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Sample records for excess pore pressure

  1. Evidence for excess pore pressures in southwest Indian Ocean sediments

    SciTech Connect

    Abbott, D.; Menke, W.; Hobart, M.; Anderson, R.

    1981-03-10

    Brown clay cores from the Madagascar and Crozet basins show the following evidence of excess pore pressures: large amounts of flow-in, increasing average sedimentation rate with age, and nonlinear temperature gradients. Additionally, many hilltops in these basins have no visible sediment cover. The bare hilltops may result from periodic slumping caused by excess pore pressures. Calculated excess pore pressures which equal or exceed the overburden pressure were inferred from water fluxes predicted by nonlinear temperature gradients and laboratory permeability measurements by using Darcy's law. Since pore pressures which exceed the overburden pressure are unreasonable, we attribute this discrepancy to laboratory measures which underestimate the in situ permeability. The widespread presence of overpressured sediments in areas of irregular topography provides a process for resuspension of clay-sized particles. This mechanism does not require high current velocities for the erosion of clay and therefore can be applied to many areas where no strong currents are evident. Carbonate-rich sediments from the Madagascar Ridge, the Mozambique Ridge, and the Agulhas Plateau had almost no flow-in and occurred in areas where all topography was thickly draped with sediment, Since the age and tectonic location of the ridges and plateaus preclude water circulation in the basement, we attribute these differences between the brown clay and the carbonate-rich material to an absence of significant excess pore pressures in the plateau and ridge sediments.

  2. Excess pore water pressure due to ground surface erosion

    NASA Astrophysics Data System (ADS)

    Llewellyn Smith, Stefan; Gagniere, Steven

    2015-11-01

    Erosional unloading is the process whereby surface rocks and soil are removed by external processes, resulting in changes to water pressure within the underlying aquifer. We consider a mathematical model of changes in excess pore water pressure as a result of erosional unloading. Neuzil and Pollock (1983) studied this process in the case where the water table initially coincides with the surface. In contrast, we analyze an ideal aquifer which is initially separated from the ground surface by an unsaturated zone. The model is solved using Laplace Transform methods in conjunction with a boost operator derived by King (1985). The boost operator is used to boost the solution (in the Laplace domain) to a frame of reference moving at constant velocity with respect to the original frame. We use our solution to analyze the evolution of the pressure during erosion of the aquifer itself for small and large erosion rates. We also examine the flux at the upper boundary as a function of time and present a quasi-steady approximation valid for very small erosion rates in the appendix.

  3. Using seismic reflection surveying to map gas-generated excess pore pressures at Finneidfjord, Norway

    NASA Astrophysics Data System (ADS)

    Baise, L. G.; Morgan, E. C.; Vanneste, M. W.; Longva, O.; Lecomte, I.; McAdoo, B. G.

    2009-12-01

    On the 20th of June, 1996, a multi-phase landslide that initiated under water and retrogressed onto land ultimately killed 4 people, destroyed several houses, and undermined a major highway in Finneidfjord, Norway, an area with a known history of landsliding in the Holocene. Geological and environmental conditions inherent to the 1996 slide include excess fluid/gas pressure (particularly in gas-bearing sediment), lateral and vertical lithological variability, slide-prone sediment layers, and changes in the water table due to heavy rainfall. In this study, we quantify pore pressures within the free gas accumulation at very shallow sub-surface depths using seismic reflection data. The trapped gas is thought to originate from the decomposition of river-deposited organic material. The gas front (a few meters below the seabed) produces a strong, polarity-reversed reflection, dramatically attenuating sub-surface reflections. On X-ray images of cores collected from the 5 km2 large gas zone, gas appears as vesicular spots. We use a previously published method incorporating continuous wavelet transforms to quantify attenuation produced by gas-bearing sediment. Taking the output from this method, and knowing or assuming values for other physical parameters, we invert for in situ pressure and equivalent thickness of the free gas layer. We compare our results to pressure data collected from a single piezometer penetrating the gas front, and then incorporate geostatistical methods to interpolate between our seismic profiles. The end product is a map of excess pore pressure estimates, which can be used in conjunction with bathymetry data and cores for more accurate slope stability analyses, ultimately identifying the more sensitive areas of the fjord.

  4. Episodic Sediment Failure in Northern Flemish Pass, Eastern Canadian Margin: Interplay of Seismicity, Contour Current Winnowing, and Excess Pore Pressures

    NASA Astrophysics Data System (ADS)

    Piper, D.

    2015-12-01

    preconditioned the slope for earthquake triggering. There is circumstantial evidence that such preconditioning is related to excess pore pressures, released by fluid drainage at head scarps.

  5. Gas Hydrate and Pore Pressure

    NASA Astrophysics Data System (ADS)

    Tinivella, Umberta; Giustiniani, Michela

    2014-05-01

    Many efforts have been devoted to quantify excess pore pressures related to gas hydrate dissociation in marine sediments below the BSR using several approaches. Dissociation of gas hydrates in proximity of the BSR, in response to a change in the physical environment (i.e., temperature and/or pressure regime), can liberate excess gas incrising the local pore fluid pressure in the sediment, so decreasing the effective normal stress. So, gas hydrate dissociation may lead to excess pore pressure resulting in sediment deformation or failure, such as submarine landslides, sediment slumping, pockmarks and mud volcanoes, soft-sediment deformation and giant hummocks. Moreover, excess pore pressure may be the result of gas hydrate dissociation due to continuous sedimentation, tectonic uplift, sea level fall, heating or inhibitor injection. In order to detect the presence of the overpressure below the BSR, we propose two approachs. The fist approach models the BSR depth versus pore pressure; in fact, if the free gas below the BSR is in overpressure condition, the base of the gas hydrate stability is deeper with respect to the hydrostatic case. This effect causes a discrepancy between seismic and theoretical BSR depths. The second approach models the velocities versus gas hydrate and free gas concentrations and pore pressure, considering the approximation of the Biot theory in case of low frequency, i.e. seismic frequency. Knowing the P and S seismic velocity from seismic data analysis, it is possibile to jointly estimate the gas hydrate and free gas concentrations and the pore pressure regime. Alternatively, if the S-wave velocity is not availbale (due to lack of OBS/OBC data), an AVO analysis can be performed in order to extract information about Poisson ratio. Our modeling suggests that the areas characterized by shallow waters (i.e., areas in which human infrastructures, such as pipelines, are present) are significantly affected by the presence of overpressure condition

  6. The role of fine material and grain size distribution on excess pore pressure dissipation and particle support mechanisms in granular deposits based in large-scale physical experiments

    NASA Astrophysics Data System (ADS)

    Palucis, M. C.; Kaitna, R.; Tewoldebrhan, B.; Hill, K. M.; Dietrich, W. E.

    2011-12-01

    most of the particle's weight, before the pressure slowly declined. When the same boulder was placed on the water-gravel flows, there was no change in fluid pressure, as the mass was supported entirely by grain-grain contacts. These observations suggest that the sustained, but slowly declining elevated pressure in the fines-rich case arises from the boulder forcing fluid displacement, which due to the fluid's high viscosity, only slowly squeezes through the coarse gravel pore space. Hence, the excess fluid pore pressure, in which the fluid fully supports the coarse fractions, observed in experiments and field observations, is not a buoyancy-like effect. Rather, it is the cumulative effect of particles settling against a highly viscous fluid that can sustain and transmit the settling forces through out the flow, as it slowly advects between the particles. These observations are being used to inform models of particle-fluid interactions.

  7. Pore pressure embrittlement in a volcanic edifice

    NASA Astrophysics Data System (ADS)

    Farquharson, Jamie; Heap, Michael J.; Baud, Patrick; Reuschlé, Thierry; Varley, Nick R.

    2016-01-01

    The failure mode of porous rock in compression—dilatant or compactant—is largely governed by the overlying lithostatic pressure and the pressure of pore fluids within the rock (Wong, Solid Earth 102:3009-3025, 1997), both of which are subject to change in space and time within a volcanic edifice. While lithostatic pressure will tend to increase monotonously with depth due to the progressive accumulation of erupted products, pore pressures are prone to fluctuations (during periods of volcanic unrest, for example). An increase in pore fluid pressure can result in rock fracture, even at depths where the lithostatic pressure would otherwise preclude such dilatant behaviour—a process termed pore fluid-induced embrittlement. We explore this phenomenon through a series of targeted triaxial experiments on typical edifice-forming andesites (from Volcán de Colima, Mexico). We first show that increasing pore pressure over a range of timescales (on the order of 1 min to 1 day) can culminate in brittle failure of otherwise intact rock. Irrespective of the pore pressure increase rate, we record comparable accelerations in acoustic emission and strain prior to macroscopic failure. We further show that oscillating pore fluid pressures can cause iterative and cumulative damage, ultimately resulting in brittle failure under relatively low effective mean stress conditions. We find that macroscopic failure occurs once a critical threshold of damage is surpassed, suggesting that only small increases in pore pressure may be necessary to trigger failure in previously damaged rocks. Finally, we observe that inelastic compaction of volcanic rock (as we may expect in much of the deep edifice) can be overprinted by shear fractures due to this mechanism of embrittlement. Pore fluid-induced embrittlement of edifice rock during volcanic unrest is anticipated to be highest closer to the conduit and, as a result, may assist in the development of a fractured halo zone surrounding the

  8. Influence of pore pressure and production-induced changes in pore pressure on in situ stress

    SciTech Connect

    Teufel, L.W.

