high pelvic incidence with diminished lumbar lordosis seems

The Munson-Nygren slide: A major lower-slope slide off Georges Bank

USGS Publications Warehouse

O'Leary, Dennis W.

1986-01-01

The Munson-Nygren slide is a large compound slide located between Munson and Nygren Canyons below 1900 m depth on the Continental Slope off Georges Bank. Its structural and morphological features are recognized in high-resolution seismic-reflection profiles. The slide comprises an axial trough which has a relief as great as 325 m and a width of 6-10 km. The trough is flanked by displaced and disrupted strata for a total lateral extent of approximately 20 km and a downslope extent of at least 35 km. The slide is unrelated genetically to the adjacent canyons and may postdate Munson Canyon. There is evidence of plastic deformation at the base of the section subjected to sliding. Certain features of the slide complex resemble those seen in landforms on the Laurentian Rise and attributed by Emery et al.* * Emery et al. (1970). to the 1929 Grand Banks earthquake. The Munson-Nygren slide may have been triggered by a large earthquake in late Pleistocene time or later. Destructional landforms associated with the slide are similar to those widely present along the lower slope off Georges Bank. ?? 1986.

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.

Alaskan North Slope Oil & Gas Transportation Support

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

Lilly, Michael Russell

North Slope oil and gas resources are a critical part of US energy supplies and their development is facing a period of new growth to meet increasing national energy needs. While this growth is taking place in areas active in development for more than 20 years, there are many increasing environmental challenges facing industry and management agencies. A majority of all exploration and development activities, pipeline maintenance and other field support activities take place in the middle of winter, when the fragile tundra surface is more stable. The window for the critical oil and gas winter operational season has beenmore » steadily decreasing over the last 25 years. The number of companies working on the North Slope is increasing. Many of these companies are smaller and working with fewer resources than the current major companies. The winter operations season starts with the tundra-travel opening, which requires 15 cm of snow on the land surface in the coastal management areas and 23 cm in the foothills management areas. All state managed areas require -5°C soil temperatures at a soil depth of 30 cm. Currently there are no methods to forecast this opening date, so field mobilization efforts are dependent on agency personnel visiting field sites to measure snow and soil temperature conditions. Weeks can be easily lost in the winter operating season due to delays in field verification of tundra conditions and the resulting mobilization. After the season is open, a significant percentage of exploration, construction, and maintenance do not proceed until ice roads and pads can be built. This effort is dependent on access to lake ice and under-ice water. Ice chipping is a common ice-road construction technique used to build faster and stronger ice roads. Seasonal variability in water availability and permitting approaches are a constant constraint to industry. At the end of the winter season, projects reliant on ice-road networks are often faced with ending

Size cues and the adjacency principle.

DOT National Transportation Integrated Search

1963-11-01

The purpose of the present study was to apply the adjacency principle to the perception of relative depth from size cues. In agreement with the adjacency principle, it was found that the size cue between adjacent objects was more effective than the s...

Frosty Slopes in Late Spring

NASA Image and Video Library

2014-12-18

This image from NASA Mars Reconnaissance Orbiter shows frosted gullies on a south-facing slope within a crater. At this time of year only south-facing slopes retain the frost, while the north-facing slopes have melted.

Effects of grapevine root density and reinforcement on slopes prone to shallow slope instability

NASA Astrophysics Data System (ADS)

Meisina, Claudia; Bordoni, Massimiliano; Bischetti, Gianbattista; Vercesi, Alberto; Chiaradia, Enrico; Cislaghi, Alessio; Valentino, Roberto; Bittelli, Marco; Vergani, Chiara; Chersich, Silvia; Giuseppina Persichillo, Maria; Comolli, Roberto

2016-04-01

Slope erosion and shallow slope instabilities are the major factors of soil losses in cultivated steep terrains. These phenomena also cause loss of organic matter and plants nutrients, together with the partial or total destruction of the structures, such as the row tillage pattern of the vineyards, which allow for the plants cultivation. Vegetation has long been used as an effective tool to decrease the susceptibility of a slope to erosion and to shallow landslides. In particular, the scientific research focused on the role played by the plant roots, because the belowground biomass has the major control on the potential development of soil erosion and of shallow failures. Instead, a comprehensive study that analyzes the effects of the roots of agricultural plants on both soil erosion and slope instability has not been carried out yet. This aspect should be fundamental where sloped terrains are cultivated with plants of great economical relevance, as grapevine. To contribute to fill this gap, in this study the features of root density in the soil profile have been analyzed in slopes cultivated with vineyards, located on a sample hilly area of Oltrepò Pavese (northern Italy). In this area, the viticulture is the most important branch of the local economy. Moreover, several events of rainfall-induced slope erosion and shallow landslides have occurred in this area in the last 6 years, causing several economical damages linked to the destruction of the vineyards and the loss of high productivity soils. Grapevine root distribution have been measured in different test-site slopes, representative of the main geological, geomorphological, pedological, landslides distribution, agricultural features, in order to identify particular patterns on root density that can influence the development of slope instabilities. Roots have been sampled in each test-site for characterizing their strength, in terms of the relation between root diameter and root force at rupture. Root

Analysis of the origin of Aufeis feed-water on the arctic slope of Alaska

NASA Technical Reports Server (NTRS)

Hall, D. K.; Roswell, C. (Principal Investigator)

1980-01-01

The origin of water feeding large aufeis fields (overflow river ice) on the Arctic Slope of Alaska is analyzed. Field measurements of two large aufeis fields on the eastern Arctic Slope were taken during July of 1978 and 1979. Measurements of aufeis extent and distribution were made using LANDSAT Multispectral Scanner Subsystem (MSS) satellite data from 1973 through 1979. In addition, ice cores were analyzed in the laboratory. Results of the field and laboratory studies indicate that the water derived from aufeis melt water has a chemical composition different from the adjacent upstream river water. Large aufeis fields are found in association with springs and faults thus indicating a subterranean origin of the feed water. In addition, the maximum extent of large aufeis fields was not found to follow meteorological patterns which would only be expected if the origin of the feed water were local. It is concluded that extent of large aufeis in a given river channel on the Arctic Slope is controlled by discharge from reservoirs of groundwater. It seems probable that precipitation passes into limestone aquifers in the Brooks Range, through an interconnecting system of subterranean fractures in calcareous rocks and ultimately discharges into alluvial sediments on the coastal plain to form aufeis. It is speculated that only small aufeis patches are affected by local meteorological parameters in the months just prior to aufeis formation.

Regional Guidebook for Applying the Hydrogeomorphic Approach to Assessing the Functions of Headwater Slope Wetlands on the South Carolina Coastal Plain

DTIC Science & Technology

2011-09-01

movement of the groundwater that sustains Headwater Slope wetlands are not regulated and continue to affect their distribution, character, and functions...permeability and soil porosity, thereby affecting the subsurface movement and storage of water in the soil. Soil permeability will affect the rate at...discharge time to the adjacent stream occurs over a longer period. Soil porosity will affect the volume of space available below the ground surface

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.

Minimal feedback to a rhythm generator improves the robustness to slope variations of a compass biped.

PubMed

Spitz, Jonathan; Evstrachin, Alexandrina; Zacksenhouse, Miriam

2015-08-20

In recent years there has been a growing interest in the field of dynamic walking and bio-inspired robots. However, while walking and running on a flat surface have been studied extensively, walking dynamically over terrains with varying slope remains a challenge. Previously we developed an open loop controller based on a central pattern generator (CPG). The controller applied predefined torque patterns to a compass-gait biped, and achieved stable gaits over a limited range of slopes. In this work, this range is greatly extended by applying a once per cycle feedback to the CPG controller. The terrain's slope is measured and used to modify both the CPG frequency and the torque amplitude once per step. A multi-objective optimization algorithm was used to tune the controller parameters for a simulated CB model. The resulting controller successfully traverses terrains with slopes ranging from +7° to -8°, comparable to most slopes found in human constructed environments. Gait stability was verified by computing the linearized Poincaré Map both numerically and analytically.

46 CFR 148.445 - Adjacent spaces.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 5 2011-10-01 2011-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by natural...

46 CFR 148.445 - Adjacent spaces.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 5 2014-10-01 2014-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by natural...

46 CFR 148.445 - Adjacent spaces.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 5 2013-10-01 2013-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by natural...

46 CFR 148.445 - Adjacent spaces.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 5 2012-10-01 2012-10-01 false Adjacent spaces. 148.445 Section 148.445 Shipping COAST... THAT REQUIRE SPECIAL HANDLING Additional Special Requirements § 148.445 Adjacent spaces. When... following requirements must be met: (a) Each space adjacent to a cargo hold must be ventilated by natural...

Assessment of Coalbed Gas Resources in Cretaceous and Tertiary Rocks on the North Slope, Alaska, 2006

USGS Publications Warehouse

Roberts, Steve; Barker, Charles E.; Bird, Kenneth J.; Charpentier, Ronald R.; Cook, Troy; Houseknecht, David W.; Klett, Timothy R.; Pollastro, Richard M.; Schenk, Christopher J.

2006-01-01

The North Slope of Alaska is a vast area of land north of the Brooks Range, extending from the Chukchi Sea eastward to the Canadian border. This Arctic region is known to contain extensive coal deposits; hypothetical coal resource estimates indicate that nearly 4 trillion short tons of coal are in Cretaceous and Tertiary rocks. Because of the large volume of coal, other studies have indicated that this region might also have potential for significant coalbed gas resources. The present study represents the first detailed assessment of undiscovered coalbed gas resources beneath the North Slope by the USGS. The assessment is based on the total petroleum system (TPS) concept. Geologic elements within a TPS relate to hydrocarbon source rocks (maturity, hydrocarbon generation, migration), the characteristics of reservoir rocks, and trap and seal formation. In the case of coalbed gas, the coal beds serve as both source rock and reservoir. The Brookian Coalbed Gas Composite TPS includes coal-bearing rocks in Cretaceous and Tertiary strata underlying the North Slope and adjacent Alaska State waters. Assessment units (AUs) within the TPS (from oldest to youngest) include the Nanushuk Formation Coalbed Gas AU, the Prince Creek and Tuluvak Formations Coalbed Gas AU, and the Sagavanirktok Formation Coalbed Gas AU.

Unexpectedly higher metazoan meiofauna abundances in the Kuril-Kamchatka Trench compared to the adjacent abyssal plains

NASA Astrophysics Data System (ADS)

Schmidt, Christina; Martínez Arbizu, Pedro

2015-01-01

We studied meiofauna standing stocks and community structure in the Kuril-Kamchatka Trench and its adjacent abyssal plains in the northwestern Pacific Ocean. In general, the Nematoda were dominant (93%) followed by the Copepoda (4%). Nematode abundances ranged from 87% to 96%; those of copepods from 2% to 7%. The most diverse deployment yielded 17 taxa: Acari, Amphipoda, Annelida, Bivalvia, Coelenterata, Copepoda, Cumacea, Gastrotricha, Isopoda, Kinorhyncha, Loricifera, Nematoda, Ostracoda, Priapulida, Tanaidacea, Tantulocarida, and Tardigrada. Nauplii were also present. Generally, the trench slope and the southernmost deployments had the highest abundances (850-1392 individuals/cm2). The results of non-metric multidimensional scaling indicated that these deployments were similar to each other in meiofauna community structure. The southernmost deployments were located in a zone of higher particulate organic carbon (POC) flux (g Corg m-2 yr-1), whereas the trench slope should have low POC flux due to depth attenuation. Also, POC and abundance were significantly correlated in the abyssal plains. This correlation may explain the higher abundances at the southernmost deployments. Lateral transport was also assumed to explain high meiofauna abundances on the trench slope. Abundances were generally higher than expected from model results. ANOSIM revealed significant differences between the trench slope and the northern abyssal plains, between the central abyssal plains and the trench slope, between the trench slope and the southern abyssal plains, between the central and the southern abyssal plains, and between the central and northern deployments. The northern and southern abyssal plains did not differ significantly. In addition, a U-test revealed highly significant differences between the trench-slope and abyssal deployments. The taxa inhabited mostly the upper 0-3 cm of the sediment layer (Nematoda 80-90%; Copepoda 88-100%). The trench-slope and abyssal did not differ

Geologic controls on submarine slope failure along the central U.S. Atlantic margin: Insights from the Currituck Slide Complex

USGS Publications Warehouse

Hill, Jenna C.; Brothers, Daniel S.; Craig, Bradley K.; ten Brink, Uri S.; Chaytor, Jason D.; Flores, Claudia

2017-01-01

Multiple styles of failure, ranging from densely spaced, mass transport driven canyons to the large, slab-type slope failure of the Currituck Slide, characterize adjacent sections of the central U.S. Atlantic margin that appear to be defined by variations in geologic framework. Here we use regionally extensive, deep penetration multichannel seismic (MCS) profiles to reconstruct the influence of the antecedent margin physiography on sediment accumulation along the central U.S. Atlantic continental shelf-edge, slope, and uppermost rise from the Miocene to Present. These data are combined with high-resolution sparker MCS reflection profiles and multibeam bathymetry data across the Currituck Slide Complex. Pre-Neogene allostratigraphic horizons beneath the slope are generally characterized by low gradients and convex downslope profiles. This is followed by the development of thick, prograded deltaic clinoforms during the middle Miocene. Along-strike variations in morphology of a regional unconformity at the top of this middle Miocene unit appear to have set the stage for differing styles of mass transport along the margin. Areas north and south of the Currituck Slide are characterized by oblique margin morphology, defined by an angular shelf-edge and a relatively steep (> 8°), concave slope profile. Upper slope sediment bypass, closely spaced submarine canyons, and small, localized landslides confined to canyon heads and sidewalls characterize these sectors of the margin. In contrast, the Currituck region is defined by a sigmoidal geometry, with a rounded shelf-edge rollover and gentler slope gradient (< 6°). Thick (> 800 m), regionally continuous stratified slope deposits suggest the low gradient Currituck region was a primary depocenter for fluvial inputs during multiple sea level lowstands. These results imply that the rounded, gentle slope physiography developed during the middle Miocene allowed for a relatively high rate of subsequent sediment accumulation

Evidence for submarine landslides and continental slope erosion related to fault reactivation during the last glaciation offshore eastern Canada

NASA Astrophysics Data System (ADS)

Saint-Ange, F.; Campbell, C.; MacKillop, K.; Mosher, D. C.; Piper, D. J.; Roger, J.

2012-12-01

Many studies have proposed that reactivation of dormant faults during deglaciation is a source of neotectonic activity in glaciated regions, but few have demonstrated the relationship to submarine landslides. In this study, seabed morphology and shallow geology of the outer continental margin adjacent to the Charlie Gibbs Fracture Zone off Newfoundland, Canada was investigated for evidence of this relationship. The glacial history and morphology of the margin suggest that the entire continental shelf in the area, coincident with major continental crustal lineaments, was ice-covered during the Last glacial cycle, and transverse troughs delineate the paleo-icestream drainage patterns. A recent investigation of Notre Dame Trough revealed the existence of large sediment failures on the shelf. The current study investigates complex seafloor erosion and widespread mass transport deposition (MTD) on the continental slope seaward of Notre Dame Trough, using recently-acquired high resolution seismic reflection data and piston cores. The new data reveal that a trough mouth fan (TMF) is present on the slope seaward of Notre Dame Trough. The Notre Dame TMF is characterized by a succession of stacked debris flows, but does not show a lobate shape in plan view like other classic TMFs. Instead, the Notre Dame TMF has abruptly-truncated margins suggesting post-depositional failure and erosion of the fan deposits. Seismic reflection data show that the locations of the failures along the TMF margin are coincident with a set of shallow faults; however the current dataset does not image the deeper portion of the faults. On the upper slope immediately south of the TMF, a narrow and deeply incised canyon is located along-trend with the Notre Dame Trough. The location of this canyon appears to be controlled by a fault. Downslope from this canyon, along the southern margin of the TMF, a 25 km wide, flat-floored, U-shaped valley was eroded into a succession of stacked MTD-filled channels

Does permanent extensional deformation in lower forearc slopes indicate shallow plate-boundary rupture?

NASA Astrophysics Data System (ADS)

Geersen, J.; Ranero, C. R.; Kopp, H.; Behrmann, J. H.; Lange, D.; Klaucke, I.; Barrientos, S.; Diaz-Naveas, J.; Barckhausen, U.; Reichert, C.

2018-05-01

Seismic rupture of the shallow plate-boundary can result in large tsunamis with tragic socio-economic consequences, as exemplified by the 2011 Tohoku-Oki earthquake. To better understand the processes involved in shallow earthquake rupture in seismic gaps (where megathrust earthquakes are expected), and investigate the tsunami hazard, it is important to assess whether the region experienced shallow earthquake rupture in the past. However, there are currently no established methods to elucidate whether a margin segment has repeatedly experienced shallow earthquake rupture, with the exception of mechanical studies on subducted fault-rocks. Here we combine new swath bathymetric data, unpublished seismic reflection images, and inter-seismic seismicity to evaluate if the pattern of permanent deformation in the marine forearc of the Northern Chile seismic gap allows inferences on past earthquake behavior. While the tectonic configuration of the middle and upper slope remains similar over hundreds of kilometers along the North Chilean margin, we document permanent extensional deformation of the lower slope localized to the region 20.8°S-22°S. Critical taper analyses, the comparison of permanent deformation to inter-seismic seismicity and plate-coupling models, as well as recent observations from other subduction-zones, including the area that ruptured during the 2011 Tohoku-Oki earthquake, suggest that the normal faults at the lower slope may have resulted from shallow, possibly near-trench breaking earthquake ruptures in the past. In the adjacent margin segments, the 1995 Antofagasta, 2007 Tocopilla, and 2014 Iquique earthquakes were limited to the middle and upper-slope and the terrestrial forearc, and so are upper-plate normal faults. Our findings suggest a seismo-tectonic segmentation of the North Chilean margin that seems to be stable over multiple earthquake cycles. If our interpretations are correct, they indicate a high tsunami hazard posed by the yet un

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

A Different Pitch to Slope

ERIC Educational Resources Information Center

Wolbert, William

2017-01-01

The query "When are we ever going to use this?" is easily answered when discussing the slope of a line. The pitch of a roof, the grade of a road, and stair stringers are three applications of slope that are used extensively. The concept of slope, which is introduced fairly early in the mathematics curriculum has hands-on applications…

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

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.

Antecedent topography and morphological controls on sediment accumulation and slope stability of the U.S. Atlantic margin

NASA Astrophysics Data System (ADS)

Hill, J. C.; Brothers, D. S.; Ten Brink, U. S.; Andrews, B. D.

2017-12-01

The U.S. Atlantic margin encompasses a wide variety of slope failure processes, ranging from small canyon-confined failures on the upper slope to large, open slope landslides originating in deeper water. Here we used a suite of high-resolution multibeam bathymetry and detailed multichannel seismic data coverage to investigate the relationship between modern seafloor morphology, pre-existing stratigraphy and sediment accumulation patterns. We suggest that a combination of sediment supply and antecedent margin physiography, whereby variations in margin evolution during the Miocene have influenced the modern seafloor morphology, controls both the location of slope sediment accumulation and the style of slope failure. Oversteepened margins with angular shelf breaks and steep upper slopes, referred to as oblique margins, are characterized by downslope mass transport and densely-spaced canyon formation. These margins are most likely the locus of canyon-confined failures and smaller lower slope fan-apron failures (e.g., much of the Mid-Atlantic). Sigmoidal margins with prograded slopes, a rounded shelf edge, and a low gradient slope morphology can support significant sediment accumulation across a broad area, with limited canyon development. These margins are often associated with high sediment supply and are prone to large, upper slope slab-style failures (e.g., the Hudson Apron, southwestern New England, the Currituck and Cape Fear Slide complexes). Areas with morphologies in between these two end members are characterized by limited shelf-edge accommodation space and large-scale lower slope accumulation and onlap, representing transitional stages of equilibrium slope adjustment. Large failures along these intermediate-type margins tend to develop lower on the slope where thick wedges of onlapping sediment are found (e.g., around Washington Canyon, Cape Lookout and southeastern New England). As antecedent topography and sediment loading appear to play an important role

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.

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.

Workflow for the fast evaluation of rock mass properties and stability of rock slopes along trafficways in Lower Austria

NASA Astrophysics Data System (ADS)

Straka, Wolfgang; Zangerl, Christian

2016-04-01

In Lower Austria there is a total of 17.000 km of provincial and 24.000 km of communal roads, to be maintained by the province and the municipalities. In addition, there are approx. 1.500 km of railroads, and the Danube as a major waterway. A large part of this infrastructure is, or is potentially, affected by various types of instability of adjacent slopes. Due to insufficient knowledge, as well as slope design and management practice in the past, every year, especially in connection to weather extremes, slopes known to be critical become active landslides again, and unexpected new ones arise, causing damage as well as financial stress. Engineering intervention, if possible, should be quick and effective. Geologists and engineers in public service, not having the means for detailed investigation in most cases, are using guidelines to assess the requirements to be met by slope design on traffic ways. But these guidelines don't reflect many of the newer scientific advances. Therefore, scientists at BOKU and backers in the administration want to gain more insight into causative factors, which, if successful, may render maintenance of traffic lines under critical conditions more effective and predictable. The specific project goal is to produce new guidelines to allow quick assessment of the most likely behaviour of rock masses common in the area, especially when cut into shape along infrastructure lines, using readily available information. The scientific investigations include simple and ready tests (like Schmidt hammer), as well as photogrammetry, laserscanning, and other complex geophysical and numerical techniques, but the final product (guidelines) is expected to work without such difficult methods. It is important to note, on the other hand, that the rock mass stability classification inherent in the new guidelines must allow distinction between conclusions which are safe, and conjectures which are in need of validation by contracted experts. It is planned to

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

The northern slope of South China Sea: an ideal site for studying passive margin extension and breakup

NASA Astrophysics Data System (ADS)

Zhou, D.; Sun, Z.; Pang, X.; Wu, X.; Xu, H.; Qiu, N.

2011-12-01

With the advance of hydrocarbon exploration into deep waters of the northern SCS, structural details from continental slope to deepsea basin have been revealed. A striking feature is the dramatic change in Cenozoic extension along and across the strike as well as with the time. Along strike the slope is seperated by lithospheric faults into segments with different amount of Cenozoic extension. The breakup occurred in the no-extension eastern segment (the Chaoshan depression), the most strongly extended central segment (the Baiyun sag) but failed in the western segment of intermediate extension (the Qingdongnan basin). This pattern violates the expectation that breakup occurs at first where the extension reached the maximum. In the central segment, the style of extension varies significantly in dip direction. Differing from the belts of half grabens in the shelf, the extension is expressed as a large downwarp (the Baiyun sag) in the slope, and as irregularly shaped sags (the Liwan sag) near the continental-oceanic boundary (COB). The Baiyun sag (BYS) is the largest and deepest sag in the Pearl River Mouth basin (PRMB). Long-cable MCS revealed that at the center of the BYS the crust thinned to <7 km. Grabens and half-grabens are seen only along the SW border of the BYS in Paleogene and did not control the main subsidence of the sag. In Neogene, swarms of NWW-striking small faults developed in the SW and NE flanks of the sag. These features indicate that ductile extension had dominated the formation of the BYS. Suppose the SCS started opening at 30 Ma (although no breakup unconformity found at 30 Ma in the ODP#1148 well adjacent to the COB), the anomalous post-breakup subsidence in the BYS exceeds that predicted by classical model by 1~2 km and occurred most strongly in several periods. Similar anomalous post-breakup subsidence has been observed also in the shelf. The Liwan sag (LWS) SE of the BYS is an aggregate of NS-, NW-, EW-, and NE-elongated narrow and short

Recent seasonal hypoxia on the Western Black Sea shelf recorded in adjacent slope sediments

NASA Astrophysics Data System (ADS)

Roepert, Anne; Jilbert, Tom S.; Slomp, Caroline P.

2015-04-01

Bottom water hypoxia is a major environmental problem afflicting estuarine and marine environments across the globe (Diaz and Rosenberg, 2008). Hypoxia is often attributed to human-induced increased nutrient discharge from rivers and related eutrophication. The Western Black Sea shelf is a typical example of a system where such anthropogenic impacts are thought to have contributed to the development of seasonal hypoxia in the late 20th century. However, due to the lack of spatially and temporally consistent monitoring in the region, questions remain about the evolution, causes and consequences of the seasonal hypoxia on the Western Black Sea shelf and whether or not the ecological state has recently improved (Capet et al., 2013). In this study a resin-embedded sediment core from a location below the chemocline on the Western Black Sea slope (water depth 377 m) was analyzed for its elemental composition by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), recovering a continuous geochemical record at a sub-annual resolution for the last 100 years. Relative enrichments in organic carbon, Pb, Fe, S, and Mo were observed in the depth interval corresponding to the 1970s until the 1990s, suggesting an increased carbon flux to the sediments as well as an anthropogenic pollution signal. We propose that the expansion of eutrophication on the Western Black Sea shelf was responsible for the enhanced carbon flux to our study site, while the associated hypoxia enhanced the shuttling of redox-sensitive elements to locations below the chemocline. The subsequent decrease in organic carbon and metal enrichments at the core top suggests a recent rise in oxygen concentrations and improvement of the ecological state of the Western Black Sea shelf. References: Capet, A., Beckers, J.-M., Grégoire, M. (2013). "Drivers, mechanisms and long-term variability of seasonal hypoxia on the Black Sea northwestern shelf-is there any recovery after eutrophication

Characterization of Unstable Rock Slopes Through Passive Seismic Measurements

NASA Astrophysics Data System (ADS)

Kleinbrod, Ulrike; Burjánek, Jan; Fäh, Donat

2014-05-01

Catastrophic rock slope failures have high social impact, causing significant damage to infrastructure and many casualties throughout the world each year. Both detection and characterization of rock instabilities are therefore of key importance. Analysing unstable rock slopes by means of ambient vibrations might be a new alternative to the already existing methods as for example geotechnical displacement measurements. A systematic measurement campaign has been initiated recently in Switzerland in order to study the seismic response of potential rockslides concerning a broad class of slope failure mechanisms and material conditions. First results are presented in this contribution. Small aperture seismic arrays were deployed at sites of interest for a short period of time (several hours) in order to record ambient vibrations. During each measurement a reference station was installed on a stable part close to the instability. The total number of stations used varies from 16 down to 2, depending on the site scope and resource availability. Instable rock slopes show a highly directional ground motion which is significantly amplified with respect to stable areas. These effects are strongest at certain frequencies which are identified as eigenfrequencies of the unstable rock mass. The eigenfrequencies and predominant directions have been estimated by frequency dependent polarization analysis. Site-to-reference spectral ratios have been calculated as well in order to estimate the relative amplification of ground motion at unstable parts. The retrieved results were compared with independent in-situ observations and other available data. The directions of maximum amplification are in most cases perpendicular to open cracks mapped on the surface and in good agreement with the deformation directions obtained by geodetic measurements. The interpretation of the observed wave field is done through numerical modelling of seismic wave propagation in fractured media with complex

Geophysical observations on northern part of Georges Bank and adjacent basins of Gulf of Maine

USGS Publications Warehouse

Oldale, R.N.; Hathaway, J.C.; Dillon, William P.; Hendricks, J.D.; Robb, James M.

1974-01-01

Continuous-seismic-reflection and magnetic-intensity profiles provide data for inferences about the geology of the northern part of Georges Bank and the basins of the Gulf of Maine adjacent to the bank.Basement is inferred to be mostly sedimentary and volcanic rocks of Paleozoic age that were metamorphosed and intruded locally by felsic and mafic plutons near the end of the Paleozoic Era. During Late Triassic time, large fault basins formed within the Gulf of Maine and probably beneath Georges Bank. The fault basins and a possible major northeast-trending fault zone beneath the northern part of the bank probably formed as a result of the opening Atlantic during the Mesozoic. Nonmarine sediments, associated with mafic flows and intrusive rocks, were deposited in the fault basins as they formed. The upper surface of the Triassic and pre-Triassic rocks that comprise basement is an unconformity that makes up much of the bottom of the Gulf of Maine. Depth to the basement surface beneath the gulf differ greatly because of fluvial erosion in Tertiary time and glacial erosion in Pleistocene time. Beneath the northern part of Georges Bank the basement surface is smoother and slopes southward. Prominent valleys, cut before Late Cretaceous time, are present beneath this part of the bank.Cretaceous, Tertiary, and possibly Jurassic times were characterized by episodes of coastal-plain deposition and fluvial erosion. During this time a very thick wedge of sediment, mostly of Jurassic(?) and Cretaceous ages, was deposited on the shelf. Major periods of erosion took place at the close of the Cretaceous and during the Pliocene. Fluvial erosion during the Pliocene removed much of the coastal-plain sedimentary wedge and formed the Gulf of Maine.Pleistocene glaciers eroded all but a few remnants of the coastal-plain sediments within the gulf and deposited a thick section of drift against the north slope of Georges Bank and a thin veneer of outwash on the bank. Marine sediments were

Denitrification in sediments from the hyporheic zone adjacent to a small forested stream

USGS Publications Warehouse

Duff, J.H.; Triska, F.J.

1990-01-01

Denitrifying potentials increased with increasing distance from the stream channel. Dissolved oxygen was 100% of the concentration expected in equilibrium with the atmosphere in water obtained from monitoring wells immediately adjacent to the stream but was as low as 7% of the expected value in water 11.4 m inland. Both nitrate and dissolved organic carbon decreased over summer in wells at the base of the alder-forested slope. A 48-h injection of nitrate-amended stream water into hyporheic water 8.4 m inland stimulated nitrous oxide production in the presence of acetylene. Nitrous oxide was generated as nitrate and acetylene were co-transported to a well 13 m down-gradient. Acetylene-block experiments coupled with the chemistry data suggest that denitrification can modify the chemistry of water during passage through the hyporheic zone. -from Authors

Does partial tear repair of adjacent tendons improve the outcome of supraspinatus tendonfull-thickness tear reinsertion?

PubMed

Nich, C; Dhiaf, N; Di Schino, M; Augereau, B

2014-11-01

Partial tearing of the infraspinatus and/or subscapularis tendon(s) is frequently associated with supraspinatus full-thickness tears. However, limited data regarding its influence on supraspinatus surgical repair is available. Our aim was to assess the functional and anatomical outcomes of open repair of supraspinatus full-thickness tears combined with adjacent partial tearing, comparatively to a control. We retrospectively identified 22 patients (22 shoulders) with a partial tear, most of them being a delamination tear, of the infraspinatus and/or subscapularis tendons associated with a complete detachment of the supraspinatus tendon. Twenty-seven patients (27 shoulders) treated for an isolated complete detachment of the supraspinatus tendon by open repair served as controls. The mean age was 58 years. A proximalized trans-osseous reinsertion of the supraspinatus tendon was combined with a curettage-closure of the delamination tear. Patients were evaluated with standardized MRI at last follow-up. At a mean of 75-month follow-up, the presence of a partial tear of either infraspinatus or subscapularis, or both, did not influence function and healing rates of supraspinatus tendon repair. Conversely to the control, when a retear occurred, the functional score tended to worsen. Preoperatively, fatty muscular degeneration was more pronounced when a partial tear was present. Fatty degeneration worsened regardless of repair healing. Open reinsertion of a supraspinatus full-thickness tear associated with a thorough treatment of partial tear of adjacent tendons led to optimal functional and anatomical mid term outcomes. Our results suggest the presence of a partial tear of adjacent tendons could be associated with poorer function in case of supraspinatus tendon re-rupture. Level III case-control study. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

Slope-scale dynamic states of rockfalls

NASA Astrophysics Data System (ADS)

Agliardi, F.; Crosta, G. B.

2009-04-01

Rockfalls are common earth surface phenomena characterised by complex dynamics at the slope scale, depending on local block kinematics and slope geometry. We investigated the nature of this slope-scale dynamics by parametric 3D numerical modelling of rockfalls over synthetic slopes with different inclination, roughness and spatial resolution. Simulations were performed through an original code specifically designed for rockfall modeling, incorporating kinematic and hybrid algorithms with different damping functions available to model local energy loss by impact and pure rolling. Modelling results in terms of average velocity profiles suggest that three dynamic regimes (i.e. decelerating, steady-state and accelerating), previously recognized in the literature through laboratory experiments on granular flows, can set up at the slope scale depending on slope average inclination and roughness. Sharp changes in rock fall kinematics, including motion type and lateral dispersion of trajectories, are associated to the transition among different regimes. Associated threshold conditions, portrayed in "phase diagrams" as slope-roughness critical lines, were analysed depending on block size, impact/rebound angles, velocity and energy, and model spatial resolution. Motion in regime B (i.e. steady state) is governed by a slope-scale "viscous friction" with average velocity linearly related to the sine of slope inclination. This suggest an analogy between rockfall motion in regime B and newtonian flow, whereas in regime C (i.e. accelerating) an analogy with a dilatant flow was observed. Thus, although local behavior of single falling blocks is well described by rigid body dynamics, the slope scale dynamics of rockfalls seem to statistically approach that of granular media. Possible outcomes of these findings include a discussion of the transition from rockfall to granular flow, the evaluation of the reliability of predictive models, and the implementation of criteria for a

Using Opposing Slope Aspects to Understand Water and Energy Flow Controls on Critical Zone Architecture

NASA Astrophysics Data System (ADS)

Anderson, S. P.; Barnhart, K. R.; Kelly, P. K.; Foster, M. A.; Langston, A. L.

2014-12-01

A long-standing problem is to understand how climate controls the structure of the critical zone, including the depth of weathering, thickness and character of soils, and morphology of hillslopes. We exploit microclimates on opposing aspects in a watershed in the Boulder Creek CZO to investigate the role of water and energy fluxes on development of critical zone architectures. The 2.6 km2 Gordon Gulch, located at ~2500 m a.s.l. at 40°N latitude, is elongated east-west, and consequently is predominantly composed of north and south-facing soil-mantled slopes, dotted with tors, developed on Precambrian gneiss. The depth to fresh rock ranges from about 8 to 12 m, and is up to 2 m deeper on north-facing slopes. In addition to greater thickness, weathered rock is measurably lower in tensile strength on north-facing slopes. While characteristics of weathered rock vary with aspect, the overlying mobile regolith is relatively uniform in thickness at ~0.5 m across the catchment, and its mineralogy shows only minor chemical alteration from parent rock. These features of the critical zone architecture arise in the face of systematic differences in energy and water delivery by aspect. About 40-50% of the ~500 mm annual precipitation is delivered as snow. During spring, the south-facing slopes receive up to 50% greater direct solar radiation than the north-facing slopes. Consequently, snow cover is ephemeral in the open Ponderosa forests on south-facing slopes, and soil wetting and drying events are frequent. Frost penetration is shallow, and short lived. On north-facing slopes, less direct radiation and a dense Lodgepole pine forest cover leads to snowpack retention. Soils are colder and soil moisture stays elevated for long periods in spring on these slopes. We postulate that deeper and more sustained frost penetration on north-facing slopes enhances the damage rate by frost cracking. Deeper water delivery further aids this process, and supports chemical alteration processes

Non-target adjacent stimuli classification improves performance of classical ERP-based brain computer interface

NASA Astrophysics Data System (ADS)

Ceballos, G. A.; Hernández, L. F.

2015-04-01

Objective. The classical ERP-based speller, or P300 Speller, is one of the most commonly used paradigms in the field of Brain Computer Interfaces (BCI). Several alterations to the visual stimuli presentation system have been developed to avoid unfavorable effects elicited by adjacent stimuli. However, there has been little, if any, regard to useful information contained in responses to adjacent stimuli about spatial location of target symbols. This paper aims to demonstrate that combining the classification of non-target adjacent stimuli with standard classification (target versus non-target) significantly improves classical ERP-based speller efficiency. Approach. Four SWLDA classifiers were trained and combined with the standard classifier: the lower row, upper row, right column and left column classifiers. This new feature extraction procedure and the classification method were carried out on three open databases: the UAM P300 database (Universidad Autonoma Metropolitana, Mexico), BCI competition II (dataset IIb) and BCI competition III (dataset II). Main results. The inclusion of the classification of non-target adjacent stimuli improves target classification in the classical row/column paradigm. A gain in mean single trial classification of 9.6% and an overall improvement of 25% in simulated spelling speed was achieved. Significance. We have provided further evidence that the ERPs produced by adjacent stimuli present discriminable features, which could provide additional information about the spatial location of intended symbols. This work promotes the searching of information on the peripheral stimulation responses to improve the performance of emerging visual ERP-based spellers.

Scenarios to prioritize observing activities on the North Slope, Alaska in the context of resource development, climate change and socio-economic uncertainties

NASA Astrophysics Data System (ADS)

Lee, O. A.; Eicken, H.; Payne, J. F.; Lassuy, D.

2014-12-01

The North Slope of Alaska is experiencing rapid changes in response to interacting climate and socioeconomic drivers. The North Slope Science Initiative (NSSI) is using scenarios as a tool to identify plausible, spatially explicit future states of resource extraction activities on the North Slope and adjacent seas through the year 2040. The objective of the scenarios process is to strategically assess research and monitoring needs on the North Slope. The participatory scenarios process involved stakeholder input (including Federal, State, local, academic, industry and non-profit representatives) to identify key drivers of change related to resource extraction activities on the North Slope. While climate change was identified as a key driver in the biophysical system, economic drivers related to oil and gas development were also important. Expert-reviewed informational materials were developed to help stakeholders obtain baseline knowledge and stimulate discussions about interactions between drivers, knowledge gaps and uncertainties. Map-based scenario products will allow mission-oriented agencies to jointly explore where to prioritize research investments and address risk in a complex, changing environment. Scenarios consider multidecadal timescales. However, tracking of indicator variables derived from scenarios can lead to important insights about the trajectory of the North Slope social-environmental system and inform management decisions to reduce risk on much shorter timescales. The inclusion of stakeholders helps provide a broad spectrum of expert viewpoints necessary for considering the range of plausible scenarios. A well-defined focal question, transparency in the participation process and continued outreach about the utility and limitations of scenarios are also important components of the scenarios process.

Slope seeking for autonomous lift improvement by plasma surface discharge

NASA Astrophysics Data System (ADS)

Benard, Nicolas; Moreau, Eric; Griffin, John; Cattafesta, Louis N., III

2010-05-01

The present paper describes an experimental investigation of closed-loop separation control using plasma actuators. The post-stall-separated flow over a NACA 0015 airfoil is controlled using a single dielectric barrier discharge actuator located at the leading edge. Open-loop measurements are first performed to highlight the effects of the voltage amplitude on the control authority for freestream velocities of 10-30 m/s (chord Re = 1.3 × 105 to 4 × 105). The results indicate that partial or full reattachment can be achieved and motivate the choice of the slope seeking approach as the control algorithm. A single-input/single-output algorithm is used to autonomously seek the optimal voltage required to achieve the control objective (full flow reattachment associated with maximum lift). The paper briefly introduces the concept of slope seeking, and a detailed parameterization of the controller is considered. Static (fixed speed) closed-loop experiments are then discussed, which demonstrate the capability of the algorithm. In each case, the flow can be reattached in an autonomous fashion. The last part of the paper demonstrates the robustness of the gradient-based, model-free scheme for dynamic freestream conditions. This paper highlights the capability of slope seeking to autonomously achieve high lift when used to drive the voltage of a plasma actuator. It also describes the advantages and drawbacks of such a closed-loop approach.

Radiocesium distribution along the slope in the Iput river basin as a tracer of the contaminant secondary migration

NASA Astrophysics Data System (ADS)

Korobova, Elena; Romanov, Sergey; Beriozkin, Victor; Dogadkin, Nikolay

2016-04-01

The main goal of the study performed in 2014-2015 at the test site located in the abandoned zone of the Iput river basin was to study detailed patterns of Cs-137 redistribution along the terrace slope and the adjacent floodplain depression almost 30 years after the Chernobyl accident. Cs-137 surface activity was measured with the help of modified field gamma-spectrometer Violinist III (USA) in a grid 2 m x 2 m within the test plot sized 10 m x 24 m. Gamma-spectrometry was accompanied by topographical survey. Cs-137 depth distribution was studied by soil core sampling in increments of 2 cm and 5 cm down to 40 cm depth. Cs-137 activity in soil samples was measured in laboratory conditions by Nokia gamma-spectrometer. The results showed distinct natural dissimilarity of Cs-137 surface activity within the undisturbed soil of slope. Cs-137 depth migration in successive soil cores marked different patterns correlated with the position in relief. In particular cores Cs-137 depth variation correlated with water regime that shows that the processes of secondary distribution of Cs-137 along the slope obviously depend upon water migration. The finding is important for understanding of regularities in patterns of radiocesium spatial distribution.

Slope Stability Analysis for Shallow Landslides using TRIGRS: A Case Study for Sta. Cruz, Zambales, Philippines

NASA Astrophysics Data System (ADS)

Mendoza, J. P. A.

2016-12-01

The Philippines, being located in the circum-Pacific, bounded by multiple subduction zones, open seas and ocean, is one of the most hazard-prone countries in the world (Benson, 1997). This widespread recurrence of natural hazards in the country requires much attention for disaster management (Aurelio, 2006). On the average, 21 typhoons enter the Philippine area of responsibility annually with 6-9 making a landfall. Several rainfall-induced landslide events are reported annually particularly during and after the inundation of major typhoons which imposes hazards to communities and causes destruction of properties due to the moving mass and possible flash floods it may induce. Shallow landslides are the most commonly observed failure involving soil-mantled slopes and are considered major geohazards, often causing property damage and other economic loss. Hence numerous studies on landslide susceptibility including numerical models based on infinite slope equation are used in order to identify slopes prone to occurrences of shallow landslides. The study aims to determine the relationships between the slope and elevation to the factor of safety for laterite-mantled topography by incorporating precipitation values in the determination of landslide susceptibility. Using a DEM, flow direction map and slope map of the Sta Cruz (Zambales, Philippines), the FORTRAN based program TRIGRS, was used to generate the values for the factors of safety in the study area. Overlays with a generated slope map and elevation map were used to determine relationships of the mentioned factors and the factors of safety. A slope in a topography mantled with lateritic soil will fail at a slope angle higher than 20 degrees. Generally, the factor of safety decreases as the slope angle increases; this increases the probability and risk of slope failure. Elevation has no bearing on the computation for the factor of safety. The factor of safety is heavily dependent on the slope angle. The value of

Empirical correspondence between trophic transfer efficiency in freshwater food webs and the slope of their size spectra.

PubMed

Mehner, Thomas; Lischke, Betty; Scharnweber, Kristin; Attermeyer, Katrin; Brothers, Soren; Gaedke, Ursula; Hilt, Sabine; Brucet, Sandra

2018-06-01

The density of organisms declines with size, because larger organisms need more energy than smaller ones and energetic losses occur when larger organisms feed on smaller ones. A potential expression of density-size distributions are Normalized Biomass Size Spectra (NBSS), which plot the logarithm of biomass independent of taxonomy within bins of logarithmic organismal size, divided by the bin width. Theoretically, the NBSS slope of multi-trophic communities is exactly -1.0 if the trophic transfer efficiency (TTE, ratio of production rates between adjacent trophic levels) is 10% and the predator-prey mass ratio (PPMR) is fixed at 10 4 . Here we provide evidence from four multi-trophic lake food webs that empirically estimated TTEs correspond to empirically estimated slopes of the respective community NBSS. Each of the NBSS considered pelagic and benthic organisms spanning size ranges from bacteria to fish, all sampled over three seasons in 1 yr. The four NBSS slopes were significantly steeper than -1.0 (range -1.14 to -1.19, with 95% CIs excluding -1). The corresponding average TTEs were substantially lower than 10% in each of the four food webs (range 1.0% to 3.6%, mean 1.85%). The overall slope merging all biomass-size data pairs from the four systems (-1.17) was almost identical to the slope predicted from the arithmetic mean TTE of the four food webs (-1.18) assuming a constant PPMR of 10 4 . Accordingly, our empirical data confirm the theoretically predicted quantitative relationship between TTE and the slope of the biomass-size distribution. Furthermore, we show that benthic and pelagic organisms can be merged into a community NBSS, but future studies have yet to explore potential differences in habitat-specific TTEs and PPMRs. We suggest that community NBSS may provide valuable information on the structure of food webs and their energetic pathways, and can result in improved accuracy of TTE-estimates. © 2018 by the Ecological Society of America.