    1996-02-01

    Knowledge of in situ stress and how stress changes with reservoir depletion and pore pressure drawdown is important in a multi-disciplinary approach to reservoir characterization, reservoir management, and improved oil recovery projects. This report summarizes a compilation of in situ stress data from six fields showing the effects of pore pressure and production-induced changes in pore pressure on the minimum horizontal stress. The in situ stress data and corresponding pore pressure data were obtained from field records of the operating companies and published reports. Horizontal stress was determined from closure pressure data of hydraulic fractures and leak-off tests. The stress measurements clearly demonstrate that the total minimum-horizontal stress is dependent on pore pressure. A decrease in pore pressure either by geologic processes or production of a reservoir will result in a decrease in the total minimum-horizontal stress. The magnitude of changes in stress state with net changes in pore pressure is dependent on local field conditions and cannot be accurately predicted by the uniaxial strain model that is commonly used by the petroleum industry.

  9. Design of a Dual-Pressure Port Penetration Probe for Pore Pressure Measurements in Ocean Drilling

    NASA Astrophysics Data System (ADS)

    Long, H.; Flemings, P. B.; Germaine, J. T.; Chartier, M.

    2004-12-01

    We are building a tapered probe to measure pore pressure and hydraulic properties in low permeability sediments within boreholes. To minimize the time required for measurement we are using two pressure ports: one close to the narrow diameter tip and one on the large-diameter shaft. In-situ pore pressure is estimated within a short time by a two-point intersection method using the pressure dissipation recorded at the two pressure ports. A parametric study is presented to evaluate how possible changes in the probe geometry affects pore pressure dissipation at the pressure ports. The Strain Path Method (SPM) and a total stress soil model (MIT-T1) are used to predict the initial undrained pore pressure response upon insertion of series of hypothetical geometries. Uncoupled-isotropic consolidation is applied to simulate the subsequent excess pore pressure dissipation. The modeled response to insertion in normally consolidated Boston Blue Clay includes the following. Decreasing the length of the thin probe or increasing the diameter of the large shaft results in more rapid two-point intersection and a higher pressure at the two-point intersection. If the second pressure port is placed on the face of the tapered section, instead of the larger-diameter shaft, the intersection time is reduced. We are striving for a tool geometry that generates a consistent two-point intersection time that occurs as rapidly as possible in a range of soil properties.

  10. Evaluation Of Liner Back-pressure Due To Concrete Pore Pressure At Elevated Temperatures

    SciTech Connect

    James, R.J.; Rashid, Y.R.; Liu, A.S.; Gou, B.

    2006-07-01

    GE's latest evolution of the boiling water reactor, the ESBWR, has innovative passive design features that reduce the number and complexity of active systems, which in turn provide economic advantages while also increasing safety. These passive systems used for emergency cooling also mean that the primary containment system will experience elevated temperatures with longer durations than conventional plants in the event of design basis accidents. During a Loss of Coolant Accident (LOCA), the drywell in the primary containment structure for the ESBWR will be exposed to saturated steam conditions for up to 72 hours following the accident. A containment spray system may be activated that sprays the drywell area with water to condense the steam as part of the recovery operations. The liner back-pressure will build up gradually over the 72 hours as the concrete temperatures increase, and a sudden cool down could cause excessive differential pressure on the liner to develop. For this analysis, it is assumed that the containment spray is activated at the end of the 72-hour period. A back-pressure, acting between the liner and the concrete wall of the containment, can occur as a result of elevated temperatures in the concrete causing steam and saturated vapor pressures to develop from the free water remaining in the pores of the concrete. Additional pore pressure also develops under the elevated temperatures from the non-condensable gases trapped in the concrete pores during the concrete curing process. Any buildup of this pore pressure next to the liner, in excess of the drywell internal pressure, will act to push the liner away from the concrete with a potential for tearing at the liner anchorages. This paper describes the methods and analyses used to quantify this liner back-pressure so that appropriate measures are included in the design of the liner and anchorage system. A pore pressure model is developed that calculates the pressure distribution across the concrete

  11. Debris-flow deposition: Effects of pore-fluid pressure and friction concentrated at flow margins

    USGS Publications Warehouse

    Major, J.J.; Iverson, R.M.

    1999-01-01

    Measurements of pore-fluid pressure and total bed-normal stress at the base of several ???10 m3 experimental debris flows provide new insight into the process of debris-flow deposition. Pore-fluid pressures nearly sufficient to cause liquefaction were developed and maintained during flow mobilization and acceleration, persisted in debris-flow interiors during flow deceleration and deposition, and dissipated significantly only during postdepositional sediment consolidation. In contrast, leading edges of debris flows exhibited little or no positive pore-fluid pressure. Deposition therefore resulted from grain-contact friction and bed friction concentrated at flow margins. This finding contradicts models that invoke widespread decay of excess pore-fluid pressure, uniform viscoplastic yield strength, or pervasive grain-collision stresses to explain debris-flow deposition. Furthermore, the finding demonstrates that deposit thickness cannot be used to infer the strength of flowing debris.

  12. Pore-water pressures associated with clogging of soil pipes: Numerical analysis of laboratory experiments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clogging of soil pipes due to excessive internal erosion has been hypothesized to cause extreme erosion events such as landslides, debris flows, and gullies, but confirmation of this phenomenon has been lacking. Laboratory and field measurements have failed to measure pore water pressures within pip...

  13. The effect of pore water pressure on debris flow dynamics

    NASA Astrophysics Data System (ADS)

    Okura, Y.; Parker, G.; Marr, J. G.; Yu, B.; Ochiai, H.

    2003-12-01

    Pore-water likely plays an important role to reduce shear force in debris flow. In experiments, we observed pore-water pressure during flow to clarify the relationship between the flow speed and pore water pressure which would be affected by flow depth and particle size distribution. Soil materials were prepared with mixing materials of sand, silt and clay. Pore-water pressure on the flume bed, flow depth, velocity and run out distance was observed, and the following results were quantitatively obtained in this series of experiments. 1. A positive relation was observed between strain rate and pore-water pressure ratio in the flow. The strain rate and pressure ratio were dimensionless parameters of the ratios of surface velocity to flow depth and pore-water pressure head to flow depth, respectively. This relationship indicated that shear resistance decreased as the pressure potential leading to acceleration of flow velocity increased. 2. A positive relation was also observed between flow depth and pore-water pressure ratio. This indicated that the pore pressure diffusion became increasingly obstructed as the flow depth increased. 3. The pore-water pressure ratio tended to increase with the uniformity coefficient of debris flow materials. The reason for this might have been that smaller particles suspended in the flow increased pore-water pressure, and the wider range of particle distribution effectively prevented pore-water pressure diffusion. 4. There was an apparently negative correlation between the equivalent coefficient of frictions and the pressure ratios. Equivalent friction is apparent friction during flow. The most likely reason for this is that shear resistance would decrease and run out distance increase as the pressure ratio increased. These results indicated that the effect of pore water fluctuations should be one of the most important factors affecting the shear resistance in debris flows. This work was supported by the National Science Foundation

  14. Compaction and Permeability Reduction of Castlegate Sandstone under Pore Pressure Cycling

    NASA Astrophysics Data System (ADS)

    Bauer, S. J.

    2014-12-01

    We investigate time-dependent compaction and permeability changes by cycling pore pressure with application to compressed air energy storage (CAES) in a reservoir. Preliminary experiments capture the impacts of hydrostatic stress, pore water pressure, pore pressure cycling, chemical, and time-dependent considerations near a borehole in a CAES reservoir analog. CAES involves creating an air bubble in a reservoir. The high pressure bubble serves as a mechanical battery to store potential energy. When there is excess grid energy, bubble pressure is increased by air compression, and when there is energy needed on the grid, stored air pressure is released through turbines to generate electricity. The analog conditions considered are depth ~1 km, overburden stress ~20 MPa and a pore pressure ~10MPa. Pore pressure is cycled daily or more frequently between ~10 MPa and 6 MPa, consistent with operations of a CAES facility at this depth and may continue for operational lifetime (25 years). The rock can vary from initially fully-to-partially saturated. Pore pressure cycling changes the effective stress.Jacketed, room temperature tap water-saturated samples of Castlegate Sandstone are hydrostatically confined (20 MPa) and subjected to a pore pressure resulting in an effective pressure of ~10 MPa. Pore pressure is cycled between 6 to 10 MPa. Sample displacement measurements yielded determinations of volumetric strain and from water flow measurements permeability was determined. Experiments ran for two to four weeks, with 2 to 3 pore pressure cycles per day. The Castlegate is a fluvial high porosity (>20%) primarily quartz sandstone, loosely calcite cemented, containing a small amount of clay.Pore pressure cycling induces compaction (~.1%) and permeability decreases (~20%). The results imply that time-dependent compactive processes are operative. The load path, of increasing and decreasing pore pressure, may facilitate local loosening and grain readjustments that results in the

  15. Connecting Wastewater Injection and Seismicity through Pore Pressure

    NASA Astrophysics Data System (ADS)

    Ge, S.; Weingarten, M.; Person, M. A.; Bekins, B. A.

    2014-12-01

    Increased seismicity in recent years in some geologically quiescent regions in the US has been linked to wastewater injection associated with oil and gas production. While seismicity in some cases appears to be well correlated with injection activities, in many other injection locations no seismicity has been reported. How pore pressures generated from injection propagate spatially and evolve temporally is likely a key control in inducing earthquakes, providing a physical linkage between injection activity and seismicity occurrence. Yet, the linkage remains controversial and inconclusive, in spite of the basic physics of pore pressure propagation being well established. This study aims at better understanding the physical processes of pore pressure propagation around injection sites and identifying factors that are most likely contributors to induced seismicity. Numerical modeling suggests that pore pressure increases in the Jones seismicity swarm northeast of Oklahoma City were primarily from several high rate injection wells. Preliminary analysis on injection and seismicity data from Greeley, Colorado also points to a potential pore pressure link between high injection rates and seismicity. Modeling of pore pressures in the Lake County, Ohio, illustrates that permeable faults in the crystalline basement could facilitate pore pressure propagation from injection in the basal aquifer and host earthquakes, which could explain the earthquakes that occurred in the mid-1980s. In many of the above examples, wastewater injection in basal aquifers promoted downward propagation of pore pressures into the crystalline basement. In connecting injection and seismicity through pore pressure propagation, high rate injection wells and permeable basement faults are merging as important players contributing to induced seismicity. It is the intention of this study that findings like these would provide a scientific basis to inform future regulations and policies on wastewater

  16. Regulation of landslide motion by dilatancy and pore pressure feedback

    USGS Publications Warehouse

    Iverson, R.M.