Tiltmeter Indicates Sense of Slope

NASA Technical Reports Server (NTRS)

Lonborg, J. O.

1985-01-01

Tiltmeter indicates sense and magnitude of slope used in locations where incline not visible to operator. Use of direct rather than alternating current greatly simplifies design of instrument capable of indicating sense of slope.

A comparative study on seismic response of two unstable rock slopes within same tectonic setting but different activity level

NASA Astrophysics Data System (ADS)

Kleinbrod, Ulrike; Burjánek, Jan; Hugentobler, Marc; Amann, Florian; Fäh, Donat

2017-12-01

In this study, the seismic response of two slope instabilities is investigated with seismic ambient vibration analysis. Two similar sites have been chosen: an active deep-seated slope instability at Cuolm da Vi and the geologically, structurally and morphologically similar, but presently not moving Alp Caschlè slope. Both slopes are located at the upper Vorderrheintal (Canton Graubünden, Switzerland). Ambient vibrations were recorded on both slopes and processed by time-frequency polarization and site-to-reference spectral ratio analysis. The data interpretation shows correlations between degree of disintegration of the rock mass and amplification. However, the ambient vibration analysis conducted, does not allow retrieving a resonance frequency that can be related to the total depth of the instability of Cuolm da Vi. Even though seismic waves can be hardly traced in rock instabilities containing open fractures, it was possible to retrieve a dispersion curve and a velocity profile from the array measurement at Cuolm da Vi due to the high level of disintegration of the rock material down to a depth of about 100 m. From the similar amplification pattern at the two sites, we expect a similar structure, indicating that also the slope at Alp Caschlè was active in the past in a similar manner as Cuolm da Vi. However, a smoother increase of amplification with frequency is observed at Alp Caschlè, which might indicate less disintegration of the rock mass in a particular depth range at this site, when comparing to Cuolm da Vi where a high level of disintegration is observed, resulting from the high activity at the slope. From the frequency-dependent amplification, we can distinguish between two parts within both instabilities, one part showing decreasing disintegration of the rock mass with increasing depth, for the other parts less-fractured blocks are observed. Since the block structures are found in the lower part of the instabilities, they might contribute to the

The influence of terracettes on surface hydrology and erosion on vegetated Alpine, mountain and steep-sloping environments

NASA Astrophysics Data System (ADS)

Kuhn, Nikolaus; (Phil) Greenwood, Philip

2014-05-01

Alpine and mountain slopes represent important pathways that link high altitude grazing areas to meadows and rangelands at lower elevations. Given the often acute gradient of mountain slopes, they represent a convenient and potentially highly efficient runoff conveyance route that facilitates the downslope transfer of fine-sediment and sediment-bound nutrients and contaminants during erosion events. Above a certain gradient, many slopes host small steps, or `terracettes`. As these are generally orientated across slope, their genesis is usually attributed to a combination of soil creep, coupled with (and often accentuated by) grazing animals. Motivated by the prevalence of these distinct landform features and lack of information on their role as runoff conveyance routes, this communication reports preliminary results from an investigation to explore the possibility that terracettes may act as preferential flow-paths, with an as yet undocumented ability to greatly influence surface hydrology in mountainous and steeply-sloping environments. A ca. 40 m2 area of vegetated terracettes and section of adjacent thalweg, with gradients ranging from approximately 25-35o, were scanned using an automated Topcon IS03 Total Station at a resolution of 0.1 * 0.1 m. Data were converted to a Digital Elevation Model (DEM) in ArcGIS 10 Geographical Information System (GIS), and queried using Spatial Analyst (Surface Hydrology; Flow Accumulation function) to identify slope-sections that could act as preferential flow-pathways during runoff events. These data were supplemented by information on soil physical properties that included grain size composition, bulk density and porosity, in order to establish spatial variations in soil characteristics associated with the vertical and horizontal terracette features. Combining the digital and in-situ data indicate that the technique is able to identify preferential surface flow-paths. Such information could greatly benefit the future management

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).

Linear chirped slope profile for spatial calibration in slope measuring deflectometry

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

Siewert, F., E-mail: frank.siewert@helmholtz-berlin.de; Zeschke, T.; Arnold, T.

2016-05-15

Slope measuring deflectometry is commonly used by the X-ray optics community to measure the long-spatial-wavelength surface figure error of optical components dedicated to guide and focus X-rays under grazing incidence condition at synchrotron and free electron laser beamlines. The best performing instruments of this kind are capable of absolute accuracy on the level of 30-50 nrad. However, the exact bandwidth of the measurements, determined at the higher spatial frequencies by the instrument’s spatial resolution, or more generally by the instrument’s modulation transfer function (MTF) is hard to determine. An MTF calibration method based on application of a test surface withmore » a one-dimensional (1D) chirped height profile of constant amplitude was suggested in the past. In this work, we propose a new approach to designing the test surfaces with a 2D-chirped topography, specially optimized for MTF characterization of slope measuring instruments. The design of the developed MTF test samples based on the proposed linear chirped slope profiles (LCSPs) is free of the major drawback of the 1D chirped height profiles, where in the slope domain, the amplitude strongly increases with the local spatial frequency of the profile. We provide the details of fabrication of the LCSP samples. The results of first application of the developed test samples to measure the spatial resolution of the BESSY-NOM at different experimental arrangements are also presented and discussed.« less

Bottom currents observed in and around a submarine valley on the continental slope of the northern South China Sea

NASA Astrophysics Data System (ADS)

Wu, Lunyu; Xiong, Xuejun; Li, Xiaolong; Shi, Maochong; Guo, Yongqing; Chen, Liang

2016-12-01

Bottom currents at about 1000 m depth in and around a submarine valley on the continental slope of the northern South China Sea were studied by a 14-month long experiment from July 2013 to September 2014. The observations reveal that bottom currents are strongly influenced by the topography, being along valley axis or isobaths. Power density spectrum analysis shows that all the currents have significant peaks at diurnal and semi-diurnal frequencies. Diurnal energy is dominant at the open slope site, which is consistent with many previous studies. However, at the site inside the valley the semi-diurnal energy dominates, although the distance between the two sites of observation is quite small (11 km) compared to a typical horizontal first-mode internal tide wavelength (200 km). We found this phenomenon is caused by the focusing of internal waves of certain frequencies in the valley. The inertial peak is found only at the open slope site in the first deployment but missing at the inside valley site and the rest of the deployments. Monthly averaged residual currents reveal that the near-bottom currents on the slope flow southwestward throughout the year except in August and September, 2013, from which we speculate that this is a result of the interaction between a mesoscale eddy and the canyon/sag topography. Currents inside the valley within about 10 mab basically flow along slope and in the layers above the 10 mab the currents are northwestward, that is, from the deep ocean to the shelf. The monthly mean current vectors manifest an Ekman layer-like vertical structure at both sites, which rotate counter-clockwise looking from above.

Study on the response of unsaturated soil slope based on the effects of rainfall intensity and slope angle

NASA Astrophysics Data System (ADS)

Ismail, Mohd Ashraf Mohamad; Hamzah, Nur Hasliza

2017-07-01

Rainfall has been considered as the major cause of the slope failure. The mechanism leading to slope failures included the infiltration process, surface runoff, volumetric water content and pore-water pressure of the soil. This paper describes a study in which simulated rainfall events were used with 2-dimensional soil column to study the response of unsaturated soil behavior based on different slope angle. The 2-dimensional soil column is used in order to demonstrate the mechanism of the slope failure. These unsaturated soil were tested with four different slope (15°, 25°, 35° and 45°) and subjected to three different rainfall intensities (maximum, mean and minimum). The following key results were obtained: (1) the stability of unsaturated soil decrease as the rainwater infiltrates into the soil. Soil that initially in unsaturated state will start to reach saturated state when rainwater seeps into the soil. Infiltration of rainwater will reduce the matric suction in the soil. Matric suction acts in controlling soil shear strength. Reduction in matric suction affects the decrease in effective normal stress, which in turn diminishes the available shear strength to a point where equilibrium can no longer be sustained in the slope. (2) The infiltration rate of rainwater decreases while surface runoff increase when the soil nearly achieve saturated state. These situations cause the soil erosion and lead to slope failure. (3) The steepness of the soil is not a major factor but also contribute to slope failures. For steep slopes, rainwater that fall on the soil surface will become surface runoff within a short time compare to the water that infiltrate into the soil. While for gentle slopes, water that becomes surface runoff will move slowly and these increase the water that infiltrate into the soil.

Precipitation measurements on wind-swept slopes

Treesearch

Austin E. Helmers

1954-01-01

Precipitation catch for three calendar years is compared for four types of gage installation on a wind-swept south-facing slope with a 22° gradient at elevation 5500 ft. The 1950 precipitation catch by (1) weighing-recording gage with the orifice and an Alter type wind shield sloped parallel to the ground surface, (2) unshielded nonrecording gage with orifice sloped...

Factors affecting temporal and spatial soil moisture variation in and adjacent to group selection openings

Treesearch

W.H. McNab

1991-01-01

Soil moisture content was intensively sampled in three, 1-acre blocks containing an opening and surrounding mature upland hardwoods. Openings covering 0.19-0.26 ac were created by group-selection cutting, and they were occupied by 1-year-old trees and shrubs.

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

Coupling photogrammetric data with DFN-DEM model for rock slope hazard assessment

NASA Astrophysics Data System (ADS)

Donze, Frederic; Scholtes, Luc; Bonilla-Sierra, Viviana; Elmouttie, Marc

2013-04-01

Structural and mechanical analyses of rock mass are key components for rock slope stability assessment. The complementary use of photogrammetric techniques [Poropat, 2001] and coupled DFN-DEM models [Harthong et al., 2012] provides a methodology that can be applied to complex 3D configurations. DFN-DEM formulation [Scholtès & Donzé, 2012a,b] has been chosen for modeling since it can explicitly take into account the fracture sets. Analyses conducted in 3D can produce very complex and unintuitive failure mechanisms. Therefore, a modeling strategy must be established in order to identify the key features which control the stability. For this purpose, a realistic case is presented to show the overall methodology from the photogrammetry acquisition to the mechanical modeling. By combining Sirovision and YADE Open DEM [Kozicki & Donzé, 2008, 2009], it can be shown that even for large camera to rock slope ranges (tested about one kilometer), the accuracy of the data are sufficient to assess the role of the structures on the stability of a jointed rock slope. In this case, on site stereo pairs of 2D images were taken to create 3D surface models. Then, digital identification of structural features on the unstable block zone was processed with Sirojoint software [Sirovision, 2010]. After acquiring the numerical topography, the 3D digitalized and meshed surface was imported into the YADE Open DEM platform to define the studied rock mass as a closed (manifold) volume to define the bounding volume for numerical modeling. The discontinuities were then imported as meshed planar elliptic surfaces into the model. The model was then submitted to gravity loading. During this step, high values of cohesion were assigned to the discontinuities in order to avoid failure or block displacements triggered by inertial effects. To assess the respective role of the pre-existing discontinuities in the block stability, different configurations have been tested as well as different degree of

Caanyon Mediated Cross-Slope Transport

NASA Astrophysics Data System (ADS)

Mihaly, S. F.; Cabrera De Leo, F.; Sastri, A. R.; Matabos, M.; Heesemann, M.; Ogata, B.

2017-12-01

Three current meter and water property stations along the west coast of Vancouver Island along with video and acoustic backscatter observations are used to gain insight into mechanisms of cross-slope transport. The setting is an eastern boundary current region with a active poleward flowing countercurrent. The significant effects of these currents flowing over a strongly incised continental slope along with cross-slope density flows are contrasted with the seasonally varying upwelling and downwelling regime. The video and acoustic backscatter enabled by Ocean Networks Canada's NEPTUNE observatory provide a view on the materials being transported between the abyssal plain and the continental shelf.

Importance of tibial slope for stability of the posterior cruciate ligament deficient knee.

PubMed

Giffin, J Robert; Stabile, Kathryne J; Zantop, Thore; Vogrin, Tracy M; Woo, Savio L-Y; Harner, Christopher D

2007-09-01

Previous studies have shown that increasing tibial slope can shift the resting position of the tibia anteriorly. As a result, sagittal osteotomies that alter slope have recently been proposed for treatment of posterior cruciate ligament (PCL) injuries. Increasing tibial slope with an osteotomy shifts the resting position anteriorly in a PCL-deficient knee, thereby partially reducing the posterior tibial "sag" associated with PCL injury. This shift in resting position from the increased slope causes a decrease in posterior tibial translation compared with the PCL-deficient knee in response to posterior tibial and axial compressive loads. Controlled laboratory study. Three knee conditions were tested with a robotic universal force-moment sensor testing system: intact, PCL-deficient, and PCL-deficient with increased tibial slope. Tibial slope was increased via a 5-mm anterior opening wedge osteotomy. Three external loading conditions were applied to each knee condition at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 120 degrees of knee flexion: (1) 134-N anterior-posterior (A-P) tibial load, (2) 200-N axial compressive load, and (3) combined 134-N A-P and 200-N axial loads. For each loading condition, kinematics of the intact knee were recorded for the remaining 5 degrees of freedom (ie, A-P, medial-lateral, and proximal-distal translations, internal-external and varus-valgus rotations). Posterior cruciate ligament deficiency resulted in a posterior shift of the tibial resting position to 8.4 +/- 2.6 mm at 90 degrees compared with the intact knee. After osteotomy, tibial slope increased from 9.2 degrees +/- 1.0 degrees in the intact knee to 13.8 degrees +/- 0.9 degrees. This increase in slope reduced the posterior sag of the PCL-deficient knee, shifting the resting position anteriorly to 4.0 +/- 2.0 mm at 90 degrees. Under a 200-N axial compressive load with the osteotomy, an additional increase in anterior tibial translation to 2.7 +/- 1.7 mm at 30 degrees was

FAST OPENING SWITCH

DOEpatents

Bender, M.; Bennett, F.K.; Kuckes, A.F.

1963-09-17

A fast-acting electric switch is described for rapidly opening a circuit carrying large amounts of electrical power. A thin, conducting foil bridges a gap in this circuit and means are provided for producing a magnetic field and eddy currents in the foil, whereby the foil is rapidly broken to open the circuit across the gap. Advantageously the foil has a hole forming two narrow portions in the foil and the means producing the magnetic field and eddy currents comprises an annular coil having its annulus coaxial with the hole in the foil and turns adjacent the narrow portions of the foil. An electrical current flows through the coil to produce the magnetic field and eddy currents in the foil. (AEC)

Centrifuge Modeling of Rainfall Induced Slope Failure

NASA Astrophysics Data System (ADS)

Ling, H.; Wu, M.

2006-12-01

Rainfall induces slope failure and debris flow which are considered as one of the major natural disasters. The scope of such failure is very large and it cannot be studied easily in the laboratory. Traditionally, small scale model tests are used to study such problem. Knowing that the behavior of soil is affected by the stress level, centrifuge modeling technique has been used to simulate more realistically full scale earth structures. In this study, two series of tests were conducted on slopes under the centrifugal field with and without the presence of rainfall. The soil used was a mixture of sand and 15 percent fines. The slopes of angle 60 degrees were prepared at optimum water content in order to achieve the maximum density. In the first series of tests, three different slope heights of 10 cm, 15 cm and 20 cm were used. The gravity was increased gradually until slope failure in order to obtain the prototype failure height. The slope model was cut after the test in order to obtain the configuration of failure surface. It was found that the slope geometry normalized by the height at failure provided unique results. Knowing the slope height or gravity at failure, the second series of tests with rainfall were conducted slightly below the critical height. That is, after attaining the desired gravity, the rainfall was induced in the centrifuge. Special nozzles were used and calibrated against different levels of gravity in order to obtain desired rainfall intensity. Five different rainfall intensities were used on the 15-cm slopes at 80g and 60g, which corresponded to 12 m and 9 m slope height, respectively. The duration until failure for different rainfall intensities was obtained. Similar to the first series of tests, the slope model was cut and investigated after the test. The results showed that the failure surface was not significantly affected by the rainfall. That is, the excess pore pressure induced by rainfall generated slope failure. The prediction curves

A new vision of carbonate slopes: the Little Bahama Bank

NASA Astrophysics Data System (ADS)

Mulder, Thierry; Gillet, Hervé; Hanquiez, Vincent; Reijmer, John J.; Tournadour, Elsa; Chabaud, Ludivine; Principaud, Mélanie; Schnyder, Jara; Borgomano, Jean

2015-04-01

Recent data collected in November 2014 (RV Walton Smith) on the upper slope of the Little Bahama Bank (LBB) between 30 and 400 m water depth allowed to characterize the uppermost slope (Rankey et al., 2012) over a surface of 170 km2. The new data set includes multibeam bathymetry and acoustic imagery, 3.5 kHz very-high resolution (VHR) seismic reflection lines, 21 gravity cores and 11 Van Veen grabs. The upper slope of the LBB does not show a steep submarine cliff as known from western Great Bahama Bank. The carbonate bank progressively deepens towards the basin through a slighty inclined plateau. The slope value is < 6° down to a water depth of about 70 m. The plateau is incised by decameter-wide gullies that covered with indurated sediment. Some of the gullies like Roberts Cuts show a larger size and may play an important role in sediment transfer from the shallow-water carbonate bank down to the canyon heads at 400-500 m water depth (Mulder et al., 2012). In the gully area, the actual reef rests on paleo-reefs that outcrop at a water depth of about 40 m. These paleo-reef structures could represent reefs that established themselves during past periods of sea-level stagnation. Below this water depth, the slope steepens up to 30° to form the marginal escarpment (Rankey et al., 2012), which is succeeded by the open margin realm (Rankey et al., 2012). The slope inclination value decreases at about 180-200 m water depth. Between 20 and 200 m of water depth, the VHR seismic shows no seafloor sub-bottom reflector. Between 180 and 320 m water depth, the seafloor smoothens. The VHR seismic shows an onlapping sediment wedge, which starts in this water depth and shows a blind or very crudely stratified echo facies. The sediment thickness of this Holocene unit may exceed 20 m. It fills small depressions in the substratum and thickens in front of gullies that cut the carbonate platform edge. Sediment samples show the abundancy of carbonate mud on the present Bahamian

Rock slope instabilities in Norway: First systematic hazard and risk classification of 22 unstable rock slopes

NASA Astrophysics Data System (ADS)

Böhme, Martina; Hermanns, Reginald L.; Oppikofer, Thierry; Penna, Ivanna

2016-04-01

Unstable rock slopes that can cause large failures of the rock-avalanche type have been mapped in Norway for almost two decades. Four sites have earlier been characterized as high-risk objects based on expertise of few researchers. This resulted in installing continuous monitoring systems and set-up of an early-warning system for those four sites. Other unstable rock slopes have not been ranked related to their hazard or risk. There are ca. 300 other sites known of which 70 sites were installed for periodic deformation measurements using multiple techniques (Global Navigation Satellite Systems, extensometers, measurement bolts, and others). In 2012 a systematic hazard and risk classification system for unstable rock slopes was established in Norway and the mapping approach adapted to that in 2013. Now, the first 22 sites were classified for hazard, consequences and risk using this classification system. The selection of the first group of sites to be classified was based on an assumed high hazard or risk and importance given to the sites by Norwegian media and the public. Nine of the classified 22 unstable rock slopes are large sites that deform inhomogeneously or are strongly broken up in individual blocks. This suggests that different failure scenarios are possible that need to be analyzed individually. A total of 35 failure scenarios for those nine unstable rock slopes were considered. The hazard analyses were based on 9 geological parameters defined in the classification system. The classification system will be presented based on the Gamanjunni unstable rock slope. This slope has a well developed back scarp that exposes 150 m preceding displacement. The lateral limits of the unstable slope are clearly visible in the morphology and InSAR displacement data. There have been no single structures observed that allow sliding kinematically. The lower extend of the displacing rock mass is clearly defined in InSAR data and by a zone of higher rock fall activity. Yearly

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.

The microbiota of traumatic, open fracture wounds is associated with mechanism of injury.

PubMed

Bartow-McKenney, Casey; Hannigan, Geoffrey D; Horwinski, Joseph; Hesketh, Patrick; Horan, Annamarie D; Mehta, Samir; Grice, Elizabeth A

2018-05-26

Open fractures are characterized by disruption of the skin and soft tissue, which allows for microbial contamination and colonization. Preventing infection-related complications of open fractures and other acute wounds remains an evolving challenge due to an incomplete understanding of how microbial colonization and contamination influence healing and outcomes. Culture-independent molecular methods are now widely used to study human-associated microbial communities without introducing culture biases. Using such approaches, the objectives of this study were to 1) define the long-term temporal microbial community dynamics of open fracture wounds and 2) examine microbial community dynamics with respect to clinical and demographic factors. Fifty-two subjects with traumatic open fracture wounds (32 blunt and 20 penetrating injuries) were enrolled prospectively and sampled longitudinally from presentation to the emergency department and at each subsequent inpatient or outpatient encounter. Specimens were collected from both the wound center and adjacent skin. Culture-independent sequencing of the 16S ribosomal RNA gene was employed to identify and characterize microbiota. Upon presentation to the emergency department and time points immediately following, sample collection site (wound or adjacent skin) was the most defining feature discriminating microbial profiles. Microbial composition of adjacent skin and wound center converged over time. Mechanism of injury most strongly defined the microbiota after initial convergence. Further analysis controlling for race, gender, and age revealed that mechanism of injury remained a significant discriminating feature throughout the continuum of care. We conclude that the microbial communities associated with open fracture wounds are dynamic in nature until eventual convergence with the adjacent skin community during healing, with mechanism of injury as an important feature affecting both diversity and composition of the microbiota

Database on unstable rock slopes in Norway

NASA Astrophysics Data System (ADS)

Oppikofer, Thierry; Nordahl, Bo; Bunkholt, Halvor; Nicolaisen, Magnus; Hermanns, Reginald L.; Böhme, Martina; Yugsi Molina, Freddy X.

2014-05-01

Several large rockslides have occurred in historic times in Norway causing many casualties. Most of these casualties are due to displacement waves triggered by a rock avalanche and affecting coast lines of entire lakes and fjords. The Geological Survey of Norway performs systematic mapping of unstable rock slopes in Norway and has detected up to now more than 230 unstable slopes with significant postglacial deformation. This systematic mapping aims to detect future rock avalanches before they occur. The registered unstable rock slopes are stored in a database on unstable rock slopes developed and maintained by the Geological Survey of Norway. The main aims of this database are (1) to serve as a national archive for unstable rock slopes in Norway; (2) to serve for data collection and storage during field mapping; (3) to provide decision-makers with hazard zones and other necessary information on unstable rock slopes for land-use planning and mitigation; and (4) to inform the public through an online map service. The database is organized hierarchically with a main point for each unstable rock slope to which several feature classes and tables are linked. This main point feature class includes several general attributes of the unstable rock slopes, such as site name, general and geological descriptions, executed works, recommendations, technical parameters (volume, lithology, mechanism and others), displacement rates, possible consequences, hazard and risk classification and so on. Feature classes and tables linked to the main feature class include the run-out area, the area effected by secondary effects, the hazard and risk classification, subareas and scenarios of an unstable rock slope, field observation points, displacement measurement stations, URL links for further documentation and references. The database on unstable rock slopes in Norway will be publicly consultable through the online map service on www.skrednett.no in 2014. Only publicly relevant parts of

A reevaluation of the Munson-Nygren-Retriever submarine landslide complex, Georges bank lower slope, western north Atlantic

USGS Publications Warehouse

Chaytor, Jason D.; Twichell, David C.; ten Brink, Uri S.

2012-01-01

The Munson-Nygren-Retriever (MNR) landslide complex is a series of distinct submarine landslides located between Nygren and Powell canyons on the Georges Bank lower slope. These landslides were first imaged in 1978 using widely-spaced seismic reflection profiles and were further investigated using continuous coverage GLORIA sidescan imagery collected over the landslide complex in 1987. Recent acquisition of highresolution multibeam bathymetry across these landslides has provided an unprecedented view of their complex morphology and allows for a more detailed investigation of their evacuation and deposit morphologies and sizes, modes of failure, and relationship to the adjacent sections of the margin, including the identification of an additional landslide within the MNR complex, referred to here as the Pickett slide. The evacuation zone of these landslides covers an area of approximately 1,780 km2 . The headwalls of these landslides are at a depth of approximately 1,800 m, with evacuation extending for approximately 60 km downslope to the top of the continental rise. High-relief debris deposits, in the form of blocks and ridges, are present down the length of the majority of the evacuation zones and within the deposition area at the base of the slope. On the continental rise, the deposits from each of the most recent failures of the MNR complex landslides merge with debris from earlier continental slope failures, canyon and alongslope derived deposits, and prominent upper-rise failures.

Comparative geochemistry of Indian margin (Arabian Sea) sediments: Estuary to continental slope.

NASA Astrophysics Data System (ADS)

Cowie, Greg; Mowbray, Stephen; Kurian, Siby; Sarkar, Amit; White, Carol; Anderson, Amy; Vergnaud, Bianca; Johnstone, Gisele; Brear, Samuel; Woulds, Clare; Naqvi, Wajih; Kitazato, Hiroshi

2014-05-01

Factors controlling the distribution of organic matter in the Arabian Sea have been the subject of much research and debate ever since organic-rich slope deposits were associated with the mid-water oxygen minimum zone (OMZ) However, the debate remains open, and numerous interacting factors have been invoked as important controls. A limitation of most previous studies is that they have been restricted to limited portions of the margin, and have not included molecular-level tracers that allow distinction of organic matter (OM) source and degradation state as factors in OM distribution. We report results from sites across the Indian margin of the Arabian Sea, which were analysed for carbon and nitrogen compositions (elemental and isotopic), grain size and indices of OM source and degradation state. Site locations ranged from the Mandovi/Zuari estuaries to depths of ~2000m on the continental slope, thus spanning both the semi-permanent OMZ on the upper slope (~200-1300m) and the seasonal hypoxic zone that impinges on the shelf. Source indices showed mixed marine and terrigenous OM within the estuaries, but overwhelming predominance (80%+) of marine OM on the shelf and slope, even in nearshore deposits. Thus, riverine OM is heavily diluted or efficiently remineralised within or immediately offshore of the estuaries. Any terrigenous OM that is exported appears to be retained in nearshore muds; lignin phenols indicate that the small terrigenous OM content of slope sediments is of different origin, potentially from rivers to the north. Organic C contents of surface shelf and slope sediments varied from <0.5 wt% in relict shelf sands to a maximum of >7 wt% at upper slope sites within the OMZ, then decreasing to ≤1wt% at 2000m. However, major variability (~5 wt%) occured within the OMZ at sites with near-identical depths and bottom-water oxygen. A strong relationship between organic C and grain size was seen for OMZ sediments, but lower C loadings were found for sites on

The Problem of Alluvial Fan Slopes

NASA Astrophysics Data System (ADS)

Stock, J. D.; Schmidt, K.

2005-12-01

Water and debris flows exiting confined valleys have a tendency to deposit sediment on steep fans. On alluvial fans, where water transport predominates, channel slopes tend to decrease downfan from ~0.08 to ~0.01 across wide ranges of climate and tectonism. Some have argued that this pattern reflects downfan grainsize fining so that higher slopes are required just to entrain coarser particles in the waters of the upper fan, while entrainment of finer grains downfan requires lower slopes (threshold hypothesis). An older hypothesis is that slope is adjusted to transport the supplied sediment load, which decreases downfan as deposition occurs (transport hypothesis). We have begun to test these hypotheses using detailed field measurements of hydraulic and sediment variables in sediment transport models. On some fans in the western U.S. we find that alluvial fan channel bankfull depths are largely 0.5-1.5 m at fan heads, decreasing to 0.1-0.2 m at distal margins. Contrary to many previous studies, we find that median gravel diameter does not change systematically along the upper 60- 80% of active fan channels. So downstream gravel fining cannot explain most of the observed channel slope reduction. However, as slope declines, surface sand cover increases systematically downfan from values of <20% above fan heads to distal fan values in excess of 70%. As a result, the threshold for sediment motion might decrease systematically downfan, leading to lower slopes. However, current models of this effect alone tend to underpredict downfan slope changes. This is likely due to off- channel gravel deposition. Calculations that match observed fan long-profiles require an exponential decline in gravel transport rate, so that on some fans approximately half of the load must be deposited off-channel every ~0.25-1.25 km downfan. This leads us to hypothesize that alluvial fan long- profiles are largely statements about the rate of deposition downfan. If so, there may be climatic and

Response mechanism of post-earthquake slopes under heavy rainfall

NASA Astrophysics Data System (ADS)

Qiu, Hong-zhi; Kong, Ji-ming; Wang, Ren-chao; Cui, Yun; Huang, Sen-wang

2017-07-01

This paper uses the catastrophic landslide that occurred in Zhongxing Town, Dujiangyan City, as an example to study the formation mechanism of landslides induced by heavy rainfall in the post-Wenchuan earthquake area. The deformation characteristics of a slope under seismic loading were investigated via a shaking table test. The results show that a large number of cracks formed in the slope due to the tensile and shear forces of the vibrations, and most of the cracks had angles of approximately 45° with respect to the horizontal. A series of flume tests were performed to show how the duration and intensity of rainfall influence the responses of the shaken and non-shaken slopes. Wetting fronts were recorded under different rainfall intensities, and the depth of rainfall infiltration was greater in the shaken slope than in the non-shaken slope because the former experienced a greater extreme rainfall intensity under the same early rainfall and rainfall duration conditions. At the beginning of the rainfall infiltration experiment, the pore water pressure in the slope was negative, and settling occurred at the top of the slope. With increasing rainfall, the pore water pressure changed from negative to positive, and cracks were observed on the back surface of the slope and the shear outlet of the landslide on the front of the slope. The shaken slope was more susceptible to crack formation than the non-shaken slope under the same rainfall conditions. A comparison of the responses of the shaken and non-shaken slopes under heavy rainfall revealed that cracks formed by earthquakes provided channels for infiltration. Soil particles in the cracks of slopes were washed away, and the pore water pressure increased rapidly, especially the transient pore water pressure in the slope caused by short-term concentrated rainfall which decreased rock strength and slope stability.

Ten-year diameter and basal area growth of trees surrounding small group selection openings

Treesearch

Philip M. McDonald; Martin W. Ritchie; Celeste S. Abbott

1996-01-01

The effects of small openings in forest stands has interested silviculturists and ecologists for years. Interest generally has centered on the vegetation in the openings, not on that immediately outside of them. Quantitative information on the growth of trees adjacent to group-selection openings, although often mentioned in forestry textbooks as contributing to cost...

A Laboratory Study of Slope Flows Dynamics

NASA Astrophysics Data System (ADS)

Capriati, Andrea; Cenedese, Antonio; Monti, Paolo

2003-11-01

Slope flows currents can contribute significantly in the diurnal circulation and air quality of complex terrain regions (mountains, valleys, etc.). During the daytime, solar heating warms the valley sides, causing up-slope (or anabatic) winds. In contrast, radiative cooling of the valley sides results in cold down-slope (drainage or katabatic) flows, characterized by small vertical extensions (usually 10-200 m) and with the typical features of dense gravity currents. In this paper, some preliminary results on slope flows obtained by means of a series of experiments conducted in the laboratory using a temperature controlled water tank are shown. Rakes of thermocouples are used to determine the temperature structure and particle tracking velocimetry is used for the velocity measurements. A simple slope consisting of a plate in which the temperature is forced via a set of Peltier Cells is used. The analysis is performed considering different slope angles, background thermal stratifications and surface heat fluxes as well. Comparisons with theoretical and empirical laws found in literature are reported.

Shoaling internal solitary waves of depression over gentle slopes

NASA Astrophysics Data System (ADS)

Rivera, Gustavo; Diamessis, Peter

2017-11-01

The shoaling of an internal solitary wave (ISW) of depression over gentle slopes is explored through fully nonlinear and non-hydrostatic simulations using a high resolution/accuracy deformed spectral multidomain penalty method. During shoaling, the wave does not disintegrate as in the case of steeper slope but, instead, maintains its symmetric shape. At the core of the wave, an unstable region forms, characterized by the entrapment of heavier-over-light fluid. The formation of this convective instability is attributed to the vertical stretching by the ISW of the near-surface vorticity layer associated with the baroclinic background current. According to recent field observations in the South China Sea, the unstable region drives localized turbulent mixing within the wave, estimated to be up to four times larger than that in the open ocean, in the form of a recirculating trapped core. In this talk, emphasis is placed on the structure of the unstable region and the persistence of a possible recirculating core using simulations which capture 2D wave propagation combined with 3D representation of the transition to turbulence. As such, a preliminary understanding of the underlying fluid mechanics and the potential broader oceanic significance of ISWs with trapped cores is offered. Financial support gratefully acknowledged to NSF OCE Grant 1634257.

Progressive failure of sheeted rock slopes: the 2009–2010 Rhombus Wall rock falls in Yosemite Valley, California, USA

USGS Publications Warehouse

Stock, Greg M.; Martel, Stephen J.; Collins, Brian D.; Harp, Edwin L.

2012-01-01

Progressive rock-fall failures in natural rock slopes are common in many environments, but often elude detailed quantitative documentation and analysis. Here we present high-resolution photography, video, and laser scanning data that document spatial and temporal patterns of a 15-month-long sequence of at least 14 rock falls from the Rhombus Wall, a sheeted granitic cliff in Yosemite Valley, California. The rock-fall sequence began on 26 August 2009 with a small failure at the tip of an overhanging rock slab. Several hours later, a series of five rock falls totaling 736 m3progressed upward along a sheeting joint behind the overhanging slab. Over the next 3 weeks, audible cracking occurred on the Rhombus Wall, suggesting crack propagation, while visual monitoring revealed opening of a sheeting joint adjacent to the previous failure surface. On 14 September 2009 a 110 m3 slab detached along this sheeting joint. Additional rock falls between 30 August and 20 November 2010, totaling 187 m3, radiated outward from the initial failure area along cliff (sub)parallel sheeting joints. We suggest that these progressive failures might have been related to stress redistributions accompanying propagation of sheeting joints behind the cliff face. Mechanical analyses indicate that tensile stresses should occur perpendicular to the cliff face and open sheeting joints, and that sheeting joints should propagate parallel to a cliff face from areas of stress concentrations. The analyses also account for how sheeting joints can propagate to lengths many times greater than their depths behind cliff faces. We posit that as a region of failure spreads across a cliff face, stress concentrations along its margin will spread with it, promoting further crack propagation and rock falls.

Side-sloped surfaces substantially affect lower limb running kinematics.

PubMed

Damavandi, Mohsen; Eslami, Mansour; Pearsall, David J

2017-03-01

Running on side-sloped surfaces is a common obstacle in the environment; however, how and to what extent the lower extremity kinematics adapt is not well known. The purpose of this study was to determine the effects of side-sloped surfaces on three-dimensional kinematics of hip, knee, and ankle during stance phase of running. Ten healthy adult males ran barefoot along an inclinable runway in level (0°) and side-sloped (10° up-slope and down-slope inclinations, respectively) configurations. Right hip, knee, and ankle angles along with their time of occurrence were analysed using repeated measures MANOVA. Up-slope hip was more adducted (p = 0.015) and internally rotated (p = 0.030). Knee had greater external rotations during side-sloped running at heel-strike (p = 0.005), while at toe-off, it rotated externally and internally during up-slope and down-slope running, respectively (p = 0.001). Down-slope ankle had greatest plantar flexion (p = 0.001). Up-slope ankle had greatest eversion compared with down-slope (p = 0.043), while it was more externally rotated (p = 0.030). These motion patterns are necessary to adjust the lower extremity length during side-sloped running. Timing differences in the kinematic events of hip adduction and external rotation, and ankle eversion were observed (p = 0.006). Knowledge on these alterations is a valuable tool in adopting strategies to enhance performance while preventing injury.

Hues in a Crater Slope

NASA Image and Video Library

2017-01-02

Impact craters expose the subsurface materials on steep slopes. However, these slopes often experience rockfalls and debris avalanches that keep the surface clean of dust, revealing a variety of hues, like in this enhanced-color image, representing different rock types. The bright reddish material at the top of the crater rim is from a coating of the Martian dust. The long streamers of material are from downslope movements. Also revealed in this slope are a variety of bedrock textures, with a mix of layered and jumbled deposits. This sample is typical of the Martian highlands, with lava flows and water-lain materials depositing layers, then broken up and jumbled by many impact events. http://photojournal.jpl.nasa.gov/catalog/PIA14454

The great slippery-slope argument.

PubMed

Burgess, J A

1993-09-01

Whenever some form of beneficent killing--for example, voluntary euthanasia--is advocated, the proposal is greeted with a flood of slippery-slope arguments warning of the dangers of a Nazi-style slide into genocide. This paper is an attempt systematically to evaluate arguments of this kind. Although there are slippery-slope arguments that are sound and convincing, typical formulations of the Nazi-invoking argument are found to be seriously deficient both in logical rigour and in the social history and psychology required as a scholarly underpinning. As an antidote, an attempt is made both to identify some of the likely causes of genocide and to isolate some of the more modest but legitimate fears that lie behind slippery-slope arguments of this kind.

The great slippery-slope argument.

PubMed Central

Burgess, J A

1993-01-01

Whenever some form of beneficent killing--for example, voluntary euthanasia--is advocated, the proposal is greeted with a flood of slippery-slope arguments warning of the dangers of a Nazi-style slide into genocide. This paper is an attempt systematically to evaluate arguments of this kind. Although there are slippery-slope arguments that are sound and convincing, typical formulations of the Nazi-invoking argument are found to be seriously deficient both in logical rigour and in the social history and psychology required as a scholarly underpinning. As an antidote, an attempt is made both to identify some of the likely causes of genocide and to isolate some of the more modest but legitimate fears that lie behind slippery-slope arguments of this kind. PMID:8230150

Slope activity in Gale crater, Mars

USGS Publications Warehouse

Dundas, Colin M.; McEwen, Alfred S.

2015-01-01

High-resolution repeat imaging of Aeolis Mons, the central mound in Gale crater, reveals active slope processes within tens of kilometers of the Curiosity rover. At one location near the base of northeastern Aeolis Mons, dozens of transient narrow lineae were observed, resembling features (Recurring Slope Lineae) that are potentially due to liquid water. However, the lineae faded and have not recurred in subsequent Mars years. Other small-scale slope activity is common, but has different spatial and temporal characteristics. We have not identified confirmed RSL, which Rummel et al. (Rummel, J.D. et al. [2014]. Astrobiology 14, 887–968) recommended be treated as potential special regions for planetary protection. Repeat images acquired as Curiosity approaches the base of Aeolis Mons could detect changes due to active slope processes, which could enable the rover to examine recently exposed material.

47 CFR 101.1421 - Coordination of adjacent area MVDDS stations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... SPECIAL RADIO SERVICES FIXED MICROWAVE SERVICES Multichannel Video Distribution and Data Service Rules for... compatible with adjacent and co-channel operations in the adjacent areas on all its frequencies; and (2... adjacent and co-channel operations in adjacent areas. (b) Harmful interference to public safety stations...

Different slopes of a mountain can determine the structure of ferns and lycophytes communities in a tropical forest of Brazil.

PubMed

Nettesheim, Felipe C; Damasceno, Elaine R; Sylvestre, Lana S

2014-03-01

A community of Ferns and Lycophytes was investigated by comparing the occurrence of species on different slopes of a paleoisland in Southeastern Brazil. Our goal was to evaluate the hypothesis that slopes with different geographic orientations determine a differentiation of Atlantic Forest ferns and lycophytes community. We recorded these plants at slopes turned towards the continent and at slopes turned towards the open sea. Analysis consisted of a preliminary assessment on fern beta diversity, a Non Metric Multidimensional Scaling (NMDS) and a Student t-test to confirm if sites sampling units ordination was different at each axis. We further used the Pearson coefficient to relate fern species to the differentiation pattern and again Student's t-test to determine if richness, plant cover and abundance varied between the two sites. There was a relatively low number of shared species between the two sites and ferns and lycophytes community variation was confirmed. Some species were detected as indicators of the community variation but we were unable to detect richness, plant cover or abundance differences. Despite the evidence of this variation between the slopes, further works are needed to evaluate which processes are contributing to determine this pattern.

Storm-Induced Slope Failure Susceptibility Mapping

DOT National Transportation Integrated Search

2018-01-01

A pilot study was conducted to characterize and map the areas susceptible to slope failure using state-wide available data. The objective was to determine whether it would be possible to provide slope-failure susceptibility mapping that could be used...

Slope Estimation in Noisy Piecewise Linear Functions✩

PubMed Central

Ingle, Atul; Bucklew, James; Sethares, William; Varghese, Tomy

2014-01-01

This paper discusses the development of a slope estimation algorithm called MAPSlope for piecewise linear data that is corrupted by Gaussian noise. The number and locations of slope change points (also known as breakpoints) are assumed to be unknown a priori though it is assumed that the possible range of slope values lies within known bounds. A stochastic hidden Markov model that is general enough to encompass real world sources of piecewise linear data is used to model the transitions between slope values and the problem of slope estimation is addressed using a Bayesian maximum a posteriori approach. The set of possible slope values is discretized, enabling the design of a dynamic programming algorithm for posterior density maximization. Numerical simulations are used to justify choice of a reasonable number of quantization levels and also to analyze mean squared error performance of the proposed algorithm. An alternating maximization algorithm is proposed for estimation of unknown model parameters and a convergence result for the method is provided. Finally, results using data from political science, finance and medical imaging applications are presented to demonstrate the practical utility of this procedure. PMID:25419020

Slope Estimation in Noisy Piecewise Linear Functions.

PubMed

Ingle, Atul; Bucklew, James; Sethares, William; Varghese, Tomy

2015-03-01

This paper discusses the development of a slope estimation algorithm called MAPSlope for piecewise linear data that is corrupted by Gaussian noise. The number and locations of slope change points (also known as breakpoints) are assumed to be unknown a priori though it is assumed that the possible range of slope values lies within known bounds. A stochastic hidden Markov model that is general enough to encompass real world sources of piecewise linear data is used to model the transitions between slope values and the problem of slope estimation is addressed using a Bayesian maximum a posteriori approach. The set of possible slope values is discretized, enabling the design of a dynamic programming algorithm for posterior density maximization. Numerical simulations are used to justify choice of a reasonable number of quantization levels and also to analyze mean squared error performance of the proposed algorithm. An alternating maximization algorithm is proposed for estimation of unknown model parameters and a convergence result for the method is provided. Finally, results using data from political science, finance and medical imaging applications are presented to demonstrate the practical utility of this procedure.

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.

Slump dominated upper slope reservoir facies, Intra Qua Iboe (Pliocene), Edop Field, offshore Nigeria

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

Shanmugam, G.; Hermance, W.E.; Olaifa, J.O.

An integration of sedimentologic and 3D seismic data provides a basis for unraveling complex depositional processes and sand distribution of the Intra Qua Iboe (IQI) reservoir (Pliocene), Edop Field, offshore Nigeria. Nearly 3,000 feet of conventional core was examined in interpreting slump/slide/debris flow, bottom current, turbidity current, pelagic/hemipelagic, wave and tide dominated facies. The IQI was deposited on an upper slope in close proximity to the shelf edge. Through time, as the shelf edge migrated seaward, deposition began with a turbidite channel dominated slope system (IQI 1 and 2) and progressed through a slump/debris flow dominated slope system (IQI 3,more » the principal reservoir) to a tide and wave dominated, collapsed shelf-edge deltaic system (IQI 4). Using seismic time slices and corresponding depositional facies in the core, a sandy {open_quotes}fairway{open_quotes} has been delineated in the IQI 3. Because of differences in stacking patterns of sandy and muddy slump intervals, seismic facies show: (1) both sheet-like and mounded external forms (geometries), and (2) parallel/continuous as well as chaotic/hummocky internal reflections. In wireline logs, slump facies exhibits blocky, coarsening-up, fining-up, and serrated motifs. In the absence of conventional core, slump facies may be misinterpreted and even miscorrelated because seismic facies and log motifs of slumps and debris flows tend to mimic properties of turbidite fan deposits. The slump dominated reservoir facies is composed of unconsolidated fine-grained sand. Thickness of individual units varies from 1 to 34 feet, but amalgamated intervals reach a thickness of up to 70 feet and apparently form connected sand bodies. Porosity commonly ranges from 20 to 35%. Horizontal permeability commonly ranges from 1,000 to 3,000 md.« less

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.

Dewatering of the Jenkins open pit uranium mine

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

Straskraba, V.; Kissinger, L.E.

Mining of low grade uranium sandstones in the Jenkins open pit mine in the Shirley Basin, Wyoming was troubled by slope failures and wet conditions in the pit. Since the mine was expanding toward a river, the possibility of drainage from this river into the mine raised serious concern during the mine planning. A baseline hydrogeologic study was performed and dewatering measures were designed with the help of a numerical mathematical model. A combination of dewatering wells installed from the surface around the perimeter of the pit and horizontal drains in areas of high slope failure potential substantially improved themore » mining conditions and slope stability. This procedure consequently led to the successful ore recovery from the highly saturated sandstone strata. The development of drawdown during the dewatering of two separated aquifers in the overburden was close to that predicted by the model.« less

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.

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.

33 CFR 80.1395 - Puget Sound and adjacent waters.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake Union...

33 CFR 80.1395 - Puget Sound and adjacent waters.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake Union...

33 CFR 80.1395 - Puget Sound and adjacent waters.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake Union...

33 CFR 80.1395 - Puget Sound and adjacent waters.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake Union...

33 CFR 80.1395 - Puget Sound and adjacent waters.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Puget Sound and adjacent waters... INTERNATIONAL NAVIGATION RULES COLREGS DEMARCATION LINES Thirteenth District § 80.1395 Puget Sound and adjacent waters. The 72 COLREGS shall apply on all waters of Puget Sound and adjacent waters, including Lake Union...

Cryopreserved embryo transfer: adjacent or non-adjacent to failed fresh long GnRH-agonist protocol IVF cycle.

PubMed

Volodarsky-Perel, Alexander; Eldar-Geva, Talia; Holzer, Hananel E G; Schonberger, Oshrat; Reichman, Orna; Gal, Michael

2017-03-01

The optimal time to perform cryopreserved embryo transfer (CET) after a failed oocyte retrieval-embryo transfer (OR-ET) cycle is unknown. Similar clinical pregnancy rates were recently reported in immediate and delayed CET, performed after failed fresh OR-ET, in cycles with the gonadotrophin-releasing hormone (GnRH) antagonist protocol. This study compared outcomes of CET performed adjacently (<50 days, n = 67) and non-adjacently (≥50 to 120 days, n = 62) to the last OR-day of cycles with the GnRH agonist down-regulation protocol. Additional inclusion criteria were patients' age 20-38 years, the transfer of only 1-2 cryopreserved embryos, one treatment cycle per patient and artificial preparation for CET. Significantly higher implantation, clinical pregnancy and live birth rates were found in the non-adjacent group than in the adjacent group: 30.5% versus 11.3% (P = 0.001), 41.9% versus 17.9% (P = 0.003) and 32.3% versus 13.4% (P = 0.01), respectively. These results support the postponement of CET after a failed OR-ET for at least one menstrual cycle, when a preceding long GnRH-agonist protocol is used. Copyright © 2016 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

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.

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

A method for determining average beach slope and beach slope variability for U.S. sandy coastlines

USGS Publications Warehouse

Doran, Kara S.; Long, Joseph W.; Overbeck, Jacquelyn R.

2015-01-01

The U.S. Geological Survey (USGS) National Assessment of Hurricane-Induced Coastal Erosion Hazards compares measurements of beach morphology with storm-induced total water levels to produce forecasts of coastal change for storms impacting the Gulf of Mexico and Atlantic coastlines of the United States. The wave-induced water level component (wave setup and swash) is estimated by using modeled offshore wave height and period and measured beach slope (from dune toe to shoreline) through the empirical parameterization of Stockdon and others (2006). Spatial and temporal variability in beach slope leads to corresponding variability in predicted wave setup and swash. For instance, seasonal and storm-induced changes in beach slope can lead to differences on the order of 1 meter (m) in wave-induced water level elevation, making accurate specification of this parameter and its associated uncertainty essential to skillful forecasts of coastal change. A method for calculating spatially and temporally averaged beach slopes is presented here along with a method for determining total uncertainty for each 200-m alongshore section of coastline.

Up by upwest: Is slope like north?

PubMed

Weisberg, Steven M; Nardi, Daniele; Newcombe, Nora S; Shipley, Thomas F

2014-10-01

Terrain slope can be used to encode the location of a goal. However, this directional information may be encoded using a conceptual north (i.e., invariantly with respect to the environment), or in an observer-relative fashion (i.e., varying depending on the direction one faces when learning the goal). This study examines which representation is used, whether the sensory modality in which slope is encoded (visual, kinaesthetic, or both) influences representations, and whether use of slope varies for men and women. In a square room, with a sloped floor explicitly pointed out as the only useful cue, participants encoded the corner in which a goal was hidden. Without direct sensory access to slope cues, participants used a dial to point to the goal. For each trial, the goal was hidden uphill or downhill, and the participants were informed whether they faced uphill or downhill when pointing. In support of observer-relative representations, participants pointed more accurately and quickly when facing concordantly with the hiding position. There was no effect of sensory modality, providing support for functional equivalence. Sex did not interact with the findings on modality or reference frame, but spatial measures correlated with success on the slope task differently for each sex.

Automatic approach to deriving fuzzy slope positions

NASA Astrophysics Data System (ADS)

Zhu, Liang-Jun; Zhu, A.-Xing; Qin, Cheng-Zhi; Liu, Jun-Zhi

2018-03-01

Fuzzy characterization of slope positions is important for geographic modeling. Most of the existing fuzzy classification-based methods for fuzzy characterization require extensive user intervention in data preparation and parameter setting, which is tedious and time-consuming. This paper presents an automatic approach to overcoming these limitations in the prototype-based inference method for deriving fuzzy membership value (or similarity) to slope positions. The key contribution is a procedure for finding the typical locations and setting the fuzzy inference parameters for each slope position type. Instead of being determined totally by users in the prototype-based inference method, in the proposed approach the typical locations and fuzzy inference parameters for each slope position type are automatically determined by a rule set based on prior domain knowledge and the frequency distributions of topographic attributes. Furthermore, the preparation of topographic attributes (e.g., slope gradient, curvature, and relative position index) is automated, so the proposed automatic approach has only one necessary input, i.e., the gridded digital elevation model of the study area. All compute-intensive algorithms in the proposed approach were speeded up by parallel computing. Two study cases were provided to demonstrate that this approach can properly, conveniently and quickly derive the fuzzy slope positions.

Soil properties in high-elevation ski slopes

NASA Astrophysics Data System (ADS)

Filippa, Gianluca; Freppaz, Michele; Letey, Stéphanie; Corti, Giuseppe; Cocco, Stefania; Zanini, Ermanno

2010-05-01

The development of winter sports determines an increasing impact on the high altitude ecosystems, as a consequence of increased participation and an increasing demand of high quality standards for skiable areas. The construction of a ski slope is associated with a certain impact on soil, which varies as a function of the degree of human-induced disturbance to the native substrata. In this work, we provide a description of the characteristics of alpine tundra ski-slope soils and their nutrient status, contrasted with undisturbed areas. The study site is located in the Monterosaski Resort, Aosta Valley, NW Italy (45°51' N; 7°48' E). We chose 5 sites along an altitudinal gradient between 2700 and 2200 m a.s.l.. Per each site, one plot was established on the ski slope, while a control plot was chosen under comparable topographic conditions a few meters apart. Soils were described and samples were collected and analysed for main chemical-physical properties. In addition an evaluation of N forms, organic matter fractionation and microbial biomass was carried out. Soil depth ranged between 10 to more than 70 cm, both on the ski slope and in the undisturbed areas. A true organo-mineral (A) horizon was firstly identified at 2500 m a.s.l., while a weathering horizon (Bw) was detected at 2400 m a.s.l.. However, a Bw horizon thick enough to be recognised as diagnostic for shifting soil classification order from Entisols to Inceptisols (USDA-Soil Taxonomy) was detected only below 2400 m a.s.l.. Lithic Cryorthents were predominant in the upper part of the sequence (above 2500 m a.s.l.), both in the ski slope and the undisturbed areas; Typic Cryorthents were identified between 2500 and 2400 m a.s.l., while Inceptisols were predominant between 2400 and 2200 m a.s.l.. Chemical-physical properties will be discussed focusing on the main differences between ski slope and undisturbed soils, as determined by the ski slope construction. Pedogenetic processes at high altitude are

The Slope Imaging Multi-Polarization Photon-Counting Lidar: Development and Performance Results

NASA Technical Reports Server (NTRS)

Dabney, Phillip

2010-01-01

The Slope Imaging Multi-polarization Photon-counting Lidar is an airborne instrument developed to demonstrate laser altimetry measurement methods that will enable more efficient observations of topography and surface properties from space. The instrument was developed through the NASA Earth Science Technology Office Instrument Incubator Program with a focus on cryosphere remote sensing. The SIMPL transmitter is an 11 KHz, 1064 nm, plane-polarized micropulse laser transmitter that is frequency doubled to 532 nm and split into four push-broom beams. The receiver employs single-photon, polarimetric ranging at 532 and 1064 nm using Single Photon Counting Modules in order to achieve simultaneous sampling of surface elevation, slope, roughness and depolarizing scattering properties, the latter used to differentiate surface types. Data acquired over ice-covered Lake Erie in February, 2009 are documenting SIMPL s measurement performance and capabilities, demonstrating differentiation of open water and several ice cover types. ICESat-2 will employ several of the technologies advanced by SIMPL, including micropulse, single photon ranging in a multi-beam, push-broom configuration operating at 532 nm.

US North Slope gas and Asian LNG markets

USGS Publications Warehouse

Attanasi, E.D.

1994-01-01

Prospects for export of liquified natural gas (LNG) from Alaska's North Slope are assessed. Projected market conditions to 2010 show that new LNG capacity beyond announced expansions will be needed to meet regional demand and that supplies will probably come from outside the region. The estimated delivered costs of likely suppliers show that Alaska North Slope gas will not be competitive. The alternative North Slope gas development strategies of transport and sale to the lower 48 states and use on the North Slope for either enhanced oil recovery or conversion to liquids are examined. The alternative options require delaying development until US gas prices increase, exhaustion of certain North Slope oil fields, or advances occur in gas to liquid fuels conversion technology. ?? 1995.

Louisiana continental slope: geologic and seismic stratigraphic framework

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

Ray, P.K.; Cooke, D.W.

1987-05-01

The continental slope of Louisiana from Green Canyon to Mississippi Canyon was studied by interpreting seismic CDP data and wells in the area. The slope is characterized by blocked canyon intraslope basins of various dimensions with maximum thickness of sediments in excess of 21,000 ft, rotational slump blocks and large-scale submarine slides. In the subsurface, the outer shelf and upper slope show contrasting character with that of the lower slope, especially below the Sigsbee Scarp. The seismic stratigraphic units established for the deep sea area can be recognized in their entirety up to a water depth of 6000 to 5500more » ft. In shallower water salt tectonics obliterates the sequence. Fragmental records of the sequence, especially the top of Challenger boundary, have been recognized in as shallow as 2000 to 3000 ft of water. The Tertiary units often downlap and onlap directly on the Challenger unit, indicating the progradational nature of the clastic slope. The Sigsbee unit has been traced through the entire slope area and can be divided into five subunits of unique acoustical characteristics. The slope constantly regrades in response to Neogene sea level fluctuations. Loading of the shelf by deltaic deposition contributes to salt sill formation and flowage of salt over deep-water sediments on the slope during high sea level. Regressive sea is represented by slope failure, formation of large-scale submarine slides, filling of blocked canyon intraslope basins which show similar seismic facies to that of Orca and Pigmy basins as reported from DSDP studies, and sporadic uplifting of salt diapirs and massifs and the formation of linear transverse salt ridges.« less

Hydrogeochemical Investigations of Historic Mining Districts, Central Western Slope of Colorado, Including Influence on Surface-Water Quality

USGS Publications Warehouse

Nash, J. Thomas

2002-01-01

This report describes reconnaissance hydrogeochemical investigations of 22 mining districts on the Western Slope of Colorado in the Gunnison and Uncompahgre National Forests and adjacent public lands administered by the Bureau of Land Management. Sources and fates of contaminants from historic mines, mine waste, and mill tailings are interpreted from chemical analyses for 190 samples of surface waters; 185 samples of mined rocks, mill tailings, and altered rocks; and passive leach analyses of 116 samples of those mineralized materials. Short reaches of several headwater streams show relatively low level effects of historic mining; the headwaters of the Uncompahgre River are highly contaminated by mines and unmined altered rocks in the Red Mountain district. There is encouraging evidence that natural processes attenuate mine-related contamination in most districts.

Contrasting rainfall generated debris flows from adjacent watersheds at Forest Falls, southern California, USA

USGS Publications Warehouse

Morton, D.M.; Alvarez, R.M.; Ruppert, K.R.; Goforth, B.

2008-01-01

Debris flows are widespread and common in many steeply sloping areas of southern California. The San Bernardino Mountains community of Forest Falls is probably subject to the most frequently documented debris flows in southern California. Debris flows at Forest Falls are generated during short-duration high-intensity rains that mobilize surface material. Except for debris flows on two consecutive days in November 1965, all the documented historic debris flows have occurred during high-intensity summer rainfall, locally referred to as 'monsoon' or 'cloudburst' rains. Velocities of the moving debris range from about 5??km/h to about 90??km/h. Velocity of a moving flow appears to be essentially a function of the water content of the flow. Low velocity debris flows are characterized by steep snouts that, when stopped, have only small amounts of water draining from the flow. In marked contrast are high-velocity debris flows whose deposits more resemble fluvial deposits. In the Forest Falls area two adjacent drainage basins, Snow Creek and Rattlesnake Creek, have considerably different histories of debris flows. Snow Creek basin, with an area about three times as large as Rattlesnake Creek basin, has a well developed debris flow channel with broad levees. Most of the debris flows in Snow Creek have greater water content and attain higher velocities than those of Rattlesnake Creek. Most debris flows are in relative equilibrium with the geometry of the channel morphology. Exceptionally high-velocity flows, however, overshoot the channel walls at particularly tight channel curves. After overshooting the channel, the flows degrade the adjacent levee surface and remove trees and structures in the immediate path, before spreading out with decreasing velocity. As the velocity decreases the clasts in the debris flows pulverize the up-slope side of the trees and often imbed clasts in them. Debris flows in Rattlesnake Creek are relatively slow moving and commonly stop in the

Human gene therapy and slippery slope arguments.

PubMed Central

McGleenan, T

1995-01-01

Any suggestion of altering the genetic makeup of human beings through gene therapy is quite likely to provoke a response involving some reference to a 'slippery slope'. In this article the author examines the topography of two different types of slippery slope argument, the logical slippery slope and the rhetorical slippery slope argument. The logical form of the argument suggests that if we permit somatic cell gene therapy then we are committed to accepting germ line gene therapy in the future because there is no logically sustainable distinction between them. The rhetorical form posits that allowing somatic cell therapy now will be taking the first step on a slippery slope which will ultimately lead to the type of genocide perpetrated by the Nazis. The author tests the validity of these lines of argument against the facts of human gene therapy and concludes that because of their dependence on probabilities that cannot be empirically proven they should be largely disregarded in the much more important debate on moral line-drawing in gene therapy. PMID:8778459

Human gene therapy and slippery slope arguments.

PubMed

McGleenan, T

1995-12-01

Any suggestion of altering the genetic makeup of human beings through gene therapy is quite likely to provoke a response involving some reference to a 'slippery slope'. In this article the author examines the topography of two different types of slippery slope argument, the logical slippery slope and the rhetorical slippery slope argument. The logical form of the argument suggests that if we permit somatic cell gene therapy then we are committed to accepting germ line gene therapy in the future because there is no logically sustainable distinction between them. The rhetorical form posits that allowing somatic cell therapy now will be taking the first step on a slippery slope which will ultimately lead to the type of genocide perpetrated by the Nazis. The author tests the validity of these lines of argument against the facts of human gene therapy and concludes that because of their dependence on probabilities that cannot be empirically proven they should be largely disregarded in the much more important debate on moral line-drawing in gene therapy.

Dark Slope Streak

NASA Image and Video Library

2010-03-25

Dark slope streaks, like the ones in this unnamed crater in Terra Sabaea, are believed to be formed when surface dust is displaced and the darker rock below is exposed. Rocks falling due to gravity likely formed these streaks.

Development of improved connection details for adjacent prestressed member bridges.

DOT National Transportation Integrated Search

2017-06-01

Adjacent prestressed member girder bridges are economical systems for short spans and generally come in two types: adjacent box beam bridges and adjacent voided slab bridges. Each type provides the advantages of having low clearances because of their...

Conceptualizations of Slope: A Review of State Standards

ERIC Educational Resources Information Center

Stanton, Michael; Moore-Russo, Deborah

2012-01-01

Since slope is a fundamental topic that is embedded throughout the U.S. secondary school curriculum, this study examined standards documents for all 50 states to determine how they address the concept of slope. The study used eleven conceptualizations of slope as categories to classify the material in the documents. The findings indicate that all…

Hippocampal place cell encoding of sloping terrain.

PubMed

Porter, Blake S; Schmidt, Robert; Bilkey, David K

2018-05-21

Effective navigation relies on knowledge of one's environment. A challenge to effective navigation is accounting for the time and energy costs of routes. Irregular terrain in ecological environments poses a difficult navigational problem as organisms ought to avoid effortful slopes to minimize travel costs. Route planning and navigation have previously been shown to involve hippocampal place cells and their ability to encode and store information about an organism's environment. However, little is known about how place cells may encode the slope of space and associated energy costs as experiments are traditionally carried out in flat, horizontal environments. We set out to investigate how dorsal-CA1 place cells in rats encode systematic changes to the slope of an environment by tilting a shuttle box from flat to 15° and 25° while minimizing external cue change. Overall, place cell encoding of tilted space was as robust as their encoding of flat ground as measured by traditional place cell metrics such as firing rates, spatial information, coherence, and field size. A large majority of place cells did, however, respond to slope by undergoing partial, complex remapping when the environment was shifted from one tilt angle to another. The propensity for place cells to remap did not, however, depend on the vertical distance the field shifted. Changes in slope also altered the temporal coding of information as measured by the rate of theta phase precession of place cell spikes, which decreased with increasing tilt angles. Together these observations indicate that place cells are sensitive to relatively small changes in terrain slope and that terrain slope may be an important source of information for organizing place cell ensembles. The terrain slope information encoded by place cells could be utilized by efferent regions to determine energetically advantageous routes to goal locations. This article is protected by copyright. All rights reserved. © 2018 Wiley

Effect of regional slope on drainage networks

NASA Astrophysics Data System (ADS)

Phillips, Loren F.; Schumm, S. A.

1987-09-01

Drainage networks that develop under conditions of no structural control and homogeneous lithology are generally dendritic, depending upon the shape and inclination of the surface on which they form. An experimental study was designed to investigate the effect of an increase of slope on the evolution and development of dendritic drainage patterns. As slope steepens, the pattern changes from dendritic at 1% slope, to subdendritic at 2%, to subparallel at 3%, to parallel at 5% and higher. The change from a dendritic-type pattern to a parallel-type pattern occurs at a low slope, between 2% and 3%, and primary channel junction angles decrease abruptly from about 60° to 43°. *Present address: U.S. Army Environmental Hygiene Agency, Attn: HSHB-ME-WM, Aberdeen Proving Ground, Maryland 21010-5422

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.

Improved connection details for adjacent prestressed bridge beams.

DOT National Transportation Integrated Search

2015-03-01

Bridges with adjacent box beams and voided slabs are simply and rapidly constructed, and are well suited to : short to medium spans. The traditional connection between the adjacent members is a shear key lled with a : conventional non-shrink grout...

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.

THE FUNCTIONAL ROLES OF MUSCLES DURING SLOPED WALKING

PubMed Central

Pickle, Nathaniel T.; Grabowski, Alena M.; Auyang, Arick G.; Silverman, Anne K.

2016-01-01

Sloped walking is biomechanically different from level-ground walking, as evidenced by changes in joint kinematics and kinetics. However, the changes in muscle functional roles underlying these altered movement patterns have not been established. In this study, we developed a total of 273 muscle-actuated simulations to assess muscle functional roles, quantified by induced body center-of-mass accelerations and trunk and leg power, during walking on slopes of 0°, ±3°, ±6°, and ±9° at 1.25 m/s. The soleus and gastrocnemius both provided greater forward acceleration of the body parallel to the slope at +9° compared to level ground (+126% and +66%, respectively). However, while the power delivered to the trunk by the soleus varied with slope, the magnitude of net power delivered to the trunk and ipsilateral leg by the biarticular gastrocnemius was similar across all slopes. At +9°, the hip extensors absorbed more power from the trunk (230% hamstrings, 140% gluteus maximus) and generated more power to both legs (200% hamstrings, 160% gluteus maximus) compared to level ground. At −9°, the knee extensors (rectus femoris and vasti) accelerated the body upward perpendicular to the slope at least 50% more and backward parallel to the slope twice as much as on level ground. In addition, the knee extensors absorbed greater amounts of power from the ipsilateral leg on greater declines to control descent. Future studies can use these results to develop targeted rehabilitation programs and assistive devices aimed at restoring sloped walking ability in impaired populations. PMID:27553849

Integrating concepts and skills: Slope and kinematics graphs

NASA Astrophysics Data System (ADS)

Tonelli, Edward P., Jr.

The concept of force is a foundational idea in physics. To predict the results of applying forces to objects, a student must be able to interpret data representing changes in distance, time, speed, and acceleration. Comprehension of kinematics concepts requires students to interpret motion graphs, where rates of change are represented as slopes of line segments. Studies have shown that majorities of students who show proficiency with mathematical concepts fail accurately to interpret motion graphs. The primary aim of this study was to examine how students apply their knowledge of slope when interpreting kinematics graphs. To answer the research questions a mixed methods research design, which included a survey and interviews, was adopted. Ninety eight (N=98) high school students completed surveys which were quantitatively analyzed along with qualitative information collected from interviews of students (N=15) and teachers ( N=2). The study showed that students who recalled methods for calculating slopes and speeds calculated slopes accurately, but calculated speeds inaccurately. When comparing the slopes and speeds, most students resorted to calculating instead of visual inspection. Most students recalled and applied memorized rules. Students who calculated slopes and speeds inaccurately failed to recall methods of calculating slopes and speeds, but when comparing speeds, these students connected the concepts of distance and time to the line segments and the rates of change they represented. This study's findings will likely help mathematics and science educators to better assist their students to apply their knowledge of the definition of slope and skills in kinematics concepts.

Benthic Community Structure and Sediment Geochemical Properties at Hydrocarbon Seeps Along the Continental Slope of the Western North Atlantic

NASA Astrophysics Data System (ADS)

Demopoulos, A. W.; Bourque, J. R.; Brooke, S.

2015-12-01

Hydrocarbon seeps support distinct benthic communities capable of utilizing reduced chemical compounds for nutrition. In recent years, methane seepage has been increasingly documented along the continental slope of the U.S. Atlantic margin. In 2012 and 2013, two seeps were investigated in this region: a shallow site near Baltimore Canyon (410-450 m) and a deep site near Norfolk Canyon (1600 m). Both sites contain extensive mussel beds and microbial mats. Sediment cores and grab samples were collected to quantify the abundance, diversity, and community structure of benthic macrofauna (>300 mm) in relationship to the associated sediment environment (organic carbon and nitrogen, stable isotopes 13C and 15N, grain size, and depth) of mussel beds, mats, and slope habitats. Macrofaunal densities in microbial mats were four times greater than those present in mussel beds and slope sediments. Macrofaunal communities were distinctly different both between depths and among habitat types. Specifically, microbial mat sediments were dominated by the annelid families Dorvilleidae, Capitellidae, and Tubificidae, while mussel habitats had higher proportions of crustaceans. Diversity was lower in Baltimore microbial mat habitats, but higher in mussel and slope sediments compared to Norfolk seep habitats found at deeper depths. Multivariate statistical analysis identified sediment carbon:nitrogen (C:N) ratios and 13C values as important variables for structuring the macrofaunal communities. Higher C:N ratios were present within microbial mat habitats and depleted 13C values occurred in sediments adjacent to mussel beds found in Norfolk Canyon seeps. Differences in the quality and source of organic matter present in the seep habitats are known to be important drivers in macrofaunal community structure and associated food webs. The multivariate analysis provides new insight into the relative importance of the seep sediment quality in supporting dense macrofaunal communities compared

Surface energy fluxes on four slope sites during FIFE 1988

NASA Technical Reports Server (NTRS)

Nie, D.; Demetriades-Shah, T.; Kanemasu, E. T.

1992-01-01

Four slopes (facing north, south, east, and west) in the Konza Prairie Research Natural Area were selected to study the effect of topography on surface energy balance and other micrometeorological variables. Energy fluxes, air temperature, and vapor pressure were measured on the slopes throughout the 1988 growing season. Net radiation was highest on the south facing slope and lowest on the north facing slope, and the difference was more than 150 W/sq m (20-30 percent) at solar noon. For daily averages the difference was about 25 W/sq m (15 percent) early in the season and increased to about 60 W/sq m (30-50 percent) in September. Soil heat fluxes were similar for all the slopes. The absolute values of sensible heat flux were consistently lower on the north facing slope compared with other slopes. The south facing slope had the greatest day-to-day fluctuation in latent heat flux as a result of the interaction of net radiation, soil moisture, and green leaf area. Differences were found in the partitioning of the available energy among the slopes, and the north facing slope had a higher percentage of energy dissipated into latent heat flux. The north facing slope had higher air temperatures during the day and higher vapor pressures both during the day and at night when the wind was from the south.

Effectiveness Using Circular Fibre Steel Flap Gate As a Control Structure Towards the Hydraulic Characteristics in Open Channel

NASA Astrophysics Data System (ADS)

Adib, M. R. M.; Amirza, A. R. M.; Wardah, T.; Junaidah, A.

2016-07-01

Hydraulic control gate structure plays an important role in regulating the flow of water in river, canal or water reservoir. One of the most appropriate structures in term of resolving the problem of flood occured is the construction of circular fibre steel flap gate. Therefore, an experiment has been conducted by using an open channel model at laboratory. In this case, hydraulic jump and backwater were the method to determined the hydraulic characteristics of circular fibre steel flap gate in an open channel model. From the experiment, the opening angle of flap gate can receive discharges with the highest flow rate of 0.035 m3/s with opening angle was 47°. The type of jump that occurs at the slope of 1/200 for a distance of 5.0 m is a standing jump or undulating wave. The height of the backwater can be identified based on the differences of specific force which is specific force before jump, F1 and specific force after jump, F2 from the formation of backwater. Based on the research conducted, the tendency of incident backwater wave occurred was high in every distance of water control location from water inlet is flap slope and the slope of 1/300 which is 0.84 m/s and 0.75 m/s of celerity in open channel model.

Sloping fan travertine, Belen, New Mexico, USA

NASA Astrophysics Data System (ADS)

Cook, Megan; Chafetz, Henry S.

2017-05-01

Pliocene to Quaternary age travertines are very well-exposed in quarries near Belen, New Mexico, U.S.A., on the western edge of the Rio Grande Rift system. A series of hillside springs produced travertine tongues tens of meters thick and hundreds of meters long. The accumulations represent deposits from individual springs as well as the amalgamation of deposits. The overall architecture is predominantly composed of sloping fans with a smaller component of terrace mounds. The sloping fan deposits commonly have a dip of < 10°, however, they range from horizontal to near vertical. Individual strata display significant changes in depositional dip, beds pinch and swell, and some are completely truncated. Centimeter to meter scale terrace mounds exhibit the common stair-step morphology. As a consequence of vertical accretion in the pools, terrace mounds morphed into sloping fans. The travertine is composed of a variety of commonly reported constituents, i.e., centimeter thick laminae of bacterial shrubs and oncoids, foam rock, sheets and rafts, and finely crystalline crusts that occur throughout the sloping fan and terrace mound accumulations. Sheets and rafts formed as precipitates in pools on the surfaces of the fans and terraces as well as spelean deposits on the water surfaces of pools within cavities in the overall accumulation. Thus, the spelean rafts provide valuable indicators of original horizontality in the sloping fan strata. In addition, intraformational breccias, composed of locally torn-up travertine intraclastic boulders and deposited in with other travertine, and extraformational breccias, composed of torn-up travertine intraclasts mixed with siliciclastic fines and sand and Paleozoic limestone clasts transported downslope from higher on the hillside, are a common constituent in the sloping fan accumulation. The Belen travertines provide a very well-exposed example of sloping fan travertines and may provide relevant data with regard to the subsurface

Detailed analysis of the Valdes slide: a landward facing slope failure off Chile

NASA Astrophysics Data System (ADS)

Anasetti, Andrea; Krastel, Sebastian; Weinrebe, Willy; Klaucke, Ingo; Bialas, Jorge

2010-05-01

The Chilean continental margin is a very active area interested by important tectonic movements and characterized by a fast morphological evolution. Geophysical data acquired during cruise JC 23, aboard RV JAMES COOK in March/April 2008 and previous cruises cover most of the active Chilean continental margin between 33° and 37° S. Integrated interpretation of multi-beam bathymetric, sub-bottom profiles, side-scan sonar and seismic data allowed the identification of a number of slope failures. The main topic of this project is the morphological and sedimentological analysis of the Valdes slide, a medium-sized submarine landslide offshore the city of Talcahuano (300 km south of Santiago). In contrast to most other slides along continental margins, the Valdes slide is located on the landward facing eastern slope of a submarine ridge. This setting has important implications for the associated tsunami wave field (first arrival of positive amplitude). We measured geometrical parameters of the failure and adjacent slope. The slide affected an area of 19 km2 between ~1060 m and >1700 m water depths. Its is ~ 6 km long, up to 3 km wide and involved a total sedimentary volume of about 0,8 km3. The failure process was characterized by a multiple-event and we assume its tsunami potential to be high. Using the high resolution bathymetric data and the seismic profiles along the slide deposit it was possible to reconstruct the original morphology of the area in order to understand the relation between the slide event and the structural evolution of the ridge. Through the analysis of the data and bibliographic information about the Chilean margin, we analyzed potential trigger mechanisms for the landslide. The Valdes slide is situated on a steep ridge flank. The ridge follows an elongated fault zone running app. parallel to the margin. This fault zone has a dextral component which in combination with the faults elongation results in a compressional regime that is superimposed on

Area utilization efficiency of a sloping heliostat system for solar concentration.

PubMed

Wei, L Y

1983-02-15

Area utilization efficiency (AUE) is formulated for a sloping heliostat system facing any direction. The effects of slope shading, incidence factor, sun shading, and tower blocking by the mirrors are all taken into account. Our results show that annually averaged AUEs calculated for heliostat systems (1) increase with tower height at low slope angles but less rapidly at high slopes, (2) increase monotonically with slope angle and saturate at large slopes for systems facing due south, (3) reach a maximum at a certain slope for systems facing other directions than due south, and (4) drop sharply at slopes greater than a certain value for systems facing due east or west due to slope shading effect. The results are useful for solar energy collection on nonflat terrains.

Large landslides induced by the 2008 Wenchuan earthquake and their precursory gravitational slope deformation

NASA Astrophysics Data System (ADS)

Chigira, Masahiro; Wu, Xiyong; Wang, Gonghui; Uchida, Osamu

2010-05-01

2008 Wenchuan earthquake induced numerous large landslides, of which many large landslides had been preceded by gravitational deformation. The deformation could be detected by linear depressions and convex slopes observed on satellite images taken before the earthquake. Ground truth survey after the earthquake also found the gravitational deformation of rocks, which could be predated before the earthquake. The Daguanbao landslide, the largest landslide induced by this earthquake, occurred on a slope of bedded carbonate rocks. The area of the landslide, based on measurements made from the ALOS/PRISM images is 7.353 km2. Its volume is estimated to be 0.837 km3 based on the comparison of the PRISM data and the SRTM DEM. It had an open V-shaped main scarp, of which one linear part was along a high angle fault and the other was approximately parallel to the bedding strike. The upslope edge of the V-shaped main scarp was observed as 2- km long linear depressions along the ridge-top on satellite image before the landslide. This indicates that this slope had been already destabilized and small movement occurred along the bedding planes and along the fault before the event. The Wenchuan earthquake pulled the final trigger of this landslide. The major sliding surface was along the bedding plane, which was observed to dip 35° or slightly gentler. It was warped convex upward and the beds were fractured, which suggests that the beds were slightly buckled before the landslide. This deformation may correspond to the formation of the linear depression. The Tangjiashan landslide in Beichuan, which produced the largest landslide dam during the earthquake, occurred on a dip slope of shale and slate. The geologic structures of the landslide was observed on the side flanks of the landslide, which indicated that the beds had been buckled gravitationally beforehand and the sliding surface was made along the bedding plane and a joint parallel to the slope surface. The buckling

Wavefront analysis from its slope data

NASA Astrophysics Data System (ADS)

Mahajan, Virendra N.; Acosta, Eva

2017-08-01

In the aberration analysis of a wavefront over a certain domain, the polynomials that are orthogonal over and represent balanced wave aberrations for this domain are used. For example, Zernike circle polynomials are used for the analysis of a circular wavefront. Similarly, the annular polynomials are used to analyze the annular wavefronts for systems with annular pupils, as in a rotationally symmetric two-mirror system, such as the Hubble space telescope. However, when the data available for analysis are the slopes of a wavefront, as, for example, in a Shack- Hartmann sensor, we can integrate the slope data to obtain the wavefront data, and then use the orthogonal polynomials to obtain the aberration coefficients. An alternative is to find vector functions that are orthogonal to the gradients of the wavefront polynomials, and obtain the aberration coefficients directly as the inner products of these functions with the slope data. In this paper, we show that an infinite number of vector functions can be obtained in this manner. We show further that the vector functions that are irrotational are unique and propagate minimum uncorrelated additive random noise from the slope data to the aberration coefficients.

Patella height is not altered by descending medial open-wedge high tibial osteotomy (HTO) compared to ascending HTO.

PubMed

Krause, Matthias; Drenck, Tobias Claus; Korthaus, Alexander; Preiss, Achim; Frosch, Karl-Heinz; Akoto, Ralph

2018-06-01

The primary purpose of the study was to gain insight into geometric changes of the patellar height (PH) and posterior tibial slope (PTS) after a biplanar ascending medial open-wedge high tibial osteotomy (HTO) compared to biplanar descending medial open-wedge HTO in patients with genu varum. Sixty-four patients (mean age 45.2 ± 8.7 years, females n = 24, males n = 40) with varus malalignment and medial gonarthrosis were retrospectively studied. Patients received either a biplanar ascending or descending medial open-wedge HTO. Radiographic analysis included the assessment of standing total leg axis, PH, and PTS prior to and after surgery. In the ascending HTO group, PH decreased significantly by 4.0% (p = 0.037, Caton-Deschamps index) after an average leg axis valgus-producing correction of 7.1° ± 2.8°. In the descending HTO group, with an average leg axis correction of 7.0° ± 3.7°, there were no significant PH changes. There were no significant differences between the ascending and descending HTO groups regarding PTS or leg axis. The mean post-operative leg axis between ascending (1.6° ± 1.9°) and descending HTO (1.9° ± 2.4°) was not significantly different. Compared to the biplanar ascending medial open-wedge HTO, the descending HTO did not influence patella height or increase the posterior tibial slope. In order to respect patellofemoral and slope-related knee kinematics, a biplanar descending medial open-wedge HTO has proven useful to control patella height and posterior tibial slope. These findings underscore the importance of the preoperative patella height assessment in the osteotomy planning and subsequent choice of the biplanar osteotomy direction. IV.

The open sea as the main source of methylmercury in the water column of the Gulf of Lions (Northwestern Mediterranean margin)

NASA Astrophysics Data System (ADS)

Cossa, Daniel; Durrieu de Madron, Xavier; Schäfer, Jörg; Lanceleur, Laurent; Guédron, Stéphane; Buscail, Roselyne; Thomas, Bastien; Castelle, Sabine; Naudin, Jean-Jacques

2017-02-01

Despite the ecologic and economical importance of coastal areas, the neurotoxic bioaccumulable monomethylmercury (MMHg) fluxes within the ocean margins and exchanges with the open sea remain unassessed. The aim of this paper is to address the questions of the abundance, distribution, production and exchanges of methylated mercury species (MeHgT), including MMHg and dimethylmercury (DMHg), in the waters, atmosphere and sediments of the Northwestern Mediterranean margin including the Rhône River delta, the continental shelf and its slope (Gulf of Lions) and the adjacent open sea (North Gyre). Concentrations of MeHgT ranged from <0.02 to 0.48 pmol L-1 with highest values associated with the oxygen-deficient zone of the open sea. The methylated mercury to total mercury proportion (MeHgT/HgT) increased from 2% to 4% in the Rhône River to up to 30% (averaging 18%) in the North Gyre waters, whereas, within the shelf waters, MeHgT/HgT proportions were the lowest (1-3%). We calculate that the open sea is the major source of MeHgT for the shelf waters, with an annual flux estimated at 0.68 ± 0.12 kmol a-1 (i.e., equivalent to 12% of the HgT flux). This MeHgT influx is more than 80 times the direct atmospheric deposition or the in situ net production, more than 40 times the estimated "maximum potential" annual efflux from shelf sediment, and more than 7 times that of the continental sources. In the open sea, ratios of MMHg/DMHg in waters were always <1 and minimum in the oxygen deficient zones of the water column, where MeHg concentrations are maximum. This observation supports the idea that MMHg could be a degradation product of DMHg produced from inorganic divalent Hg.

Potential of airborne LiDAR data analysis to detect subtle landforms of slope failure: Portainé, Central Pyrenees

NASA Astrophysics Data System (ADS)

Ortuño, María; Guinau, Marta; Calvet, Jaume; Furdada, Glòria; Bordonau, Jaume; Ruiz, Antonio; Camafort, Miquel

2017-10-01

Slope failures have been traditionally detected by field inspection and aerial-photo interpretation. These approaches are generally insufficient to identify subtle landforms, especially those generated during the early stages of failures, and particularly where the site is located in forested and remote terrains. We present the identification and characterization of several large and medium size slope failures previously undetected within the Orri massif, Central Pyrenees. Around 130 scarps were interpreted as being part of Rock Slope Failures (RSFs), while other smaller and more superficial failures were interpreted as complex movements combining colluvium slow flow/slope creep and RSFs. Except for one of them, these slope failures had not been previously detected, albeit they extend across a 15% of the studied region. The failures were identified through the analysis of a high-resolution (1 m) LIDAR-derived bare earth Digital Elevation Model (DEM). Most of the scarps are undetectable either by fieldwork, photo interpretation or 5 m resolution topography analysis owing to their small heights (0.5 to 2 m) and their location within forest areas. In many cases, these landforms are not evident in the field due to the presence of other minor irregularities in the slope and the lack of open views due to the forest. 2D and 3D visualization of hillshade maps with different sun azimuths provided an overall picture of the scarp assemblage and permitted a more complete analysis of the geometry of the scarps with respect to the slope and the structural fabric. The sharpness of some of the landforms suggests ongoing activity, which should be explored in future detailed studies in order to assess potential hazards affecting the Portainé ski resort. Our results reveal that close analysis of the 1 m LIDAR-derived DEM can significantly help to detect early-stage slope deformations in high mountain regions, and that expert judgment of the DEM is essential when dealing with subtle

Monoplanar versus biplanar medial open-wedge proximal tibial osteotomy for varus gonarthrosis: a comparison of clinical and radiological outcomes.

PubMed

Elmalı, Nurzat; Esenkaya, Irfan; Can, Murat; Karakaplan, Mustafa

2013-12-01

We compared clinical and radiological results of two proximal tibial osteotomy (PTO) techniques: monoplanar medial open-wedge osteotomy and biplanar retrotubercle medial open-wedge osteotomy, stabilised by a wedged plate. We evaluated 88 knees in 78 patients. Monoplanar medial open-wedge PTO was performed on 56 knees in 50 patients with a mean age of 55 ± 9 years. Biplanar retrotubercle medial open-wedge PTO was performed on 32 knees in 28 patients with a mean age of 57 ± 7 years. Mean follow-up periods were 40.6 ± 7 months for the monoplanar PTO group and 38 ± 5 months for the biplanar retrotubercle PTO group. Clinical outcome was evaluated using the hospital for special surgery scoring system, and radiological outcome was evaluated by the measurements of femorotibial angle (FTA), patellar height and tibial slope changes. In both groups, post-operative HSS scores increased significantly. No significant difference was found between groups in FTA alteration, but the FTA decreased significantly in both groups. Patellar index ratios decreased significantly in the monoplanar PTO group (Insall-Salvati Index by 0.07, Blackburne-Peel Index by 0.07), but not in the biplanar retrotubercle PTO group. Tibial slopes were increased significantly in the monoplanar PTO group, but not in the retrotubercle PTO group. Biplanar retrotubercle medial open-wedge osteotomy and monoplanar medial open-wedge osteotomy are both clinically effective for the treatment for varus gonarthrosis. Retrotubercle osteotomy also prevents patella infera and tibial slope changes radiologically.

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.

Learning Non-Adjacent Regularities at Age 0 ; 7

ERIC Educational Resources Information Center

Gervain, Judit; Werker, Janet F.

2013-01-01

One important mechanism suggested to underlie the acquisition of grammar is rule learning. Indeed, infants aged 0 ; 7 are able to learn rules based on simple identity relations (adjacent repetitions, ABB: "wo fe fe" and non-adjacent repetitions, ABA: "wo fe wo", respectively; Marcus et al., 1999). One unexplored issue is…

Slopes To Prevent Trapping of Bubbles in Microfluidic Channels

NASA Technical Reports Server (NTRS)

Greer, Harold E.; Lee, Michael C.; Smith, J. Anthony; Willis, Peter A.

2010-01-01

The idea of designing a microfluidic channel to slope upward along the direction of flow of the liquid in the channel has been conceived to help prevent trapping of gas bubbles in the channel. In the original application that gave rise to this idea, the microfluidic channels are parts of micro-capillary electrophoresis (microCE) devices undergoing development for use on Mars in detecting compounds indicative of life. It is necessary to prevent trapping of gas bubbles in these devices because uninterrupted liquid pathways are essential for sustaining the electrical conduction and flows that are essential for CE. The idea is also applicable to microfluidic devices that may be developed for similar terrestrial microCE biotechnological applications or other terrestrial applications in which trapping of bubbles in microfluidic channels cannot be tolerated. A typical microCE device in the original application includes, among other things, multiple layers of borosilicate float glass wafers. Microfluidic channels are formed in the wafers, typically by use of wet chemical etching. The figure presents a simplified cross section of part of such a device in which the CE channel is formed in the lowermost wafer (denoted the channel wafer) and, according to the present innovation, slopes upward into a via hole in another wafer (denoted the manifold wafer) lying immediately above the channel wafer. Another feature of the present innovation is that the via hole in the manifold wafer is made to taper to a wider opening at the top to further reduce the tendency to trap bubbles. At the time of reporting the information for this article, an effort to identify an optimum technique for forming the slope and the taper was in progress. Of the techniques considered thus far, the one considered to be most promising is precision milling by use of femtosecond laser pulses. Other similar techniques that may work equally well are precision milling using a focused ion beam, or a small diamond

GIS/RS-based Rapid Reassessment for Slope Land Capability Classification

NASA Astrophysics Data System (ADS)

Chang, T. Y.; Chompuchan, C.