    2005-01-01

    A new mathematical model clarifies how diverse styles and rates of landslide motion can result from regulation of Coulomb friction by dilation or contraction of water-saturated basal shear zones. Normalization of the model equations shows that feedback due to coupling between landslide motion, shear zone volume change, and pore pressure change depends on a single dimensionless parameter ??, which, in turn, depends on the dilatancy angle ?? and the intrinsic timescales for pore pressure generation and dissipation. If shear zone soil contracts during slope failure, then ?? 0, and negative feedback permits slow, steady landslide motion to occur while positive pore pressure is supplied by rain infiltration. Steady state slip velocities v0 obey v0 = -(K/??) p*e, where K is the hydraulic conductivity and p*e is the normalized (dimensionless) negative pore pressure generated by dilation. If rain infiltration and attendant pore pressure growth continue unabated, however, their influence ultimately overwhelms the stabilizing influence of negative p*e. Then, unbounded landslide acceleration occurs, accentuated by an instability that develops if ?? diminishes as landslide motion proceeds. Nonetheless, numerical solutions of the model equations show that slow, nearly steady motion of a clay-rich landslide may persist for many months as a result of negative pore pressure feedback that regulates basal Coulomb friction. Similarly stabilized motion is less likely to occur in sand-rich landslides that are characterized by weaker negative feedback.

  17. Quantification of subsurface pore pressure through IODP drilling

    NASA Astrophysics Data System (ADS)

    Saffer, D. M.; Flemings, P. B.

    2010-12-01

    It is critical to understand the magnitude and distribution of subsurface pore fluid pressure: it controls effective stress and thus mechanical strength, slope stability, and sediment compaction. Elevated pore pressures also drive fluid flows that serve as agents of mass, solute, and heat fluxes. The Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) have provided important avenues to quantify pore pressure in a range of geologic and tectonic settings. These approaches include 1) analysis of continuous downhole logs and shipboard physical properties data to infer compaction state and in situ pressure and stress, 2) laboratory consolidation testing of core samples collected by drilling, 3) direct downhole measurements using pore pressure probes, 3) pore pressure and stress measurements using downhole tools that can be deployed in wide diameter pipe recently acquired for riser drilling, and 4) long-term monitoring of formation pore pressure in sealed boreholes within hydraulically isolated intervals. Here, we summarize key advances in quantification of subsurface pore pressure rooted in scientific drilling, highlighting with examples from subduction zones, the Gulf of Mexico, and the New Jersey continental shelf. At the Nankai, Costa Rican, and Barbados subduction zones, consolidation testing of cores samples, combined with analysis of physical properties data, indicates that even within a few km landward of the trench, pore pressures in and below plate boundary décollement zones reach a significant fraction of the lithostatic load (λ*=0.25-0.91). These results document a viable and quantifiable mechanism to explain the mechanical weakness of subduction décollements, and are corroborated by a small number of direct measurements in sealed boreholes and by inferences from seismic reflection data. Recent downhole measurements conducted during riser drilling using the modular formation dynamics tester wireline tool (MDT) in a forearc basin ~50

  18. Pore-pressure gradients, stresses, and induced earthquakes

    SciTech Connect

    Segall, P. . Geophysics Dept. Geological Survey, Menlo Park, CA )

    1992-01-01

    In the theory of poroelasticity, spatial gradients in pore-pressure enter the equilibrium equations in the same way as distributed body forces. Pore-pressure gradients are thus associated with poroelastic stresses in the same way that temperature gradients associated with thermoelastic stresses. The author has suggested that pore-pressure gradients caused by pumping are responsible for earthquakes near some oil and gas fields. Seismic data from a number of active oil and gas fields in California, Texas, Alberta, and elsewhere clearly show that earthquakes are occurring near fields where pore pressures have declined by several 10's of MPa. These observations can not be explained by changes in effective stress alone, which predicts that decreasing pore-fluid pressures tend to stabilize faults. He believes that poro-elastic stresses resulting from pore-fluid extraction are responsible for earthquakes in these situations. Fluid injection also induces poro-elastic stresses, however it is difficult to separate this effect from the destabilizing effect of increased pore-pressure within fault zones. To test the poroelastic model for induced seismicity, theoretical predictions are compared to data from a deep gas field in the Pyrenean foreland. Hundreds of shallow, small to moderate earthquakes have occurred there since 1969. The earthquakes are tightly clustered near the gas field. Reservoir pressure had declined by 30 MPa at the onset of seismicity. The relationship between average reservoir pressure decline and subsidence is remarkably linear, lending support to the linear poroelastic model. Using laboratory derived material parameters and in situ reservoir pressure measurements, it is possible to predict the surface deformations and the change in stress field without adjustable parameters. The computed vertical displacements are in good agreement with the observed subsidence. The poroelastic stress changes at the onset of seismicity are of the order of a few bars.

  19. Dynamic pore-pressure fluctuations in rapidly shearing granular materials

    USGS Publications Warehouse

    Iverson, R.M.; LaHusen, R.G.

    1989-01-01

    Results from two types of experiments show that intergranular pore pressures fluctuated dynamically during rapid, steady shear deformation of water-saturated granular materials. During some fluctuations, the pore water locally supported all normal and shear stresses, while grain-contact stresses transiently fell to zero. Fluctuations also propagated outward from the shear zone; this process modifies grain-contact stresses in adjacent areas and potentially instigates shear-zone growth.

  20. Pore fluid pressure, apparent friction, and Coulomb failure

    USGS Publications Warehouse

    Beeler, N.M.; Simpson, R.W.; Hickman, S.H.; Lockner, D.A.

    2000-01-01

    Many recent studies of stress-triggered seismicity rely on a fault failure model with a single free parameter, the apparent coefficient of friction, presumed to be a material constant with possible values 0 ≤ μ′ ≤ 1. These studies may present a misleading view of fault strength and the role of pore fluid pressure in earthquake failure. The parameter μ′ is intended to incorporate the effects of both friction and pore pressure, but is a material constant only if changes in pore fluid pressure induced by changes in stress are proportional to the normal stress change across the potential failure plane. Although specific models of fault zones permit such a relation, neither is it known that fault zones within the Earth behave this way, nor is this behavior expected in all cases. In contrast, for an isotropic homogeneous poroelastic model the pore pressure changes are proportional to changes in mean stress, μ′ is not a material constant, and −∞ ≤ μ′ ≤ +∞. Analysis of the change in Coulomb failure stress for tectonically loaded reverse and strike-slip faults shows considerable differences between these two pore pressure models, suggesting that such models might be distinguished from one another using observations of triggered seismicity (e.g., aftershocks). We conclude that using the constant apparent friction model exclusively in studies of Coulomb failure stress is unwise and could lead to significant errors in estimated stress change and seismic hazard.

  1. Reservoir hydraulic properties from oscillating pore pressure method

    NASA Astrophysics Data System (ADS)

    Hasanov, A.; Batzle, M. L.

    2014-12-01

    We use the oscillatory pore pressure method for simultaneous measurements of rock transport properties, such as intrinsic permeability and specific storage capacity. The pore pressure pulsing method has been described by several researchers; however we examine the relationship between a rock's transport properties and dynamic pressure parameters, such as amplitude and frequency. We confirm that the oscillating pore pressure method accurately measures permeability; however storage capacity values suffer from measurement uncertainties. We further developed a novel method to infer the permeabilities from frequency-dependent data. Permeabilities are calculated by non-linear least-squares fitting of the pressure attenuation and phase data, measured on three rock samples at various confining pressures and oscillating pore pressure frequencies. Permeabilities estimated for three tested specimen were in close agreement with steady-state values. Storage capacities, however, exhibit significant absolute errors. Frequency dependence of derived values were furtherexplored, and an apparent increase in permeability has been noticed. These observations do not necessarily indicate a dispersion effect of the absolute permeability of the rock sample. We explain this effect by the deviation in phase shifts, caused by non-Darcy or radial flow. Permeabilities still can be inverted with high accuracy from the frequency-dependent amplitude ratio data, as well as lower frequency limit of phase data by nonlinear least-squares fitting of the theoretical permeability curve. Our future work includes measuring lower permeability rocks, such as tight gas sandstones and shales. We also plan to expand the working frequency range by utilizing pore pressure intensifier as a source of pressure oscillations.

  2. Pore fluid pressure and shear behavior in debris flows of different compositions

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa; Yohannes, Bereket; Hill, Kimberly; Dietrich, William

    2016-04-01

    Debris flows are mixtures of sediment and water that can have a wide range of different grain size distributions and water contents. The composition of the material is expected to have a strong effect on the development of pore fluid pressures in excess to hydrostatic, which in turn might affect the internal deformation behavior. We present a set of large scale experiments with debris flow mixtures of different compositions in a 4-m diameter rotating drum. Longitudinal profiles of basal fluid pressure and normal stress were measured and a probe to determine fluid pressure at different depths within the flow was developed and tested. Additionally we determined vertical profiles of mean particle velocities in the flow interior by measuring small variations of conductivity of the passing material and calculating the time lag between signals from two independent measurements at a small, known distance apart. Mean values of basal pore fluid pressure range from hydrostatic pressure for gravel-water flows to nearly complete liquefaction for muddy mixtures having a wide grain size distribution. The data indicate that the presence of fines dampens fluctuations of normalized fluid pressure and normal stress and concentrates shear at the base. The mobility of grain-fluid flows is strongly enhanced by a combination of fines in suspension as part of the interstitial fluid and a wide grain size distribution. Excess fluid pressure may arise from fluid displacement by converging grains at the front of the flow and the slow settling of grains through a highly viscous non-Newtonian fluid. Our findings support the need for pore pressure evolution and diffusion equations in debris flow models as they depend on particle size distributions. This study contributes to the understanding of the production of excess fluid pressure in grain fluid mixtures and may guide the development of constitutive models that describe natural events.