2014-12-01

Farmland resources in Taiwan are limited because about 73% is mountainous and slope land. Moreover, the rapid urbanization and dense population resulted in the highly developed flat area. Therefore, the utilization of slope land for agriculture is more needed. In 1976, "Slope Land Conservation and Utilization Act" was promulgated to regulate the slope land utilization. Consequently, slope land capability was categorized into Class I-IV according to 4 criteria, i.e., average land slope, effective soil depth, degree of soil erosion, and parent rock. The slope land capability Class I-VI are suitable for cultivation and pasture. Whereas, Class V should be used for forestry purpose and Class VI should be the conservation land which requires intensive conservation practices. The field survey was conducted to categorize each land unit as the classification scheme. The landowners may not allow to overuse land capability limitation. In the last decade, typhoons and landslides frequently devastated in Taiwan. The rapid post-disaster reassessment of the slope land capability classification is necessary. However, the large-scale disaster on slope land is the constraint of field investigation. This study focused on using satellite remote sensing and GIS as the rapid re-evaluation method. Chenyulan watershed in Nantou County, Taiwan was selected to be a case study area. Grid-based slope derivation, topographic wetness index (TWI) and USLE soil loss calculation were used to classify slope land capability. The results showed that GIS-based classification give an overall accuracy of 68.32%. In addition, the post-disaster areas of Typhoon Morakot in 2009, which interpreted by SPOT satellite imageries, were suggested to classify as the conservation lands. These tools perform better in the large coverage post-disaster update for slope land capability classification and reduce time-consuming, manpower and material resources to the field investigation.

Performance of the Bowen ratio systems on a 22 deg slope

NASA Technical Reports Server (NTRS)

Nie, D.; Flitcroft, I.; Kanemasu, E. T.

1990-01-01

The Bowen ratio energy balance technique was used to assess the energy fluxes on inclined surfaces during the First ISLSCP Field Experiment (FIFE). Since air flow over sloping surface may differ from that over flat terrain, it is important to examine whether Bowen ratio measurements taken on sloping surfaces are valid. In this study, the suitability of using the Bowen ratio technique on sloping surfaces was tested by examining the assumptions that the technique requires for valid measurements. This was accomplished by studying the variation of Bowen ratio measurements along a selected slope at the FIFE site. In September 1988, four Bowen ratio systems were set up in a line along the 22 degree north-facing slope with northerly air flow (wind went up the slope). In July of 1989, six Bowen ratio systems were similarly installed with southerly air flow (the wind went down slope). Results indicated that, at distances between 10 to 40 meters from the top of the slope, no temperature or vapor pressure gradient parallel to the slope was detected. Uniform Bowen ratio values were obtained on the slope, and thus the sensible or latent heat flux should be similar along the slope. This indicates that the assumptions for valid flux measurements are reasonably met at the slope. The Bowen ratio technique should give the best estimates of the energy fluxes on slopes similar to that in this study.

Flow Ejecta and Slope Landslides in Small Crater

NASA Technical Reports Server (NTRS)

1998-01-01

This high resolution picture of a moderately small impact crater on Mars was taken by the Mars Global Surveyor Orbiter Camera (MOC) on October 17, 1997 at 4:11:07 PM PST, during MGS orbit 22. The image covers an area 2.9 by 48.4 kilometers (1.8 by 30 miles) at 9.6 m (31.5 feet) per picture element, and is centered at 21.3 degrees N, 179.8 degrees W, near Orcus Patera. The MOC image is a factor of 15X better than pervious Viking views of this particular crater (left, Viking image 545A49).

The unnamed crater is one of three closely adjacent impact features that display the ejecta pattern characteristic of one type of 'flow-ejecta' crater. Such patterns are considered evidence of fluidized movement of the materials ejected during the cratering event, and are believed to indicate the presence of subsurface ice or liquid water.

Long, linear features of different brightness values can be seen on the on the steep slopes inside and outside the crater rim. This type of feature, first identified in Viking Orbiter images acquired over 20 years ago, are more clearly seen in this new view (about 3 times better than the best previous observations). Their most likely explanation is that small land or dirt slides, initiated by seismic or wind action, have flowed down the steep slopes. Initially dark because of the nature of the surface disturbance, these features get lighter with time as the ubiquitous fine, bright dust settles onto them from the martian atmosphere. Based on estimates of the dust fall-out rate, many of these features are probably only a few tens to hundreds of years old. Thus, they are evidence of a process that is active on Mars today.

Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with

Snow and Frost Depths on North and South Slopes

Treesearch

Richard S. Sartz

1973-01-01

Aspect affects soil frost depth by influencing the amount of solar radiation received at the ground or snow surface. Depending on the conditions, frost can be of equal depth on north and south slopes, deeper on north slopes, or deeper on south slopes. Data illustrate all three conditions

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

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

Mapping on Slope Seepage Problem using Electrical Resistivity Imaging (ERI)

NASA Astrophysics Data System (ADS)

Hazreek, Z. A. M.; Nizam, Z. M.; Aziman, M.; Dan, M. F. Md; Shaylinda, M. Z. N.; Faizal, T. B. M.; Aishah, M. A. N.; Ambak, K.; Rosli, S.; Rais, Y.; Ashraf, M. I. M.; Alel, M. N. A.

2018-04-01

The stability of slope may influenced by several factors such as its geomaterial properties, geometry and environmental factors. Problematic slope due to seepage phenomenon will influenced the slope strength thus promoting to its failure. In the past, slope seepage mapping suffer from several limitation due to cost, time and data coverage. Conventional engineering tools to detect or mapped the seepage on slope experienced those problems involving large and high elevation of slope design. As a result, this study introduced geophysical tools for slope seepage mapping based on electrical resistivity method. Two spread lines of electrical resistivity imaging were performed on the slope crest using ABEM SAS 4000 equipment. Data acquisition configuration was based on long and short arrangement, schlumberger array and 2.5 m of equal electrode spacing interval. Raw data obtained from data acquisition was analyzed using RES2DINV software. Both of the resistivity results show that the slope studied consists of three different anomalies representing top soil (200 – 1000 Ωm), perched water (10 – 100 Ωm) and hard/dry layer (> 200 Ωm). It was found that seepage problem on slope studied was derived from perched water zones with electrical resistivity value of 10 – 100 Ωm. Perched water zone has been detected at 6 m depth from the ground level with varying thickness at 5 m and over. Resistivity results have shown some good similarity output with reference to borehole data, geological map and site observation thus verified the resistivity results interpretation. Hence, this study has shown that the electrical resistivity imaging was applicable in slope seepage mapping which consider efficient in term of cost, time, data coverage and sustainability.

Steady as a rock: Biogeomorphic influence of nurse rocks and slope processes on kūpaoa (Dubautia menziesii) shrubs in Haleakalā Crater (Maui, Hawai'i)

NASA Astrophysics Data System (ADS)

Pérez, Francisco L.

2017-10-01

This study examines biogeomorphic interactions between nurse rocks, slope processes, and 300 kūpaoa (Dubautia menziesii) shrubs in Haleakalā Crater (Maui, Hawai'i). Research objectives were to: assess the association of kūpaoa with substrates upslope and downslope of plants, and proximity to the closest rock uphill; contrast shrub/substrate relationships with site frequency of sediment types; measure surface soil shear-strength and compressibility on 50 paired locations near boulders; and investigate the aggregation characteristics and spatial patterns of kūpaoa in relation to rock and substrate variation. Data analyzed came from three 100-plant surveys at 3 sites: a plant census at 2720-2975 m altitude, and wandering-quarter transects (WQTs) across two areas (2610-2710 m); ground sediment cover was estimated along four phototransects on these sites. Data for the three 100-plant surveys included substrate type-outcrops, blocks, cobbles, pebbles, exposed soil, organic litter-upslope from each plant, and distance to the largest rock upslope. The two surveys examined along WQTs included substrate type found downslope from kūpaoa, plant height, plant diameters across and along the slope, and distance between successively censused plants. Most plants grew downslope of nurse rocks; > 74% were adjacent to blocks or outcrops, and > 17% near cobbles. Plants showed avoidance for finer substrates; only 5.3% and 2.7% grew on/near bare soils and pebbles, respectively. About 92% of kūpaoa were ≤ 10 cm downslope of rocks; > 89% grew ≤ 2 cm away, and 83% in direct contact with a rock. Some seedlings also grew on pukiawe (Leptecophylla tameiameiae) nurse plants. Several stable rock microsites protected plants from disturbance by slope processes causing debris shift. Site sediments were significantly finer than substrates near plants; shrubs grew preferentially adjacent to boulders > 20 cm wide, which were more common near plants than across sites. Soils downslope of 50

Reorienting with terrain slope and landmarks.

PubMed

Nardi, Daniele; Newcombe, Nora S; Shipley, Thomas F

2013-02-01

Orientation (or reorientation) is the first step in navigation, because establishing a spatial frame of reference is essential for a sense of location and heading direction. Recent research on nonhuman animals has revealed that the vertical component of an environment provides an important source of spatial information, in both terrestrial and aquatic settings. Nonetheless, humans show large individual and sex differences in the ability to use terrain slope for reorientation. To understand why some participants--mainly women--exhibit a difficulty with slope, we tested reorientation in a richer environment than had been used previously, including both a tilted floor and a set of distinct objects that could be used as landmarks. This environment allowed for the use of two different strategies for solving the task, one based on directional cues (slope gradient) and one based on positional cues (landmarks). Overall, rather than using both cues, participants tended to focus on just one. Although men and women did not differ significantly in their encoding of or reliance on the two strategies, men showed greater confidence in solving the reorientation task. These facts suggest that one possible cause of the female difficulty with slope might be a generally lower spatial confidence during reorientation.

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...

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 systematic review of definitions and classification systems of adjacent segment pathology.

PubMed

Kraemer, Paul; Fehlings, Michael G; Hashimoto, Robin; Lee, Michael J; Anderson, Paul A; Chapman, Jens R; Raich, Annie; Norvell, Daniel C

2012-10-15

Systematic review. To undertake a systematic review to determine how "adjacent segment degeneration," "adjacent segment disease," or clinical pathological processes that serve as surrogates for adjacent segment pathology are classified and defined in the peer-reviewed literature. Adjacent segment degeneration and adjacent segment disease are terms referring to degenerative changes known to occur after reconstructive spine surgery, most commonly at an immediately adjacent functional spinal unit. These can include disc degeneration, instability, spinal stenosis, facet degeneration, and deformity. The true incidence and clinical impact of degenerative changes at the adjacent segment is unclear because there is lack of a universally accepted classification system that rigorously addresses clinical and radiological issues. A systematic review of the English language literature was undertaken and articles were classified using the Grades of Recommendation Assessment, Development, and Evaluation criteria. RESULTS.: Seven classification systems of spinal degeneration, including degeneration at the adjacent segment, were identified. None have been evaluated for reliability or validity specific to patients with degeneration at the adjacent segment. The ways in which terms related to adjacent segment "degeneration" or "disease" are defined in the peer-reviewed literature are highly variable. On the basis of the systematic review presented in this article, no formal classification system for either cervical or thoracolumbar adjacent segment disorders currently exists. No recommendations regarding the use of current classification of degeneration at any segments can be made based on the available literature. A new comprehensive definition for adjacent segment pathology (ASP, the now preferred terminology) has been proposed in this Focus Issue, which reflects the diverse pathology observed at functional spinal units adjacent to previous spinal reconstruction and balances

Seasonal flows on warm Martian slopes

USGS Publications Warehouse

McEwen, A.S.; Ojha, L.; Dundas, C.M.; Mattson, S.S.; Byrne, S.; Wray, J.J.; Cull, S.C.; Murchie, S.L.; Thomas, N.; Gulick, V.C.

2011-01-01

Water probably flowed across ancient Mars, but whether it ever exists as a liquid on the surface today remains debatable. Recurring slope lineae (RSL) are narrow (0.5 to 5 meters), relatively dark markings on steep (25?? to 40??) slopes; repeat images from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment show them to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock outcrops, often associated with small channels, and hundreds of them form in some rare locations. RSL appear and lengthen in the late southern spring and summer from 48??S to 32??S latitudes favoring equator-facing slopes, which are times and places with peak surface temperatures from ???250 to 300 kelvin. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.

Sediment Transport and Slope Stability of Ship Shoal Borrow Areas for Coastal Restoration of Louisiana

NASA Astrophysics Data System (ADS)

Liu, H.; Xu, K.; Bentley, S. J.; Li, C.; Miner, M. D.; Wilson, C.; Xue, Z.

2017-12-01

Sandy barrier islands along Louisiana coast are degrading rapidly due to both natural and anthropogenic factors. Ship Shoal is one of the largest offshore sand resources, and has been used as a borrow area for Caminada Headland Restoration Project. Our knowledge of sediment transport and infilling processes in this new sandy and dynamic borrow area is rather limited. High resolution sub-bottom seismic data, side scan sonar images, multi-beam bathymetry and laser sediment grain size data were used to study seafloor morphological evolution and pit wall stability in response to both physical and geological processes. The multi-beam bathymetry and seismic profiling inside the pit showed that disequilibrium conditions led to rapid infilling in the pits at the beginning, but this process slowed down after the pit slope became stable and topography became smooth. We hypothesize that the erosion of the adjacent seabed sediment by energetic waves and longshore currents, the supply of suspended sediment from the rivers, and the erodible materials produced by local mass wasting on pit walls are three main types of infilling sediments. Compared with mud-capped dredge pits, this sandy dredge pit seems to have more gentle slopes on pit walls, which might be controlled by the angle of repose. Infilling sediment seems to be dominantly sandy, with some mud patches on bathymetric depressions. This study helps us better understand the impacts of mining sediment for coastal restoration and improves sand resource management efforts.

Determination Of Slope Instability Using Spatially Integrated Mapping Framework

NASA Astrophysics Data System (ADS)

Baharuddin, I. N. Z.; Omar, R. C.; Roslan, R.; Khalid, N. H. N.; Hanifah, M. I. M.

2016-11-01

The determination and identification of slope instability are often rely on data obtained from in-situ soil investigation work where it involves the logistic of machineries and manpower, thus these aspects may increase the cost especially for remote locations. Therefore a method, which is able to identify possible slope instability without frequent ground walkabout survey, is needed. This paper presents the method used in prediction of slope instability using spatial integrated mapping framework which applicable for remote areas such as tropical forest and natural hilly terrain. Spatial data such as geology, topography, land use map, slope angle and elevation were used in regional analysis during desktop study. Through this framework, the occurrence of slope instability was able to be identified and was validate using a confirmatory site- specific analysis.

Delayed Acquisition of Non-Adjacent Vocalic Distributional Regularities

ERIC Educational Resources Information Center

Gonzalez-Gomez, Nayeli; Nazzi, Thierry

2016-01-01

The ability to compute non-adjacent regularities is key in the acquisition of a new language. In the domain of phonology/phonotactics, sensitivity to non-adjacent regularities between consonants has been found to appear between 7 and 10 months. The present study focuses on the emergence of a posterior-anterior (PA) bias, a regularity involving two…

Lithospheric structure of the South China Sea and adjacent regions: Results from potential field modelling

NASA Astrophysics Data System (ADS)

Chen, Ming; Fang, Jian; Cui, Ronghua

2018-02-01

This work aims to investigate the crustal and lithospheric mantle thickness of the South China Sea (SCS) and adjacent regions. The crust-mantle interface, average crustal density, and lithospheric mantle base are calculated from free-air gravity anomaly and topographic data using an iterative inversion method. We construct a three-dimensional lithospheric model with different hierarchical layers. The satellite-derived gravity is used to invert the average crustal density and Moho (crust-mantle interface) undulations. The average crustal density and LAB (lithosphere-asthenosphere boundary) depths are further adjusted by topographic data under the assumption of local isostasy. The average difference in Moho depths between this study and the seismic measurement results is <1.5 km. The results show that in oceanic regions, the Moho depths are 7.5-30 km and the LAB depths are 65-120 km. The lithospheric thickness of the SCS basin and the adjacent regions increases from the sea basin to the continental margin with a large gradient in the ocean-continent transition zones. The Moho depths of conjugate plots during the opening of SCS, Zhongsha Islands and Reed Bank, reveal the asymmetric spreading pattern of SCS seafloor spreading. The lithospheric thinning pattern indicate two different spreading directions during seafloor spreading, which changed from N-S to NW-SE after the southward transition of the spreading axis. The lithosphere of the SCS basin and adjacent regions indicate that the SCS basin is a young basin with a stable interior lithosphere.

Sediment Pathways Across Trench Slopes: Results From Numerical Modeling

NASA Astrophysics Data System (ADS)

Cormier, M. H.; Seeber, L.; McHugh, C. M.; Fujiwara, T.; Kanamatsu, T.; King, J. W.

2015-12-01

Until the 2011 Mw9.0 Tohoku earthquake, the role of earthquakes as agents of sediment dispersal and deposition at erosional trenches was largely under-appreciated. A series of cruises carried out after the 2011 event has revealed a variety of unsuspected sediment transport mechanisms, such as tsunami-triggered sheet turbidites, suggesting that great earthquakes may in fact be important agents for dispersing sediments across trench slopes. To complement these observational data, we have modeled the pathways of sediments across the trench slope based on bathymetric grids. Our approach assumes that transport direction is controlled by slope azimuth only, and ignores obstacles smaller than 0.6-1 km; these constraints are meant to approximate the behavior of turbidites. Results indicate that (1) most pathways issued from the upper slope terminate near the top of the small frontal wedge, and thus do not reach the trench axis; (2) in turn, sediments transported to the trench axis are likely derived from the small frontal wedge or from the subducting Pacific plate. These results are consistent with the stratigraphy imaged in seismic profiles, which reveals that the slope apron does not extend as far as the frontal wedge, and that the thickness of sediments at the trench axis is similar to that of the incoming Pacific plate. We further applied this modeling technique to the Cascadia, Nankai, Middle-America, and Sumatra trenches. Where well-defined canyons carve the trench slopes, sediments from the upper slope may routinely reach the trench axis (e.g., off Costa Rica and Cascadia). In turn, slope basins that are isolated from the canyons drainage systems must mainly accumulate locally-derived sediments. Therefore, their turbiditic infill may be diagnostic of seismic activity only - and not from storm or flood activity. If correct, this would make isolated slope basins ideal targets for paleoseismological investigation.

The relevance of the slope for concentration-effect relations

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

Schobben, H.P.M.; Smit, M.; Schobben, J.H.M.

1995-12-31

Risk analysis is mostly based on a comparison of one value for the exposure to a chemical (PEC) and one value for the sensitivity of biota (NEC). This method enables the determination of an effect to be expected, but it is not possible to quantify the magnitude of that effect. Moreover, it is impossible to estimate the effect of a combination of chemicals. Therefore, it is necessary to use a mathematical function to describe the relation between a concentration and the subsequent effect. These relations are typically based on a log normal or log logistic distribution of the sensitivity ofmore » individuals of a species. This distribution is characterized by the median sensitivity (EC{sub 50}) and the variation between the sensitivity of individuals (being a measure for the slope of the relation). Presently the attention is focused on the median, while the slope might be even more important. Relevant exposure concentrations are typically in the range which are found in the left tail of the sensitivity distribution. In this study the slope was determined for 250 chemical-species combinations. The data were derived from original experiments and from literature. The slope is highly dependent on the exposure time; the shorter the exposure time the steeper the slope. If data for a standard exposure time [96 hours] are considered, the total variation in slope can partly be explained by the groups of organisms and chemicals. The slope for heavy metals tends to be less steep as compared to the slope of narcotic organic compounds. The slope for fish and molluscs is steeper than for crustaceans. The results of this study are presently applied in a number of risk analysis studies.« less

The world is not flat: can people reorient using slope?

PubMed

Nardi, Daniele; Newcombe, Nora S; Shipley, Thomas F

2011-03-01

Studies of spatial representation generally focus on flat environments and visual input. However, the world is not flat, and slopes are part of most natural environments. In a series of 4 experiments, we examined whether humans can use a slope as a source of allocentric, directional information for reorientation. A target was hidden in a corner of a square, featureless enclosure tilted at a 5° angle. Finding it required using the vestibular, kinesthetic, and visual cues associated with the slope gradient. In Experiment 1, the overall sample performed above chance, showing that slope is sufficient for reorientation in a real environment. However, a sex difference emerged; men outperformed women by 1.4 SDs because they were more likely to use a slope-based strategy. In Experiment 2, attention was drawn to the slope, and participants were prompted to rely on it to solve the task; however, men still outperformed women, indicating a greater ability to use slope. In Experiment 3, we excluded the possibility that women's disadvantage was due to wearing heeled footwear. In Experiment 4, women required more time than men to identify the uphill direction of the slope gradient; this suggests that, in a bottom-up fashion, a perceptual or attentional difficulty underlies women's disadvantage in the ability to use slope and their decreased reliance on this cue. Overall, a bi-coordinate representation was used to find the goal: The target was encoded primarily with respect to the vertical axis and secondarily with respect to the orthogonal axis of the slope. 2011 APA, all rights reserved

Role of slope on infiltration: A review

NASA Astrophysics Data System (ADS)

Morbidelli, Renato; Saltalippi, Carla; Flammini, Alessia; Govindaraju, Rao S.

2018-02-01

Partitioning of rainfall at the soil-atmosphere interface is important for both surface and subsurface hydrology, and influences many events of major hydrologic interest such as runoff generation, aquifer recharge, and transport of pollutants in surface waters as well as the vadose zone. This partitioning is achieved through the process of infiltration that has been widely investigated at the local scale, and more recently also at the field scale, by models that were designed for horizontal surfaces. However, infiltration, overland flows, and deep flows in most real situations are generated by rainfall over sloping surfaces that bring in additional effects. Therefore, existing models for local infiltration into homogeneous and layered soils and those as for field-scale infiltration, have to be adapted to account for the effects of surface slope. Various studies have investigated the role of surface slope on infiltration based on a theoretical formulations for the dynamics of infiltration, extensions of the Green-Ampt approach, and from laboratory and field experiments. However, conflicting results have been reported in the scientific literature on the role of surface slope on infiltration. We summarize the salient points from previous studies and provide plausible reasons for discrepancies in conclusions of previous authors, thus leading to a critical assessment of the current state of our understanding on this subject. We offer suggestions for future efforts to advance our knowledge of infiltration over sloping surfaces.

Multiple slope failures shaped the lower continental slope offshore NW Svalbard in the Fram Strait

NASA Astrophysics Data System (ADS)

Osti, Giacomo; Mienert, Jürgen; Forwick, Matthias; Sverre Laberg, Jan

2016-04-01

Bathymetry data show that the lower slope (between 1300 m and 3000 m water depth) of the NW-Svalbard passive margin has been affected by multiple slope failure events. The single events differ in terms of extension, volume of mobilized sediments, morphology of the slide scar, run-out distance and age. As for several mega-scale and minor Arctic slides, the trigger mechanism is still speculative and may include high sedimentation rates, dissociation of gas hydrates, excess pore pressure, or earthquakes caused by isostatic rebound. In this study, we discuss the potential trigger mechanisms that have led to the multiple slope failure events within what we suggest to be named the Fram Strait Slide Complex. The slide complex lies in proximity to the tectonically active Spitsbergen Fracture Zone where earthquakes events, occurrences of potential weak layers in the sediment column, low sedimentation rates, and extended gas hydrate-bearing sediments may all have contributed to the causes leading to multiple slope failures. Preliminary results obtained from 14C dating on N. pachyderma sin. from sediment cores from the Spitsbergen Fracture Zone slides (SFZS 1 and 2), coupled with sub-bottom profiler data (frequency 9 to 15 KHz) show that the two shallowest glide planes within one of the observed slide scars failed ~100,000 and ~115,000 yr BP. Whilst SFZS 1 affected an area of 750 km2 mobilizing a total sediment volume of 40 km3, SFZS 2 moved an area of 230 km2 with a sediment volume of 4.5 km3.

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.

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…

The Slope Test: Applications in Formative Evaluation.

ERIC Educational Resources Information Center

Baggaley, Jon; Brauer, Aaron-Henry

1989-01-01

Discusses problems with formative evaluation of educational materials and examines the slope test when used in a pretest/posttest multiple group (PPMG) design to adjust posttest scores treatment interaction studies. An example is given of the utility of the slope test and analysis of covariance procedure using an educational film about AIDS. (five…

Capturing pre-failure signs of slope instability using multi-temporal interferometry and Sentinel-1 data

NASA Astrophysics Data System (ADS)

Wasowski, Janusz; Bovenga, Fabio; Nitti, Davide Oscar; Tijani, Khalid; Morea, Alberto; Nutricato, Raffaele; Chiaradia, Maria Teresa

2017-04-01

The shorter repeat cycle (6 days since October 2016) and regularity of acquisitions of Sentinel-1A/B with respect to earlier European Space Agency (ESA) satellites with C-band sensors (ERS1/2, ENVISAT) represent the key advantages for the research-oriented and practical applications of multi-temporal interferometry (MTI). The applicability of the Interferometric Wide Swath acquisition mode of Sentinel-1 (images covering a 250 km swath on the ground) to regional scale slope instability detection through MTI has already been demonstrated, e.g., via studies of landslide-prone areas in Italy. Here we focus on the potential of Sentinel-1 data for local (site-specific), MTI-based monitoring and capturing pre-failure signs of slope instability, by exploiting the Persistent and Distributed Scatterers processing capability of the SPINUA algorithm. In particular, we present an example of a retrospective study of a large (over 2 km long) landslide, which took place in 2016 in an active open-cast coal mine in central Europe. This seemingly sudden failure caused destruction of the mining equipment, blocked the mining operations thereby resulting in significant economic losses. For the study, we exploited over 60 Sentinel-1A/B images acquired since November 2014. The MTI results furnished a valuable overview of the ground instability/stability conditions within and around the active mine, even though considerable spatial gaps in information were encountered due to surface disturbance by mining operations. Significantly, the ground surface displacement time series revealed that the 2016 slope failure was preceded by very slow (generally 1-3 cm/yr) creep-like deformations, already present in 2014. The MTI results also indicated that the slope experienced a phase of accelerated movement several weeks prior to the landslide event. Furthermore, the spatio-temporal analysis of interferometric coherence changes in the unstable area (mapped on Sentinel-2 Bottom Of Atmosphere reflectance

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.

Experimental wave attenuation study over flexible plants on a submerged slope

NASA Astrophysics Data System (ADS)

Yin, Zegao; Yang, Xiaoyu; Xu, Yuanzhao; Ding, Meiling; Lu, Haixiang

2017-12-01

Using plants is a kind of environmentally-friendly coastal protection to attenuate wave energy. In this paper, a set of experiments were conducted to investigate the wave attenuation performance using flexible grasses on a submerged slope, and the wave attenuation coefficient for these experiments was calculated for different still water depths, slope and grass configurations. It was found that the slope plays a significant role in wave attenuation. The wave attenuation coefficient increases with increasing relative row number and relative density. For a small relative row number, the two configurations from the slope top to its toe and from the slope toe to its top performed equally to a large extent. For a medium relative row number, the configuration from the slope toe to its top performed more poorly than that from the slope top to its toe; however, it performed better than that from the slope top to its toe for a high relative row number. With a single row of grasses close to the slope top from the slope toe, the wave attenuation coefficient shows double peaks. With increasing grass rows or still water depth, the grass location corresponding to the maximum wave attenuation coefficient is close to the slope top. The dimensional analysis and the least square method were used to derive an empirical equation of the wave attenuation coefficient considering the effect of relative density, the slope, the relative row number and the relative location of the middle row, and the equation was validated to experimental data.

Statewide Geotechnical Asset Management Program Development : Final Report for Rock Slopes, Unstable Soil Slopes and Embankments, Retaining Walls, and Material Sites

DOT National Transportation Integrated Search

2017-09-05

The Alaska Department of Transportation and Public Facilities (AKDOT&PF) has developed the nations first Geotechnical Asset Management Program. The program encompasses rock slopes, unstable slopes and embankments, retaining walls, and material sou...

Soil Carbon Distribution along a Hill Slope in the Siberian Arctic

NASA Astrophysics Data System (ADS)

Ludwig, S.; Bunn, A. G.; Schade, J. D.

2011-12-01

Arctic ecosystems are warming at an accelerated rate relative to lower latitudes, and this warming has significant global significance. In particular, the thawing of permafrost soils has the potential to strongly influence global carbon cycling and the functioning of terrestrial and aquatic ecosystems. Our overarching scientific goal is to study the impact of thawing permafrost on the transport and processing of carbon and other nutrients as they move with water from terrestrial ecosystems to the Arctic Ocean. Transport of materials from soil to headwater aquatic ecosystems is the first step in this movement. Processes occurring along hill slopes strongly influence the form and concentration of material available for transport. These processes include downhill accumulation of materials due to groundwater movement, or alternatively, local effects of changes in soil and vegetation characteristics. In this project, we studied a hill slope adjacent to a small first order stream in the Kolyma River in Eastern Siberia. We sampled soil at several points along three transects from the top of the hill to the riparian zone by coring and homogenizing the entire active layer at each point. We measured soil organic matter content, soil moisture, water extractable dissolved organic carbon (DOC), total dissolved nitrogen (TDN), NH4, NO3, soluble reactive phosphorus (SRP), and CDOM absorbance. We also measured soil respiration using a laboratory-based biological oxygen demand protocol conducted on soil-water slurries. Active layer depth decreased down the hillslope, while soil moisture, organic matter, and DOC all increased down the hillslope. CDOM absorbance increased downhill, which indicates a decrease in molecular weight of organic compounds at the bottom of the hill. This suggests either an input of newer carbon or processing of high molecular weight DOM down the slope. Soil respiration also increased downhill and was likely driven in part by increased OM in the shallower

Measuring acoustic emissions in an avalanche slope

NASA Astrophysics Data System (ADS)

Reiweger, Ingrid; Schweizer, Jürg

2014-05-01

Measurements of acoustic emissions are a common technique for monitoring damage and predicting imminent failure of a material. Within natural hazards it has already been used to successfully predict the break-off of a hanging glacier. To explore the applicability of the acoustic emission (AE) technique for avalanche prediction, we installed two acoustic sensors (with 30 kHz and 60 kHz resonance frequency) in an avalanche prone slope at the Mittelgrat in the Parsenn ski area above Davos, Switzerland. The slope is north-east facing, frequently wind loaded, and approximately 35° steep. The AE signals - in particular the event energy and waiting time distributions - were compared with slope stability. The latter was determined by observing avalanche activity. The results of two winter's measurements yielded that the exponent β of the inverse cumulative distribution of event energy showed a significant drop (from a value of 3.5 to roughly 2.5) at very unstable conditions, i.e. on the three days during our measurement periods when spontaneous avalanches released on our study slope.

Seasonal flows on warm Martian slopes

USGS Publications Warehouse

McEwen, Alfred S.; Ojha, Lujendra; Dundas, Colin M.; Mattson, Sarah S.; Byrne, Shane; Wray, James J.; Cull, Selby C.; Murchie, Scott L.; Thomas, Nicolas; Gulick, Virginia C.

2011-01-01

Water probably flowed across ancient Mars, but whether it ever exists as a liquid on the surface today remains debatable. Recurring slope lineae (RSL) are narrow (0.5 to 5 meters), relatively dark markings on steep (25° to 40°) slopes; repeat images from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment show them to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock outcrops, often associated with small channels, and hundreds of them form in some rare locations. RSL appear and lengthen in the late southern spring and summer from 48°S to 32°S latitudes favoring equator-facing slopes, which are times and places with peak surface temperatures from ~250 to 300 kelvin. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.

Seasonal flows on warm Martian slopes.

PubMed

McEwen, Alfred S; Ojha, Lujendra; Dundas, Colin M; Mattson, Sarah S; Byrne, Shane; Wray, James J; Cull, Selby C; Murchie, Scott L; Thomas, Nicolas; Gulick, Virginia C

2011-08-05

Water probably flowed across ancient Mars, but whether it ever exists as a liquid on the surface today remains debatable. Recurring slope lineae (RSL) are narrow (0.5 to 5 meters), relatively dark markings on steep (25° to 40°) slopes; repeat images from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment show them to appear and incrementally grow during warm seasons and fade in cold seasons. They extend downslope from bedrock outcrops, often associated with small channels, and hundreds of them form in some rare locations. RSL appear and lengthen in the late southern spring and summer from 48°S to 32°S latitudes favoring equator-facing slopes, which are times and places with peak surface temperatures from ~250 to 300 kelvin. Liquid brines near the surface might explain this activity, but the exact mechanism and source of water are not understood.

Eros: Shape, topography, and slope processes

USGS Publications Warehouse

Thomas, P.C.; Joseph, J.; Carcich, B.; Veverka, J.; Clark, B.E.; Bell, J.F.; Byrd, A.W.; Chomko, R.; Robinson, M.; Murchie, S.; Prockter, L.; Cheng, A.; Izenberg, N.; Malin, M.; Chapman, C.; McFadden, L.A.; Kirk, R.; Gaffey, M.; Lucey, P.G.

2002-01-01

Stereogrammetric measurement of the shape of Eros using images obtained by NEAR's Multispectral Imager provides a survey of the major topographic features and slope processes on this asteroid. This curved asteroid has radii ranging from 3.1 to 17.7 km and a volume of 2535 ?? 20 km3. The center of figure is within 52 m of the center of mass provided by the Navigation team; this minimal difference suggests that there are only modest variations in density or porosity within the asteroid. Three large depressions 10, 8, and 5.3 km across represent different stages of degradation of large impact craters. Slopes on horizontal scales of ???300 m are nearly all less than 35??, although locally scarps are much steeper. The area distribution of slopes is similar to those on Ida, Phobos, and Deimos. Regions that have slopes greater than 25?? have distinct brighter markings and have fewer large ejecta blocks than do flatter areas. The albedo patterns that suggest downslope transport of regolith have sharper boundaries than those on Phobos, Deimos, and Gaspra. The morphology of the albedo patterns, their lack of discrete sources, and their concentration on steeper slopes suggest transport mechanisms different from those on the previously well-observed small bodies, perhaps due to a reduced relative effectiveness of impact gardening on Eros. Regolith is also transported in talus cones and in connected, sinuous paths extending as much as 2 km, with some evident as relatively darker material. Talus material in at least one area is a discrete superposed unit, a feature not resolved on other small bodies. Flat-floored craters that apparently contain ponded material also suggest discrete units that are not well mixed by impacts. ?? 2002 Elsevier Science (USA).

Rippled Surfaces on a Slope in Coloe Fossae

NASA Image and Video Library

2014-01-09

This observation from NASA Mars Reconnaissance Orbiter shows a set of landforms that appears to form a nested chevron pattern on a slope in Coloe Fossae. Interestingly, nearby surfaces on the same slope are all parallel.

Rock slope design guide.

DOT National Transportation Integrated Search

2011-04-01

This Manual is intended to provide guidance for the design of rock cut slopes, rockfall catchment, and : rockfall controls. Recommendations presented in this manual are based on research presented in Shakoor : and Admassu (2010) entitled Rock Slop...

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 ...

Unstable slope management program.

DOT National Transportation Integrated Search

2009-08-01

This Rapid Response Project gathered information on existing unstable slope management programs, with a : focus on asset management practices in the United States and overseas. On the basis of this study, the research : team summarized and recommende...

Velocity of water flow along saturated loess slopes under erosion effects

NASA Astrophysics Data System (ADS)

Huang, Yuhan; Chen, Xiaoyan; Li, Fahu; Zhang, Jing; Lei, Tingwu; Li, Juan; Chen, Ping; Wang, Xuefeng

2018-06-01

Rainfall or snow-melted water recharge easily saturates loose top soils with a less permeable underlayer, such as cultivated soil slope and partially thawed top soil layer, and thus, may influence the velocity of water flow. This study suggested a methodology and device system to supply water from the bottom soil layer at the different locations of slopes. Water seeps into and saturates the soil, when the water level is controlled at the same height of the soil surface. The structures and functions of the device, the components, and the operational principles are described in detail. A series of laboratory experiments were conducted under slope gradients of 5°, 10°, 15°, and 20° and flow rates of 2, 4, and 8 L min-1 to measure the water flow velocities over eroding and non-eroded loess soil slopes, under saturated conditions by using electrolyte tracing. Results showed that flow velocities on saturated slopes were 17% to 88% greater than those on non-saturated slopes. Flow velocity increased rapidly under high flow rates and slope gradients. Saturation conditions were suitable in maintaining smooth rill geomorphology and causing fast water flow. The saturated soil slope had a lubricant effect on the soil surface to reduce the frictional force, resulting in high flow velocity. The flow velocities of eroding rills under different slope gradients and flow rates were approximately 14% to 33% lower than those of non-eroded rills on saturated loess slopes. Compared with that on a saturated loess slope, the eroding rill on a non-saturated loess slope can produce headcuts to reduce the flow velocity. This study helps understand the hydrodynamics of soil erosion and sediment transportation of saturated soil slopes.

Influence of slope on subtalar pronation in submaximal running performance

PubMed Central

de Oliveira, Vinicius Machado; Detoni, Guilherme Cesca; Ferreira, Cristhian; Portela, Bruno Sergio; Queiroga, Marcos Roberto; Tartaruga, Marcus Peikriszwili

2013-01-01

OBJECTIVE : To investigate the slope influence on the maximal subtalar pronation in submaximal running speeds. METHODS : Sixteen endurance runners participated of a running economy (RE) test in a treadmill with different slopes (+1%, +5%, +10%, +15%). For each slope a 4-minute run was performed with no rest break for the purpose of measuring the magnitude of kinematic variables by means of a high frequency video camera positioned in a frontal-posterior plane of the individual. RESULTS : No significant differences were verified in maximal subtalar pronation between legs and between the slopes adopted, showing that changes of running technique due to modifications of slope aren't enough to modify the behavior of maximum subtalar pronation. CONCLUSION : The subtalar pronation is independent of slope, which may be influenced by other intervening variables. Level of Evidence II, Diagnostic Study PMID:24453662

Harvesting impacts on steep slopes in Virginia

Treesearch

W.B. Stuart; S.L. Carr

1991-01-01

Ten tracts in the mountains of western Virginia were intensively sampled to determine the type and extent of soil disturbance from ground-based logging and the attendant erosion risk. Average slopes for the tracts ranged from 21 to 43 percent. Logged slopes exceeded 50 percent. All tracts surveyed were logged prior to the push for voluntary Best Management Practices...

Impact of climate change on the operation of ski slopes in South Korea

NASA Astrophysics Data System (ADS)

Kim, S.; Park, J. H.; Lee, D. K.

2017-12-01

The purpose of this study is to predict changes in the operation of ski slopes due to climate change and offer meaningful implications that the ski industry can refer to when preparing to address climate change. All 17 ski resorts in South Korea were selected as study sites. To determine the weather and managerial conditions for the operation of ski slopes, interviews with operators and a review of past weather and operational conditions were conducted. To project future changes in the season of operation for ski slopes, future weather data for the 2030s, 2060s, and 2090s from RCP scenarios were adapted to the conditions for the operation of ski slopes.The study found that the artificial snowmaking begins when the temperature reaches -2 °C, the slope is opened 9 days after artificial snowmaking starts, and the slope is closed when the temperature reaches 0 °C. By applying future weather data to these conditions, it is estimated that the ski season will decrease in the future as follows: from around 130 days at present to around 120 days based on RCP 2.0 and RCP 6.0, around 130 days based on RCP 4.5, and 90 days based on RCP 8.5 in the areas where the average temperature of the ski season is below -2 °C; from around 120 days at present to around 120 days based on RCP 2.0 and 4.5, around 100-days based on RCP 6.0, and 60 days based on RCP 8.5 in the areas where the average temperature of the ski season is below 0 °C; from around 90 days at present to around 80 days based on RCP 2.0, around 90 days based on RCP 4.5, around 50 days based on RCP 6.0, and 10 days based on RCP 8.5 in the areas where the average temperature of the ski season is above 0 °C. In addition, it is also estimated that in the 2090s, 16 of 17 ski resorts can survive based on RCP 2.6 and RCP 4.5, 13 ski resorts can survive based on RCP 6.0, and none of the resorts can survive based on RCP 8.5, according to the 100-days rule, which is the minimum required duration of the operation of ski resorts

Influence of Weathering Depth and Fracture Intensity to Cut-slope Movements

NASA Astrophysics Data System (ADS)

Yoon, W. S.; Choi, J. W.; Jeong, U.; Kim, J. H.

2003-04-01

Generally, Failure modes in cut slopes are triggered by combination of various failure factors which have different effects on failure modes according to ground condition. It is, therefore, important to identify the behavioural characteristic of cut slope in that they reflect the failure mechanism. From the careful field investigation for 373 road cuts along the national highway in Korea, we analysed various types of failure modes for different ground conditions. The ground conditions which control failure modes of cut slopes and their related failure factors are dependent on weathering (or soil) depth and intensity of discontinuities in cut slopes. Firstly, the ratio of the soil depth and slope height (soil depth ratio; SR) is important parameter to classify ground conditions into soil-like masses and rock masses. When a SR value is greater than 0.4, sliding failures on discontinuities do not occur. In this case, weathering condition, slope gradient and external rainfall play a key role on failure factors of cut-slope. The proposed 0.4, therefore, is the critical SR value to identify the soil-like masses and rock masses. Secondly, Intensity of discontinuities is expressed by block size ratio (BR), which is defined by the ratio of block size index (Ib; ISRM (1978)) and slope height. For a rock slope (SR<0.4), when BR is greater than 0.01, key failure modes in a cut slope are wedge sliding, fall and topple. In this case, attitudes and shear strength of discontinuities play an important role on behaviour of cut-slope. When BR is less than 0.01, however, behaviour of cut slope shows circular sliding and surface failure like soil-like mass. To sum up, we could divide the ground conditions in cut-slope into 3 classes on the basis of SR (soil depth ratio) and BR (block size ratio); JRM (joint rock mass), HRM (highly fractured rock mass) and SLM (soil-like mass). Moreover, to evaluate the stability of cut-slope reasonably, it needs new evaluating categories having

Shoreline Erosion and Slope Failure Detection over Southwest Lakeshore Michigan using Temporal Radar and Digital Elevation Model

NASA Astrophysics Data System (ADS)

Sataer, G.; Sultan, M.; Yellich, J. A.; Becker, R.; Emil, M. K.; Palaseanu, M.

2017-12-01

Throughout the 20th century and into the 21st century, significant losses of residential, commercial and governmental property were reported along the shores of the Great Lakes region due to one or more of the following factors: high lake levels, wave actions, groundwater discharge. A collaborative effort (Western Michigan University, University of Toledo, Michigan Geological Survey [MGS], United States Geological Survey [USGS], National Oceanographic and Atmospheric Administration [NOAA]) is underway to examine the temporal topographic variations along the shoreline and the adjacent bluff extending from the City of South Haven in the south to the City of Saugatuck in the north within the Allegan County. Our objectives include two main tasks: (1) identification of the timing of, and the areas, witnessing slope failure and shoreline erosion, and (2) investigating the factors causing the observed failures and erosion. This is being accomplished over the study area by: (1) detecting and measuring slope subsidence rates (velocities along line of site) and failures using radar interferometric persistent scatter (PS) techniques applied to ESA's European Remote Sensing (ERS) satellites, ERS-1 and -2 (spatial resolution: 25 m) that were acquired in 1995 to 2007, (2) extracting temporal high resolution (20 cm) digital elevation models (DEM) for the study area from temporal imagery acquired by Unmanned Aerial Vehicles (UAVs), and applying change detection techniques to the extracted DEMs, (3) detecting change in elevation and slope profiles extracted from two LIDAR Coastal National Elevation Database (CoNED) DEMs (spatial resolution: 0.5m), acquired on 2008 and 2012, and (4) spatial and temporal correlation of the detected changes in elevation with relevant data sets (e.g., lake levels, precipitation, groundwater levels) in search of causal effects.