  3. A laboratory study of particle ploughing and pore-pressure feedback: A velocity-weakening mechanism for soft glacier beds

    USGS Publications Warehouse

    Thomason, J.F.; Iverson, N.R.

    2008-01-01

    If basal-water discharge and pressure are sufficiently high, a soft-bedded glacier will slip over its bed by ploughing, the process in which particles that span the ice-bed interface are dragged across the bed surface. Results of laboratory experiments indicate that resistance to ploughing can decrease with increasing ploughing velocity (velocity weakening). During ploughing at various velocities (15-400 ma-1), till was compacted in front of idealized particles, causing pore pressures there that were orders of magnitude higher than the ambient value. This excess pore pressure locally weakened the till in shear, thereby decreasing ploughing resistance by a factor of 3.0-6.6 with a six-fold increase in ploughing velocity. Characteristic timescales of pore-pressure diffusion and compaction down-glacier from ploughing particles depend on till diffusivity, ploughing velocity and sizes of ploughing particles. These timescales accurately predict the ranges of these variables over which excess pore pressure and velocity weakening occurred. Existing ploughing models do not account for velocity weakening. A new ploughing model with no adjustable parameters predicts ploughing resistance to no worse than 38% but requires that excess pore pressures be measured. Velocity weakening by this mechanism may affect fast glacier flow, sediment transport by bed deformation and basal seismicity.

  4. Predicting pore pressure and porosity from VSP data

    SciTech Connect

    Stone, D.G.

    1984-04-01

    Presently, VSP is being used to predict interval velocity and depth beneath the drill bit. The method is to exploit special properties of the VSP to produce a successful inversion to acoustic impedance. Depth and interval velocity are derived from the acoustic impedance prediction. This technique is often a valuable aid in making drilling decisions. Other rock properties may be computed from the same data. Pore pressure is one such rock parameter that can be computed from interval transit times and depth. The product of interval transit times, depth, normal compaction ratios, and an area constant is pore pressure. Pore pressure prediction is as reliable as the predicted velocities and depths. In reservoir evaluation, and sometimes in the well completion program, porosity is the important rock property. The interval transit times predicted beneath the bit can be used to compute porosity. Unlike pore pressure, porosity computations require knowledge or assumptions about the rock matrix and shale percentages. For certain conditions these values are known. Further penetration of a reef in search of deeper porous zones is an example of a viable condition for porosity prediction. For both these rock properties the same conventions employed by well log analysis in modifying and interpreting results are needed. Where the parameters assumed fit the actual conditions, the results should have merit. If not, further interpretation is required.

  5. One-dimensional pore pressure diffusion of different grain-fluid mixtures

    NASA Astrophysics Data System (ADS)

    von der Thannen, Magdalena; Kaitna, Roland

    2015-04-01

    During the release and the flow of fully saturated debris, non-hydrostatic fluid pressure can build up and probably dissipate during the event. This excess fluid pressure has a strong influence on the flow and deposition behaviour of debris flows. Therefore, we investigate the influence of mixture composition on the dissipation of non-hydrostatic fluid pressures. For this we use a cylindrical pipe of acrylic glass with installed pore water pressure sensors in different heights and measure the evolution of the pore water pressure over time. Several mixtures with variable content of fine sediment (silt and clay) and variable content of coarse sediment (with fixed relative fractions of grains between 2 and 32 mm) are tested. For the fines two types of clay (smectite and kaolinite) and loam (Stoober Lehm) are used. The analysis is based on the one-dimensional consolidation theory which uses a diffusion coefficient D to model the decay of excess fluid pressure over time. Starting from artificially induced super-hydrostatic fluid pressures, we find dissipation coefficients ranging from 10-5 m²/s for liquid mixtures to 10-8 m²/s for viscous mixtures. The results for kaolinite and smectite are quite similar. For our limited number of mixtures the effect of fines content is more pronounced than the effect of different amounts of coarse particles.

  6. An Effect of pore pressure on slip strength of serpentinite

    NASA Astrophysics Data System (ADS)

    Okazaki, K.; Katayama, I.; Takahashi, M.

    2011-12-01

    Slow earthquakes (e.g. slow slip events, very low frequency earthquakes and non-volcanic tremors) have been detected in subduction zones where young and hot slabs are subducting, such as Cascadia and southwest (SW) Japan. Most slow earthquakes in the subduction zone of SW Japan occur with a depth range from 30 to 40 km located at corner of mantle wedge and at slightly deeper than seismogenic zone of Nankai megathrust earthquake (~25km). In this region of SW Japan, low velocity anomaly and high Poisson's ratio have been reported, suggesting that the region is serpentinized and maintains high pore fluid pressure. Generating mechanisms of slow earthquakes are not fully understood, which is our motivation for this experimental study of deformation styles of serpentinite under hydrothermal condition. This study will report about the slip behaviors of antigorite serpentinite under high pore pressure and hydrothermal conditions. In the experiments, we focus on an effect of the pore pressure to frictional coefficient during triaxial deformation. Stating material used in this study is highly dense and isotopic antigorite serpentinite from Nishisonogi metamorphic belts, Nagasaki, Japan, which porosity is about 0.2 to 0.3 %. Samples are grinded cylindrical shape with precut at an angle of 30 degrees, and one piece of the samples is drilled through to the slip surface. Experiments were conducted using the high-temperature and high-pressure gas confining medium apparatus at Hiroshima University, which is capable to apply confining pressure Pc and pore pressure Pp up to 200 MPa and temperature to 800 °C. Preliminary experiments were performed at Pc of 150 MPa, axial displacement rate of 1 μm/s, temperature of 400 °C and variable range of Pp (50 - 105 MPa). Under relatively low Pp conditions (< 100MPa), values of friction coefficient μ are c.a. 0.4, which are similar to these of dry experiments. However, the friction coefficient is abruptly reduced to μ ~ 0.2 when the pore

  7. Effects of confining pressure, pore pressure and temperature on absolute permeability. SUPRI TR-27

    SciTech Connect

    Gobran, B.D.; Ramey, H.J. Jr.; Brigham, W.E.

    1981-10-01

    This study investigates absolute permeability of consolidated sandstone and unconsolidated sand cores to distilled water as a function of the confining pressure on the core, the pore pressure of the flowing fluid and the temperature of the system. Since permeability measurements are usually made in the laboratory under conditions very different from those in the reservoir, it is important to know the effect of various parameters on the measured value of permeability. All studies on the effect of confining pressure on absolute permeability have found that when the confining pressure is increased, the permeability is reduced. The studies on the effect of temperature have shown much less consistency. This work contradicts the past Stanford studies by finding no effect of temperature on the absolute permeability of unconsolidated sand or sandstones to distilled water. The probable causes of the past errors are discussed. It has been found that inaccurate measurement of temperature at ambient conditions and non-equilibrium of temperature in the core can lead to a fictitious permeability reduction with temperature increase. The results of this study on the effect of confining pressure and pore pressure support the theory that as confining pressure is increased or pore pressure decreased, the permeability is reduced. The effects of confining pressure and pore pressure changes on absolute permeability are given explicitly so that measurements made under one set of confining pressure/pore pressure conditions in the laboratory can be extrapolated to conditions more representative of the reservoir.

  8. High-pressure alchemy on a small-pore zeolite

    NASA Astrophysics Data System (ADS)

    Lee, Y.

    2011-12-01

    While an ever-expanding variety of zeolites with a wide range of framework topology is available, it is desirable to have a way to tailor the chemistry of the zeolitic nanopores for a given framework topology via controlling both the coordination-inclusion chemistry and framework distortion/relaxation. This is, however, subjected to the ability of a zeolitic nanopore to allow the redistribution of cations-water assembly and/or insertion of foreign molecules into the pores and channels. Small-pore zeolites such as natrolite (Na16Al16Si24O80x16H2O), however, have been known to show very limited capacity for any changes in the confinement chemistry. We have recently shown that various cation-exchanged natrolites can be prepared under modest conditions from natural sodium natrolite and exhibit cation-dependent volume expansions by up to 18.5% via converting the elliptical channels into progressively circular ones. Here, we show that pressure can be used as a unique and clean tool to further manipulate the chemistry of the natrolite nanopores. Our recent crystallographic and spectroscopic studies of pressure-insertion of foreign molecules, trivalent-cation exchange under pressure, and pressure-induced inversion of cation-water coordination and pore geometry in various cation-exchanged natrolites will be presented.

  9. THE ROLE OF PORE PRESSURE IN DEFORMATION IN GEOLOGIC PROCESSES

    SciTech Connect

    Narasimhan, T. N.; Houston, W. N.; Nur, A. M.

    1980-03-01

    A Penrose Conference entitled, "The Role of Pore Pressure in Deformation in Geologic Processes" was convened by the authors at San Diego, California between November 9 and 13, 1979. The conference was sponsored by the Geological Society of America. This report is a summary of the highlights of the issues discussed during the conference. In addition, this report also includes a topical reference list relating to the different subject areas relevant to pore pressure and deformation. The references were compiled from a list suggested by the participants and were available for consultation during the conference. Although the list is far from complete, it should prove to be a good starting point for one who is looking for key papers in the field.

  10. Reservoir transport and poroelastic properties from oscillating pore pressure experiments

    NASA Astrophysics Data System (ADS)

    Hasanov, Azar K.

    Hydraulic transport properties of reservoir rocks, permeability and storage capacity are traditionally defined as rock properties, responsible for the passage of fluids through the porous rock sample, as well as their storage. The evaluation of both is an important part of any reservoir characterization workflow. Moreover, permeability and storage capacity are main inputs into any reservoir simulation study, routinely performed by reservoir engineers on almost any major oil and gas field in the world. An accurate reservoir simulation is essential for production forecast and economic analysis, hence the transport properties directly control the profitability of the petroleum reservoir and their estimation is vital for oil and gas industry. This thesis is devoted to an integrated study of reservoir rocks' hydraulic, streaming potential and poroelastic properties as measured with the oscillating pore pressure experiment. The oscillating pore pressure method is traditionally used to measure hydraulic transport properties. We modified the method and built an experimental setup, capable of measuring all aforementioned rock properties simultaneously. The measurements were carried out for four conventional reservoir-rock quality samples at a range of oscillation frequencies and effective stresses. An apparent frequency dependence of permeability and streaming potential coupling coefficient was observed. Measured frequency dispersion of drained poroelastic properties indicates an intrinsically inelastic nature of the porous mineral rock frame. Standard Linear Model demonstrated the best fit to the experimental dispersion data. Pore collapse and grain crushing effects took place during hydrostatic loading of the dolomitic sample and were observed in permeability, coupling coefficient and poroelastic measurements simultaneously. I established that hydraulically-measured storage capacities are overestimated by almost one order of magnitude when compared to elastically

  11. Magma chambers: Formation, local stresses, excess pressures, and compartments

    NASA Astrophysics Data System (ADS)

    Gudmundsson, Agust

    2012-09-01

    An existing magma chamber is normally a necessary condition for the generation of a large volcanic edifice. Most magma chambers form through repeated magma injections, commonly sills, and gradually expand and change their shapes. Highly irregular magma-chamber shapes are thermo-mechanically unstable; common long-term equilibrium shapes are comparatively smooth and approximate those of ellipsoids of revolution. Some chambers, particularly small and sill-like, may be totally molten. Most chambers, however, are only partially molten, the main part of the chamber being crystal mush, a porous material. During an eruption, magma is drawn from the crystal mush towards a molten zone beneath the lower end of the feeder dyke. Magma transport to the feeder dyke, however, depends on the chamber's internal structure; in particular on whether the chamber contains pressure compartments that are, to a degree, isolated from other compartments. It is only during large drops in the hydraulic potential beneath the feeder dyke that other compartments become likely to supply magma to the erupting compartment, thereby contributing to its excess pressure (the pressure needed to rupture a magma chamber) and the duration of the eruption. Simple analytical models suggest that during a typical eruption, the excess-pressure in the chamber decreases exponentially. This result applies to a magma chamber that (a) is homogeneous and totally fluid (contains no compartments), (b) is not subject to significant replenishment (inflow of new magma into the chamber) during the eruption, and (c) contains magma where exsolution of gas has no significant effect on the excess pressure. For a chamber consisting of pressure compartments, the exponential excess-pressure decline applies primarily to a single erupting compartment. When more than one compartment contributes magma to the eruption, the excess pressure may decline much more slowly and irregularly. Excess pressure is normally similar to the in

  12. Direct measurement of the effective pressure law: Deformation of joints subject to pore and confining pressures

    SciTech Connect

    Boitnott, G.N.; Scholz, C.H. )

    1990-11-10

    When describing the deformation of poro-elastic materials subject to pore pressure (P{sub p}) and confining pressure (P{sub c}), the concept of effective pressure is commonly used. In such a description the deformation is described in terms of a single stress parameter, the effective stress (P{sub e}). Experimental studies which attempt to describe the effective pressure law are troubled by the fact that deformation of geologic materials invariably exhibits loading path dependence (hysteresis). Here the authors develop an experimental technique for measuring the effective pressure law which is useful for many properties of interest, including those that are highly nonlinear and exhibit common types of hysteresis. They experimentally derive an effective pressure law which describes the values of pore and confining pressure consistent with a given joint closure for a law which describes the values of pore and confining pressure consistent with a given joint closure for a loading path of constant closure. The study can be viewed as an attempt to include both pore and confining pressure in a single constitutive law for joint closure. The constant closure loading path is such that the measurement is not affected by hysteresis caused by joint closure. The results provide insight into the microgeometrical and micromechanical properties of joints. The data are not consistent with a simple extension of commonly used linear elastic constitutive models for joint deformation which have compared favorably with experiments in the absence of pore pressure. For smooth lapped glass joints, the effective pressure relation is found to be dependent on the local joint stiffness, with the relationship between the effective pressure law and the local joint stiffness being insensitive to the measured surface topography. Similar measurements on lapped and fractured rock provide some constraints on the effective pressure behavior of jointed rock.

  13. Explicit Pore Pressure Material Model in Carbon-Cloth Phenolic

    NASA Technical Reports Server (NTRS)

    Gutierrez-Lemini, Danton; Ehle, Curt

    2003-01-01

    An explicit material model that uses predicted pressure in the pores of a carbon-cloth phenolic (CCP) composite has been developed. This model is intended to be used within a finite-element model to predict phenomena specific to CCP components of solid-fuel-rocket nozzles subjected to high operating temperatures and to mechanical stresses that can be great enough to cause structural failures. Phenomena that can be predicted with the help of this model include failures of specimens in restrained-thermal-growth (RTG) tests, pocketing erosion, and ply lifting

  14. Effects of the Earthquake Cycle Observed in Pore Pressure Measurements

    NASA Astrophysics Data System (ADS)

    Barbour, A. J.

    2014-12-01

    Well-aquifer systems respond to dynamic strains over a wide frequency band, making them sensitive to atmospheric pressure fluctuations, earth tides, and seismic waves. Dynamic pore pressures in damaged rock around active strike-slip fault systems are expected to have a reduced response to given dynamic strains: the rock will be in a drained state, with enhanced permeability and mechanical compliance, and cannot support elevated pressures over long times. Despite this expectation, spatial patterns of such a reduction in response are poorly understood. Here we use a set of strain and pressure measurements from Plate Boundary Observatory boreholes in southern California around the highly active San Jacinto fault to analyze variations in response to seismic waves. Stations near the major fault strand show a marked decrease in response compared to stations much farther away, and we show this reduction is controlled by secular shear-strain rates in the crust following an inverse power law. We propose that the spatial pattern in near-surface response is directly related to the earthquake cycle: recurring periods of high interseismic strain accumulation punctuated by large moment release reduce structural rigidity of the surrounding rock, and enhance its hydraulic transport characteristics.

  15. Investigating the Role of Dehydration Reactions in Subduction Zone Pore Pressures Using Newly-Developed Permeability-Porosity Relationships

    NASA Astrophysics Data System (ADS)

    Screaton, E.; Daigle, H.; James, S.; Meridth, L.; Jaeger, J. M.; Villaseñor, T. G.

    2014-12-01

    Dehydration reactions are linked to shallow subduction zone deformation through excess pore pressures and their effect on mechanical properties. Two reactions, the transformation of smectite to illite and of opal-A to opal-CT and then to quartz, can occur relatively early in the subduction process and may affect the propagation of the plate boundary fault, the updip limit of velocity-weakening frictional paper, and tsunamigenesis. Due to large variations between subduction zones in heat flow, sedimentation rates, and geometries, dehydration location may peak prior to subduction to as much as 100 km landward of the deformation front. The location of the dehydration reaction peak relative to when compaction occurs, causes significant differences in pore pressure generation. As a result, a key element to modeling excess pore pressures due to dehydration reactions is the assumed relationship between permeability and porosity. Data from Integrated Ocean Drilling Program (IODP) drilling of subduction zone reference sites were combined with previously collected results to develop relationships for porosity-permeability behavior for various sediment types. Comparison with measurements of deeper analog data show that porosity-permeability trends are maintained through burial and diagenesis to porosities <10%, suggesting that behavior observed in shallow samples is informative for predicting behavior at depth following subduction. We integrate these permeability-porosity relationships, compaction behavior, predictions of temperature distribution, kinetic expressions for smectite and opal-A dehydration, into fluid flow models to examine the role of dehydration reactions in pore pressure generation.

  16. Estimating pore fluid pressures during the Youngstown, Ohio earthquakes

    NASA Astrophysics Data System (ADS)

    Hsieh, P. A.

    2014-12-01

    Several months after fluid injection began in December 2010 at the Northstar 1 well in Youngstown, Ohio, low-magnitude earthquakes were detected in the Youngstown area, where no prior earthquakes had been detected. Concerns that the injection might have triggered the earthquakes lead to shutdown of the well in December 2011. Earthquake relocation analysis by Kim (2013, J. Geophy. Res., v 118, p. 3506-3518) showed that, from March 2011 to January 2012, 12 earthquakes with moment magnitudes of 1.8 to 3.9 occurred at depths of 3.5 to 4 km in the Precambrian basement along a previously unmapped vertical fault. The 2.8 km deep Northstar 1 well, which penetrated the top 60 m of the basement, appeared to have been drilled into the same fault. The earthquakes occurred at lateral distances of 0 to 1 km from the well. The present study aims to estimate the fluid pressure increase due to injection. The groundwater flow model MODFLOW is used to simulate fluid pressure propagation from the well injection interval into the basement fault and two permeable sandstone layers above the basement. The basement rock away from the fault is assumed impermeable. Reservoir properties (permeability and compressibility) of the fault and sandstone layers are estimated by calibrating the model to match injection history and wellhead pressure recorded daily during the operational period. Although the available data are not sufficient to uniquely determine reservoir properties, it is possible to determine reasonable ranges. Simulated fluid pressure increases at the locations and times of the earthquakes range from less than 0.01 MPa to about 1 MPa. Pressure measurements in the well after shut-in might enhance the estimation of reservoir properties. Such data could also improve the estimation of pore fluid pressure increase due to injection.