Effects of slope smoothing in river channel modeling

NASA Astrophysics Data System (ADS)

Kim, Kyungmin; Liu, Frank; Hodges, Ben R.

2017-04-01

In extending dynamic river modeling with the 1D Saint-Venant equations from a single reach to a large watershed there are critical questions as to how much bathymetric knowledge is necessary and how it should be represented parsimoniously. The ideal model will include the detail necessary to provide realism, but not include extraneous detail that should not exert a control on a 1D (cross-section averaged) solution. In a Saint-Venant model, the overall complexity of the river channel morphometry is typically abstracted into metrics for the channel slope, cross-sectional area, hydraulic radius, and roughness. In stream segments where cross-section surveys are closely spaced, it is not uncommon to have sharp changes in slope or even negative values (where a positive slope is the downstream direction). However, solving river flow with the Saint-Venant equations requires a degree of smoothness in the equation parameters or the equation set with the directly measured channel slopes may not be Lipschitz continuous. The results of non-smoothness are typically extended computational time to converge solutions (or complete failure to converge) and/or numerical instabilities under transient conditions. We have investigated using cubic splines to smooth the bottom slope and ensure always positive reference slopes within a 1D model. This method has been implemented in the Simulation Program for River Networks (SPRNT) and is compared to the standard HEC-RAS river solver. It is shown that the reformulation of the reference slope is both in keeping with the underlying derivation of the Saint-Venant equations and provides practical numerical stability without altering the realism of the simulation. This research was supported in part by the National Science Foundation under grant number CCF-1331610.

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.

Objectifying the adjacent and opposite angles: a cultural historical analysis

NASA Astrophysics Data System (ADS)

Daher, Wajeeh; Musallam, Nadera

2018-02-01

The angle topic is central to the development of geometric knowledge. Two of the basic concepts associated with this topic are the adjacent and opposite angles. It is the goal of the present study to analyze, based on the cultural historical semiotics framework, how high-achieving seventh grade students objectify the adjacent and opposite angles' concepts. We videoed the learning of a group of three high-achieving students who used technology, specifically GeoGebra, to explore geometric relations related to the adjacent and opposite angles' concepts. To analyze students' objectification of these concepts, we used the categories of objectification of knowledge (attention and awareness) and the categories of generalization (factual, contextual and symbolic), developed by Radford. The research results indicate that teacher's and students' verbal and visual signs, together with the software dynamic tools, mediated the students' objectification of the adjacent and opposite angles' concepts. Specifically, eye and gestures perceiving were part of the semiosis cycles in which the participating students were engaged and which related to the mathematical signs that signified the adjacent and the opposite angles. Moreover, the teacher's suggestions/requests/questions included/suggested semiotic signs/tools, including verbal signs that helped the students pay attention, be aware of and objectify the adjacent and opposite angles' concepts.

Heliostat field cost reduction by `slope drive' optimization

NASA Astrophysics Data System (ADS)

Arbes, Florian; Weinrebe, Gerhard; Wöhrbach, Markus

2016-05-01

An algorithm to optimize power tower heliostat fields employing heliostats with so-called slope drives is presented. It is shown that a field using heliostats with the slope drive axes configuration has the same performance as a field with conventional azimuth-elevation tracking heliostats. Even though heliostats with the slope drive configuration have a limited tracking range, field groups of heliostats with different axes or different drives are not needed for different positions in the heliostat field. The impacts of selected parameters on a benchmark power plant (PS10 near Seville, Spain) are analyzed.

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

Direction of Auditory Pitch-Change Influences Visual Search for Slope From Graphs.

PubMed

Parrott, Stacey; Guzman-Martinez, Emmanuel; Orte, Laura; Grabowecky, Marcia; Huntington, Mark D; Suzuki, Satoru

2015-01-01

Linear trend (slope) is important information conveyed by graphs. We investigated how sounds influenced slope detection in a visual search paradigm. Four bar graphs or scatter plots were presented on each trial. Participants looked for a positive-slope or a negative-slope target (in blocked trials), and responded to targets in a go or no-go fashion. For example, in a positive-slope-target block, the target graph displayed a positive slope while other graphs displayed negative slopes (a go trial), or all graphs displayed negative slopes (a no-go trial). When an ascending or descending sound was presented concurrently, ascending sounds slowed detection of negative-slope targets whereas descending sounds slowed detection of positive-slope targets. The sounds had no effect when they immediately preceded the visual search displays, suggesting that the results were due to crossmodal interaction rather than priming. The sounds also had no effect when targets were words describing slopes, such as "positive," "negative," "increasing," or "decreasing," suggesting that the results were unlikely due to semantic-level interactions. Manipulations of spatiotemporal similarity between sounds and graphs had little effect. These results suggest that ascending and descending sounds influence visual search for slope based on a general association between the direction of auditory pitch-change and visual linear trend.

Credit PSR. This view looks northeast (54°) at the open ...

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

Credit PSR. This view looks northeast (54°) at the open burn unit as it is seen on approach from Circle Drive. The metal shed in front of the earth mound personnel shield contained controls for a stove that was formerly used to burn scrap propellants in the adjacent pit (see HAER photo CA163-V-1). Regulations changed to permit open pit burning of such materials - Jet Propulsion Laboratory Edwards Facility, Incinerator, Edwards Air Force Base, Boron, Kern County, CA

[Analysis of related factors of slope plant hyperspectral remote sensing].

PubMed

Sun, Wei-Qi; Zhao, Yun-Sheng; Tu, Lin-Ling

2014-09-01

In the present paper, the slope gradient, aspect, detection zenith angle and plant types were analyzed. In order to strengthen the theoretical discussion, the research was under laboratory condition, and modeled uniform slope for slope plant. Through experiments we found that these factors indeed have influence on plant hyperspectral remote sensing. When choosing slope gradient as the variate, the blade reflection first increases and then decreases as the slope gradient changes from 0° to 36°; When keeping other factors constant, and only detection zenith angle increasing from 0° to 60°, the spectral characteristic of slope plants do not change significantly in visible light band, but decreases gradually in near infrared band; With only slope aspect changing, when the dome meets the light direction, the blade reflectance gets maximum, and when the dome meets the backlit direction, the blade reflectance gets minimum, furthermore, setting the line of vertical intersection of incidence plane and the dome as an axis, the reflectance on the axis's both sides shows symmetric distribution; In addition, spectral curves of different plant types have a lot differences between each other, which means that the plant types also affect hyperspectral remote sensing results of slope plants. This research breaks through the limitations of the traditional vertical remote sensing data collection and uses the multi-angle and hyperspectral information to analyze spectral characteristics of slope plants. So this research has theoretical significance to the development of quantitative remote sensing, and has application value to the plant remote sensing monitoring.

Phytoparasitic Nematodes Adjacent to Established Strawberry Plantations

PubMed Central

Crow, R. V.; MacDonald, D. H.

1978-01-01

Plant-nematode populations associated with uncultivated vegetation, adjacent strawberry plants, and alternate crop sites were studied at three locations in Minnesota. At one site (Forest Lake), Paratylenchus projectus, Meloidogyne hapla, and Pratylenchus tenuis were frequently associated with the roots of native vegetation. These nematode species were also present in adjacent strawberry beds. Among alternate crops observed, oats and muskmelon usually supported the fewest nematodes although moderate densities of Xiphinema americanum and P. tenuis were found at one location in plots planted to oats. Pratylenchus tenuis was also found on rye at one location. PMID:19305841

Stability of sulfur slopes on Io

NASA Technical Reports Server (NTRS)

Clow, G. D.; Carr, M. H.

1980-01-01

The mechanical properties of elemental sulfur are such that the upper crust of Io cannot be primarily sulfur. For heat flows in the range 100-1000 ergs/sq cm sec sulfur becomes ductile within several hundred meters of the surface and would prevent the formation of calderas with depths greater than this. However, the one caldera for which precise depth data are available is 2 km deep, and this value may be typical. A study of the mechanical equilibrium of simple slopes shows that the depth to the zone of rapid ductile flow strongly controls the maximum heights for sulfur slopes. Sulfur scarps with heights greater than 1 km will fail for all heat flows greater than 180 ergs/sq cm sec and slope angles greater than 22.5 deg. The observed relief on Io is inconsistent with that anticipated for a predominantly sulfur crust. However, a silicate crust with several percent sulfur included satisfies both the mechanical constraints and the observed presence of sulfur on Io.

An Analysis of Students' Mistakes on Routine Slope Tasks

ERIC Educational Resources Information Center

Cho, Peter; Nagle, Courtney

2017-01-01

This study extends past research on students' understanding of slope by analyzing college students' mistakes on routine tasks involving slope. We conduct quantitative and qualitative analysis of students' mistakes to extract information regarding slope conceptualizations described in prior research. Results delineate procedural proficiencies and…

The Key Factors Analysis of Palisades Temperature in Deep Open-pit Mine

NASA Astrophysics Data System (ADS)

Wang, Yuan; Du, Cuifeng; Jin, Wenbo; Wang, Puyu

2018-01-01

In order to study the key factors of palisades temperature field in a deep open-pit mine in the natural environment, the influence of natural factors on the palisades temperature in a deep open-pit mine were analysed based on the principle of heat transfer. Four typical places with different ways of solar radiation were selected to carry out the field test. The results show that solar radiation, atmospheric temperature, and wind speed are three main factors affecting the temperature of palisades and that the direct sunlight plays a leading role. The time period of the sun shining directly on the shady slope of the palisades is short because of blocking effect, whose temperature changes in a smaller scale. At the same time, the sun slope of the palisades suffers from the solar radiation for a long time, whose temperature changes in a larger scale, and the variation is similar to the air temperature.

Assessment of cropland area on sloping land in DPRK

NASA Astrophysics Data System (ADS)

Kerdiles, H.; Spyratos, S.; Gallego, F. J.

2014-03-01

Following the famines of the mid 1990s, the government of the Democratic People's Republic of Korea (DPRK) authorized cultivation on sloping land before deciding, in the years 2000, to limit this practice on slopes above 15 degrees in order to reduce erosion. There are still many cultivated fields on slopes and their total estimated area ranges from 300,000 ha to more than 2 million ha. This study aims at assessing cropland areas on slopes above 10 and 15 degrees by using high to very high resolution remote sensing satellite imagery. For this purpose, a grid of points was superimposed over the DPRK territory and stratified according to slope, as derived from two DEMs, the 30 m ASTER GDEM V2 and the 3 arc second (~90 m) SRTM Dem V4. A sample of about 2100 points was drawn using an optimal allocation sampling plan, based on a preliminary assessment of the variance of the estimated cropland percentage per class of slope. These 2100 points were interpreted into cropland, no cropland and doubt using mostly Google Earth imagery acquired after 2004. For slopes above 10 degrees, the area cropped was estimated to be around 1,000,000 ha (5.6% CV) and 742,000 ha (8.1% CV) according to the ASTER and SRTM DEM respectively. Above 15 degrees, the estimated cropland area ranges from 360,000 ha (9.7% CV) with SRTM to 540,000 ha (6.6.% CV) with ASTER. To decide between these two estimations, a validation of the two DEMs should be carried out on a region with similar relief. Alternatively, a higher accuracy DEM such as the one to be derived from the TanDEM-X mission in 2014 should provide more accurate estimates of the cropland area on sloping land.

Speaking rate effects on locus equation slope.

PubMed

Berry, Jeff; Weismer, Gary

2013-11-01

A locus equation describes a 1st order regression fit to a scatter of vowel steady-state frequency values predicting vowel onset frequency values. Locus equation coefficients are often interpreted as indices of coarticulation. Speaking rate variations with a constant consonant-vowel form are thought to induce changes in the degree of coarticulation. In the current work, the hypothesis that locus slope is a transparent index of coarticulation is examined through the analysis of acoustic samples of large-scale, nearly continuous variations in speaking rate. Following the methodological conventions for locus equation derivation, data pooled across ten vowels yield locus equation slopes that are mostly consistent with the hypothesis that locus equations vary systematically with coarticulation. Comparable analyses between different four-vowel pools reveal variations in the locus slope range and changes in locus slope sensitivity to rate change. Analyses across rate but within vowels are substantially less consistent with the locus hypothesis. Taken together, these findings suggest that the practice of vowel pooling exerts a non-negligible influence on locus outcomes. Results are discussed within the context of articulatory accounts of locus equations and the effects of speaking rate change.

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

A giant submarine slope failure on the insular slope north of Puerto Rico: A response of Arecibo basin strata to tectonic stress

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

Schwab, W.C.; Danforth, W.W.; Scanlon, K.M.

1990-06-01

An amphitheater-shaped scarp, approximately 55 km across in water depths from about 3,000 m to 6,700 m was imaged on the northern insular slope of Puerto Rico (southern slope of the Puerto Rico Trench) using the GLORIA side-scan sonar system. This scarp represents the removal of more than 1,500 m{sup 3} of Tertiary Arecibo basin strata. The head of the scarp coincides with the location of a fault zone observed on nearby seismic-reflection profiles. Interpretation of the GLORIA imagery, and a review of available bathymetric, geophysical, and stratigraphic data and tectonic-framework models suggest that the scarp formed as a consequencemore » of slope failure induced by tectonic oversteepening of the insular slope. The oversteepening may be a result of the most recent episode of convergence of the Caribbean and North American plates, which began approximately 4 million years ago. The Arecibo basin strata have been tilted approximately 4{degree} to the north and are apparently gravitationally unstable under the present seismic regime. The volume of material involved in this slope failure is comparable to the material displaced in tsunamogenic submarine landslides along the Peru Trench and Hawaiian Ridge. Therefore, if the slope failure north of Puerto Rico was catastrophic, it was large enough to have generated a tsunami that would have flooded the low ground of northern Puerto Rico.« less

Potential Risk Assessment of Mountain Torrent Disasters on Sloping Fields in China

NASA Astrophysics Data System (ADS)

GAO, X.

2017-12-01

China's sloping fields have the problems of low production and serious soil erosion, and mountain torrent disasters will bring more serious soil and water loss to traditional extensive exploitation of sloping field resources. In this paper, China's sloping fields were classified into three grades, such as slightly steep, steep and very steep grade. According to the geological hazards prevention and control regulation, the historical data of China's mountain torrent disasters were spatially interpolated and divided into five classes, such as extremely low, low, middle, high and extremely high level. And the risk level map of mountain torrents was finished in ArcGIS. By using overlaying analysis on sloping fields and risk level map, the potential risk regionalization map of sloping fields in various slope grades was obtained finally. The results shows that the very steep and steep sloping fields are mainly distributed in the first or second stage terraces in China. With the increase of hazard risk level, the area of sloping fields decreases rapidly and the sloping fields in extremely low and low risk levels of mountain torrents reach 98.9%. With the increase of slope grade, the area of sloping fields in various risk levels also declines sharply. The sloping fields take up approximately 60 65% and 26 30% in slightly steep and steep grade areas separately at different risk level. The risk regionalization map can provide effective information for returning farmland to forests or grassland and reducing water and soil erosion of sloping fields in the future.

Bright and Dark Slopes on Ganymede

NASA Technical Reports Server (NTRS)

1997-01-01

Ridges on the edge of Ganymede's north polar cap show bright east-facing slopes and dark west-facing slopes with troughs of darker material below the larger ridges. North is to the top. The bright slopes may be due to grain size differences, differences in composition between the original surface and the underlying material, frost deposition, or illumination effects. The large 2.4 kilometer (1.5 mile) diameter crater in this image shows frost deposits located on the north-facing rim slope, away from the sun. A smaller 675 meter (2200 foot) diameter crater in the center of the image is surrounded by a bright deposit which may be ejecta from the impact. Ejecta deposits such as this are uncommon for small craters on Ganymede. This image measures 18 by 19 kilometers (11 by 12 miles) and has a resolution of 45 meters (148 feet) per pixel. NASA's Galileo spacecraft obtained this image on September 6, 1996 during its second orbit around Jupiter.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

ILS Glide Slope Performance Prediction. Volume B

DTIC Science & Technology

1974-09-01

figures are identical in both volumes. 󈧔. Abottec A mathematical model for predicting the performance of ILS glide slope arrays in the presence of...irregularities on the performance of ILS Glide Slope antenna systems, a mathematical -electromagnetic scattering computer model has been developed. This work was...Antenna ........... 4-4 9. Test Case Results ..................................... r-3 ix PART I. IEO -j 1.INTRODUCTION IA mathematical model has been

Large-area landslide susceptibility with optimized slope-units

NASA Astrophysics Data System (ADS)

Alvioli, Massimiliano; Marchesini, Ivan; Reichenbach, Paola; Rossi, Mauro; Ardizzone, Francesca; Fiorucci, Federica; Guzzetti, Fausto

2017-04-01

A Slope-Unit (SU) is a type of morphological terrain unit bounded by drainage and divide lines that maximize the within-unit homogeneity and the between-unit heterogeneity across distinct physical and geographical boundaries [1]. Compared to other terrain subdivisions, SU are morphological terrain unit well related to the natural (i.e., geological, geomorphological, hydrological) processes that shape and characterize natural slopes. This makes SU easily recognizable in the field or in topographic base maps, and well suited for environmental and geomorphological analysis, in particular for landslide susceptibility (LS) modelling. An optimal subdivision of an area into a set of SU depends on multiple factors: size and complexity of the study area, quality and resolution of the available terrain elevation data, purpose of the terrain subdivision, scale and resolution of the phenomena for which SU are delineated. We use the recently developed r.slopeunits software [2,3] for the automatic, parametric delineation of SU within the open source GRASS GIS based on terrain elevation data and a small number of user-defined parameters. The software provides subdivisions consisting of SU with different shapes and sizes, as a function of the input parameters. In this work, we describe a procedure for the optimal selection of the user parameters through the production of a large number of realizations of the LS model. We tested the software and the optimization procedure in a 2,000 km2 area in Umbria, Central Italy. For LS zonation we adopt a logistic regression model implemented in an well-known software [4,5], using about 50 independent variables. To select the optimal SU partition for LS zonation, we want to define a metric which is able to quantify simultaneously: (i) slope-unit internal homogeneity (ii) slope-unit external heterogeneity (iii) landslide susceptibility model performance. To this end, we define a comprehensive objective function S, as the product of three

Adriatic storm surges and related cross-basin sea-level slope

NASA Astrophysics Data System (ADS)

Međugorac, Iva; Orlić, Mirko; Janeković, Ivica; Pasarić, Zoran; Pasarić, Miroslava

2018-05-01

Storm surges pose a severe threat to the northernmost cities of the Adriatic coast, with Venice being most prone to flooding. It has been noted that some flooding episodes cause significantly different effects along the eastern and western Adriatic coasts, with indications that the difference is related to cross-basin sea-level slope. The present study aims to determine specific atmospheric conditions under which the slope develops and to explore connection with increased sea level along the two coastlines. The analysis is based on sea-level time series recorded at Venice and Bakar over the 1984-2014 interval, from which 38 most intensive storm-surge episodes were selected, and their meteorological backgrounds (ERA-Interim) were studied. The obtained sea-level extremes were grouped into three categories according to their cross-basin sea-level slope: storm surges that slope strongly westward (W type), those that slope eastward (E type) and ordinary storm surges (O type). Results show that the slope is controlled by wind action only, specifically, by the wind component towards a particular coast and by the cross-basin shear of along-basin wind. Meteorological fields were used to force an oceanographic numerical model in order to confirm the empirically established connection between the atmospheric forcing and the slope. Finally, it has been found that the intensity of storm surges along a particular Adriatic coast is determined by an interplay of sea-level slopes in the along and cross-basin directions.

Downward Slope

NASA Technical Reports Server (NTRS)

2004-01-01

This false-color image from NASA's Mars Exploration Rover Opportunity panoramic camera shows a downward view from the rover as it sits at the edge of 'Endurance' crater. The gradual, 'blueberry'-strewn slope before the rover contains an exposed dark layer of rock that wraps around the upper section of the crater. Scientists suspect that this rock layer will provide clues about Mars' distant past. This mosaic image comprises images taken from 10 rover positions using 750, 530 and 430 nanometer filters, acquired on sol 131 (June 6, 2004).

Variable length adjacent partitioning for PTS based PAPR reduction of OFDM signal

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

Ibraheem, Zeyid T.; Rahman, Md. Mijanur; Yaakob, S. N.

2015-05-15

Peak-to-Average power ratio (PAPR) is a major drawback in OFDM communication. It leads the power amplifier into nonlinear region operation resulting into loss of data integrity. As such, there is a strong motivation to find techniques to reduce PAPR. Partial Transmit Sequence (PTS) is an attractive scheme for this purpose. Judicious partitioning the OFDM data frame into disjoint subsets is a pivotal component of any PTS scheme. Out of the existing partitioning techniques, adjacent partitioning is characterized by an attractive trade-off between cost and performance. With an aim of determining effects of length variability of adjacent partitions, we performed anmore » investigation into the performances of a variable length adjacent partitioning (VL-AP) and fixed length adjacent partitioning in comparison with other partitioning schemes such as pseudorandom partitioning. Simulation results with different modulation and partitioning scenarios showed that fixed length adjacent partition had better performance compared to variable length adjacent partitioning. As expected, simulation results showed a slightly better performance of pseudorandom partitioning technique compared to fixed and variable adjacent partitioning schemes. However, as the pseudorandom technique incurs high computational complexities, adjacent partitioning schemes were still seen as favorable candidates for PAPR reduction.« less

Predicting reading outcomes with progress monitoring slopes among middle grade students

PubMed Central

Tolar, Tammy D.; Barth, Amy E.; Fletcher, Jack M.; Francis, David J.; Vaughn, Sharon

2013-01-01

Effective implementation of response-to-intervention (RTI) frameworks depends on efficient tools for monitoring progress. Evaluations of growth (i.e., slope) may be less efficient than evaluations of status at a single time point, especially if slopes do not add to predictions of outcomes over status. We examined progress monitoring slope validity for predicting reading outcomes among middle school students by evaluating latent growth models for different progress monitoring measure-outcome combinations. We used multi-group modeling to evaluate the effects of reading ability, reading intervention, and progress monitoring administration condition on slope validity. Slope validity was greatest when progress monitoring was aligned with the outcome (i.e., word reading fluency slope was used to predict fluency outcomes in contrast to comprehension outcomes), but effects varied across administration conditions (viz., repeated reading of familiar vs. novel passages). Unless the progress monitoring measure is highly aligned with outcome, slope may be an inefficient method for evaluating progress in an RTI context. PMID:24659899

QRS slopes for assessment of myocardial damage in chronic chagasic patients

NASA Astrophysics Data System (ADS)

Pueyo, E.; Laciar, E.; Anzuola, E.; Laguna, P.; Jané, R.

2007-11-01

In this study the slopes of the QRS complex are evaluated for determination of the degree of myocardial damage in chronic chagasic patients. Previous studies have demonstrated the ability of the slope indices to reflect alterations in the conduction velocity of the cardiac impulse. Results obtained in the present study show that chronic chagasic patients have significantly flatter QRS slopes as compared to healthy subjects. Not only that but the extent of slope lessening turns out to be proportional to the degree of myocardial damage caused by the disease. Additionally, when incorporating the slope indices into a classification analysis together with other indices indicative of the presence of ventricular late potentials obtained from high resolution electrocardiography, results show that the percentages of correct classification increase up to 62.5%, which means eight points above the percentages obtained prior to incorporation of the slope indices. It can be concluded that QRS slopes have great potential for assessing the degree of severity associated with Chagas' disease.

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...

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.

30 CFR 77.1900 - Slopes and shafts; approval of plans.

Code of Federal Regulations, 2010 CFR

2010-07-01

... SAFETY AND HEALTH MANDATORY SAFETY STANDARDS, SURFACE COAL MINES AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Slope and Shaft Sinking § 77.1900 Slopes and shafts; approval of plans. (a) Each operator of... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Slopes and shafts; approval of plans. 77.1900...

Long-term effects of vertebroplasty: adjacent vertebral fractures.

PubMed

Baroud, Gamal; Vant, Christianne; Wilcox, Ruth

2006-01-01

In today's aging population, osteoporosis-related fractures are an ever-growing concern. Vertebroplasty, a promising yet cost-effective treatment for vertebral compression fractures, has an increasing role. The first vertebroplasty procedures were reported by Deramond and Galibert in France in 1987, and international interest grew with continued development of clinical techniques and augmentation materials in Europe and the United States. Initial publications and presentations at peer review meetings demonstrated 60-90% success rates in providing immediate and significant pain relief. The objective of this review is to assemble experimental and computational biomechanical research whose goal is determining and preventing the negative long-term effects ofvertebroplasty, with a specific focus on adjacent vertebral fractures. Biomechanical studies using isolated cancellous bone cylinders have shown that osteoporotic cancellous bone samples augmented by the rigid bone cement were at least 12 times stiffer and 35 times stronger than the untreated osteoporotic cancellous bone samples. The biomechanical efficacy of the procedure to repair the fractured vertebrae and prevent further collapse is determined using single-vertebra models. The strength or load-bearing capacity of a single vertebra is significantly increased following augmentation when compared to the intact strength. However, there is no dear result regarding the overall stiffness of the single vertebra, with studies reporting contradictorily that the stiffness increases, decreases, or does not significantly alter following augmentation. The effects of vertebroplasty on adjacent structures are studied via multisegment models, whose results plainly oppose the findings of the single-vertebra and intravertebral models. Here, augmentation was shown to decrease the overall segment strength by 19% when compared to the matched controls. As well, there is a significant increase in disc pressure compared to the pre

Establish Effective Lower Bounds of Watershed Slope for Traditional Hydrologic Methods

DOT National Transportation Integrated Search

2012-06-01

Equations to estimate timing parameters for a watershed contain watershed slope as a principal parameter and : estimates are usually inversely proportional to topographic slope. Hence as slope vanishes, the estimates approach : infinity. The research...

Wind-driven export of Weddell Sea slope water

NASA Astrophysics Data System (ADS)

Meijers, A. J. S.; Meredith, M. P.; Abrahamsen, E. P.; Morales Maqueda, M. A.; Jones, D. C.; Naveira Garabato, A. C.

2016-10-01

The export of waters from the Weddell Gyre to lower latitudes is an integral component of the southern subpolar contribution to the three-dimensional oceanic circulation. Here we use more than 20 years of repeat hydrographic data on the continental slope on the northern tip of the Antarctic Peninsula and 5 years of bottom lander data on the slope at 1000 m to show the intermittent presence of a relatively cold, fresh, westward flowing current. This is often bottom-intensified between 600 and 2000 dbar with velocities of over 20 cm s-1, transporting an average of 1.5 ± 1.5 Sv. By comparison with hydrography on the continental slope within the Weddell Sea and modeled tracer release experiments we show that this slope current is an extension of the Antarctic Slope Current that has crossed the South Scotia Ridge west of Orkney Plateau. On monthly to interannual time scales the density of the slope current is negatively correlated (r > 0.6 with a significance of over 95%) with eastward wind stress over the northern Weddell Sea, but lagging it by 6-13 months. This relationship holds in both the high temporal resolution bottom lander time series and the 20+ year annual hydrographic occupations and agrees with Weddell Sea export variability observed further east. We compare several alternative hypotheses for this wind stress/export relationship and find that it is most consistent with wind-driven acceleration of the gyre boundary current, possibly modulated by eddy dynamics, and represents a mechanism by which climatic perturbations can be rapidly transmitted as fluctuations in the supply of intermediate-level waters to lower latitudes.

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

Associations between Verbal Learning Slope and Neuroimaging Markers across the Cognitive Aging Spectrum.

PubMed

Gifford, Katherine A; Phillips, Jeffrey S; Samuels, Lauren R; Lane, Elizabeth M; Bell, Susan P; Liu, Dandan; Hohman, Timothy J; Romano, Raymond R; Fritzsche, Laura R; Lu, Zengqi; Jefferson, Angela L

2015-07-01

A symptom of mild cognitive impairment (MCI) and Alzheimer's disease (AD) is a flat learning profile. Learning slope calculation methods vary, and the optimal method for capturing neuroanatomical changes associated with MCI and early AD pathology is unclear. This study cross-sectionally compared four different learning slope measures from the Rey Auditory Verbal Learning Test (simple slope, regression-based slope, two-slope method, peak slope) to structural neuroimaging markers of early AD neurodegeneration (hippocampal volume, cortical thickness in parahippocampal gyrus, precuneus, and lateral prefrontal cortex) across the cognitive aging spectrum [normal control (NC); (n=198; age=76±5), MCI (n=370; age=75±7), and AD (n=171; age=76±7)] in ADNI. Within diagnostic group, general linear models related slope methods individually to neuroimaging variables, adjusting for age, sex, education, and APOE4 status. Among MCI, better learning performance on simple slope, regression-based slope, and late slope (Trial 2-5) from the two-slope method related to larger parahippocampal thickness (all p-values<.01) and hippocampal volume (p<.01). Better regression-based slope (p<.01) and late slope (p<.01) were related to larger ventrolateral prefrontal cortex in MCI. No significant associations emerged between any slope and neuroimaging variables for NC (p-values ≥.05) or AD (p-values ≥.02). Better learning performances related to larger medial temporal lobe (i.e., hippocampal volume, parahippocampal gyrus thickness) and ventrolateral prefrontal cortex in MCI only. Regression-based and late slope were most highly correlated with neuroimaging markers and explained more variance above and beyond other common memory indices, such as total learning. Simple slope may offer an acceptable alternative given its ease of calculation.

Ground reaction force adaptations during cross-slope walking and running.

PubMed

Damavandi, Mohsen; Dixon, Philippe C; Pearsall, David J

2012-02-01

Though transversely inclined (cross-sloped) surfaces are prevalent, our understanding of the biomechanical adaptations required for cross-slope locomotion is limited. The purpose of this study was to examine ground reaction forces (GRF) in cross-sloped and level walking and running. Nine young adult males walked and ran barefoot along an inclinable walkway in both level (0°) and cross-slope (10°) configurations. The magnitude and time of occurrence of selected features of the GRF were extracted from the force plate data. GRF data were collected in level walking and running (LW and LR), inclined walking and running up-slope (IWU and IRU), and down-slope (IWD and IRD), respectively. The GRF data were then analyzed using repeated measures MANOVA. In the anteroposterior direction, the timing of the peak force values differed across conditions during walking (p=.041), while the magnitude of forces were modified across conditions for running (p=.047). Most significant differences were observed in the mediolateral direction, where generally force values were up to 390% and 530% (p<.001) larger during the cross-slope conditions compared to level for walking and running, respectively. The maximum force peak during running occurred earlier at IRU compared to the other conditions (p≤.031). For the normal axis a significant difference was observed in the first maximum force peak during walking (p=.049). The findings of this study showed that compared to level surfaces, functional adaptations are required to maintain forward progression and dynamic stability in stance during cross-slope walking and running. Copyright © 2011 Elsevier B.V. All rights reserved.

Is there a distinct continental slope fauna in the Antarctic?

NASA Astrophysics Data System (ADS)

Kaiser, Stefanie; Griffiths, Huw J.; Barnes, David K. A.; Brandão, Simone N.; Brandt, Angelika; O'Brien, Philip E.

2011-02-01

The Antarctic continental slope spans the depths from the shelf break (usually between 500 and 1000 m) to ˜3000 m, is very steep, overlain by 'warm' (2-2.5 °C) Circumpolar Deep Water (CDW), and life there is poorly studied. This study investigates whether life on Antarctica's continental slope is essentially an extension of the shelf or the abyssal fauna, a transition zone between these or clearly distinct in its own right. Using data from several cruises to the Weddell Sea and Scotia Sea, including the ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) I-III, BIOPEARL (BIOdiversity, Phylogeny, Evolution and Adaptive Radiation of Life in Antarctica) 1 and EASIZ (Ecology of the Antarctic Sea Ice Zone) II cruises as well as current databases (SOMBASE, SCAR-MarBIN), four different taxa were selected (i.e. cheilostome bryozoans, isopod and ostracod crustaceans and echinoid echinoderms) and two areas, the Weddell Sea and the Scotia Sea, to examine faunal composition, richness and affinities. The answer has important ramifications to the link between physical oceanography and ecology, and the potential of the slope to act as a refuge and resupply zone to the shelf during glaciations. Benthic samples were collected using Agassiz trawl, epibenthic sledge and Rauschert sled. By bathymetric definition, these data suggest that despite eurybathy in some of the groups examined and apparent similarity of physical conditions in the Antarctic, the shelf, slope and abyssal faunas were clearly separated in the Weddell Sea. However, no such separation of faunas was apparent in the Scotia Sea (except in echinoids). Using a geomorphological definition of the slope, shelf-slope-abyss similarity only changed significantly in the bryozoans. Our results did not support the presence of a homogenous and unique Antarctic slope fauna despite a high number of species being restricted to the slope. However, it remains the case that there may be

Hydrologic behavior of a steep forested slope prone to shallow landsliding

NASA Astrophysics Data System (ADS)

Berti, Matteo; Simoni, Alessandro

2015-04-01

Over the past ten years, the frequency of debris flows in the Northern Apennines of Italy has significantly increased. Gravitational movements in the area are dominated by slow-moving landslides involving fine-grained soils and, to a lesser extent, by shallow slips in weathered arenaceous rocks. During the past 5 years, at least 20 debris flow events were triggered by exceptional rainfall events. Although no fatalities of injuries resulted from these landslides, the appearance of this new danger generated great concern among local communities. The Civil Protection Agency of the Emilia-Romagna region therefore decided to produce a debris flow susceptibility map to target high-risk zones and to help local authorities in emergency planning. This task, however, is particularly difficult due to the lack of historical data required to apply heuristic or statistical methods. In this context we installed a monitoring system on a representative slope in order to investigate the hydrologic response to rainfall and to support the choice of a suitable deterministic model. The selected slope is close to the village of Porretta Terme (Province of Bologna, Italy) at an elevation of 510 m asl. The slope has an inclination of about 30° and consists of a thin soil cover (0.5-1 thickness) lying over a fractured arenaceous bedrock. The soil is a well-graded sand with silt, gravel, cobbles, and weathered rock blocks. The slope is densely vegetated with grass, shrubs and mature trees. Part of the slope failed on the 30th November 2008 after a rainfall of 140 mm in 24 hours. A shallow slide of the soil mantle rapidly mobilized into debris flow leaving the bedrock exposed in the source area. The monitoring system is located on an unfailed slope close to the initiation area. The system consists of three stations aligned along the maximum slope at a distance of 15-20 m. Each station is equipped with: i) an open-standpipe piezometer installed near the soil-rock interface (1 m deep); ii

Large bedrock slope failures in a British Columbia, Canada fjord: first documented submarine sackungen

NASA Astrophysics Data System (ADS)

Conway, Kim W.; Vaughn Barrie, J.

2018-01-01

Very large (>60×106 m3) sackungen or deep-seated gravitational slope deformations occur below sea level along a steep fjord wall in central Douglas Channel, British Columbia. The massive bedrock blocks were mobile between 13 and 11.5 thousand radiocarbon years BP (15,800 and 13,400 BP) immediately following deglaciation. Deformation of fjord sediments is apparent in sedimentary units overlying and adjacent to the blocks. Faults bound the edges of each block, cutting the glacial section but not the Holocene sediments. Retrogressive slides, small inset landslides as well as incipient and older slides are found on and around the large failure blocks. Lineations, fractures and faults parallel the coastline of Douglas Channel along the shoreline of the study area. Topographic data onshore indicate that faults and joints demarcate discrete rhomboid-shaped blocks which controlled the form, size and location of the sackungen. The described submarine sackungen share characteristic geomorphic features with many montane occurrences, such as uphill-facing scarps, foliated bedrock composition, largely vertical dislocation and a deglacial timing of development.

Large bedrock slope failures in a British Columbia, Canada fjord: first documented submarine sackungen

NASA Astrophysics Data System (ADS)

Conway, Kim W.; Vaughn Barrie, J.

2018-06-01

Very large (>60×106 m3) sackungen or deep-seated gravitational slope deformations occur below sea level along a steep fjord wall in central Douglas Channel, British Columbia. The massive bedrock blocks were mobile between 13 and 11.5 thousand radiocarbon years BP (15,800 and 13,400 BP) immediately following deglaciation. Deformation of fjord sediments is apparent in sedimentary units overlying and adjacent to the blocks. Faults bound the edges of each block, cutting the glacial section but not the Holocene sediments. Retrogressive slides, small inset landslides as well as incipient and older slides are found on and around the large failure blocks. Lineations, fractures and faults parallel the coastline of Douglas Channel along the shoreline of the study area. Topographic data onshore indicate that faults and joints demarcate discrete rhomboid-shaped blocks which controlled the form, size and location of the sackungen. The described submarine sackungen share characteristic geomorphic features with many montane occurrences, such as uphill-facing scarps, foliated bedrock composition, largely vertical dislocation and a deglacial timing of development.

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.

Coastal cliffs, rock-slope failures and Late Quaternary transgressions of the Black Sea along southern Crimea

NASA Astrophysics Data System (ADS)

Pánek, Tomáš; Lenart, Jan; Hradecký, Jan; Hercman, Helena; Braucher, Règis; Šilhán, Karel; Škarpich, Václav

2018-02-01

Rock-slope failures represent a significant hazard along global coastlines, but their chronology remains poorly documented. Here, we focus on the geomorphology and chronology of giant rockslides affecting the Crimean Mountains along the Black Sea coast. Geomorphic evidence suggests that high (>100 m) limestone cliffs flanking the southern slopes of the Crimean Mountains are scarps of rockslides nested within larger deep-seated gravitational slope deformations (DSGSDs). Such pervasive slope failures originated due to lateral spreading of intensively faulted Late Jurassic carbonate blocks moving atop weak/plastic Late Triassic flysch and tuff layers. By introducing a dating strategy relying on the combination of the uranium-thorium dating (U-Th) of exposed calcareous speleothems covering the landslide scarps with the 36Cl exposure dating of rock walls, we are able to approximate the time interval between the origin of incipient crevices and the final collapse of limestone blocks that exposed the cliff faces. For the three representative large-scale rockslides between the towns of Foros and Yalta, the initiation of the DSGSDs as evidenced by the widening of crevices and the onset of speleothem accumulation was >300 ka BP, but the recent cliff morphology along the coast is the result of Late Pleistocene/Holocene failures spanning ∼20-0.5 ka BP. The exposures of rockslide scarps occurred mostly at ∼20-15, ∼8, ∼5-4 and ∼2-0.5 ka, which substantially coincide with the last major Black Sea transgressions and/or more humid Holocene intervals. Our study suggests that before ultimate fast and/or catastrophic slope failures, the relaxation of rock massifs correlative with karstification, cracks opening, and incipient sliding lasted on the order of 104-105 years. Rapid Late Glacial/Holocene transgressions of the Black Sea likely represented the last impulse for the collapse of limestone blocks and the origin of giant rockslides, simultaneously affecting the majority

Explaining large mortality differences between adjacent counties: a cross-sectional study.

PubMed

Schootman, M; Chien, L; Yun, S; Pruitt, S L

2016-08-02

Extensive geographic variation in adverse health outcomes exists, but global measures ignore differences between adjacent geographic areas, which often have very different mortality rates. We describe a novel application of advanced spatial analysis to 1) examine the extent of differences in mortality rates between adjacent counties, 2) describe differences in risk factors between adjacent counties, and 3) determine if differences in risk factors account for the differences in mortality rates between adjacent counties. We conducted a cross-sectional study in Missouri, USA with 2005-2009 age-adjusted all-cause mortality rate as the outcome and county-level explanatory variables from a 2007 population-based survey. We used a multi-level Gaussian model and a full Bayesian approach to analyze the difference in risk factors relative to the difference in mortality rates between adjacent counties. The average mean difference in the age-adjusted mortality rate between any two adjacent counties was -3.27 (standard deviation = 95.5) per 100,000 population (maximum = 258.80). Six variables were associated with mortality differences: inability to obtain medical care because of cost (β = 2.6), hospital discharge rate (β = 1.03), prevalence of fair/poor health (β = 2.93), and hypertension (β = 4.75) and poverty prevalence (β = 6.08). Examining differences in mortality rates and associated risk factors between adjacent counties provides additional insight for future interventions to reduce geographic disparities.

Solution algorithm of dwell time in slope-based figuring model

NASA Astrophysics Data System (ADS)

Li, Yong; Zhou, Lin

2017-10-01

Surface slope profile is commonly used to evaluate X-ray reflective optics, which is used in synchrotron radiation beam. Moreover, the measurement result of measuring instrument for X-ray reflective optics is usually the surface slope profile rather than the surface height profile. To avoid the conversion error, the slope-based figuring model is introduced introduced by processing the X-ray reflective optics based on surface height-based model. However, the pulse iteration method, which can quickly obtain the dell time solution of the traditional height-based figuring model, is not applied to the slope-based figuring model because property of the slope removal function have both positive and negative values and complex asymmetric structure. To overcome this problem, we established the optimal mathematical model for the dwell time solution, By introducing the upper and lower limits of the dwell time and the time gradient constraint. Then we used the constrained least squares algorithm to solve the dwell time in slope-based figuring model. To validate the proposed algorithm, simulations and experiments are conducted. A flat mirror with effective aperture of 80 mm is polished on the ion beam machine. After iterative polishing three times, the surface slope profile error of the workpiece is converged from RMS 5.65 μrad to RMS 1.12 μrad.

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...

Department of Energy Arm Facilities on the North Slope of Alaska and Plans for a North Slope "Mega-Site"

NASA Astrophysics Data System (ADS)

Ivey, M.; Verlinde, J.

2014-12-01

The U.S. Department of Energy (DOE), through its scientific user facility, the Atmospheric Radiation Measurement (ARM) Climate Research Facility, provides scientific infrastructure and data to the international Arctic research community via its research sites located on the North Slope of Alaska. The DOE ARM Program has operated an atmospheric measurement facility in Barrow, Alaska, since 1998. Major upgrades to this facility, including scanning radars, were added in 2010. Facilities and infrastructure to support operations of unmanned aerial systems for science missions in the Arctic and North Slope of Alaska were established at Oliktok Point Alaska in 2013. Tethered instrumented balloons will be used in the near future to make measurements of clouds in the boundary layer including mixed-phase clouds. The Atmospheric Radiation Measurement (ARM) Climate Research Facility is implementing "mega-sites" at the Southern Great Plains and North Slope of Alaska sites. Two workshops were held to gather input from the scientific community on these mega-sites. The NSA workshop was held September 10 and 11 in the Washington DC area. The workshops included discussions of additional profiling remote sensors, detailed measurements of the land-atmosphere interface, aerial operations to link the Barrow and Oliktok sites, unmanned aerial system measurements, and routine large eddy simulation model runs. The "mega-sites" represent a significant new scientific and infrastructure investment by DOE Office of Science, Office of Biological and Environmental Research. This poster will present information on plans for a North Slope "Megasite" as well as new opportunities for members of the arctic research community to make atmospheric measurements using unmanned aerial systems or tethered balloons in conjunction with the DOE ARM facilities on the North Slope of Alaska.

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.