  17. Robot Drills Holes To Relieve Excess Tire Pressures

    NASA Technical Reports Server (NTRS)

    Carrott, David T.

    1996-01-01

    Small, relatively inexpensive, remotely controlled robot called "tire assault vehicle" (TAV) developed to relieve excess tire pressures to protect ground crew, aircraft equipment, and nearby vehicles engaged in landing tests of CV-990 Landing System Research Aircraft. Reduces costs and saves time in training, maintenance, and setup related to "yellow" and "red" tire conditions. Adapted to any heavy-aircraft environment in which ground-crew safety at risk because of potential for tire explosions. Also ideal as scout vehicle for performing inspections in hazardous locations.

  18. Pore pressure sensitivities to dynamic strains: Observations in active tectonic regions

    NASA Astrophysics Data System (ADS)

    Barbour, Andrew J.

    2015-08-01

    Triggered seismicity arising from dynamic stresses is often explained by the Mohr-Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid-saturated rock. The seismic response of a fluid-rock system naturally depends on its hydromechanical properties, but accurately assessing how pore fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 to 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas Fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends nonlinearly on the inverse fault-perpendicular distance, with the response decreasing toward the fault; the SJB cluster is at the northern transition from creeping-to-locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto Fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength of the

  19. Strain localization driven by co-seismic pore fluid pressurization

    NASA Astrophysics Data System (ADS)

    Rice, James; Platt, John; Brantut, Nicolas; Rudnicki, John

    2015-04-01

    The absence of a thermal anomaly associated with the San Andreas fault, and low driving stress resolved on it, suggest that such mature faults weaken dramatically during seismic slip. Thermal pressurization (TP) and thermal decomposition (TD) are two mechanisms to explain this co-seismic weakening. Both rely on elevated pore pressures in a fluid-saturated gouge, with TP achieving this through thermal expansion of native pore fluid and TD by releasing additional pore fluid (e.g., H2O or CO2) during a reaction. We use a one-dimensional model for a fluid-saturated gouge layer sheared between two undeforming half-spaces to study how TP (Rice et al., Platt et al., JGR-B, 2014) and TD (Platt et al., submitted JGR-B) drive seismic strain localization. A linear stability analysis is first used to predict the localized zone thickness for each of the weakening mechanisms. Using representative parameters for fault gouge we predict localized zone thicknesses of a few tens of microns, in line with laboratory (Kitajima et al., 2010) and field (Chester and Chester, 1998) observations. Next we use numerical simulations to study how the localized zone develops once nonlinear effects become important. These show that the final localized zone thickness is very similar to the linear stability prediction. In the simulations, the onset of localization accelerates fault weakening, making co-seismic strain localization an important consideration, apparently neglected in all current earthquake simulations. Finally we show how a secondary instability can lead to migration of the deforming zone across the gouge layer. This instability is driven by hydrothermal diffusion for TP, and by reactant depletion for TD. Our results show that migration must be taken into account when inferring the width of the deforming zone from field observations. Even when the zone of localized straining is only a few tens of microns wide, migration can lead to a final strain profile with a zone of roughly uniform

  20. Strain localization driven by co-seismic pore fluid pressurization

    NASA Astrophysics Data System (ADS)

    Platt, J. D.; Brantut, N.; Rice, J. R.; Rudnicki, J. W.

    2014-12-01

    The absence of a thermal anomaly associated with the San Andreas fault, and low driving stress resolved on it, suggest that such mature faults weaken dramatically during seismic slip. Thermal pressurization (TP) and thermal decomposition (TD) are two mechanisms to explain this co-seismic weakening. Both rely on elevated pore pressures in a fluid-saturated gouge, with TP achieving this through thermal expansion of native pore fluid and TD by releasing additional pore fluid (e.g., H2O or CO2) during a reaction. We use a one-dimensional model for a fluid-saturated gouge layer sheared between two undeforming half-spaces to study how TP (Rice et al., Platt et al., JGR-B, 2014) and TD (Platt et al., submitted JGR-B) drive seismic strain localization. A linear stability analysis is first used to predict the localized zone thickness for each of the weakening mechanisms. Using representative parameters for fault gouge we predict localized zone thicknesses of a few tens of microns, in line with laboratory (Kitajima et al., 2010) and field (Chester and Chester, 1998) observations. Next we use numerical simulations to study how the localized zone develops once nonlinear effects become important. These show that the final localized zone thickness is very similar to the linear stability prediction. In the simulations, the onset of localization accelerates fault weakening, making co-seismic strain localization an important consideration, apparently neglected in all current earthquake simulations. Finally we show how a secondary instability can lead to migration of the deforming zone across the gouge layer. This instability is driven by hydrothermal diffusion for TP, and by reactant depletion for TD. Our results show that migration must be taken into account when inferring the width of the deforming zone from field observations. Even when the zone of localized straining is only a few tens of microns wide, migration can lead to a final strain profile with a zone of roughly uniform

  1. Movement of Landslide Triggered by Bedrock Exfiltration with Nonuniform Pore Pressure Distribution

    NASA Astrophysics Data System (ADS)

    Jan, C. D.; Jian, Z. K.

    2014-12-01

    Landslides are common phenomena of sediment movement in mountain areas and usually pose severe risks to people and infrastructure around those areas. The occurrence of landslides is influenced by groundwater dynamics and bedrock characteristics as well as by rainfall and soil-mass properties. The bedrock may drain or contribute to groundwater in the overlying soil mass, depending on the hydraulic conductivity, degree of fracturing, saturation, and hydraulic head. Our study here is based on the model proposed by Iverson (2005). The model describes the relation between landslide displacement and the shear-zone dilation/contraction of pore water pressure. To study landslide initiation and movement, a block soil mass sliding down an inclined beck-rock plane is governed by Newton's equation of motion, while both the bedrock exfiltration and excess pore pressure induced by dilatation or contraction of basal shear zone are described by diffusion equations. The Chebyshev collocation method was used to transform the governing equations to a system of first-order ordinary differential equations, without the need of iteration. Then a fourth-order Runge-Kutta scheme was used to solve these ordinary differential equations. The effects of nonuniform bedrock exfiltration pressure distributions, such as the delayed peak, central peak, and advanced peak distributions, on the time of landslide initiation and the speed of landslide movement were compared and discussed.

  2. Pore pressure prediction from well logs: Methods, modifications, and new approaches

    NASA Astrophysics Data System (ADS)

    Zhang, Jincai

    2011-09-01

    Pore pressures in most deep sedimentary formations are not hydrostatic; instead they are overpressured and elevated even to more than double of the hydrostatic pressure. If the abnormal pressures are not accurately predicted prior to drilling, catastrophic incidents, such as well blowouts and mud volcanoes, may take place. Pore pressure calculation in a hydraulically-connected formation is introduced. Fracture gradient prediction methods are reviewed, and the minimum and maximum fracture pressures are proposed. The commonly used empirical methods for abnormal pore pressure prediction from well logs are then reviewed in this paper. Eaton's resistivity and sonic methods are then adapted using depth-dependent normal compaction equations for pore pressure prediction in subsurface formations. The adapted methods provide a much easier way to handle normal compaction trendlines. In addition to the empirical methods, the theoretical pore pressure modeling is the fundamental to understand the mechanism of the abnormal pressure generation. A theoretical pore pressure-porosity model is proposed based on the primary overpressure generation mechanism — compaction disequilibrium and effective stress-porosity-compaction theory. Accordingly, pore pressure predictions from compressional velocity and sonic transit time are obtained using the new theoretical model. Case studies in deepwater oil wells illustrate how to improve pore pressure prediction in sedimentary formations.

  3. Active Faulting and Pore-Fluid Pressure in the Taiwan Thrust Belt

    NASA Astrophysics Data System (ADS)

    Yue, L.; Suppe, J.

    2004-12-01

    Pore-fluid pressures significantly in excess of hydrostatic are thought to play an important role in the mechanics of overthrust faulting (Hubbert and Rubey, 1959). However in western Taiwan we argue, based upon a regional analysis of fluid pressures in 76 deep wells, that fluid pressures on the Pliocene Chinshui Shale detachment and ramp of the Chelungpu thrust system that ruptured the surface during 1999 Chi-Chi earthquake (Mw = 7.6) are within the hydrostatic regime and not overpressured. The fluid pressure data are obtained from in-situ borehole pressure measurements (formation tests), from densities of drilling muds, and from analysis of sonic logs using standard petroleum methods show fluid pressures in western Taiwan are stratigraphically controlled, as is typical of clastic sedimentary basins. The analysis provides constraints not only on present-day fluid pressure, but also pressures before uplift and erosion of growing structures which causes a large drop in overpressures. The top of the present overpressured zone is located at Miocene Nankang-Tsouho Formation in the north of Miao-Li, rises to the south to the Nanchuang and Kueichulin Formations in central Taiwan and only reaches the level of the Pliocene Chinshui Shale near Chia-Li (north of Tainan). Therefore the Chelungpu thrust sheet is everywhere in hydrostatic since this thrust runs along the Chinshui shale. This leads us to the conclusion that the static (ambient) pore-fluid overpressure plays no role in controlling fault friction of the Chelungpu thrust. The shallow detachment must be sliding under other mechanisms. Other shallow thrusts penetrated by drilling such as the Hsincheng thrust between Chingtsaohu and Paoshan anticlines and the Luchukeng thrust west of Yunghoshan anticline are also within hydrostatic regime. None of these thrust were ever overpressured as shown by the fossil top of overpressures which is based upon the deviation of porosity controlled shale velocities from the normal

  4. Simulation of the Effects of Elevated Pore Pressure on Seismicity

    NASA Astrophysics Data System (ADS)

    Foxall, W.; Johnson, S.; Hutchings, L. J.; Richards-Dinger, K. B.; Dieterich, J. H.