Slope-velocity equilibrium and evolution of surface roughness on a stony hillslope

NASA Astrophysics Data System (ADS)

Nearing, Mark A.; Polyakov, Viktor O.; Nichols, Mary H.; Hernandez, Mariano; Li, Li; Zhao, Ying; Armendariz, Gerardo

2017-06-01

Slope-velocity equilibrium is hypothesized as a state that evolves naturally over time due to the interaction between overland flow and surface morphology, wherein steeper areas develop a relative increase in physical and hydraulic roughness such that flow velocity is a unique function of overland flow rate independent of slope gradient. This study tests this hypothesis under controlled conditions. Artificial rainfall was applied to 2 m by 6 m plots at 5, 12, and 20 % slope gradients. A series of simulations were made with two replications for each treatment with measurements of runoff rate, velocity, rock cover, and surface roughness. Velocities measured at the end of each experiment were a unique function of discharge rates, independent of slope gradient or rainfall intensity. Physical surface roughness was greater at steeper slopes. The data clearly showed that there was no unique hydraulic coefficient for a given slope, surface condition, or rainfall rate, with hydraulic roughness greater at steeper slopes and lower intensities. This study supports the hypothesis of slope-velocity equilibrium, implying that use of hydraulic equations, such as Chezy and Manning, in hillslope-scale runoff models is problematic because the coefficients vary with both slope and rainfall intensity.

Local adjacency metric dimension of sun graph and stacked book graph

NASA Astrophysics Data System (ADS)

Yulisda Badri, Alifiah; Darmaji

2018-03-01

A graph is a mathematical system consisting of a non-empty set of nodes and a set of empty sides. One of the topics to be studied in graph theory is the metric dimension. Application in the metric dimension is the navigation robot system on a path. Robot moves from one vertex to another vertex in the field by minimizing the errors that occur in translating the instructions (code) obtained from the vertices of that location. To move the robot must give different instructions (code). In order for the robot to move efficiently, the robot must be fast to translate the code of the nodes of the location it passes. so that the location vertex has a minimum distance. However, if the robot must move with the vertex location on a very large field, so the robot can not detect because the distance is too far.[6] In this case, the robot can determine its position by utilizing location vertices based on adjacency. The problem is to find the minimum cardinality of the required location vertex, and where to put, so that the robot can determine its location. The solution to this problem is the dimension of adjacency metric and adjacency metric bases. Rodrguez-Velzquez and Fernau combine the adjacency metric dimensions with local metric dimensions, thus becoming the local adjacency metric dimension. In the local adjacency metric dimension each vertex in the graph may have the same adjacency representation as the terms of the vertices. To obtain the local metric dimension of values in the graph of the Sun and the stacked book graph is used the construction method by considering the representation of each adjacent vertex of the graph.

Constrained and Unconstrained Partial Adjacent Category Logit Models for Ordinal Response Variables

ERIC Educational Resources Information Center

Fullerton, Andrew S.; Xu, Jun

2018-01-01

Adjacent category logit models are ordered regression models that focus on comparisons of adjacent categories. These models are particularly useful for ordinal response variables with categories that are of substantive interest. In this article, we consider unconstrained and constrained versions of the partial adjacent category logit model, which…

Are North Slope surface alluvial fans pre-Holocene relicts?

USGS Publications Warehouse

Reimnitz, Erk; Wolf, Stephen C.

1998-01-01

The surface morphology of the northern slope of the Brooks Range (North Slope) from the Canning River, Alaska, eastward is dominated by a series of large alluvial fans and braided streams floored by coarse alluvium. On the basis of our studies, we conclude that the fans are not prograding now nor have they been prograding at any time during the Holocene. During the latest transgression and the following sea-level highstand, the North Slope depositional environment and climate probably differed greatly from the present ones.

Advance in prediction of soil slope instabilities

NASA Astrophysics Data System (ADS)

Sigarán-Loría, C.; Hack, R.; Nieuwenhuis, J. D.

2012-04-01

Six generic soils (clays and sands) were systematically modeled with plane-strain finite elements (FE) at varying heights and inclinations. A dataset was generated in order to develop predictive relations of soil slope instabilities, in terms of co-seismic displacements (u), under strong motions with a linear multiple regression. For simplicity, the seismic loads are monochromatic artificial sinusoidal functions at four frequencies: 1, 2, 4, and 6 Hz, and the slope failure criterion used corresponds to near 10% Cartesian shear strains along a continuous region comparable to a slip surface. The generated dataset comprises variables from the slope geometry and site conditions: height, H, inclination, i, shear wave velocity from the upper 30 m, vs30, site period, Ts; as well as the input strong motion: yield acceleration, ay (equal to peak ground acceleration, PGA in this research), frequency, f; and in some cases moment magnitude, M, and Arias intensity, Ia, assumed from empirical correlations. Different datasets or scenarios were created: "Magnitude-independent", "Magnitude-dependent", and "Soil-dependent", and the data was statistically explored and analyzed with varying mathematical forms. Qualitative relations show that the permanent deformations are highly related to the soil class for the clay slopes, but not for the sand slopes. Furthermore, the slope height does not constrain the variability in the co-seismic displacements. The input frequency decreases the variability of the co-seismic displacements for the "Magnitude-dependent" and "Soil-dependent" datasets. The empirical models were developed with two and three predictors. For the sands it was not possible because they could not satisfy the constrains from the statistical method. For the clays, the best models with the smallest errors coincided with the simple general form of multiple regression with three predictors (e.g. near 0.16 and 0.21 standard error, S.E. and 0.75 and 0.55 R2 for the "M

Three Dimensional Underwater Sound Propagation Over Sloping Bottoms

NASA Astrophysics Data System (ADS)

Glegg, Stewart A. L.; Riley, J. M.

This article reviews the work which has been carried out over the past few years on three dimensional underwater sound propagation over sloping bottoms. When sound propagates across a slope three dimensional effects can cause shadow zones and mode cut off effects to occur, which could not be predicted by a two dimensional model. For many years the theory for this type of propagation over realistic ocean floors, which can support both compressional and shear waves, eluded workers in this field. Recently the complete solution for the acoustic field in a "wedge domain with penetrable boundaries" has been developed, and this has allowed for complete understanding of three dimensional bottom interacting sound propagation. These theories have been verified by a series of laboratory scale experiments and excellent agreement has been obtained. However only one full scale ocean experiment has been carried out on three dimensional, bottom interacting, acoustic propagation. This showed significant horizontal refraction of sound propagating across a continental slope and further verifies the importance of bottom slopes on underwater sound propagation.

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.

Mediterranean undercurrent sandy contourites, Gulf of Cadiz, Spain

USGS Publications Warehouse

Hans, Nelson C.; Baraza, J.; Maldonado, A.

1993-01-01

The Pliocene-Quaternary pattern of contourite deposits on the eastern Gulf of Cadiz continental slope results from an interaction between linear diapiric ridges that are perpendicular to slope contours and the Mediterranean undercurrent that has flowed northwestward parallel to the slope contours and down valleys between the ridges since the late Miocene opening of the Strait of Gibraltar. Coincident with the northwestward decrease in undercurrent speeds from the Strait there is the following northwestward gradation of sediment facies associations: (1) upper slope facies, (2) sand dune facies on the upstream mid-slope terrace, (3) large mud wave facies on the lower slope, (4) sediment drift facies banked against the diapiric ridges, and (5) valley facies between the ridges. The southeastern sediment drift facies closest to Gibraltar contains medium-fine sand beds interbedded with mud. The adjacent valley floor facies is composed of gravelly, shelly coarse to medium sand lags and large sand dunes on the valley margins. Compared to this, the northwestern drift contains coarse silt interbeds and the adjacent valley floors exhibit small to medium sand dunes of fine sand. Further northwestward, sediment drift grades to biogenous silt near the Faro Drift at the Portuguese border. Because of the complex pattern of contour-parallel and valley-perpendicular flow paths of the Mediterranean undercurrent, the larger-scale bedforms and coarser-grained sediment of valley facies trend perpendicular to the smaller-scale bedforms and finer-grained contourite deposits of adjacent sediment drift facies. The bottom-current deposits of valleys and the contourites of the Cadiz slope intervalley areas are distinct from turbidite systems. The valley sequences are not aggradational like turbidite channel-levee complexes, but typically exhibit bedrock walls against ridges, extensive scour and fill into adjacent contourites, transverse bedform fields and bioclastic lag deposits. Both valley

Analysing hydro-mechanical behaviour of reinforced slopes through centrifuge modelling

NASA Astrophysics Data System (ADS)

Veenhof, Rick; Wu, Wei

2017-04-01

Every year, slope instability is causing casualties and damage to properties and the environment. The behaviour of slopes during and after these kind of events is complex and depends on meteorological conditions, slope geometry, hydro-mechanical soil properties, boundary conditions and the initial state of the soils. This study describes the effects of adding reinforcement, consisting of randomly distributed polyolefin monofilament fibres or Ryegrass (Lolium), on the behaviour of medium-fine sand in loose and medium dense conditions. Direct shear tests were performed on sand specimens with different void ratios, water content and fibre or root density, respectively. To simulate the stress state of real scale field situations, centrifuge model tests were conducted on sand specimens with different slope angles, thickness of the reinforced layer, fibre density, void ratio and water content. An increase in peak shear strength is observed in all reinforced cases. Centrifuge tests show that for slopes that are reinforced the period until failure is extended. The location of shear band formation and patch displacement behaviour indicate that the design of slope reinforcement has a significant effect on the failure behaviour. Future research will focus on the effect of plant water uptake on soil cohesion.

Effects of lava heating on volatile-rich slopes on Io

USGS Publications Warehouse

Dundas, Colin M.

2017-01-01

The upper crust of Io may be very rich in volatile sulfur and SO2. The surface is also highly volcanically active, and slopes may be warmed by radiant heat from the lava. This is particularly the case in paterae, which commonly host volcanic eruptions and long-lived lava lakes. Paterae slopes are highly variable, but some are greater than 70°. I model the heating of a volatile slope for two end-member cases: instantaneous emplacement of a large sheet flow, and persistent heating by a long-lived lava lake. In general, single flows can briefly raise sulfur to the melting temperature, or drive a modest amount of sublimation of SO2. Persistently lava-covered surfaces will drive much more significant geomorphic effects, with potentially significant sublimation and slope retreat. In addition to the direct effects, heating is likely to weaken slope materials and may trigger mass wasting. Thus, if the upper crust of Io is rich in these volatile species, future missions with high-resolution imaging are likely to observe actively retreating slopes around lava lakes and other locations of frequent eruptions.

Highway rock slope management program.

DOT National Transportation Integrated Search

2001-06-30

Development of a comprehensive geotechnical database for risk management of highway rock slope problems is described. Computer software selected to program the client/server application in windows environment, components and structure of the geote...

Structural Damage Detection Using Slopes of Longitudinal Vibration Shapes

DOE PAGES

Xu, W.; Zhu, W. D.; Smith, S. A.; ...

2016-03-18

While structural damage detection based on flexural vibration shapes, such as mode shapes and steady-state response shapes under harmonic excitation, has been well developed, little attention is paid to that based on longitudinal vibration shapes that also contain damage information. This study originally formulates a slope vibration shape for damage detection in bars using longitudinal vibration shapes. To enhance noise robustness of the method, a slope vibration shape is transformed to a multiscale slope vibration shape in a multiscale domain using wavelet transform, which has explicit physical implication, high damage sensitivity, and noise robustness. These advantages are demonstrated in numericalmore » cases of damaged bars, and results show that multiscale slope vibration shapes can be used for identifying and locating damage in a noisy environment. A three-dimensional (3D) scanning laser vibrometer is used to measure the longitudinal steady-state response shape of an aluminum bar with damage due to reduced cross-sectional dimensions under harmonic excitation, and results show that the method can successfully identify and locate the damage. Slopes of longitudinal vibration shapes are shown to be suitable for damage detection in bars and have potential for applications in noisy environments.« less

How Do Adults Perceive, Analyse and Measure Slope?

ERIC Educational Resources Information Center

Duncan, Bruce; Chick, Helen

2013-01-01

Slope is a mathematical concept that is both fundamental to the study of advanced calculus and commonly perceived in everyday life. The measurement of steepness of terrain as a ratio is an example of an everyday application the concept of slope. In this study, a group of pre-service teachers were tested for their capacity to mathematize the…

30 CFR 817.13 - Casing and sealing of exposed underground openings: General requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... underground openings: General requirements. Each exploration hole, other drillhole or borehole, shaft, well..., fish and wildlife, and machinery in the permit area and adjacent area. Each exploration hole, drill hole or borehole or well that is uncovered or exposed by mining activities within the permit area shall...

30 CFR 817.13 - Casing and sealing of exposed underground openings: General requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... underground openings: General requirements. Each exploration hole, other drillhole or borehole, shaft, well..., fish and wildlife, and machinery in the permit area and adjacent area. Each exploration hole, drill hole or borehole or well that is uncovered or exposed by mining activities within the permit area shall...

30 CFR 817.13 - Casing and sealing of exposed underground openings: General requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... underground openings: General requirements. Each exploration hole, other drillhole or borehole, shaft, well..., fish and wildlife, and machinery in the permit area and adjacent area. Each exploration hole, drill hole or borehole or well that is uncovered or exposed by mining activities within the permit area shall...

30 CFR 817.13 - Casing and sealing of exposed underground openings: General requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... underground openings: General requirements. Each exploration hole, other drillhole or borehole, shaft, well..., fish and wildlife, and machinery in the permit area and adjacent area. Each exploration hole, drill hole or borehole or well that is uncovered or exposed by mining activities within the permit area shall...

30 CFR 817.13 - Casing and sealing of exposed underground openings: General requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... underground openings: General requirements. Each exploration hole, other drillhole or borehole, shaft, well..., fish and wildlife, and machinery in the permit area and adjacent area. Each exploration hole, drill hole or borehole or well that is uncovered or exposed by mining activities within the permit area shall...

Spatial variability in the response of surface-water extent to climate extremes across the Prairie Pothole Region and adjacent Northern Prairie, United States

NASA Astrophysics Data System (ADS)

Vanderhoof, M.; Lane, C.; McManus, M.; Alexander, L. C.; Christensen, J.

2017-12-01

Surface-water extent, duration and movement will depend not only on climatic inputs but also the relative importance of different hydrologic pathways (e.g., surface storage, infiltration, evapotranspiration, stream outflows). We mapped surface-water extent from historic drought years to historic wet years spanning 1985 - 2015 across eleven Landsat path/rows representing the Prairie Pothole Region (PPR) and adjacent Northern Prairie of the United States. The PPR not only experienced a greater surface water extent under median conditions (2.6 times more) relative to the adjacent Northern Prairie, but showed a greater difference between drought and deluge conditions as well (range averaged 8.5 ha surface water km-2 relative to 2.5 ha surface water km-2 for the PPR and Northern Prairie, respectively). To explain the spatial variability in the amount of surface water expansion and contraction we used a two-stage modeling approach. First, surface-water extent was regressed on accumulated water availability (precipitation minus potential evapotranspiration). The slope of surface-water extent to climate inputs (per watershed) was our dependent variable in the second stage. That slope was regressed against independent variables representing hydrology-related landscape characteristics (e.g., infiltration capacity, surface storage capacity, stream density). Stream-connected surface water can leave via stream flow, influencing the rate at which surface-water may leave a location, therefore stream-connected and disconnected surface water were analyzed separately. Stream-connected surface water responded more strongly to wetter climatic conditions (i.e., accumulated) in landscapes with more lakes and less artificial drainage (e.g., ditching, tile drainage). Disconnected surface water responded more strongly to wetter climatic conditions when landscapes contained greater wetland density, fewer streams and a lower predicted rate of infiltration. From these findings, we can expect

PIXE analysis of elements in gastric cancer and adjacent mucosa

NASA Astrophysics Data System (ADS)

Liu, Qixin; Zhong, Ming; Zhang, Xiaofeng; Yan, Lingnuo; Xu, Yongling; Ye, Simao

1990-04-01

The elemental regional distributions in 20 resected human stomach tissues were obtained using PIXE analysis. The samples were pathologically divided into four types: normal, adjacent mucosa A, adjacent mucosa B and cancer. The targets for PIXE analysis were prepared by wet digestion with a pressure bomb system. P, K, Fe, Cu, Zn and Se were measured and statistically analysed. We found significantly higher concentrations of P, K, Cu, Zn and a higher ratio of Cu compared to Zn in cancer tissue as compared with normal tissue, but statistically no significant difference between adjacent mucosa and cancer tissue was found.

Misalignment of Lava Flows from Topographic Slope Directions Reveals Late Amazonian Deformation at Arsia Mons, Mars

NASA Astrophysics Data System (ADS)

Waring, B. A.; Chadwick, J.; McGovern, P. J., Jr.; Tucker, W.

2017-12-01

Arsia Mons is the southernmost of the three large Tharsis Montes near the equator of Mars and one of the largest volcanoes in the solar system. The main edifice of Arsia is about 440 km in diameter, the summit is over 9 km above the surrounding plains and has a pronounced 110 km caldera. Like the other Tharsis volcanoes, Arsia has a large, Late Amazonian glacial deposit on its NW flank. Previous crater retention studies for lava flows on Arsia have shown that the volcano experienced significant volcanic activity in the past 200 Ma. In this study, numerous long (>25 km), thin lava flows on the plains surrounding Arsia were mapped and used as indicators of the topographic slope direction at the time of their emplacement. The azimuthal orientation of each flow was compared with the present-day slope directions on the surrounding plains, derived from Mars Orbiter Laser Altimeter (MOLA) topographic data. The results reveal regions around Arsia where the flows no longer conform to the topography, indicating deformation in the time since the flows where emplaced. In a region of Daedalia Planum to the SE of Arsia, modern slope directions adjacent to 40 long lava flows are consistently misaligned from the paleo-slopes indicated by the lava flow orientations, with an angular offset that averages 7.2° in the clockwise direction. Crater size-frequency measurements for these tilted plains using CraterStats software indicate that the deformation responsible for the misaligned flows took place since 330 ± 10 Ma. Conversely, part of Daedalia Planum to the southwest of Arsia is younger, with a crater retention age of 160 ± 6 Ma, and this area shows no consistent flow-topography misalignments. These observations suggest that extensive regional deformation occurred between the two dates, consistent with other evidence for significant volcanism at Arsia in the Late Amazonian at about 200 Ma. Geophysical modelling using the finite element program COMSOL Multiphysics is planned to

The North Slope of Alaska and Tourism: Potential Impacts on the Arctic National Wildlife Refuge (ANWR)

NASA Astrophysics Data System (ADS)

Everett, L. R.

2004-12-01

The hydrocarbon industry of Alaska is currently the leading producer of revenue for the Alaskan state economy. Second only to hydrocarbons is the tourism industry. Tourism has been a viable industry since the 1890's when cruises touted the beauty of glaciers and icebergs along the Alaskan coastline. This industry has seen a steady growth for the past few decades throughout the state. The North Slope of Alaska, particularly Prudhoe Bay and the National Petroleum Reserve, has long been associated with hydrocarbon development and today displays a landscape dotted with gravel drill pads, gas and oil pipelines and housing for the oil workers. While tourism is not usually considered hand in hand with the hydrocarbon industry, it has mimicked the development of hydrocarbons almost since the beginning. Today one not only sees the effects of the oil industry on the North Slope, but also the tourist industry as planes unload dozens of tourists, or tour buses and private vehicles arrive daily via the Dalton Highway. In Deadhorse, hotels that once only housed the oil workers now welcome the tourist, offering tours of the oil fields and adjacent areas and have become jumping off sites for wilderness trips. Tourism will create jobs as well as revenue. However, at present, there are few restrictions or guidelines in place that will deal with the potential impacts of increased tourism. Because of this there are many concerns about the possible impacts tourism and the infrastructure development will have on the North Slope. To list several concerns: (1) What are the impacts of increased tourism and the infrastructure development? (2) What will the impacts be on the Arctic National Wildlife Refuge (ANWR), which sits a mere 60 miles to the east of Deadhorse? (3) Will hydrocarbon development in ANWR and the associated infrastructure exacerbate potential impact by encouraging greater use of the Refuge by tourists? (4) Will tourism itself have a negative impact on this fragile

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.

Cultural Resource Inventory of Lands in and Adjacent to the City of Rochester, Minnesota Flood Control Project on the South Fork Zumbro River,

DTIC Science & Technology

1981-09-14

the area directly east of present- day Rochester contained fire-maintained oak openings and barrens . This area consisted of oak groves or single trees...Archaeological Survey of Lands Adjacent to the Pine River Reservoir; University of Minnesota and St. Paul District Corps of Engineers; Archaeological Field...Archaeological Field Services, Inc.; Principal Investigator. 1980 An Archaeological Reconnaissance Survey of the Harrison Hills Project, Plymouth , Hennepin

Diffusion-Weighted MRI Assessment of Adjacent Disc Degeneration After Thoracolumbar Vertebral Fractures

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

Noriega, David C., E-mail: dcnoriega1970@gmail.com; Marcia, Stefano, E-mail: stemarcia@gmail.com; Ardura, Francisco, E-mail: fardura@ono.com

ObjectiveThe purpose of this study was to assess, by the mean apparent diffusion coefficient (ADC), if a relationship exists between disc ADC and MR findings of adjacent disc degeneration after thoracolumbar fractures treated by anatomic reduction using vertebral augmentation (VAP).Materials and MethodsTwenty non-consecutive patients (mean age 50.7 years; range 45–56) treated because of vertebral fractures, were included in this study. There were 10 A3.1 and 10 A1.2 fractures (AO classification). Surgical treatment using VAP was applied in 14 cases, and conservative in 6 patients. MRI T2-weighted images and mapping of apparent diffusion coefficient (ADC) of the intervertebral disc adjacent to themore » fractured segment were performed after a mean follow-up of 32 months. A total of 60 discs, 3 per patient, were analysed: infra-adjacent, supra-adjacent and a control disc one level above the supra-adjacent.ResultsNo differences between patients surgically treated and those following a conservative protocol regarding the average ADC values obtained in the 20 control discs analysed were found. Considering all discs, average ADC in the supra-adjacent level was lower than in the infra-adjacent (1.35 ± 0.12 vs. 1.53 ± 0.06; p < 0.001). Average ADC values of the discs used as a control were similar to those of the infra-adjacent level (1.54 ± 0.06). Compared to surgically treated patients, discs at the supra-adjacent fracture level showed statistically significant lower values in cases treated conservatively (p < 0.001). The variation in the delay of surgery had no influence on the average values of ADC at any of the measured levels.ConclusionsADC measurements of the supra-adjacent discs after a mean follow-up of 32 months following thoracolumbar fractures, showed that restoration of the vertebral collapse by minimally invasive VAP prevents posttraumatic disc degeneration.« less

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.

Thermal circulation patterns and turbulent fluxes along steep mountain slopes

NASA Astrophysics Data System (ADS)

Nadeau, D. F.; Pardyjak, E.; Higgins, C. W.; Huwald, H.; Baerenbold, F.; Parlange, M. B.

2010-12-01

In hydrology, it is crucial to understand the atmospheric flow dynamics in mountainous terrain to predict turbulent exchanges of heat and moisture accurately at the regional scale. Under clear sky and weak synoptic conditions, these land-atmosphere interactions are driven by thermal circulations that take place over a strong diurnal cycle. During the day, winds travel up the mountain slopes and at night, they travel down toward to the bottom of the valley. Little is known about how the transition between these two regimes takes place over steep slopes. The Slope Experiment at La Fouly (SELF) in the Swiss Alps was designed to investigate these transition periods throughout summer 2010. In this paper, we will present the first results obtained from this field campaign. Data from a network of 16 wireless surface stations is used to define catchment wide micrometeorological processes such as slope and valley wind system development, while detailed measurements of the turbulent processes on a steep idealized slope (20 to 45 degrees) were also made. The slope was instrumented along a transect with four towers (including a surface energy budget station and 10 m tower with sonic anemometers), 13 surface temperature measurement stations and a tethered balloon system to capture the complex interplay between surface and atmosphere. Initial data presented will include basic circulation pattern development and measurements of the turbulent fluxes of water vapor, heat and momentum on the slope.

Evaluation of Thermoelectric Devices by the Slope-Efficiency Method

DTIC Science & Technology

2016-09-01

ARL-TR-7837 ● SEP 2016 US Army Research Laboratory Evaluation of Thermoelectric Devices by the Slope-Efficiency Method by...Evaluation of Thermoelectric Devices by the Slope-Efficiency Method by Patrick J Taylor Sensors and Electron Devices Directorate, ARL Jay R...

A Study on Project Priority Evaluation Method on Road Slope Disaster Prevention Management

NASA Astrophysics Data System (ADS)

Sekiguchi, Nobuyasu; Ohtsu, Hiroyasu; Izu, Ryuutarou

To improve the safety and security of driving while coping with today's stagnant economy and frequent natural disasters, road slopes should be appropriately managed. To achieve the goals, road managers should establish project priority evaluation methods for each stage of road slope management by clarifying social losses that would result by drops in service levels. It is important that road managers evaluate a project priority properly to manage the road slope effectively. From this viewpoint, this study proposed "project priority evaluation methods" in road slope disaster prevention, which use available slope information at each stage of road slope management under limited funds. In addition, this study investigated the effect of managing it from the high slope of the priority by evaluating a risk of slope failure. In terms of the amount of available information, staged information provision is needed ranging from macroscopic studies, which involves evaluation of the entire route at each stage of decision making, to semi- and microscopic investigations for evaluating slopes, and microscopic investigations for evaluating individual slopes. With limited funds, additional detailed surveys are difficult to perform. It is effective to use the slope risk assessment system, which was constructed to complement detailed data, to extract sites to perform precise investigations.

Valuing urban open space using the travel-cost method and the implications of measurement error.

PubMed

Hanauer, Merlin M; Reid, John

2017-08-01

Urbanization has placed pressure on open space within and adjacent to cities. In recent decades, a greater awareness has developed to the fact that individuals derive multiple benefits from urban open space. Given the location, there is often a high opportunity cost to preserving urban open space, thus it is important for both public and private stakeholders to justify such investments. The goals of this study are twofold. First, we use detailed surveys and precise, accessible, mapping methods to demonstrate how travel-cost methods can be applied to the valuation of urban open space. Second, we assess the degree to which typical methods of estimating travel times, and thus travel costs, introduce bias to the estimates of welfare. The site we study is Taylor Mountain Regional Park, a 1100-acre space located immediately adjacent to Santa Rosa, California, which is the largest city (∼170,000 population) in Sonoma County and lies 50 miles north of San Francisco. We estimate that the average per trip access value (consumer surplus) is $13.70. We also demonstrate that typical methods of measuring travel costs significantly understate these welfare measures. Our study provides policy-relevant results and highlights the sensitivity of urban open space travel-cost studies to bias stemming from travel-cost measurement error. Copyright © 2017 Elsevier Ltd. All rights reserved.

Tidally induced residual current over the Malin Sea continental slope

NASA Astrophysics Data System (ADS)

Stashchuk, Nataliya; Vlasenko, Vasiliy; Hosegood, Phil; Nimmo-Smith, W. Alex M.

2017-05-01

Tidally induced residual currents generated over shelf-slope topography are investigated analytically and numerically using the Massachusetts Institute of Technology general circulation model. Observational support for the presence of such a slope current was recorded over the Malin Sea continental slope during the 88-th cruise of the RRS ;James Cook; in July 2013. A simple analytical formula developed here in the framework of time-averaged shallow water equations has been validated against a fully nonlinear nonhydrostatic numerical solution. A good agreement between analytical and numerical solutions is found for a wide range of input parameters of the tidal flow and bottom topography. In application to the Malin Shelf area both the numerical model and analytical solution predicted a northward moving current confined to the slope with its core located above the 400 m isobath and with vertically averaged maximum velocities up to 8 cm s-1, which is consistent with the in-situ data recorded at three moorings and along cross-slope transects.

Slope gradient and shape effects on soil profiles in the northern mountainous forests of Iran

NASA Astrophysics Data System (ADS)

Fazlollahi Mohammadi, M.; Jalali, S. G. H.; Kooch, Y.; Said-Pullicino, D.

2016-12-01

In order to evaluate the variability of the soil profiles at two shapes (concave and convex) and five positions (summit, shoulder, back slope, footslope and toeslope) of a slope, a study of a virgin area was made in a Beech stand of mountain forests, northern Iran. Across the slope positions, the soil profiles demonstrated significant changes due to topography for two shape slopes. The solum depth of the convex slope was higher than the concave one in all five positions, and it decreased from the summit to shoulder and increased from the mid to lower slope positions for both convex and concave slopes. The thin solum at the upper positions and concave slope demonstrated that pedogenetic development is least at upper slope positions and concave slope where leaching and biomass productivity are less than at lower slopes and concave slope. A large decrease in the thickness of O and A horizons from the summit to back slope was noted for both concave and convex slopes, but it increased from back slope toward down slope for both of them. The average thickness of B horizons increased from summit to down slopes in the case of the concave slope, but in the case of convex slope it decreased from summit to shoulder and afterwards it increased to the down slope. The thicknesses of the different horizons varied in part in the different positions and shape slopes because they had different plant species cover and soil features, which were related to topography.

Nonmonotonic and spatial-temporal dynamic slope effects on soil erosion during rainfall-runoff processes

NASA Astrophysics Data System (ADS)

Wu, Songbai; Yu, Minghui; Chen, Li

2017-02-01

The slope effect on flow erosivity and soil erosion still remains a controversial issue. This theoretical framework explained and quantified the direct slope effect by coupling the modified Green-Ampt equation accounting for slope effect on infiltration, 1-D kinematic wave overland flow routing model, and WEPP soil erosion model. The flow velocity, runoff rate, shear stress, interrill, and rill erosion were calculated on 0°-60° isotropic slopes with equal horizontal projective length. The results show that, for short-duration rainfall events, the flow erosivity and erosion amounts exhibit a bell-shaped trend which first increase with slope gradient, and then decrease after a critical slope angle. The critical slope angles increase significantly or even vanish with increasing rainfall duration but are nearly independent of the slope projective length. The soil critical shear stress, rainfall intensity, and temporal patterns have great influences on the slope effect trend, while the other soil erosion parameters, soil type, hydraulic conductivity, and antecedent soil moisture have minor impacts. Neglecting the slope effect on infiltration would generate smaller erosion and reduce critical slope angles. The relative slope effect on soil erosion in physically based model WEPP was compared to those in the empirical models USLE and RUSLE. The trends of relative slope effect were found quite different, but the difference may diminish with increasing rainfall duration. Finally, relatively smaller critical slope angles could be obtained with the equal slope length and the range of variation provides a possible explanation for the different critical slope angles reported in previous studies.

Role of adjacency-matrix degeneracy in maximum-entropy-weighted network models

NASA Astrophysics Data System (ADS)

Sagarra, O.; Pérez Vicente, C. J.; Díaz-Guilera, A.

2015-11-01

Complex network null models based on entropy maximization are becoming a powerful tool to characterize and analyze data from real systems. However, it is not easy to extract good and unbiased information from these models: A proper understanding of the nature of the underlying events represented in them is crucial. In this paper we emphasize this fact stressing how an accurate counting of configurations compatible with given constraints is fundamental to build good null models for the case of networks with integer-valued adjacency matrices constructed from an aggregation of one or multiple layers. We show how different assumptions about the elements from which the networks are built give rise to distinctively different statistics, even when considering the same observables to match those of real data. We illustrate our findings by applying the formalism to three data sets using an open-source software package accompanying the present work and demonstrate how such differences are clearly seen when measuring network observables.

Slope failure investigation management system.

DOT National Transportation Integrated Search

2013-03-01

Highway slopes are exposed to a variety of environmental and climatic conditions, such as deforestation, cycles of : freezing and thawing weather, and heavy storms. Over time, these climatic conditions, in combination with other : factors such as geo...

Adjacent-level arthroplasty following cervical fusion.

PubMed

Rajakumar, Deshpande V; Hari, Akshay; Krishna, Murali; Konar, Subhas; Sharma, Ankit

2017-02-01

OBJECTIVE Adjacent-level disc degeneration following cervical fusion has been well reported. This condition poses a major treatment dilemma when it becomes symptomatic. The potential application of cervical arthroplasty to preserve motion in the affected segment is not well documented, with few studies in the literature. The authors present their initial experience of analyzing clinical and radiological results in such patients who were treated with arthroplasty for new or persistent arm and/or neck symptoms related to neural compression due to adjacent-segment disease after anterior cervical discectomy and fusion (ACDF). METHODS During a 5-year period, 11 patients who had undergone ACDF anterior cervical discectomy and fusion (ACDF) and subsequently developed recurrent neck or arm pain related to adjacent-level cervical disc disease were treated with cervical arthroplasty at the authors' institution. A total of 15 devices were implanted (range of treated levels per patient: 1-3). Clinical evaluation was performed both before and after surgery, using a visual analog scale (VAS) for pain and the Neck Disability Index (NDI). Radiological outcomes were analyzed using pre- and postoperative flexion/extension lateral radiographs measuring Cobb angle (overall C2-7 sagittal alignment), functional spinal unit (FSU) angle, and range of motion (ROM). RESULTS There were no major perioperative complications or device-related failures. Statistically significant results, obtained in all cases, were reflected by an improvement in VAS scores for neck/arm pain and NDI scores for neck pain. Radiologically, statistically significant increases in the overall lordosis (as measured by Cobb angle) and ROM at the treated disc level were observed. Three patients were lost to follow-up within the first year after arthroplasty. In the remaining 8 cases, the duration of follow-up ranged from 1 to 3 years. None of these 8 patients required surgery for the same vertebral level during the follow

A study of the surface energy balance on slopes in a tallgrass prairie

NASA Technical Reports Server (NTRS)

Nie, D.; Demetriades-Shah, T.; Kanemasu, E. T.

1990-01-01

Four slopes (north, south, east, and west) were selected on the Konza Prairie Research Natural Area to study the effect of topography on surface energy balance and other micrometeorological variables. Energy fluxes, air temperature, and vapor pressure were measured on the sloped throughout the 1988 growing season. Net radiation was the highest on the south-facing slope and lowest on the north-facing slope, and the difference was more than 150 W/sq m (20 to 30 percent) at solar noon. For daily averages, the difference was 25 W/sq m (15 percent) early in the season and increased to 60 W/sq m (30 to 50 percent) in September. The east-facing and west-facing slopes had the same daily average net radiation, but the time of day when maximum net radiation occurred was one hour earlier for the east-facing slope and one hour later for the west-facing slope relative to solar noon. Soil heat fluxes were similar for all the slopes. The absolute values of sensible heat flux (h) was consistently lower on the north-facing slope compared with other slopes. Typical difference in the values of H between the north-facing and the south-facing slopes was 15 to 30 W/sq m. The south-facing slope had the greatest day to day fluctuation in latent heat flux as a result of interaction of net radiation, soil moisture, and green leaf area. The north-facing slope had higher air temperatures during the day and higher vapor pressures both during the day and at night when the wind was from the south.

Landscape Evolution Associated with Recurring Slope Lineae (RSL) on Mars

NASA Astrophysics Data System (ADS)

McEwen, A. S.; Dundas, C. M.; Chojnacki, M.; Ojha, L.

2016-12-01

RSL are low-albedo features that initiate at bedrock outcrops and extend down steep slopes. Individual slopes may have hundreds of lineae, with widths up to 5 m and lengths up to 1.5 km. RSL appear and lengthen gradually or incrementally, fade when inactive, and recur each year, normally in the warmest season. Small channels (1-20 m wide) are often present and control RSL paths. We have also detected newly-formed topographic land slumps associated with RSL fans in at least 7 locations—4 around a hill in Juventae Chasma, 2 in Garni crater in Melas Chasma, and 1 along wall slopes in Coprates Chasma. This distinctive landform assemblage is seen at several other locations within central and eastern Valles Marineris (VM): Small channels on most slope aspects of isolated hills or crater walls, extending very nearly to the tops of the hills or crater rim, associated with RSL that match the channels in size, and with a set of lobate deposits at the base of RSL fans. RSL activity in VM changes slope aspect with season—N-facing slopes in northern summer and S-facing slopes in southern summer. The slumps form midway down the RSL fans, and have a different seasonality—most active from Ls 0-120, the coldest time of year in VM. Assuming this association between gullies, RSL, and slumps is not coincidental, an integrated landscape evolution model is needed. Perhaps RSL activity carves the small gullies and deposits sediment near the base of angle-of-repose slopes, locally oversteepening the slope, which episodically slumps. RSL activity is seasonal and associated with the transient presence of hydrated salts, which indicates some role for salty water. If the RSL were caused by fluid flow, they should not be precisely confined to angle-of-repose or steeper slopes (>28 deg.), so these seem to be dry granular flows whose activity is triggered by or somehow associated with small amounts of water. There are multiple mysteries, such as how the activity recurs at the same

Bowhead whale acoustic activity in the southeast Beaufort Sea during late summer 2008-2010.

PubMed

Charif, Russell A; Rahaman, Ashakur; Muirhead, Charles A; Pitzrick, Michael S; Warde, Ann M; Hall, James; Pyć, Cynthia; Clark, Christopher W

2013-12-01

Autonomous passive acoustic recorders were deployed to record sounds of bowhead whales (Balaena mysticetus) in the southeast Beaufort Sea for periods of 30-55 days during the late summer, open-water seasons of 2008-2010. Recordings were made in three areas licensed for hydrocarbon exploration, spanning the continental slope and adjacent outer shelf, and in a shallow inner-shelf area where bowheads have been observed congregating to feed in recent decades. Bowhead sounds were counted in samples comprising 10% of each recorded hour. In mid-August and September in all 3 years, the rate of bowhead calling at outer shelf sites exceeded that at adjacent continental slope sites by one to two orders of magnitude. Higher rates of calling occurred on the slope in late July and early August than at later dates. Calling rates varied by an order of magnitude between years in the one area that was monitored in different years. The highest rates of calling occurred on the inner shelf, offshore of the northern Tuktoyaktuk Peninsula. These trends are consistent with patterns of habitat use previously reported from aerial surveys in this and nearby areas of the Beaufort Sea and with the results of satellite tagging studies.

DESIGN INFORMATION REPORT: PROTECTION OF WASTEWATER LAGOON INTERIOR SLOPES

EPA Science Inventory

A problem common to many wastewater treatment and storage lagoons is erosion of the interior slopes. Erosion may be caused by surface runoff and wind-induced wave action. The soils that compose the steep interior slopes of lagoons are especially susceptible to erosion and slumpin...

The quadruped robot adaptive control in trotting gait walking on slopes

NASA Astrophysics Data System (ADS)

Zhang, Shulong; Ma, Hongxu; Yang, Yu; Wang, Jian

2017-10-01

The quadruped robot can be decomposed into a planar seven-link closed kinematic chain in the direction of supporting line and a linear inverted pendulum in normal direction of supporting line. The ground slope can be estimated by using the body attitude information and supporting legs length. The slope degree is used in feedback, to achieve the point of quadruped robot adaptive control walking on slopes. The simulation results verify that the quadruped robot can achieves steady locomotion on the slope with the control strategy proposed in this passage.

49 CFR 214.107 - Working over or adjacent to water.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 4 2014-10-01 2014-10-01 false Working over or adjacent to water. 214.107 Section 214.107 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD WORKPLACE SAFETY Bridge Worker Safety Standards § 214.107 Working over or adjacent to water. (a)...

49 CFR 214.107 - Working over or adjacent to water.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 49 Transportation 4 2012-10-01 2012-10-01 false Working over or adjacent to water. 214.107 Section 214.107 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD WORKPLACE SAFETY Bridge Worker Safety Standards § 214.107 Working over or adjacent to water. (a)...

49 CFR 214.107 - Working over or adjacent to water.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 4 2011-10-01 2011-10-01 false Working over or adjacent to water. 214.107 Section 214.107 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION RAILROAD WORKPLACE SAFETY Bridge Worker Safety Standards § 214.107 Working over or adjacent to water. (a)...

The coupled response to slope-dependent basal melting

NASA Astrophysics Data System (ADS)

Little, C. M.; Goldberg, D. N.; Sergienko, O. V.; Gnanadesikan, A.

2009-12-01

Ice shelf basal melting is likely to be strongly controlled by basal slope. If ice shelves steepen in response to intensified melting, it suggests instability in the coupled ice-ocean system. The dynamic response of ice shelves governs what stable morphologies are possible, and thus the influence of melting on buttressing and grounding line migration. Simulations performed using a 3-D ocean model indicate that a simple form of slope-dependent melting is robust under more complex oceanographic conditions. Here we utilize this parameterization to investigate the shape and grounding line evolution of ice shelves, using a shallow-shelf approximation-based model that includes lateral drag. The distribution of melting substantially affects the shape and aspect ratio of unbuttressed ice shelves. Slope-dependent melting thins the ice shelf near the grounding line, reducing velocities throughout the shelf. Sharp ice thickness gradients evolve at high melting rates, yet grounding lines remain static. In foredeepened, buttressed ice shelves, changes in grounding line flux allow two additional options: stable or unstable retreat. Under some conditions, slope-dependent melting results in stable configurations even at high melt rates.

Recurring Lineae on Slopes at Hale Crater, Mars

NASA Image and Video Library

2015-09-28

Dark, narrow streaks on Martian slopes such as these at Hale Crater are inferred to be formed by seasonal flow of water on contemporary Mars. The streaks are roughly the length of a football field. The imaging and topographical information in this processed, false-color view come from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. These dark features on the slopes are called "recurring slope lineae" or RSL. Planetary scientists using observations with the Compact Reconnaissance Imaging Spectrometer on the same orbiter detected hydrated salts on these slopes at Hale Crater, corroborating the hypothesis that the streaks are formed by briny liquid water. The image was produced by first creating a 3-D computer model (a digital terrain map) of the area based on stereo information from two HiRISE observations, and then draping a false-color image over the land-shape model. The vertical dimension is exaggerated by a factor of 1.5 compared to horizontal dimensions. The camera records brightness in three wavelength bands: infrared, red and blue-green. The draped image is one product from HiRISE observation ESP_03070_1440. http://photojournal.jpl.nasa.gov/catalog/PIA19916

Slope basins, headless canyons, and submarine palaeoseismology of the Cascadia accretionary complex

USGS Publications Warehouse

McAdoo, B.G.; Orange, D.L.; Screaton, Elizabeth; Lee, H.; Kayen, R.

1997-01-01

A combination of geomorphological, seismic reflection and geotechnical data constrains this study of sediment erosion and deposition at the toe of the Cascadia accretionary prism. We conducted a series of ALVIN dives in a region south of Astoria Canyon to examine the interrelationship of fluid flow and slope failure in a series of headless submarine canyons. Elevated head gradients at the inflection point of canyons have been inferred to assist in localized failures that feed sediment into a closed slope basin. Measured head gradients are an order of magnitude too low to cause seepage-induced slope failure alone; we therefore propose transient slope failure mechanisms. Intercanyon slopes are uniformly unscarred and smooth, although consolidation tests indicate that up to several metres of material may have been removed. A sheet-like failure would remove sediment uniformly, preserving the observed smooth intercanyon slope. Earthquake-induced liquefaction is a likely trigger for this type of sheet failure as the slope is too steep and short for sediment flow to organize itself into channels. Bathymetric and seismic reflection data suggest sediment in a trench slope basin between the second and third ridges from the prism's deformation is derived locally. A comparison of the amounts of material removed from the slopes and that in the basin shows that the amount of material removed from the slopes may slightly exceed the amount of material in the basin, implying that a small amount of sediment has escaped the basin, perhaps when the second ridge was too low to form a sufficient dam, or through a gap in the second ridge to the south. Regardless, almost 80% of the material shed off the slopes around the basin is deposited locally, whereas the remaining 20% is redeposited on the incoming section and will be re-accreted.

Macrobenthos of Yenisei Bay and the adjacent Kara Sea shelf

NASA Astrophysics Data System (ADS)

Galkin, S. V.; Vedenin, A. A.

2015-07-01

Trawl samples were collected in the northern region of Yenisei Bay and adjacent parts of the Kara Sea shelf. A total of eight stations were taken. We found more than 200 species of benthic organisms. A consecutive replacement of benthic communities is observed when going to the north from the Ob and Yenisei estuaries to the open parts of the sea. We could distinguish four different species complexes in the investigated area: a brackish-water complex where Saduria entomon is dominant; an intermediate complex where S. sibirica, S. sabini and Portlandia aestuariorum are dominant; a transitional complex with P. arctica as a dominant species and with a small amount of Ophiocten sericeum; a marine complex where O. sericeum is dominant. When salinity increased, some brackish-water species were replaced by related euryhaline species. One such example was the replacement of brackish-water Saduria entomon isopods by two euryhaline species: S. sibirica and S. sabini. The consecutive replacement of benthic communities showed a break near Sverdrup Island. In this area the marine complex was replaced by a transitional complex with P. arctica.

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...

Compost for steep slope erosion.

DOT National Transportation Integrated Search

2008-06-01

This study was initiated to develop guidelines for maintenance erosion control measures for steep slopes. The study focused on evaluating and monitoring KY-31 fescue germination rates using two media treatments 1) 100 percent by weight compost and 2)...

Turbulent properties under sloping Ice-wall in polar water

NASA Astrophysics Data System (ADS)

Mondal, Mainak; Gayen, Bishakhdatta; Griffiths, Ross W.; Kerr, Ross C.

2017-11-01

Ice-shelves around West Antarctic basins are the most vulnerable to melting in the presence of warmer continental shelf water. A large extent of slope exists under these ice-shelves, where turbulent transport of salt and heat into the ice wall drives a convective melt-water plume against it. Large scale ice-ocean models neglect the effect of convection which can lead to a wrong estimation of melt rate. We perform direct numerical simulations under sloping ice-shelves with realistic ambient conditions. We estimated the melt rates, boundary layer thicknesses and entrainment coefficients as a function of slope angle. The numerical results are further supported by theoretical predictions. Over the range of slope angles, different mechanisms are active for sustaining turbulence. For near vertical case, buoyancy production is the primary source of turbulent kinetic energy whereas for shallower angles turbulence is produced by velocity shear in the meltwater plume. Australian Research Council.

[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.

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

Slope Error Measurement Tool for Solar Parabolic Trough Collectors: Preprint

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

Stynes, J. K.; Ihas, B.

2012-04-01

The National Renewable Energy Laboratory (NREL) has developed an optical measurement tool for parabolic solar collectors that measures the combined errors due to absorber misalignment and reflector slope error. The combined absorber alignment and reflector slope errors are measured using a digital camera to photograph the reflected image of the absorber in the collector. Previous work using the image of the reflection of the absorber finds the reflector slope errors from the reflection of the absorber and an independent measurement of the absorber location. The accuracy of the reflector slope error measurement is thus dependent on the accuracy of themore » absorber location measurement. By measuring the combined reflector-absorber errors, the uncertainty in the absorber location measurement is eliminated. The related performance merit, the intercept factor, depends on the combined effects of the absorber alignment and reflector slope errors. Measuring the combined effect provides a simpler measurement and a more accurate input to the intercept factor estimate. The minimal equipment and setup required for this measurement technique make it ideal for field measurements.« less

Early Verb Constructions in French: Adjacency on the Left Edge

ERIC Educational Resources Information Center

Veneziano, Edy; Clark, Eve V.

2016-01-01

Children acquiring French elaborate their early verb constructions by adding adjacent morphemes incrementally at the left edge of core verbs. This hypothesis was tested with 2657 verb uses from four children between 1;3 and 2;7. Consistent with the Adjacency Hypothesis, children added clitic subjects frst only to present tense forms (as in…

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...

Adjacent bin stability evaluating for feature description

NASA Astrophysics Data System (ADS)

Nie, Dongdong; Ma, Qinyong

2018-04-01

Recent study improves descriptor performance by accumulating stability votes for all scale pairs to compose the local descriptor. We argue that the stability of a bin depends on the differences across adjacent pairs more than the differences across all scale pairs, and a new local descriptor is composed based on the hypothesis. A series of SIFT descriptors are extracted from multiple scales firstly. Then the difference value of the bin across adjacent scales is calculated, and the stability value of a bin is calculated based on it and accumulated to compose the final descriptor. The performance of the proposed method is evaluated with two popular matching datasets, and compared with other state-of-the-art works. Experimental results show that the proposed method performs satisfactorily.

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.

Covariant open bosonic string field theory on multiple D-branes in the proper-time gauge

NASA Astrophysics Data System (ADS)

Lee, Taejin

2017-12-01

We construct a covariant open bosonic string field theory on multiple D-branes, which reduces to a non-Abelian group Yang-Mills gauge theory in the zero-slope limit. Making use of the first quantized open bosonic string in the proper time gauge, we convert the string amplitudes given by the Polyakov path integrals on string world sheets into those of the second quantized theory. The world sheet diagrams generated by the constructed open string field theory are planar in contrast to those of the Witten's cubic string field theory. However, the constructed string field theory is yet equivalent to the Witten's cubic string field theory. Having obtained planar diagrams, we may adopt the light-cone string field theory technique to calculate the multi-string scattering amplitudes with an arbitrary number of external strings. We examine in detail the three-string vertex diagram and the effective four-string vertex diagrams generated perturbatively by the three-string vertex at tree level. In the zero-slope limit, the string scattering amplitudes are identified precisely as those of non-Abelian Yang-Mills gauge theory if the external states are chosen to be massless vector particles.

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.

Change Analysis of Laser Scans of Laboratory Rock Slopes Subject to Wave Attack Testing

NASA Astrophysics Data System (ADS)

Shen, Y.; Lindenbergh, R.; Hofland, B.; Kramer, R.

2017-09-01

For better understanding how coastal structures with gentle slopes behave during high energy events, a wave attack experiment representing a storm of 3000 waves was performed in a flume facility. Two setups with different steepness of slope were compared under the same conditions. In order to quantify changes in the rock slopes after the wave attack, a terrestrial laser scanner was used to obtain 3D coordinates of the rock surface before and after each experiment. Next, through a series of processing steps, the point clouds were converted to a suitable 2D raster for change analysis. This allowed to estimate detailed and quantitative change information. The results indicate that the area around the artificial coast line, defined as the intersection between sloped surface and wave surface, is most strongly affected by wave attacks. As the distances from the sloped surface to the waves are shorter, changes for the mildly sloped surface, slope 1 (1 : 10), are distributed over a larger area compared to the changes for the more steeply sloped surface, slope 2 (1 : 5). The results of this experiment show that terrestrial laser scanning is an effective and feasible method for change analysis of rock slopes in a laboratory setting. Most striking results from a process point of view is that the transport direction of the rocks change between the two different slopes: from seaward transport for the steeper slope to landward transport for the milder slope.

Objectifying the Adjacent and Opposite Angles: A Cultural Historical Analysis

ERIC Educational Resources Information Center

Daher, Wajeeh; Musallam, Nadera

2018-01-01

The angle topic is central to the development of geometric knowledge. Two of the basic concepts associated with this topic are the adjacent and opposite angles. It is the goal of the present study to analyze, based on the cultural historical semiotics framework, how high-achieving seventh grade students objectify the adjacent and opposite angles'…

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

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

Plant succession on talus slopes in northern Idaho as influenced by slope exposure

Treesearch

R. Daubenmire; A. W. Slipp

1943-01-01

One of the most conspicuous features of the forested regions of northern Idaho is the small treeless areas which occupy portions of the southerly exposures of especially prominent peaks and ridges. These areas, sometimes referred to as parks or balds, begin at the summits of the prominences and extend down over the south-facing slopes sometimes as much as approximately...

Do Mangroves Subsidize Carbon to Adjacent Mudflat Fish Communities?

NASA Astrophysics Data System (ADS)

Henkel, S.; Kasten, S.; Hartmann, J.; Staubwasser, M.; Hernandez, M. F.; West, L.; Midway, S. R.; Polito, M. J.

2017-12-01

Mangroves are often implicated as energetic sources for fisheries productivity. However, the validity of this connection still remains in contention. Stable isotopes may provide answers by tracking the use of specific basal carbon sources in fish and invertebrates living in mangrove-mudflat habitat mosaics. We analyzed 307 consumer samples representing n=44 fish and invertebrate species collected from mangrove forest creeks and adjacent mudflats in coastal Tanzania using bulk carbon and nitrogen stable isotope analysis. Given the proposed high productivity of mangrove habitats, we hypothesize that mudflat communities will have carbon stable isotope values similar to mangrove communities either through the flux of mangrove carbon into adjacent mudflats and/or via the movement of mudflat fish communities into and out of mangrove habitats. Alternatively, mangrove carbon is often refractory, which may result in mudflat communities with isotopic values that differ from those found in adjacent mangrove communities. This scenario would suggest limited carbon flow between mudflat and mangrove food webs and that the movement of fish into and out of mangrove habitats is related to shelter from predation more than feeding. Data analysis is ongoing to test these competing hypotheses. By understanding the contribution of mangrove carbon to adjacent habitats, managers in Tanzania can make better informed decisions regarding the protection of mangroves and the local fisheries, which are a crucial source of income and food.

Determination of slope failure using 2-D resistivity method

NASA Astrophysics Data System (ADS)

Muztaza, Nordiana Mohd; Saad, Rosli; Ismail, Nur Azwin; Bery, Andy Anderson

2017-07-01

Landslides and slope failure may give negative economic effects including the cost to repair structures, loss of property value and medical costs in the event of injury. To avoid landslide, slope failure and disturbance of the ecosystem, good and detailed planning must be done when developing hilly area. Slope failure classification and various factors contributing to the instability using 2-D resistivity survey conducted in Selangor, Malaysia are described. The study on landslide and slope failure was conducted at Site A and Site B, Selangor using 2-D resistivity method. The implications of the anticipated ground conditions as well as the field observation of the actual conditions are discussed. Nine 2-D resistivity survey lines were conducted in Site A and six 2-D resistivity survey lines with 5 m minimum electrode spacing using Pole-dipole array were performed in Site B. The data were processed using Res2Dinv and Surfer10 software to evaluate the subsurface characteristics. 2-D resistivity results from both locations show that the study areas consist of two main zones. The first zone is alluvium or highly weathered with the resistivity of 100-1000 Ωm at 20-70 m depth. This zone consists of saturated area (1-100 Ωm) and boulders with resistivity value of 1200-3000 Ωm. The second zone with resistivity values of > 3000 Ωm was interpreted as granitic bedrock. The study area was characterized by saturated zones, highly weathered zone, highly contain of sand and boulders that will trigger slope failure in the survey area. Based on the results obtained from the study findings, it can be concluded that 2-D resistivity method is useful method in determination of slope failure.

[Effects of slopes on nitrogen transport along with runoff from sloping plots on a lateritic red soil amended with sewage sludge].

PubMed

Chen, Yan-Hui; Chen, Ming-Hua; Wang, Guo; Chen, Wen-Xiang; Yang, Shun-Cheng; Chai, Peng

2010-10-01

The effects of different slopes on nitrogen transport along with runoff from sloping plots amended with sewage sludge on a lateritic red soil were studied under simulated rainfall conditions. When the sludge was broadcasted and mixed with surface soils (BM), the MTN (total nitrogen of mixing sample), STN (total nitrogen of settled sample), TPN (total particulate nitrogen), TSN (total suspended nitrogen), TDN (total dissolved nitrogen) and NH4(+) -N concentrations and nitrogen loss amounts in runoff of all treatments were highest at 1 day or 18 days after application. The highest concentrations and the loss amounts of MTN and STN in the slope runoff for the BM treatment increased with slope degree, showing increasing pollution risks to the surface waters. The STN concentration and loss amounts from the 25 degrees plots were 126.1 mg x L(-1) and 1788.6 mg x m(-2), respectively, being 4.6 times and 5.8 times of the corresponding values from the 10 degrees plots, respectively. Then the concentrations and the loss amounts of nitrogen (except NO3(-) -N) from the BM plots diminished rapidly first and then tended to be stable with dwindling differences between the slopes. The loss of MTN and STN in early runoff (1 day and 18 days) accounted for 68.6% -73.4% and 62.3% -66.7% of the cumulative loss amounts during the experimental period for all the broadcasted treatments. Runoff loss coefficients of MTN increased in the order of 20 degrees > 25 degrees > 15 degrees > 10 degrees. Nitrogen was largely lost in dissolved species while large portion of NH4(+) -N was lost with particulates.

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.

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

Submarine slope failures along the convergent continental margin of the Middle America Trench

NASA Astrophysics Data System (ADS)

Harders, Rieka; Ranero, CéSar R.; Weinrebe, Wilhelm; Behrmann, Jan H.

2011-06-01

We present the first comprehensive study of mass wasting processes in the continental slope of a convergent margin of a subduction zone where tectonic processes are dominated by subduction erosion. We have used multibeam bathymetry along ˜1300 km of the Middle America Trench of the Central America Subduction Zone and deep-towed side-scan sonar data. We found abundant evidence of large-scale slope failures that were mostly previously unmapped. The features are classified into a variety of slope failure types, creating an inventory of 147 slope failure structures. Their type distribution and abundance define a segmentation of the continental slope in six sectors. The segmentation in slope stability processes does not appear to be related to slope preconditioning due to changes in physical properties of sediment, presence/absence of gas hydrates, or apparent changes in the hydrogeological system. The segmentation appears to be better explained by changes in slope preconditioning due to variations in tectonic processes. The region is an optimal setting to study how tectonic processes related to variations in intensity of subduction erosion and changes in relief of the underthrusting plate affect mass wasting processes of the continental slope. The largest slope failures occur offshore Costa Rica. There, subducting ridges and seamounts produce failures with up to hundreds of meters high headwalls, with detachment planes that penetrate deep into the continental margin, in some cases reaching the plate boundary. Offshore northern Costa Rica a smooth oceanic seafloor underthrusts the least disturbed continental slope. Offshore Nicaragua, the ocean plate is ornamented with smaller seamounts and horst and graben topography of variable intensity. Here mass wasting structures are numerous and comparatively smaller, but when combined, they affect a large part of the margin segment. Farther north, offshore El Salvador and Guatemala the downgoing plate has no large seamounts but

Are Icelandic rock-slope failures paraglacial? Age evaluation of seventeen rock-slope failures in the Skagafjörður area, based on geomorphological stacking, radiocarbon dating and tephrochronology

NASA Astrophysics Data System (ADS)

Mercier, Denis; Coquin, Julien; Feuillet, Thierry; Decaulne, Armelle; Cossart, Etienne; Jónsson, Helgi Pall; Sæmundsson, Þorstein

2017-11-01

In Iceland there are numerous rock-slope failures, especially in the Tertiary basaltic formations of the northern, eastern and northwestern regions. The temporal pattern of rock-slope failures is fundamental for understanding post-glacial events. In the Skagafjörður district, central northern Iceland, 17 rock-slope failures were investigated to determine the age of their occurrence. A geomorphic survey was carried out to identify and characterize landform units, both on the rock-slope failures and in their immediate vicinity. In this coastal area, we used geomorphological stacking which included the relationship between rock-slope failures and raised beaches caused by glacial isostatic rebounds, the chronology of which was established in previous studies. We searched for depressions on the rock-slope failures to then excavate a series of pits and map the stratigraphy. The resulting stratigraphic framework was then validated using (i) radiocarbon dating of wood remains, and (ii) tephrochronology, both of which were complemented by age-depth model calibration. The results confirm that all the rock-slope failures potentially occurred before the Boreal (8 ka), while 94% occurred before the Preboreal (10 ka). They all potentially occurred after the glacial retreat following the maximal ice extent and the Preboreal. More precisely, 11 of them potentially occurred between the Preboreal and the first half of the Holocene. This study demonstrates the relationship between the deglaciation and destabilization of slopes during the paraglacial phase (debuttressing, decompression, glacial isostatic rebound, seismic activity, etc.), which are also controlling factors favouring landsliding, but are difficult to identify for each individual rock-slope failure.

Effect of Angle of Attack on Slope Climbing Performance

NASA Technical Reports Server (NTRS)

Creager, Colin M.; Jones, Lucas; Smith, Lauren M.

2017-01-01

Ascending steep slopes is often a very difficult challenge for off-road vehicles, whether on Earth or on extraterrestrial bodies. This challenge is even greater if the surface consists of loose granular soil that does not provide much shear strength. This study investigated how the path at which a vehicle traverses a slope, specifically the angle that it is commanded to drive relative to the base of the hill (the angle of attack), can affect its performance. A vehicle was driven in loose sand at slope angles up to 15 degrees and angles of attack ranging from 10 to 90 degrees. A novel photogrammetry technique was implemented to both track vehicle motion and create a three-dimensional profile of the terrain. This allowed for true wheel sinkage measurements. The study showed that though low angles of attack result in lower wheel slip and sinkage, the efficiency of the vehicles uphill motion increased at higher angles of attack. For slopes up to 15 degrees, a 90 degree angle of attack provided the greatest likelihood of successful ascent.

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%.

After the slippery slope: Dutch experiences on regulating active euthanasia.

PubMed

Boer, Theo A

2003-01-01

"When a country legalizes active euthanasia, it puts itself on a slippery slope from where it may well go further downward." If true, this is a forceful argument in the battle of those who try to prevent euthanasia from becoming legal. The force of any slippery slope argument, however, is by definition limited by its reference to future developments which cannot empirically be sustained. Experience in the Netherlands--where a law regulating active euthanasia was accepted in April 2001--may shed light on the strengths as well as the weaknesses of the slippery slope argument in the context of the euthanasia debate. This paper consists of three parts. First, it clarifies the Dutch legislation on euthanasia and explains the cultural context in which it originated. Second, it looks at the argument of the slippery slope. A logical and an empirical version are distinguished, and the latter, though philosophically less interesting, proves to be most relevant in the discussion on euthanasia. Thirdly, it addresses the question whether Dutch experiences in the process of legalizing euthanasia justify the fear of the slippery slope. The conclusion is that Dutch experiences justify some caution.

Exploring Slope with Stairs & Steps

ERIC Educational Resources Information Center

Smith, Toni M.; Seshaiyer, Padmanabhan; Peixoto, Nathalia; Suh, Jennifer M.; Bagshaw, Graham; Collins, Laurena K.

2013-01-01

As much as ever before, mathematics teachers are searching for ways to connect mathematics to real-life scenarios within STEM contexts. As students develop skill in proportional reasoning, they examine graphical representations of linear functions, learn to associate "slope" with "steepness" and rate of change, and develop…

Meter-scale slopes of candidate MER landing sites from point photoclinometry

USGS Publications Warehouse

Beyer, R.A.; McEwen, A.S.; Kirk, R.L.

2003-01-01

Photoclinometry was used to analyze the small-scale roughness of areas that fall within the proposed Mars Exploration Rover (MER) 2003 landing ellipses. The landing ellipses presented in this study were those in Athabasca Valles, Elysium Planitia, Eos Chasma, Gusev Crater, Isidis Planitia, Melas Chasma, and Meridiani Planum. We were able to constrain surface slopes on length scales comparable to the image resolution (1.5 to 12 m/pixel). The MER 2003 mission has various engineering constraints that each candidate landing ellipse must satisfy. These constraints indicate that the statistical slope values at 5 m baselines are an important criterion. We used our technique to constrain maximum surface slopes across large swaths of each image, and built up slope statistics for the images in each landing ellipse. We are confident that all MER 2003 landing site ellipses in this study, with the exception of the Melas Chasma ellipse, are within the small-scale roughness constraints. Our results have provided input into the landing hazard assessment process. In addition to evaluating the safety of the landing sites, our mapping of small-scale roughnesses can also be used to better define and map morphologic units. The morphology of a surface is characterized by the slope distribution and magnitude of slopes. In looking at how slopes are distributed, we can better define landforms and determine the boundaries of morphologic units. Copyright 2003 by the American Geophysical Union.

Adjacent-Categories Mokken Models for Rater-Mediated Assessments

PubMed Central

Wind, Stefanie A.

2016-01-01

Molenaar extended Mokken’s original probabilistic-nonparametric scaling models for use with polytomous data. These polytomous extensions of Mokken’s original scaling procedure have facilitated the use of Mokken scale analysis as an approach to exploring fundamental measurement properties across a variety of domains in which polytomous ratings are used, including rater-mediated educational assessments. Because their underlying item step response functions (i.e., category response functions) are defined using cumulative probabilities, polytomous Mokken models can be classified as cumulative models based on the classifications of polytomous item response theory models proposed by several scholars. In order to permit a closer conceptual alignment with educational performance assessments, this study presents an adjacent-categories variation on the polytomous monotone homogeneity and double monotonicity models. Data from a large-scale rater-mediated writing assessment are used to illustrate the adjacent-categories approach, and results are compared with the original formulations. Major findings suggest that the adjacent-categories models provide additional diagnostic information related to individual raters’ use of rating scale categories that is not observed under the original formulation. Implications are discussed in terms of methods for evaluating rating quality. PMID:29795916

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

A combined endovascular and open ''reverse hybrid'' technique for repair of complex juxtarenal inflammatory aortic aneurysms.

PubMed

Rigberg, David; Jimenez, Juan Carlos; Lawrence, Peter; Gelabert, Hugh

2009-01-01

Inflammatory abdominal aortic aneurysms (IAAA) can present significant challenges to surgeons, especially in the juxtarenal location where they may not be amenable to endovascular repair. The dense, inflammatory component of these lesions can encase adjacent structures including the duodenum, ureters, and inferior vena cava putting them at risk for injury during open exposure. We report a novel ''reverse hybrid'' technique using a combined endovascular and open approach for repair of large, juxtarenal IAAA's.

Correlation of heart rate/ST slope and coronary angiographic findings.

PubMed Central

Balcon, R; Brooks, N; Layton, C

1984-01-01

The heart rate/ST slope was evaluated in 49 patients undergoing routine investigation for possible coronary artery disease. The slope correctly predicted the absence of any 75% stenoses in the seven patients to whom this applied; it was, however, correct for only four of 30 with one stenosis, one of 10 with two, and neither of the patients with three. Distinct slope ranges were not found, and the previously published ranges said to be specific for no significant stenosis and one, two, and three vessel disease were not. PMID:6466516

Mycorrhizal aspects in slope stabilisation

NASA Astrophysics Data System (ADS)

Graf, Frank

2016-04-01

In order to re-colonise and stabilise slopes affected by superficial soil failure with plants essential requirements have to be met: the plants must grow the plants must survive sustainably plant succession must start and continuously develop These requirements, however, are anything but easy given, particularly under the often hostile environmental conditions dominating on bare and steep slopes. Mycorrhizal fungi, the symbiotic partners of almost all plants used in eco-engineering, are said to improve the plants' ability to overcome periods governed by strongly (growth) limiting factors. Subsequently, results of investigations are presented of mycorrhizal effects on different plant and soil functions related to eco-engineering in general and soil and slope stabilisation in particular. Generally, inoculation yielded higher biomass of the host plants above as well as below ground. Furthermore, the survival rate was higher for mycorrhized compared to non-mycorrhized plants, particularly under extreme environmental conditions. However, the scale of the mycorrhizal impact may be species specific of both the plant host as well as the fungal partner(s) and often becomes evident only after a certain time lag. Depending on the plant-fungus combination the root length per soil volume was found to be between 0 and 2.5 times higher for inoculated compared to non-inoculated specimens. On an alpine graded ski slope the survival of inoculated compared to non-treated Salix herbacea cuttings was significant after one vegetation period only for one of the three added mycorrhizal fungus species. However, after three years all of the inoculated plantlets performed significantly better than the non-inoculated controls. The analysis of the potential for producing and stabilising soil aggregates of five different ectomycorrhizal fungi showed high variation and, for the species Inocybe lacera, no significant difference compared to untreated soil. Furthermore, inoculation of Salix

Heterogeneous Landscapes on Steep Slopes at Low Altitudes as Hotspots of Bird Diversity in a Hilly Region of Nepal in the Central Himalayas.

PubMed

Basnet, Tej B; Rokaya, Maan B; Bhattarai, Bishnu P; Münzbergová, Zuzana

2016-01-01

Understanding factors determining the distribution of species is a key requirement for protecting diversity in a specific area. The aim of this study was to explore the factors affecting diversity and distribution of species of birds on different forested hills in central Nepal. The area is rich in species of birds. Because the area is characterized by steep gradients, we were also interested in the importance of altitude in determining the diversity and species composition of the bird communities. We assessed bird diversity and species composition based on point observations along a gradient of increasing altitude in two valleys (Kathmandu and Palung) in central Nepal. Data on environmental variables were also collected in order to identify the main determinants of bird diversity and species composition of the bird communities. We recorded 6522 individual birds belonging to 146 species, 77 genera and 23 families. Resident birds made up 80% (117 species) of the total dataset. The study supported the original expectation that altitude is a major determinant of species richness and composition of bird communities in the area. More diverse bird communities were found also in areas with steeper slopes. This together with the positive effect of greater heterogeneity suggests that forests on steep slopes intermixed with patches of open habitats on shallow soil at large spatial scales are more important for diverse bird communities than more disturbed habitats on shallow slopes. In addition, we demonstrated that while different habitat characteristics such as presence of forests edges and shrubs play an important role in driving species composition, but they do not affect species richness. This indicates that while habitat conditions are important determinants of the distribution of specific species, the number of niches is determined by large scale characteristics, such as landscape level habitat heterogeneity and altitude. Thus, to protect bird diversity in the mid

Heterogeneous Landscapes on Steep Slopes at Low Altitudes as Hotspots of Bird Diversity in a Hilly Region of Nepal in the Central Himalayas

PubMed Central

Basnet, Tej B.; Rokaya, Maan B.; Bhattarai, Bishnu P.; Münzbergová, Zuzana

2016-01-01

Understanding factors determining the distribution of species is a key requirement for protecting diversity in a specific area. The aim of this study was to explore the factors affecting diversity and distribution of species of birds on different forested hills in central Nepal. The area is rich in species of birds. Because the area is characterized by steep gradients, we were also interested in the importance of altitude in determining the diversity and species composition of the bird communities. We assessed bird diversity and species composition based on point observations along a gradient of increasing altitude in two valleys (Kathmandu and Palung) in central Nepal. Data on environmental variables were also collected in order to identify the main determinants of bird diversity and species composition of the bird communities. We recorded 6522 individual birds belonging to 146 species, 77 genera and 23 families. Resident birds made up 80% (117 species) of the total dataset. The study supported the original expectation that altitude is a major determinant of species richness and composition of bird communities in the area. More diverse bird communities were found also in areas with steeper slopes. This together with the positive effect of greater heterogeneity suggests that forests on steep slopes intermixed with patches of open habitats on shallow soil at large spatial scales are more important for diverse bird communities than more disturbed habitats on shallow slopes. In addition, we demonstrated that while different habitat characteristics such as presence of forests edges and shrubs play an important role in driving species composition, but they do not affect species richness. This indicates that while habitat conditions are important determinants of the distribution of specific species, the number of niches is determined by large scale characteristics, such as landscape level habitat heterogeneity and altitude. Thus, to protect bird diversity in the mid

Characteristics of low-slope streams that affect O2 transfer rates

USGS Publications Warehouse

Parker, Gene W.; Desimone, Leslie A.

1991-01-01

Multiple-regression techniques were used to derive the reaeration coefficients estimating equation for low sloped streams: K2 = 3.83 MBAS-0.41 SL0.20 H-0.76, where K2 is the reaeration coefficient in base e units per day; MBAS is the methylene blue active substances concentration in milligrams per liter; SL is the water-surface slope in foot per foot; and H is the mean-flow depth in feet. Fourteen hydraulic, physical, and water-quality characteristics were regressed against 29 measured-reaeration coefficients for low-sloped (water surface slopes less than 0.002 foot per foot) streams in Massachusetts and New York. Reaeration coefficients measured from May 1985 to October 1988 ranged from 0.2 to 11.0 base e units per day for 29 low-sloped tracer studies. Concentration of methylene blue active substances is significant because it is thought to be an indicator of concentration of surfactants which could change the surface tension at the air-water interface.

[Community structure of soil fauna in Eucalyptus grandis plantations at different slope locations].

PubMed

Zhao, Yu; Zhong, Yu; Zhang, Jian; Yang, Wan-qin

2010-09-01

To understand the effects of slope location on the community structure of soil fauna in Eucalyptus grandis plantation, an investigation was made on the soil fauna in 3 E. grandis plantations at different slope locations in the hilly area of Sichuan Province from January to October 2009. A total of 39,2762 individuals were observed, belonging to 146 groups, 7 phyla, 16 classes, and 31 orders. The community composition, trophic group, diversity, and seasonal dynamics of soil fauna in the plantations all varied with slope. The abundance of macro-fauna, xeric meso- and micro-fauna, saprophagous macro-fauna, and omnivorous xeric meso- and micro-fauna increased with the decrease of slope, indicating that soil fauna had sensitive responses to the soil environmental factors affected by slope. Significant differences in the diversity of soil saprophagous macro-fauna and hygrophilous meso- and micro-fauna were observed at different slope locations, suggesting that these two faunal groups could be used as the indicators of the habitat heterogeneity of E. grandis plantations at different slope. Overall, slope location had definite effects on the community structure and distribution of soil fauna in the E. grandis plantations, but the effects were not statistically significant.

Slope Streaks on a Dusty Planet

NASA Image and Video Library

2015-05-06

Mars is a dusty place and in some locations thick blankets of its characteristically red dust can slowly settle out of the atmosphere and accumulate on slopes. This dust is also a lot brighter than the dust-free terrain on Mars; so, if you scrape off the dust, you'll see a darker surface underneath. This particular image shows one of these dusty areas. The dark streaks on the slopes are locations where the dust has slumped downhill revealing a less dusty surface underneath. In some cases, these slope streaks might be triggered by Marsquakes or nearby meteorite impacts. Scientists think they form quickly: more like an avalanche than dust slowly creeping downhill. Look more closely and you'll notice that some streaks are darker than others. Dust is settling out of the atmosphere all the time and these dark streaks get slowly buried by fresh dust so that they fade back into their brighter redder surroundings. It's not certain how long this fading takes to happen, but it's probably close to a few decades. Dust is an important player in the weather and climate on Mars. Images like this are used to monitor slow changes in these streaks over time to better understand how much dust is settling on the surface. http://photojournal.jpl.nasa.gov/catalog/PIA19456

Java Programs for Using Newmark's Method and Simplified Decoupled Analysis to Model Slope Performance During Earthquakes

USGS Publications Warehouse

Jibson, Randall W.; Jibson, Matthew W.

2003-01-01

Landslides typically cause a large proportion of earthquake damage, and the ability to predict slope performance during earthquakes is important for many types of seismic-hazard analysis and for the design of engineered slopes. Newmark's method for modeling a landslide as a rigid-plastic block sliding on an inclined plane provides a useful method for predicting approximate landslide displacements. Newmark's method estimates the displacement of a potential landslide block as it is subjected to earthquake shaking from a specific strong-motion record (earthquake acceleration-time history). A modification of Newmark's method, decoupled analysis, allows modeling landslides that are not assumed to be rigid blocks. This open-file report is available on CD-ROM and contains Java programs intended to facilitate performing both rigorous and simplified Newmark sliding-block analysis and a simplified model of decoupled analysis. For rigorous analysis, 2160 strong-motion records from 29 earthquakes are included along with a search interface for selecting records based on a wide variety of record properties. Utilities are available that allow users to add their own records to the program and use them for conducting Newmark analyses. Also included is a document containing detailed information about how to use Newmark's method to model dynamic slope performance. This program will run on any platform that supports the Java Runtime Environment (JRE) version 1.3, including Windows, Mac OSX, Linux, Solaris, etc. A minimum of 64 MB of available RAM is needed, and the fully installed program requires 400 MB of disk space.

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.

Geological Characteristics of Active Methane Expulsion In Accretionary Prism Kaoping Slope Off SW Taiwan

NASA Astrophysics Data System (ADS)

Huang, C.; Chien, C.; Yang, T. F.; Lin, S.

2005-12-01

The Kaoping Slope off SW Taiwan represents the syn-collision accretionary prism characterized by active NW-trending folding - thrusting structures and high sedimentation rate favoring the formation of gas hydrate. For an assessment of gas hydrate potential in the Kaoping Slope off SW Taiwan, sedimentology, paleontology and geochemistry in box cores and piston cores were studied. BSRs are commonly found in seismic profiles in 400-600 m below seafloor of water depth 2500-1000 m. Active expulsions of methane were found along active thrust faults where sulfate/methane interface could be as shallow as 30 cm and the methane concentration of dissolved gases in bottom water and in pore-space of drilled core samples could be three-four order higher than the normal marine environments. Occurrences of authigenic carbonate and elongated pyrite tubes are correlated with shallow SMI depth and high methane content in bottom water and pore-space of sediment cores. Authigenic carbonates were found in seafloor surface and in 20-25 meters below seafloor. The authigenic carbonate nodules are characterized by irregular shape, whitish color, no visible microfossil, containing native sulfur, pyrites, gypsum, small open spaces, and very depleted carbon isotope (-54 ~ -43 per mil PDB). Tiny native sulfur and gypsum crystals were commonly found either on surface of foraminiferal tests and elongated pyrite tubes or in the authigenic carbonate nodules. Morphological measurements of elongated pyrite tubes show that they could represent pseudomorphs after three types of Pogonophora tube worm. Foraminifers are commonly filled by rhomboidal pyrites or cemented by pyrite crystals. Normal marine benthic foraminifers predominated by calcareous tests of slope fauna are associated with authigenic carbonate nodules in the study area, suggesting no major geochemistry effect on distribution of benthic foraminifers. Integrating sedimentology, paleontology and geochemistry characters, there could be high

Adjacent Habitat Influence on Stink Bug (Hemiptera: Pentatomidae) Densities and the Associated Damage at Field Corn and Soybean Edges

PubMed Central

Venugopal, P. Dilip; Coffey, Peter L.; Dively, Galen P.; Lamp, William O.

2014-01-01

The local dispersal of polyphagous, mobile insects within agricultural systems impacts pest management. In the mid-Atlantic region of the United States, stink bugs, especially the invasive Halyomorpha halys (Stål 1855), contribute to economic losses across a range of cropping systems. Here, we characterized the density of stink bugs along the field edges of field corn and soybean at different study sites. Specifically, we examined the influence of adjacent managed and natural habitats on the density of stink bugs in corn and soybean fields at different distances along transects from the field edge. We also quantified damage to corn grain, and to soybean pods and seeds, and measured yield in relation to the observed stink bug densities at different distances from field edge. Highest density of stink bugs was limited to the edge of both corn and soybean fields. Fields adjacent to wooded, crop and building habitats harbored higher densities of stink bugs than those adjacent to open habitats. Damage to corn kernels and to soybean pods and seeds increased with stink bug density in plots and was highest at the field edges. Stink bug density was also negatively associated with yield per plant in soybean. The spatial pattern of stink bugs in both corn and soybeans, with significant edge effects, suggests the use of pest management strategies for crop placement in the landscape, as well as spatially targeted pest suppression within fields. PMID:25295593

Adjacent habitat influence on stink bug (Hemiptera: Pentatomidae) densities and the associated damage at field corn and soybean edges.

PubMed

Venugopal, P Dilip; Coffey, Peter L; Dively, Galen P; Lamp, William O

2014-01-01

The local dispersal of polyphagous, mobile insects within agricultural systems impacts pest management. In the mid-Atlantic region of the United States, stink bugs, especially the invasive Halyomorpha halys (Stål 1855), contribute to economic losses across a range of cropping systems. Here, we characterized the density of stink bugs along the field edges of field corn and soybean at different study sites. Specifically, we examined the influence of adjacent managed and natural habitats on the density of stink bugs in corn and soybean fields at different distances along transects from the field edge. We also quantified damage to corn grain, and to soybean pods and seeds, and measured yield in relation to the observed stink bug densities at different distances from field edge. Highest density of stink bugs was limited to the edge of both corn and soybean fields. Fields adjacent to wooded, crop and building habitats harbored higher densities of stink bugs than those adjacent to open habitats. Damage to corn kernels and to soybean pods and seeds increased with stink bug density in plots and was highest at the field edges. Stink bug density was also negatively associated with yield per plant in soybean. The spatial pattern of stink bugs in both corn and soybeans, with significant edge effects, suggests the use of pest management strategies for crop placement in the landscape, as well as spatially targeted pest suppression within fields.

Flow Ejecta and Slope Landslides in Small Crater - High Resolution Image

NASA Technical Reports Server (NTRS)

1998-01-01

This high resolution picture of a moderately small impact crater on Mars was taken by the Mars Global Surveyor Orbiter Camera (MOC) on October 17, 1997 at 4:11:07 PM PST, during MGS orbit 22. The image covers an area 2.9 by 48.4 kilometers (1.8 by 30 miles) at 9.6 m (31.5 feet) per picture element, and is centered at 21.3 degrees N, 179.8 degrees W, near Orcus Patera. The MOC image is a factor of 15X better than pervious Viking views of this particular crater.

The unnamed crater is one of three closely adjacent impact features that display the ejecta pattern characteristic of one type of 'flow-ejecta' crater. Such patterns are considered evidence of fluidized movement of the materials ejected during the cratering event, and are believed to indicate the presence of subsurface ice or liquid water.

Long, linear features of different brightness values can be seen on the on the steep slopes inside and outside the crater rim. This type of feature, first identified in Viking Orbiter images acquired over 20 years ago, are more clearly seen in this new view (about 3 times better than the best previous observations). Their most likely explanation is that small land or dirt slides, initiated by seismic or wind action, have flowed down the steep slopes. Initially dark because of the nature of the surface disturbance, these features get lighter with time as the ubiquitous fine, bright dust settles onto them from the martian atmosphere. Based on estimates of the dust fall-out rate, many of these features are probably only a few tens to hundreds of years old. Thus, they are evidence of a process that is active on Mars today.

Malin Space Science Systems (MSSS) and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner

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.

Analysis of Local Slopes at the InSight Landing Site on Mars

NASA Astrophysics Data System (ADS)

Fergason, R. L.; Kirk, R. L.; Cushing, G.; Galuszka, D. M.; Golombek, M. P.; Hare, T. M.; Howington-Kraus, E.; Kipp, D. M.; Redding, B. L.

2017-10-01

To evaluate the topography of the surface within the InSight candidate landing ellipses, we generated Digital Terrain Models (DTMs) at lander scales and those appropriate for entry, descent, and landing simulations, along with orthoimages of both images in each stereopair, and adirectional slope images. These products were used to assess the distribution of slopes for each candidate ellipse and terrain type in the landing site region, paying particular attention to how these slopes impact InSight landing and engineering safety, and results are reported here. Overall, this region has extremely low slopes at 1-meter baseline scales and meets the safety constraints of the InSight lander. The majority of the landing ellipse has a mean slope at 1-meter baselines of 3.2°. In addition, a mosaic of HRSC, CTX, and HiRISE DTMs within the final landing ellipse (ellipse 9) was generated to support entry, descent, and landing simulations and evaluations. Several methods were tested to generate this mosaic and the NASA Ames Stereo Pipeline program dem_mosaic produced the best results. For the HRSC-CTX-HiRISE DTM mosaic, more than 99 % of the mosaic has slopes less than 15°, and the introduction of artificially high slopes along image seams was minimized.

Effect of bottom slope on the nonlinear triad interactions in shallow water

NASA Astrophysics Data System (ADS)

Chen, Hongzhou; Tang, Xiaocheng; Zhang, Ri; Gao, Junliang

2018-05-01

This paper aims at investigating the effect of bottom slope to the nonlinear triad interactions for irregular waves propagating in shallow water. The physical experiments are conducted in a wave flume with respect to the transformation of waves propagating on three bottom slopes ( β = 1/15, 1/30, and 1/45). Irregular waves with different type of breaking that are mechanically generated based on JONSWAP spectra are used for the test. The obviously different variations of spectra measured on each bottom reveal a crucial role of slope effect in the energy transfer between harmonics. The wavelet-based bispectrum were used to examine the bottom slope effect on the nonlinear triad interactions. Results show that the different bottom slopes which waves are propagated on will cause a significant discrepancy of triad interactions. Then, the discussions on the summed bicoherence which denote the distribution of phase coupling on each frequency further clarify the effect of bottom slope. Furthermore, the summed of the real and imaginary parts of bispectrum which could reflect the intensity of frequency components participating in the wave skewness and asymmetry were also investigated. Results indicate that the value of these parameters will increase as the bottom slope gets steeper.

Analysis of local slopes at the InSight landing site on Mars

USGS Publications Warehouse

Fergason, Robin L.; Kirk, Randolph L.; Cushing, Glen; Galuszka, Donna M.; Golombek, Matthew P.; Hare, Trent M.; Howington-Kraus, Elpitha; Kipp, Devin M; Redding, Bonnie L.

2017-01-01

To evaluate the topography of the surface within the InSight candidate landing ellipses, we generated Digital Terrain Models (DTMs) at lander scales and those appropriate for entry, descent, and landing simulations, along with orthoimages of both images in each stereopair, and adirectional slope images. These products were used to assess the distribution of slopes for each candidate ellipse and terrain type in the landing site region, paying particular attention to how these slopes impact InSight landing and engineering safety, and results are reported here. Overall, this region has extremely low slopes at 1-meter baseline scales and meets the safety constraints of the InSight lander. The majority of the landing ellipse has a mean slope at 1-meter baselines of 3.2°. In addition, a mosaic of HRSC, CTX, and HiRISE DTMs within the final landing ellipse (ellipse 9) was generated to support entry, descent, and landing simulations and evaluations. Several methods were tested to generate this mosaic and the NASA Ames Stereo Pipeline program dem_mosaic produced the best results. For the HRSC-CTX-HiRISE DTM mosaic, more than 99 % of the mosaic has slopes less than 15°, and the introduction of artificially high slopes along image seams was minimized.

Quantification of Shear-Relative Asymmetries in Eyewall Slope Using Airborne Doppler Radar Composites

NASA Astrophysics Data System (ADS)

Hazelton, A.; Rogers, R.; Hart, R. E.

2013-12-01

Recently, it has become apparent that typical methods for analyzing tropical cyclones (TCs), such as track and intensity, are insufficient for evaluating TC structural evolution and numerical model forecasts of that evolution. Many studies have analyzed different metrics related to TC inner-core structure in an attempt to better understand the processes that drive changes in core structure. One important metric related to vertical TC structure is the slope of the eyewall. Hazelton and Hart (2013) discussed azimuthal mean eyewall slope based on radar reflectivity data, and its relationship with TC intensity and core structure. That study also noted significant azimuthal variation in slopes, but did not significantly explore reasons for this variation. Accordingly, in this study, we attempt to quantify the role of vertical wind shear in causing azimuthal variance of slope, using research quality Doppler radar composites from the NOAA Hurricane Research Division (HRD). We analyze the slope of the 20 dBZ surface as in Hazelton and Hart (2013), and also look at azimuthal variation in other measures of eyewall slope, such as the slope of the radius of maximum winds (RMW), which has been analyzed in an azimuthal mean sense by Stern and Nolan (2009), and an angular momentum surface. The shear-relative slopes are quantified by separating the radar data into four quadrants relative to the vertical shear vector: Downshear Left (DSL), Upshear Left (USL), Upshear Right (USR), and Downshear Right (DSR). This follows the method employed in shear-relative analyses of other aspects of TC core structure, such as Rogers et al. (2013) and Reasor et al. (2013). The data suitable for use in this study consist of 36 flights into 15 different TCs (14 Atlantic, 1 Eastern Pacific) between 1997 and 2010. Preliminary results show apparent shear-induced asymmetries in eyewall slope. The slope of the RMW shows an asymmetry due to the tilt of the vortex approximately along the shear vector, with

Gravitational slope-deformation of a resurgent caldera: New insights from the mechanical behaviour of Mt. Nuovo tuffs (Ischia Island, Italy)

NASA Astrophysics Data System (ADS)

Marmoni, G. M.; Martino, S.; Heap, M. J.; Reuschlé, T.