    2012-12-01

    Risks associated with induced seismicity are a significant factor in the design, permitting and operation of stimulation and other fluid injection operations, especially enhanced geothermal, geological CO2 sequestration and wastewater disposal. Conventional risk assessment for such operations usually neglects treatment of site-specific conditions, such as in situ stress, pore pressure evolution, and the mechanical and hydrologic properties of the reservoir. As one component of a physics-based probabilistic seismic hazard approach designed to address these issues, we discuss the development of an induced earthquake simulation method that represents hydromechanical effects explicitly. This capability is developed within the GEOS framework [Settgast and Johnson, 37th Stanford Geothermal Workshop, 2012], and is based on the earthquake simulation code RSQSim [Dieterich and Richards-Dinger, PAGEOP, 2010]. The GEOS implementation augments RSQSim by coupling an evolving pore pressure distribution into the fault response via multi-phase flow simulations of fluid injection and plume migration over relevant time scales. The present implementation is uni-directional (effective stress effects) with no feedback to the permeability response. The application allows for the use of realistic fault geometries and fractal spatial distributions of constitutive properties generated along two-dimensional fault surfaces. Constant strain rate boundary conditions are applied to mimic regional tectonic loading. RSQSim uses a rate- and state-dependent friction law to evolve the stresses along the fault. In general, significant uncertainties remain in the scaling of empirically determined constitutive parameters from laboratory to field scale, particularly at the shallow crustal depths characteristic of injection-induced seismicity. In order to understand the sensitivity of the simulations to these parameters, we have sampled multiple model realizations using Livermore's PSUADE code [Tong

  5. Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa C.; Yohannes, Bereket; Hill, Kimberly M.; Dietrich, William E.

    2016-02-01

    Debris flows are typically a saturated mixture of poorly sorted particles and interstitial fluid, whose density and flow properties depend strongly on the presence of suspended fine sediment. Recent research suggests that grain size distribution (GSD) influences excess pore pressures (i.e., pressure in excess of predicted hydrostatic pressure), which in turn plays a governing role in debris flow behaviors. We report a series of controlled laboratory experiments in a 4 m diameter vertically rotating drum where the coarse particle size distribution and the content of fine particles were varied independently. We measured basal pore fluid pressures, pore fluid pressure profiles (using novel sensor probes), velocity profiles, and longitudinal profiles of the flow height. Excess pore fluid pressure was significant for mixtures with high fines fraction. Such flows exhibited lower values for their bulk flow resistance (as measured by surface slope of the flow), had damped fluctuations of normalized fluid pressure and normal stress, and had velocity profiles where the shear was concentrated at the base of the flow. These effects were most pronounced in flows with a wide coarse GSD distribution. Sustained excess fluid pressure occurred during flow and after cessation of motion. Various mechanisms may cause dilation and contraction of the flows, and we propose that the sustained excess fluid pressures during flow and once the flow has stopped may arise from hindered particle settling and yield strength of the fluid, resulting in transfer of particle weight to the fluid. Thus, debris flow behavior may be strongly influenced by sustained excess fluid pressures controlled by particle settling rates.

  6. Investigation of Microseismicity Triggered by Raised Pore Pressure through Laboratory CO2 Injection Tests in Berea Sandstone

    NASA Astrophysics Data System (ADS)

    Lee, S.; Chang, C.

    2014-12-01

    One of the critical problems for carbon dioxide capture and storage projects is the occurrence of microseismicity due to increased pore pressure during CO2 injection. The mechanism of microseismicity can be explained by the notion that the injection-induced pore pressure increase can potentially alter the reservoir rock in the form of either creating fractures or triggering slip on pre-existing discontinuities by reducing the effective normal stress. Therefore, it is important to estimate the critical pore pressure (Pcr) to prevent excessive seismicity. The purpose of this study is to attempt to simulate the microseismicity induced from increased pore pressure by CO2 injection into Berea sandstone. Cylindrical specimens were saw-cut at 30° from the specimen axis. Specimens were either dry or saturated by tap water. The frictional coefficients of the fractures were determined from triaxial shear tests to be 0.71 (dry) and 0.65 (water-saturated). With the frictional coefficients known, we then injected CO2 (either gaseous of liquid state) into the specimens (either dry or water-saturated) subjected to triaxial stress conditions. Under the conditions of constant confining pressures and axial stresses, we increased pore pressure in steps by injecting CO2 using a syringe pump. We monitored shear slip along the fracture using axial LVDTs and microseismicity using an acoustic emission sensor. The critical pore pressure that would initiate shear slip along the fracture was calculated from the Coulomb friction law. When CO2 was injected into dry specimens, shear slip and associated microseismicity started to occur at the pore pressure levels exactly estimated from the Coulomb theory. However, when CO2 (both gaseous and liquid states) was injected into water-saturated specimens, the same were initiated at pore pressures slightly higher (by 1.2-3.7 MPa) than that estimated from the Coulomb friction law. These results suggest that the presence of water and associated water

  7. Small-pore, big opportunity: searching for novel applications of small-pore zeolites by means of pressure and temperature

    NASA Astrophysics Data System (ADS)

    Im, J.; Lee, Y.

    2013-12-01

    Pressure-induced structural and chemical changes observed in small-pore zeolite natrolites are especially encouraging in terms of finding appropriate applications as they occur in the industrially-achievable low-pressure regime, i.e., as low as a few kilobars. After identifying the systematics of structural and chemical behaviors of natrolites in relation to the composition of pressure media, we have developed a procedure to exchange and sequestrate both Cs cation and I anion under intermediate pressure and temperature conditions. This result points towards the possibility of designing novel storage means for important radionuclides. Another avenue to utilize the unique pressure-induced chemistry of small-pore zeolite natrolite is to trap nominally non-adsorbable gas molecules via auxetic expansion under pressure. We have recently succeeded in pressure-induced insertion of Xe into silver-natrolite. Intriguingly, Xe adsorption occurs concomitant with charge disproportionation of silver cations to form silver nano-blobs on the surface of natrolite crystals. We will also present here various usages of laboratory-based high-pressure devices and characterization tools, which play important roles to confirm the synchrotron-based high-pressure experiments involving synthesis of new materials.

  8. The influence of stormwater pathways on pore-pressure timescales near shallow landslide sites

    NASA Astrophysics Data System (ADS)

    Stock, J. D.; Perkins, K. S.; Collins, B. D.; Mirus, B. B.

    2013-12-01

    Intense storms striking the west coast of the US from mid-December through March have a higher likelihood of triggering positive pore pressures and shallow landslides because the steep slopes they rain on often already store significant soil moisture. USGS monitors soil moisture at four landslide-prone sites around San Francisco Bay Area to understand conditions that precede widespread landsliding. The record of historic events from here and elsewhere in California indicates that shallow landslide abundance in a landscape, normalized by susceptible area, increases as a power law with ~6-hour storm rainfall intensity. We hypothesize that this timescale represents a combination of the movement of rainfall towards the failure plane by pore-pressure diffusion and by film flow along macropores. We explored this hypothesis using rainfall and pressure head records from winter storms in 2012, laboratory estimates of soil water retention characteristics, field experiments and one-dimensional modeling. Storms with hourly rainfall rates in excess of 20 mm/hour generated pressure heads commonly up to several decimeters at soil bases. Peaks in the rainfall rate were mirrored at later times in the pressure head at depth. Modeling of pressure heads observed at several sites indicates hydraulic diffusivities of 10-5 m/s, with response times to rainfall input of 5-8 hours. This instrumental response was more rapid, and the variation in head more detailed than that predicted by one-dimensional forward modeling with Richards' equation with laboratory parameters. To refine this effort and to explore the role that film flow might have, we used tracer experiments to explore moisture pathways through this soil. At historic landslide scars near the monitoring sites, we used falling head tests to explore the rate at which the saprolite can transmit water as a lower boundary condition on pressure head. These field measurements and post-storm observations of exfiltration from saprolite

  9. Effects of intermediate wettability on entry capillary pressure in angular pores.

    PubMed

    Rabbani, Harris Sajjad; Joekar-Niasar, Vahid; Shokri, Nima

    2016-07-01

    Entry capillary pressure is one of the most important factors controlling drainage and remobilization of the capillary-trapped phases as it is the limiting factor against the two-phase displacement. It is known that the entry capillary pressure is rate dependent such that the inertia forces would enhance entry of the non-wetting phase into the pores. More importantly the entry capillary pressure is wettability dependent. However, while the movement of a meniscus into a strongly water-wet pore is well-defined, the invasion of a meniscus into a weak or intermediate water-wet pore especially in the case of angular pores is ambiguous. In this study using OpenFOAM software, high-resolution direct two-phase flow simulations of movement of a meniscus in a single capillary channel are performed. Interface dynamics in angular pores under drainage conditions have been simulated under constant flow rate boundary condition at different wettability conditions. Our results shows that the relation between the half corner angle of pores and contact angle controls the temporal evolution of capillary pressure during the invasion of a pore. By deviating from pure water-wet conditions, a dip in the temporal evolution of capillary pressure can be observed which will be pronounced in irregular angular cross sections. That enhances the pore invasion with a smaller differential pressure. The interplay between the contact angle and pore geometry can have significant implications for enhanced remobilization of ganglia in intermediate contact angles in real porous media morphologies, where pores are very heterogeneous with small shape factors. PMID:27042823

  10. Condensation pressures in small pores: An analytical model based on density functional theory

    SciTech Connect

    R. H. Nilson; S. K. Griffiths

    1999-02-01

    Adsorption and condensation are critical to many applications of porous materials including filtration, separation, and the storage of gases. Integral methods are used to derive an analytical expression describing fluid condensation pressures in slit pores bounded by parallel plane walls. To obtain this result, the governing equations of Density Functional Theory (DFT) are integrated across the pore width assuming that fluid densities within adsorbed layers are spatially uniform. The thickness, density, and energy of these layers are expressed as composite functions constructed from asymptotic limits applicable to small and large pores. By equating the total energy of the adsorbed layers to that of a liquid-full pore, the authors arrive at a closed-form expression for the condensation pressure in terms of the pore size, surface tension, and Lennard-Jones parameters of the adsorbent and adsorbate molecules. The resulting equation reduces to the Kelvin equation in the large-pore limit. It further reproduces the condensation pressures computed by means of the full DFT equations for all pore sizes in which phase transitions are abrupt. Finally, in the limit of extremely small pores, for which phase transitions may be smooth and continuous, this simple analytical expression provides a good approximation to the apparent condensation pressure indicated by the steepest portion of the adsorption isotherm computed via DFT.