2017-10-01

Ischia Island (Italy) is an impressive example of the rare phenomenon of caldera resurgence. The emplacement and replenishment of magmas at shallow depth resulted in a vertical uplift of about 900 m, concentrated in the western portion of Mt. Epomeo (789 m a.s.l.). As a consequence of this uplift, the island has experienced several slope instabilities at different scales since the Holocene, from shallow mass movements to large rock and debris avalanches. These mass wasting events, which mobilised large volumes of greenish alkali-trachytic tuff (the Mt. Epomeo Green Tuff, MEGT), were strictly related to volcano-tectonic activity and the interaction between the volcanic slopes and the hydrothermal system beneath the island. Deep-Seated Gravitational Slope Deformation (DSGSD) at Mt. Nuovo, located adjacent to densely populated coastal villages, is an ongoing process that covers an area of 1.6 km2. The Mt. Nuovo DSGSD involves a rock mass volume of 190 Mm3 and is accommodated by a main shear zone and a series of sub-vertical fault zones associated with high-angle joint sets. To improve our understanding of this gravity-induced process, we performed a physical (porosity and permeability) and mechanical (uniaxial and triaxial deformation experiments) characterisation of two ignimbrite deposits - both from the MEGT - that form a significant component of the NW sector of Mt. Epomeo. The main conclusions drawn from our experiments are twofold. First, the presence of water dramatically reduces the strength of the tuffs, suggesting that the movement of fluids within the hydrothermal system could greatly impact slope stability. Second, the transition from brittle (dilatant) to ductile (compactant) behaviour in the tuffs of the MEGT occurs at a very low effective pressure, analogous to a depth of a couple of hundred metres, and that this transition is likely moved closer to the surface in the presence of water. We hypothesise that compactant (porosity decreasing) behaviour at

Interesting insights into instability of slopes and rock fall in the morphodynamic Himalayan terrane

NASA Astrophysics Data System (ADS)

Singh, T. N.; Vishal, V.; Pradhan, S. P.

2015-12-01

Himalayan mountain ranges are tectonically and seismically very active and experience many disastrous events with time due to slope failure. Frequent failures of rock cut slopes cause obstruction in traffic and often lead to fatalities. In recent years, the number of tragedies has increased when associated with regional phenomena such at the Kedarnath tragedy of 2013 and the Gorkha earthquake of 2015. The influence of such phenomena on the stability of slopes along important national highways and key settlement areas only raise the risk to lives and property. We conducted a multi-approach investigation for some key slopes along the National Highway 58 in Uttarakhand Himalaya, India. A very detailed field work was conducted to identify the unstable slopes and those with some history of failure. The pertinent geomechanical characteristics of the representative rock samples were determined in the laboratory. Based on the structural data, kinematic analysis was carried out. Finally the slopes were simulated using FDM based simulator, Flac/Slope for analysing the health of the slopes and Rockfall 4.0 to investigate the phenomenon of rockfall along the Highway. It was found that few slopes were weak due to the inherent weak rock materials while few slopes made up of high strength rocks were effectively weak due to prone-to-failure orientation of the joints. Quantification of bounce-height of rock blocks during fall, their energy, velocity and displacement along the slope was also done. Using 3-D simulations, few critically-stable slopes that appear to be stable, were identified. Little ground movement could be capable of triggering a large scale failure in the area. Slopes in the studied region are under threat to failure and need immediate proper planning using the suggested remedial measures.

Green technologies for reducing slope erosion.

DOT National Transportation Integrated Search

2010-01-01

As climate change alters precipitation patterns, departments of transportation will increasingly face the problem of : slope failures, which already cost California millions of dollars in repair work annually. Caltrans hopes to prevent : these failur...

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

The empirical slippery slope from voluntary to non-voluntary euthanasia.

PubMed

Lewis, Penney

2007-01-01

This article examines the evidence for the empirical argument that there is a slippery slope between the legalization of voluntary and non-voluntary euthanasia. The main source of evidence in relation to this argument comes from the Netherlands. The argument is only effective against legalization if it is legalization which causes the slippery slope. Moreover, it is only effective if it is used comparatively-to show that the slope is more slippery in jurisdictions which have legalized voluntary euthanasia than it is in jurisdictions which have not done so. Both of these elements are examined comparatively.

An open source high-performance solution to extract surface water drainage networks from diverse terrain conditions

USGS Publications Warehouse

Stanislawski, Larry V.; Survila, Kornelijus; Wendel, Jeffrey; Liu, Yan; Buttenfield, Barbara P.

2018-01-01

This paper describes a workflow for automating the extraction of elevation-derived stream lines using open source tools with parallel computing support and testing the effectiveness of procedures in various terrain conditions within the conterminous United States. Drainage networks are extracted from the US Geological Survey 1/3 arc-second 3D Elevation Program elevation data having a nominal cell size of 10 m. This research demonstrates the utility of open source tools with parallel computing support for extracting connected drainage network patterns and handling depressions in 30 subbasins distributed across humid, dry, and transitional climate regions and in terrain conditions exhibiting a range of slopes. Special attention is given to low-slope terrain, where network connectivity is preserved by generating synthetic stream channels through lake and waterbody polygons. Conflation analysis compares the extracted streams with a 1:24,000-scale National Hydrography Dataset flowline network and shows that similarities are greatest for second- and higher-order tributaries.

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

Quantity and location of groundwater recharge in the Sacramento Mountains, south-central New Mexico (USA), and their relation to the adjacent Roswell Artesian Basin

NASA Astrophysics Data System (ADS)

Rawling, Geoffrey C.; Newton, B. Talon

2016-06-01

The Sacramento Mountains and the adjacent Roswell Artesian Basin, in south-central New Mexico (USA), comprise a regional hydrologic system, wherein recharge in the mountains ultimately supplies water to the confined basin aquifer. Geologic, hydrologic, geochemical, and climatologic data were used to delineate the area of recharge in the southern Sacramento Mountains. The water-table fluctuation and chloride mass-balance methods were used to quantify recharge over a range of spatial and temporal scales. Extrapolation of the quantitative recharge estimates to the entire Sacramento Mountains region allowed comparison with previous recharge estimates for the northern Sacramento Mountains and the Roswell Artesian Basin. Recharge in the Sacramento Mountains is estimated to range from 159.86 × 106 to 209.42 × 106 m3/year. Both the location of recharge and range in estimates is consistent with previous work that suggests that ~75 % of the recharge to the confined aquifer in the Roswell Artesian Basin has moved downgradient through the Yeso Formation from distal recharge areas in the Sacramento Mountains. A smaller recharge component is derived from infiltration of streamflow beneath the major drainages that cross the Pecos Slope, but in the southern Sacramento Mountains much of this water is ultimately derived from spring discharge. Direct recharge across the Pecos Slope between the mountains and the confined basin aquifer is much smaller than either of the other two components.

Experimental study on waves propagation over a coarse-grained sloping beach

NASA Astrophysics Data System (ADS)

Hsu, Tai-Wen; Lai, Jian-Wu

2013-04-01

This study investigates velocity fields of wave propagation over a coarse-grained sloping beach using laboratory experiments. The experiment was conducted in a wave flume of 25 m long, 0.5 m wide and 0.6 m high in which a coarse-grained sloping 1:5 beach was placed with two layers ball. The glass ball is D=7.9 cm and the center to center distance of each ball is 8.0 cm. The test section for observing wave and flow fields is located at the middle part of the flume. A piston type wave maker driven by an electromechanical hydraulic serve system is installed at the end of the flume. The intrinsic permeability Kp and turbulent drag coefficient Cf were obtained from steady flow water-head experiments. The flow velocity was measured by the particle image velocimeter (PIV) and digital image process (DIP) techniques. Eleven fields of view (FOVS) were integrated into a complete representation including the outer, surf and swash zone. Details of the definition sketch of the coarse-grained sloping beach model as well as experimental setup are referred to Lai et al. (2008). A high resolution of CCD camera was used to capture the images which was calibrated by the direct linear transform (DCT) algorithm proposed by Abed El-Aziz and Kar-Ara (1971). The water surface between the interface of air and water at each time step are calculated by Otsu' (1978) detect algorithm. The comparison shows that the water surface elevation observed by integrated image agrees well with that of Otsu' detection results. For the flow field measurement, each image pair was cross correlated with 32X32 pixel inter rogation window and a half overlap between adjacent windows. The repeatability and synchronization are the key elements for both wave motion and PIV technique. The wave profiles and flow field were compared during several wave periods to ensure that they can be reproduced by the present system. The water depth is kept as a constant of h=32 cm. The incident wave conditions are set to be wave

Significance of the actual nonlinear slope geometry for catastrophic failure in submarine landslides.

PubMed

Puzrin, Alexander M; Gray, Thomas E; Hill, Andrew J

2015-03-08

A simple approach to slope stability analysis of naturally occurring, mild nonlinear slopes is proposed through extension of shear band propagation (SBP) theory. An initial weak zone appears in the steepest part of the slope where the combined action of gravity and seismic loads overcomes the degraded peak shear resistance of the soil. If the length of this steepest part is larger than the critical length, the shear band will propagate into the quasi-stable parts of the slope, where the gravitational and seismically induced shear stresses are smaller than the peak but larger than the residual shear strength of the soil. Growth of a shear band is strongly dependent on the shape of the slope, seismic parameters and the strength of soil and less dependent on the slope inclination and the sensitivity of clay. For the slope surface with faster changing inclination, the criterion is more sensitive to the changes of the parameters. Accounting for the actual nonlinear slope geometry eliminates the main challenge of the SBP approach-determination of the length of the initial weak zone, because the slope geometry can be readily obtained from submarine site investigations. It also helps to identify conditions for the early arrest of the shear band, before failure in the sliding layer or a change in loading or excess pore water pressures occurs. The difference in the size of a landslide predicted by limiting equilibrium and SBP approaches can reach orders of magnitude, potentially providing an explanation for the immense dimensions of many observed submarine landslides that may be caused by local factors acting over a limited portion of the slope.

Significance of the actual nonlinear slope geometry for catastrophic failure in submarine landslides

PubMed Central

Puzrin, Alexander M.; Gray, Thomas E.; Hill, Andrew J.

2015-01-01

A simple approach to slope stability analysis of naturally occurring, mild nonlinear slopes is proposed through extension of shear band propagation (SBP) theory. An initial weak zone appears in the steepest part of the slope where the combined action of gravity and seismic loads overcomes the degraded peak shear resistance of the soil. If the length of this steepest part is larger than the critical length, the shear band will propagate into the quasi-stable parts of the slope, where the gravitational and seismically induced shear stresses are smaller than the peak but larger than the residual shear strength of the soil. Growth of a shear band is strongly dependent on the shape of the slope, seismic parameters and the strength of soil and less dependent on the slope inclination and the sensitivity of clay. For the slope surface with faster changing inclination, the criterion is more sensitive to the changes of the parameters. Accounting for the actual nonlinear slope geometry eliminates the main challenge of the SBP approach—determination of the length of the initial weak zone, because the slope geometry can be readily obtained from submarine site investigations. It also helps to identify conditions for the early arrest of the shear band, before failure in the sliding layer or a change in loading or excess pore water pressures occurs. The difference in the size of a landslide predicted by limiting equilibrium and SBP approaches can reach orders of magnitude, potentially providing an explanation for the immense dimensions of many observed submarine landslides that may be caused by local factors acting over a limited portion of the slope. PMID:25792958

Relative Error Evaluation to Typical Open Global dem Datasets in Shanxi Plateau of China

NASA Astrophysics Data System (ADS)

Zhao, S.; Zhang, S.; Cheng, W.

2018-04-01

Produced by radar data or stereo remote sensing image pairs, global DEM datasets are one of the most important types for DEM data. Relative error relates to surface quality created by DEM data, so it relates to geomorphology and hydrologic applications using DEM data. Taking Shanxi Plateau of China as the study area, this research evaluated the relative error to typical open global DEM datasets including Shuttle Radar Terrain Mission (SRTM) data with 1 arc second resolution (SRTM1), SRTM data with 3 arc second resolution (SRTM3), ASTER global DEM data in the second version (GDEM-v2) and ALOS world 3D-30m (AW3D) data. Through process and selection, more than 300,000 ICESat/GLA14 points were used as the GCP data, and the vertical error was computed and compared among four typical global DEM datasets. Then, more than 2,600,000 ICESat/GLA14 point pairs were acquired using the distance threshold between 100 m and 500 m. Meanwhile, the horizontal distance between every point pair was computed, so the relative error was achieved using slope values based on vertical error difference and the horizontal distance of the point pairs. Finally, false slope ratio (FSR) index was computed through analyzing the difference between DEM and ICESat/GLA14 values for every point pair. Both relative error and FSR index were categorically compared for the four DEM datasets under different slope classes. Research results show: Overall, AW3D has the lowest relative error values in mean error, mean absolute error, root mean square error and standard deviation error; then the SRTM1 data, its values are a little higher than AW3D data; the SRTM3 and GDEM-v2 data have the highest relative error values, and the values for the two datasets are similar. Considering different slope conditions, all the four DEM data have better performance in flat areas but worse performance in sloping regions; AW3D has the best performance in all the slope classes, a litter better than SRTM1; with slope increasing

Spectral slopes of the absorption coefficient of colored dissolved and detrital material inverted from UV-visible remote sensing reflectance

PubMed Central

Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy

2017-01-01

The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), Scdm (units: nm−1), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving Scdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360–500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized data set to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of Scdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors. PMID:29201583

Spectral slopes of the absorption coefficient of colored dissolved and detrital material inverted from UV-visible remote sensing reflectance.

PubMed

Wei, Jianwei; Lee, Zhongping; Ondrusek, Michael; Mannino, Antonio; Tzortziou, Maria; Armstrong, Roy

2016-03-01

The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), S cdm (units: nm -1 ), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving S cdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm. Unique features of hyperspectral remote sensing reflectance in the UV-visible wavelengths (360-500 nm) have been observed in various waters across a range of coastal and open ocean environments. Our data and analyses indicate that ocean color in the UV domain is particularly sensitive to the variation of the CDM spectral slope. Here, we used a synthesized data set to show that adding UV wavelengths to the ocean color measurements will improve the retrieval of S cdm from remote sensing reflectance considerably, while the spectral band settings of past and current satellite ocean color sensors cannot fully account for the spectral variation of remote sensing reflectance. Results of this effort support the concept to include UV wavelengths in the next generation of satellite ocean color sensors.

Shelf-Slope Exchanges near Submarine Canyons in the Southern Mid-Atlantic Bight

NASA Astrophysics Data System (ADS)

Wang, H.; Gong, D.

2016-02-01

Shelf-slope exchange processes are major physical drivers of biological productivity near the shelf-break. Observations from two Slocum ocean gliders in Fall 2013 are used to explore the driving mechanisms of cross-shelf-slope exchanges near Norfolk Canyon and Washington Canyon in the southern Mid-Atlantic Bight. Offshore excursion of bottom "cold pool" water, and shoreward intrusion of slope water at surface layer and thermocline depth occurred during northeasterly along-shelf winds. The saline intrusions of surface slope water resided between the cold pool and surface shelf water, and reached the bottom on the outer and mid-shelf, while the offshore excursion of cold pool water was found between the surface and intermediate slope-water over the canyon. Ekman transport calculation shows wind-driven cross-shelf transport can partially explain this interleaving pattern of intrusions. Scaling analysis of double diffusive processes demonstrate that they also likely played a role in the cross-shelf-slope exchange. A unique canyon upwelling event was captured in and around Washington Canyon during a period of southwesterly along-shelf wind and along-shelf flow to the northeast. The water mass distributions and isopycnal responses in both along-canyon and cross-canyon transects are consistent with scaling analysis and numerical studies of canyon upwelling. Temperature-Salinity properties of water masses in the canyon suggest active mixing between shelf and slope water masses near the canyon head. These results point to the importance of wind, double diffusion, and canyon topography on shelf-slope exchange in the MAB.

A framework for identifying plant species to be used as 'ecological engineers' for fixing soil on unstable slopes.

PubMed

Ghestem, Murielle; Cao, Kunfang; Ma, Wenzhang; Rowe, Nick; Leclerc, Raphaëlle; Gadenne, Clément; Stokes, Alexia

2014-01-01

Major reforestation programs have been initiated on hillsides prone to erosion and landslides in China, but no framework exists to guide managers in the choice of plant species. We developed such a framework based on the suitability of given plant traits for fixing soil on steep slopes in western Yunnan, China. We examined the utility of 55 native and exotic species with regard to the services they provided. We then chose nine species differing in life form. Plant root system architecture, root mechanical and physiological traits were then measured at two adjacent field sites. One site was highly unstable, with severe soil slippage and erosion. The second site had been replanted 8 years previously and appeared to be physically stable. How root traits differed between sites, season, depth in soil and distance from the plant stem were determined. Root system morphology was analysed by considering architectural traits (root angle, depth, diameter and volume) both up- and downslope. Significant differences between all factors were found, depending on species. We estimated the most useful architectural and mechanical traits for physically fixing soil in place. We then combined these results with those concerning root physiological traits, which were used as a proxy for root metabolic activity. Scores were assigned to each species based on traits. No one species possessed a suite of highly desirable traits, therefore mixtures of species should be used on vulnerable slopes. We also propose a conceptual model describing how to position plants on an unstable site, based on root system traits.

Handling Correlations between Covariates and Random Slopes in Multilevel Models

ERIC Educational Resources Information Center

Bates, Michael David; Castellano, Katherine E.; Rabe-Hesketh, Sophia; Skrondal, Anders

2014-01-01

This article discusses estimation of multilevel/hierarchical linear models that include cluster-level random intercepts and random slopes. Viewing the models as structural, the random intercepts and slopes represent the effects of omitted cluster-level covariates that may be correlated with included covariates. The resulting correlations between…

Measurements of slope currents and internal tides on the Continental Shelf and slope off Newport Beach, California

USGS Publications Warehouse

Rosenberger, Kurt J.; Noble, Marlene A.; Norris, Benjamin

2014-01-01

An array of seven moorings housing current meters and oceanographic sensors was deployed for 6 months at 5 sites on the Continental Shelf and slope off Newport Beach, California, from July 2011 to January 2012. Full water-column profiles of currents were acquired at all five sites, and a profile of water-column temperature was also acquired at two of the five sites for the duration of the deployment. In conjunction with this deployment, the Orange County Sanitation District deployed four bottom platforms with current meters on the San Pedro Shelf, and these meters provided water-column profiles of currents. The data from this program will provide the basis for an investigation of the interaction between the deep water flow over the slope and the internal tide on the Continental Shelf.

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.

Sub-microradian Surface Slope Metrology with the ALS Developmental Long Trace Profiler

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

Yashchuk, Valeriy V; Barber, Samuel; Domning, Edward E.

2009-09-11

A new low budget slope measuring instrument, the Developmental Long Trace Profiler (DLTP), was recently brought to operation at the ALS Optical Metrology Laboratory. The design, instrumental control and data acquisition system, initial alignment and calibration procedures, as well as the developed experimental precautions and procedures are described in detail. The capability of the DLTP to achieve sub-microradian surface slope metrology is verified via cross-comparison measurements with other high performance slope measuring instruments when measuring the same high quality test optics. The directions of future work to develop a surface slope measuring profiler with nano-radian performance are also discussed.

Unusual megafaunal assemblages on the continental slope off Cape Hatteras

NASA Astrophysics Data System (ADS)

Hecker, Barbara

Megafaunal assemblages were studied in August-September 1992 using a towed camera sled along seven cross-isobath transects on the continental slope off Cape Hatteras. A total of 20,722 megafaunal organisms were observed on 10,918 m 2 of the sea floor between the depths of 157 and 1 924 m. These data were compared with data previously collected off Cape Hatteras in 1985 and at other locations along the eastern U.S. coast between 1981 and 1987. Megafaunal populations on the upper and lower slopes off Cape Hatteras were fouond to be similar, in terms of density and species composition, to those observed at the other locations. In contrast, megafaunal abundances were found to be elevated (0.88 and 2.65 individuals per m 2 during 1985 and 1992, respectively) on the middle slope off Cape Hatteras when compared to most other slope locations (<0.5individuals per m 2). These elevated abundances mainly reflect dense populations of three demersal fish, two eel pouts ( Lysenchelys verrilli and Lycodes atlanticus) and the witch flounder Glyptocephalus cynoglossus, and a large anemone ( Actinauge verrilli). These four species dominated the megafauna off Cape Hatteras, whereas they represented only a minor component of megafaunal populations found at other slope locations. Additionally, numerous tubes of the foraminiferan Bathysiphon filiformis were observed off Cape Hatteras, but not elsewhere. The high density of demersal fish found off Cape Hatteras appears to be related to the high densities of infaunal prey reported from this area. The high densities of A. verrilli and B. fuliformis may be related to the same factors responsible for the high infaunal densities, namely enhanced nutrient inputs in the form of fine particles. Extreme patchiness also was observed in the distributions of the middle slope taxa off Cape Hatteras. This patchiness may reflect the habitat heterogeneity of this exceptionally rugged slope and the sedentary nature of the organisms inhabiting it.

Granular flow behavior at sharp changes in slope

NASA Astrophysics Data System (ADS)

Crosta, Giovanni; De Blasio, Fabio; Locatelli, Michele

2015-04-01

This study extends some recent experiments and analyses performed by the authors to examine the behavior of granular flows along path characterised by sharp changes in slope. In particular, various series of experiments along a bi-linear broken slope (an inclined initial sector followed by a horizontal one) have been completed using a uniform (Hostun, 0.32 mm) sand and a uniform fine gravel (2 mm grains). 60 new have been performed by releasing different volumes (1.5, 2.1 and 5.1 L) on surfaces characterized by different slope angles (35-60°), type of materials (wood and plexiglass), with or without an erodible layer (sand), or in presence of a shallow water pond (0.5 cm). These geometrical features are typical of many large rock and snow avalanches, rock falls and of chalk flows. The latter are usually typical of coastal cliffs where a shallow water environment is typical. The evolution of the flow has been monitored through a laser profilometer at 120 Hz sampling frequency and high speed camera, and in this way it has been possible to follow the evolution of the flow and deposition, and to analyse the change in deposition mode at varying the slope angle, the material and the basal friction. This is an extremely interesting development in the study of the evolution of the deposition and of the final morphology typical of such phenomena, and can support the testing of numerical models. Propagation and deposition occur forward or backward accordingly to the slope angle and the basal friction. Forward movement and deposition occur at high slope angles and with low basal friction. The opposite is true for the backward deposition. The internal "layering" within the deposit is also strongly controlled by the combination of such parameters. The time evolution of the flow allowed to determine the velocity of flow and the mode of deposition through the analysis of the change in thickness, position of the front and of the flow tail. Presence of water reduces the runout of

Circummandibular Wires for Treatment of Dentoalveolar Fractures Adjacent to Edentulous Areas: A Report of Two Cases.

PubMed

Maloney, Karl

2015-09-01

In general, dentoalveolar fractures are a common injury seen in emergency departments, dental offices, and oral and maxillofacial surgery practices. These injuries can be the result of direct trauma or indirect trauma. Direct trauma more often causes trauma to the maxillary dentition due to the exposure of the maxillary anterior teeth. Indirect trauma is usually the result of forced occlusion secondary to a blow to the chin or from a whiplash injury. Falls are the most common mechanism of injury seen in the pediatric group. In adolescents, many of these fractures are sustained during sporting activities. However, the use of mouth guards and other protective equipment has decreased this number. Most adult injuries are caused by motor vehicle accidents, contact sports, falls, bicycles, interpersonal violence, medical/dental mishaps, and industrial accidents. Early intervention to reduce and stabilize the fracture is required to establish a bony union and ensure correct function. Most dentoalveolar fractures have bilateral stable adjacent dentition and are treated with a closed technique utilizing an acid-etch/resin splint followed by splint removal at 4 weeks. Other inferior stabilization treatments used are arch bars and other wiring techniques. It is widely accepted that semirigid stabilization techniques, such as an acid-etch/resin splint or wiring procedures, are adequate to treat dentoalveolar fractures. This is in contrast to the treatment of mandible fractures where AO principles of rigid fixation are often followed. Fractures that are unable to be reduced sometimes necessitate an open reduction followed by internal fixation, sometimes using a secondary splint for mobile teeth. In those rare cases when there are not stable adjacent teeth bilaterally other modalities must be considered. In the present report, two cases are presented where circummandibular wires were used to treat fractured mandibular dentoalveolar segments adjacent to edentulous areas.

Rock-slope failure activity and geological crises in western Norway

NASA Astrophysics Data System (ADS)

Hilger, Paula; Hermanns, Reginald L.; Myhra, Kristin S.; Gosse, John C.; Ivy-Ochs, Susan; Etzelmüller, Bernd

2017-04-01

In Norway a compilation of terrestrial cosmogenic nuclide (TCN) ages of rock-avalanche deposits suggests a close link of rock-slope failures related to deglaciation. Although ages spread over several thousand years at the end of the Late Pleistocene, 50% of all documented events occurred within 1000 years after deglaciation. It is therefore likely that debuttressing triggered most of the events. The same data set suggests that 25% of the events occurred during a period stretching until the Holocene thermal maximum (HTM). These events might be interpreted as possible reactions to additional factors such as the thawing of high-altitude permafrost. An example of a geological crisis following deglaciation and before the HTM are seven lobate rock-avalanche deposits mapped under the slope of the Vora mountain (1450 m asl.) in the Nordfjord area of western Norway. Three events of this rock-slope failure cluster date within a short time period of 2000 years, where modelling studies indicate that high-altitude permafrost was present. After the HTM rock-slope failures are distributed temporally and spatially rather evenly throughout the Holocene and western Norway. But there are two independent local clusters with frequent rock slides during a short time span. (1) At the active Mannen rock-slope instability several rock-avalanche and rockslide deposits were mapped on the valley bottom. Stratigraphic relations combined with TCN dating suggest that at least one event occurred when the valley bottom was below the marine limit. TCN ages of further four lobes cluster around 5.2 ka BP, which does not coincide with any other rock-avalanche occurrence in the region. The top of the north facing 1295 m high unstable slope concurs with the currently estimated permafrost boundary. Preliminary TCN ages of the sliding surface indicate that larger parts of the mountain did not become active until the climate maximum. It is likely that due to structural complexity not allowing for any easy

Probabilistic Rock Slope Engineering.

DTIC Science & Technology

1984-06-01

4 U rmy Corps PROBABILISTIC ROCK SLOPE ENGINEERING by Stanley M. Miller jGeotechnical Engineer 509 E. Calle Avenue Tucson, Arizona 85705 Co N 00 IFI...NUMBERS Geological Engineer CW71 1ork Unit 31755 509 E. Calle Avenue, Tucson, Arizona 85705 11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE...communication, J. P. Sa,.-1Iy, Inspiration Consolidated Copper Co., Inspiration, Ariz., 1980. Personal communication, R. D. Call, Pincock, Allen, and

Surface area and the seabed area, volume, depth, slope, and topographic variation for the world's seas, oceans, and countries.

PubMed

Costello, Mark John; Cheung, Alan; De Hauwere, Nathalie

2010-12-01

Depth and topography directly and indirectly influence most ocean environmental conditions, including light penetration and photosynthesis, sedimentation, current movements and stratification, and thus temperature and oxygen gradients. These parameters are thus likely to influence species distribution patterns and productivity in the oceans. They may be considered the foundation for any standardized classification of ocean ecosystems and important correlates of metrics of biodiversity (e.g., species richness and composition, fisheries). While statistics on ocean depth and topography are often quoted, how they were derived is rarely cited, and unless calculated using the same spatial resolution the resulting statistics will not be strictly comparable. We provide such statistics using the best available resolution (1-min) global bathymetry, and open source digital maps of the world's seas and oceans and countries' Exclusive Economic Zones, using a standardized methodology. We created a terrain map and calculated sea surface and seabed area, volume, and mean, standard deviation, maximum, and minimum, of both depth and slope. All the source data and our database are freely available online. We found that although the ocean is flat, and up to 71% of the area has a < 1 degree slope. It had over 1 million approximately circular features that may be seamounts or sea-hills as well as prominent mountain ranges or ridges. However, currently available global data significantly underestimate seabed slopes. The 1-min data set used here predicts there are 68,669 seamounts compared to the 30,314 previously predicted using the same method but lower spatial resolution data. The ocean volume exceeds 1.3 billion km(3) (or 1.3 sextillion liters), and sea surface and seabed areas over 354 million km(2). We propose the coefficient of variation of slope as an index of topographic heterogeneity. Future studies may improve on this database, for example by using a more detailed bathymetry

Mars Exploration Rover Landing Site Hectometer Slopes

NASA Astrophysics Data System (ADS)

Haldemann, A. F.; Anderson, F. S.

2002-12-01

The Mars Exploration Rover (MER) airbag landing system imposes a maximum slope of 5 degrees over 100 m length-scales. This limit avoids dangerous changes in elevation over the horizontal travel distance of the lander on its parachute between the time of the last radar altimeter detection of the surface and the time the retro-rockets fire and the bridle to the airbags is cut. Stereo imagery from the MGS MOC can provide information at this length scale, but MOC stereo coverage is sparse, even when targeted to MER landing sites. Additionally, MGS spacecraft stability issues affect the DEMs at precisely the hectometric length-scale1. The MOLA instrument provides global coverage pulse-width measurements2 over a single MOLA-pulse footprint, which is about 100 m in diameter. However, the pulse spread only provides an upper bound on the 100 m slope. We chose another approach. We sample the inter-pulse root-mean-square (RMS) height deviations for MOLA track segments restricted to pixels of 0.1 deg latitude by 0.1 deg longitude. Then, under the assumption of self-affine topography, we determine the scale-dependence of the RMS deviations and extrapolate that behavior over the range of 300 m to 1.2 km downward to the 100 m scale. Shepard et al.3 clearly summarize the statistical properties of the RMS deviation (noting that it also goes by the name structure function, variogram or Allan deviation), and we follow their nomenclature. The RMS deviation is a useful measure in that it can be directly converted to RMS-slope for a given length-scale. We map the results of this self-affine extrapolation method for each of the proposed MER landing sites as well as Viking Lander 1 (VL1) and Pathfiner (MPF). In order of decreasing average hectometer RMS-slopes, Melas (about 4.5 degrees) > Elysium EP80 > Gusev > MPF > Elysium EP78 > VL1 > Athabasca > Isidis > Hematite (about 1 degree). We also map the scaling parameter (Hurst exponent); its behavior in the MER landing site regions is

Teachers' Personal Agency: Making Sense of Slope through Additive Structures

ERIC Educational Resources Information Center

Walter, Janet G.; Gerson, Hope

2007-01-01

In the context of a three-year professional development program in mathematics, practicing elementary teachers persistently engaged in collaborative inquiry and reflection to build connected meanings for slope. One teacher invented a compelling representation for slope as a process of repeated addition, using Cuisenaire rods, based on teachers'…

Warm-Season Flows on Slope in Horowitz Crater Nine-Image Sequence

NASA Image and Video Library

2011-08-04

This image comes from observations of Horowitz crater by the HiRISE camera onboard NASA Mars Reconnaissance Orbiter. The features that extend down the slope during warm seasons are called recurring slope lineae.

Do Recurring Slope Lineae (RSL) Shape their Local Landscapes?

NASA Astrophysics Data System (ADS)

McEwen, A. S.; Dundas, C. M.; Chojnacki, M.; Ojha, L.

2017-12-01

RSL are low-albedo features on Mars that initiate at or near bedrock outcrops and extend down steep slopes, with widths up to 5 m and lengths up to 1.5 km. RSL appear and lengthen gradually or incrementally, fade when inactive, and recur each martian year in the warmest season. There are hundreds of likely RSL sites, each with up to hundreds of lineae. Small gullies (1-20 m wide) are often present and control RSL paths; such small, fresh gullies are otherwise rare in equatorial regions. The RSL flow out to the ends of distinctive fans, which may get reworked by wind-driven ripples or dunes. The fans are often relatively bright but transiently become darker, and may have a distinctive color. We have detected newly-formed topographic slumps associated with RSL fans in 12 locations in Valles Marineris (VM). A distinctive landform assemblage is seen within central and eastern VM: Small channels occur on most slope aspects of isolated hills or crater walls, extend very nearly to the tops of the hills or crater rims, are associated with seasonal RSL that extend the full length of the channels and fans, and there is a set of lobate deposits (from slumps) at the base of RSL fans. RSL activity in VM changes slope aspect with season to favor warm temperatures, but the slumps are most active from Ls 0-120, the coldest time of year in VM, especially on south-facing slopes where most of the new slumps have been seen. This association between gullies, RSL, fans, and slumps suggests integrated landscape evolution. Perhaps RSL activity erodes the small gullies and deposits sediment, creating angle-of-repose sloping fans, sometimes oversteepening the fans to cause slumping. RSL activity is associated with the transient presence of hydrated salts, which may indicate some role for salty water. If the RSL mark fluid flow, they should not be precisely confined to angle-of-repose or steeper slopes (>28°), so these must be dry granular flows with activity possibly triggered by or

Derivation of martian surface slope characteristics from directional thermal infrared radiometry

NASA Astrophysics Data System (ADS)

Bandfield, Joshua L.; Edwards, Christopher S.

2008-01-01

Directional thermal infrared measurements of the martian surface is one of a variety of methods that may be used to characterize surface roughness and slopes at scales smaller than can be obtained by orbital imagery. Thermal Emission Spectrometer (TES) emission phase function (EPF) observations show distinct apparent temperature variations with azimuth and emission angle that are consistent with the presence of warm, sunlit and cool, shaded slopes at typically ˜0.1 m scales. A surface model of a Gaussian distribution of azimuth independent slopes (described by θ-bar) is combined with a thermal model to predict surface temperature from each viewing angle and azimuth of the TES EPF observation. The models can be used to predict surface slopes using the difference in measured apparent temperature from 2 separate 60-70° emission angle observations taken ˜180° in azimuth relative to each other. Most martian surfaces are consistent with low to moderate slope distributions. The slope distributions display distinct correlations with latitude, longitude, and albedo. Exceptionally smooth surfaces are located at lower latitudes in both the southern highlands as well as in high albedo dusty terrains. High slopes are associated with southern high-latitude patterned ground and north polar sand dunes. There is little apparent correlation between high resolution imagery and the derived θ-bar, with exceptions such as duneforms. This method can be used to characterize potential landing sites by assuming fractal scaling behavior to meter scales. More precisely targeted thermal infrared observations from other spacecraft instruments are capable of significantly reducing uncertainty as well as reducing measurement spot size from 10s of kilometers to sub-kilometer scales.

Overnight changes in the slope of sleep slow waves during infancy.

PubMed

Fattinger, Sara; Jenni, Oskar G; Schmitt, Bernhard; Achermann, Peter; Huber, Reto

2014-02-01

Slow wave activity (SWA, 0.5-4.5 Hz) is a well-established marker for sleep pressure in adults. Recent studies have shown that increasing sleep pressure is reflected by an increased synchronized firing pattern of cortical neurons, which can be measured by the slope of sleep slow waves. Thus we aimed at investigating whether the slope of sleep slow waves might provide an alternative marker to study the homeostatic regulation of sleep during early human development. All-night sleep electroencephalography (EEG) was recorded longitudinally at 2, 4, 6, and 9 months after birth. Home recording. 11 healthy full-term infants (5 male, 6 female). None. The slope of sleep slow waves increased with age. At all ages the slope decreased from the first to the last hour of non rapid-eye-movement (NREM) sleep, even when controlling for amplitude differences (P < 0.002). The decrease of the slope was also present in the cycle-by-cycle time course across the night (P < 0.001) at the age of 6 months when the alternating pattern of low-delta activity (0.75-1.75 Hz) is most prominent. Moreover, we found distinct topographical differences exhibiting the steepest slope over the occipital cortex. The results suggest an age-dependent increase in synchronization of cortical activity during infancy, which might be due to increasing synaptogenesis. Previous studies have shown that during early postnatal development synaptogenesis is most pronounced over the occipital cortex, which could explain why the steepest slope was found in the occipital derivation. Our results provide evidence that the homeostatic regulation of sleep develops early in human infants.

Effect of Different Groundwater Levels on Seismic Dynamic Response and Failure Mode of Sandy Slope

PubMed Central

Huang, Shuai; Lv, Yuejun; Peng, Yanju; Zhang, Lifang; Xiu, Liwei

2015-01-01

Heavy seismic damage tends to occur in slopes when groundwater is present. The main objectives of this paper are to determine the dynamic response and failure mode of sandy slope subjected simultaneously to seismic forces and variable groundwater conditions. This paper applies the finite element method, which is a fast and efficient design tool in modern engineering analysis, to evaluate dynamic response of the slope subjected simultaneously to seismic forces and variable groundwater conditions. Shaking table test is conducted to analyze the failure mode and verify the accuracy of the finite element method results. The research results show that dynamic response values of the slope have different variation rules under near and far field earthquakes. And the damage location and pattern of the slope are different in varying groundwater conditions. The destruction starts at the top of the slope when the slope is in no groundwater, which shows that the slope appears obvious whipping effect under the earthquake. The destruction starts at the toe of the slope when the slope is in the high groundwater levels. Meanwhile, the top of the slope shows obvious seismic subsidence phenomenon after earthquake. Furthermore, the existence of the groundwater has a certain effect of damping. PMID:26560103

Consequentialism and the slippery slope: a response to Clark.

PubMed

Hughes, J

2000-01-01

Michael Clark has recently argued that the slippery slope argument against voluntary euthanasia is 'entirely consequentialist' and that its use to justify continued prohibition of voluntary euthanasia involves a failure to treat patients who request assistance in ending their lives as ends in themselves. This article argues that in fact the slippery slope is consistent with most forms of deontology, and that it need not involve any violation of the principle that people should be treated as ends, depending upon how that principle is construed. It is concluded that supporters of voluntary euthanasia cannot dismiss the slippery slope argument on the basis of deontological principles but must take seriously the consequences that it postulates and engage in factual argument about their likely extent and about the likely effectiveness of any proposed safeguards.

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

Seismic monitoring of the unstable rock slope at Aaknes, Norway

NASA Astrophysics Data System (ADS)

Roth, M.; Blikra, L. H.

2009-04-01

The unstable rock slope at Aaknes has an estimated volume of about 70 million cubic meters, and parts of the slope are moving at a rate between 2-15 cm/year. Amongst many other direct monitoring systems we have installed a small-scale seismic network (8 three-component geophones over an area of 250 x 150 meters) in order to monitor microseismic events related to the movement of the slope. The network has been operational since November 2005 with only a few short-term outages. Seismic data are transferred in real-time from the site to NORSAR for automatic detection processing. The resulting detection lists and charts and the associated waveform are forwarded immediately to the early warning centre of the Municipality of Stranda. Furthermore, we make them available after a delay of about 10-15 minutes on our public project web page (http://www.norsar.no/pc-47-48-Latest-Data.aspx). Seismic monitoring provides independent and complementary data to the more direct monitoring systems at Aaknes. We observe increased seismic activity in periods of heavy rain fall or snow melt, when laser ranging data and extensometer readings indicate temporary acceleration phases of the slope. The seismic network is too small and the velocity structure is too heterogeneous in order to obtain reliable localizations of the microseismic events. In summer 2009 we plan to install a high-sensitive broadband seismometer (60 s - 100 Hz) in the middle of the unstable slope. This will allow us to better constrain the locations of the microseismic events and to investigate potential low-frequency signals associated with the slope movement.

Numerical Modelling of Seismic Slope Stability

NASA Astrophysics Data System (ADS)

Bourdeau, Céline; Havenith, Hans-Balder; Fleurisson, Jean-Alain; Grandjean, Gilles

Earthquake ground-motions recorded worldwide have shown that many morphological and geological structures (topography, sedimentary basin) are prone to amplify the seismic shaking (San Fernando, 1971 [Davis and West 1973] Irpinia, 1980 [Del Pezzo et al. 1983]). This phenomenon, called site effects, was again recently observed in El Salvador when, on the 13th of January 2001, the country was struck by a M = 7.6 earthquake. Indeed, while horizontal accelerations on a rock site at Berlin, 80 km from the epicentre, did not exceed 0.23 g, they reached 0.6 g at Armenia, 110 km from the epicentre. Armenia is located on a small hill underlaid by a few meters thick pyroclastic deposits. Both the local topography and the presence of surface layers are likely to have caused the observed amplification effects, which are supposed to have contributed to the triggering of some of the hundreds of landslides related to this seismic event (Murphy et al. 2002). In order to better characterize the way site effects may influence the triggering of landslides along slopes, 2D numerical elastic and elasto-plastic models were developed. Various geometrical, geological and seismic conditions were analysed and the dynamic behaviour of the slope under these con- ditions was studied in terms of creation and location of a sliding surface. Preliminary results suggest that the size of modelled slope failures is dependent on site effects.

Assessing slope dynamics in a climate-sensitive high arctic region with Sentinel-1 dataset

NASA Astrophysics Data System (ADS)

Mantovani, Matteo; Pasuto, Alessandro; Soldati, Mauro; Popovic, Radmil; Berthling, Ivar

2017-04-01

As witnessed by an increasing number of studies, the evidence of ongoing climate change and its geomorphological effects is unquestionable. In the Svalbard archipelago, the Arctic amplification of global warming trends currently has a significant effect on permafrost temperatures and active layer thickness. Combined with altered intensity and variability of precipitation, slopes are likely to become more active in terms of both rapid and slow (creep) processes - at least as a temporary effect where the ice-rich transient layer of soils or jointed permafrost rock walls are starting to thaw. The slopes of the Kongsfjorden area aroundNy-Ålesund, NW Spitzbergen comprise a variable set of slopes systems on which to evaluate current modifications of slope sediment transfer; from low-angle fined-grained vegetated slopes to steep rock walls, talus slopes and rock glaciers. In addition, systems influenced by currently retreating glaciers and thermokarst processes are also found, in some settings interfering with the rock wall and talus slope systems. Within the framework of the SLOPES project, we provide baseline data on slope geometry from detailed terrestrial laser scanning and drone aerial image acquisition. Further, in order to document current dynamics, we employ interferometric analysis of data gathered by the new ESA mission SENTINEL. This presentation will report on data from the interferometric analysis.

Mass conservation: 1-D open channel flow equations

USGS Publications Warehouse

DeLong, Lewis L.

1989-01-01

Unsteady flow simulation in natural rivers is often complicated by meandering channels of compound section. Hydraulic properties and the length of the wetted channel may vary significantly as a meandering river inundates its adjacent floodplain. The one-dimensional, unsteady, open-channel flow equations can be extended to simulate floods in channels of compound section. It will be shown that equations derived from the addition of differential equations individually describing flow in main and overbank channels do not in general conserve mass when overbank and main channels are of different lengths.

Land-Surface Subsidence and Open Bedrock Fractures in the Tully Valley, Onondaga County, New York

USGS Publications Warehouse

Hackett, William R.; Gleason, Gayle C.; Kappel, William M.

2009-01-01

Open bedrock fractures were mapped in and near two brine field areas in Tully Valley, New York. More than 400 open fractures and closed joints were mapped for dimension, orientation, and distribution along the east and west valley walls adjacent to two former brine fields. The bedrock fractures are as much as 2 feet wide and over 50 feet deep, while linear depressions in the soil, which are 3 to 10 feet wide and 3 to 6 feet deep, indicate the presence of open bedrock fractures below the soil. The fractures are probably the result of solution mining of halite deposits about 1,200 feet below the land surface.

Environmental characteristics of the Grand Fir Mosaic and adjacent habitat types

Treesearch

Dennis E. Ferguson; John C. Byrne

2000-01-01

Grand Fir Mosaic habitats differ from adjacent forest habitats in their slow rate of secondary succession to woody vegetation. Remote monitoring stations were used to sample the environment at a Grand Fir Mosaic site and three adjacent habitat types. The Grand Fir Mosaic site has shorter growing seasons, cooler temperatures, and more soil moisture than the other sites...

Processing multiple non-adjacent dependencies: evidence from sequence learning