  11. Active structural growth in central Taiwan in relationship to large earthquakes and pore-fluid pressures

    NASA Astrophysics Data System (ADS)

    Yue, Li-Fan

    Central Taiwan is subject to a substantial long-term earthquake risk with a population of five million and two disastrous earthquakes in the last century, the 1935 ML=7.1 Tuntzuchiao and 1999 Mw=7.6 Chi-Chi earthquakes. Rich data from these earthquakes combined with substantial surface and subsurface data accumulated from petroleum exploration form the basis for these studies of the growth of structures in successive large earthquakes and their relationships to pore-fluid pressures. Chapter 1 documents the structural context of the bedding-parallel Chelungpu thrust that slipped in the Chi-Chi earthquake by showing for this richly instrumented earthquake the close geometric relationships between the complex 3D fault shape and the heterogeneous coseismic displacements constrained by geodesy and seismology. Chapter 2 studies the accumulation of deformation by successive large earthquakes by studying the deformation of flights of fluvial terraces deposited over the Chelungpu and adjacent Changhua thrusts, showing the deformation on a timescale of tens of thousands of years. Furthermore these two structures, involving the same stratigraphic sequence, show fundamentally different kinematics of deformation with associated contrasting hanging-wall structural geometries. The heights and shapes of deformed terraces allowed testing of existing theories of fault-related folding. Furthermore terrace dating constrains a combined shortening rate of 37 mm/yr, which is 45% of the total Taiwan plate-tectonic rate, and indicates a substantial earthquake risk for the Changhua thrust. Chapter 3 addresses the long-standing problem of the mechanics of long-thing thrust sheets, such as the Chelungpu and Changhua thrusts in western Taiwan, by presenting a natural test for the classic Hubbert-Rubey hypothesis, which argues that ambient excess pore-fluid pressure substantially reduces the effective fault friction allowing the thrusts to move. Pore-fluid pressure data obtained from 76 wells

  12. Pore-pressure gradients in the proximity of a submarine buried pipeline

    SciTech Connect

    Magda, W.

    1995-12-31

    This paper is concerned with the two-dimensional finite-element modeling of the wave-induced pore-pressure field in the proximity of a submarine pipeline buried in sandy seabed sediments subject to continuous loading of regular surface waves. Neglecting inertial forces, a linear elastic stress-strain relationship for the soil, and Darcy`s law for the flow of pore-fluid are assumed. The model takes into account the compressibility of both components (i.e., pore-fluid and soil skeleton) of the two-phase medium. The results of numerical computations are discussed with respect to the hydraulic gradient in the upper part of seabed sediments just above the buried submarine pipeline. The pore-pressure gradient is studied as a function of geometry (depth of burial) as well as soil and pore-fluid compressibility parameters where the later of which is defined in terms of soil saturation conditions.

  13. Sudden pore pressure rise and rapid landslide initiation induced under extreme rainfall conditions - a case study

    NASA Astrophysics Data System (ADS)

    Fukuoka, Hiroshi; Wang, Fawu; Wang, Gonghui

    2010-05-01

    sliding surface of one of the upstream small-scale landslides. Those contained finer grains and lower permeability rather than the one sampled in the Hiroshima case. Sample was consolidated by smaller stress corresponding to the site condition, and saturated by overnight circulating de-aired water. Normal stress and shear stress corresponding the slope condition was given, then, pore pressure (back pressure) was raised artificially at constant rate. When the effective stress reached the failure line, suddenly measured pore pressure monitored at about 2 mm above the shear plane, quickly increased. This sudden change abruptly accelerate the shear displacement. Stress condition soon reached the steady state and remained there thereafter. The reason of the excess pore pressure generation was the negative dilatancy, following a slight positive dilatancy. Most of the negative dilatancy could be explained by collapse of loose soil skelton as well as grain crushing during deformation and shearing.

  14. Field evidence of pore pressure diffusion in clayey soils prone to landsliding

    NASA Astrophysics Data System (ADS)

    Berti, Matteo; Simoni, Alessandro

    2010-09-01

    The hydrologic behavior of shallow weathered soils commonly determines the propensity for slope failure. Here we use laboratory data and field data collected by an automated monitoring system to assess the character of pore water pressure responses in a natural clay slope subject to intermittent rainfall. Although we did not measure pore pressure distributions that triggered slope failure, we obtained three years of field data that provided reliable and largely reproducible documentation of transient pore pressure responses. At depths of tens of centimeters to a few meters below the ground surface, moisture and pressure sensors recorded relatively fast, transient responses to precipitation. The speeds of pore pressure pulses advancing downward in the saturated zone were much larger than those of advective fronts driven by gravity, and the amplitudes of the pulses attenuated with depth. Statistical assessment of 129 pressure head responses demonstrates that this behavior is consistent with predictions of a linear, one-dimensional pore pressure diffusion model. However, the model best simulates measurements if diffusivity is treated as a calibration parameter and if initial moisture conditions match model assumptions. For regional assessment of slope stability, the predictive accuracy of the linear-diffusion model is limited by inherent uncertainties in defining the initial conditions and in assigning the values of hydraulic parameters.

  15. Change of permeability caused by 2011 Tohoku earthquake detected from pore pressure monitoring

    NASA Astrophysics Data System (ADS)

    Kinoshita, C.; Kano, Y.; Ito, H.

    2013-12-01

    Earthquake-induced groundwater changes which are the pre- and co-seismic changes have been long reported (e.g. Roeloffs, 1996). For example, 1995 Kobe earthquake, water inflow into observation tunnel changed at Rokko (Fujimori et al., 1995), at the times of 1964 Alaska earthquake (M8.6) (Coble, 1967) and 1999 Taiwan Chi-Chi earthquake (M7.6) (Chia et al., 2001), groundwater leve were fluctuated. The shaking of seismic waves and crack formation by crustal deformation are proposed as one causes but the mechanism is controversial. We are monitoring pore pressure from 2005 to measure the stress changes at Kamioka mine, Gifu prefecture, central Japan. Barometric pressure and strain are observed to correct the pore pressure data. In general, the pore pressure changes associate with the meteorological effects, Earth tides and crustal deformation. Increase of pore pressure depends on the precipitation which flows into the ground. Especially, snow effects are bigger than the usual rainfall because our observation site has heavy snow in winter season. Melted snow flows in the ground and pore pressure increases at the March to April every year. When the 2011 Tohoku earthquake (M9.0) occurred, pore pressure remarkably decreased because the permeability increases by crustal deformation at Kamioka region. Thus, we estimated the hydraulic diffusivity before and after the earthquake from pore pressure response to crustal deformation. We made separated analyses on three frequency bands. First is the high frequency band, especially, seismic response. Second is response to Earth tides. Third frequency band is that of barometric response which is lower than other two bands. At high frequency band, we confirmed that the deformation occurred under undrained condition and estimated the bulk modulus from pore pressure and strain data. Next, tidal response is extracted from pore pressure which applied to every three months data of pore pressure, barometric pressure and strain. Time window

  16. Temporal and Spatial Pore Water Pressure Distribution Surrounding a Vertical Landfill Leachate Recirculation Well

    PubMed Central

    Kadambala, Ravi; Townsend, Timothy G.; Jain, Pradeep; Singh, Karamjit

    2011-01-01

    Addition of liquids into landfilled waste can result in an increase in pore water pressure, and this in turn may increase concerns with respect to geotechnical stability of the landfilled waste mass. While the impact of vertical well leachate recirculation on landfill pore water pressures has been mathematically modeled, measurements of these systems in operating landfills have not been reported. Pressure readings from vibrating wire piezometers placed in the waste surrounding a liquids addition well at a full-scale operating landfill in Florida were recorded over a 2-year period. Prior to the addition of liquids, measured pore pressures were found to increase with landfill depth, an indication of gas pressure increase and decreasing waste permeability with depth. When liquid addition commenced, piezometers located closer to either the leachate injection well or the landfill surface responded more rapidly to leachate addition relative to those far from the well and those at deeper locations. After liquid addition stopped, measured pore pressures did not immediately drop, but slowly decreased with time. Despite the large pressures present at the bottom of the liquid addition well, much smaller pressures were measured in the surrounding waste. The spatial variation of the pressures recorded in this study suggests that waste permeability is anisotropic and decreases with depth. PMID:21655145

  17. Temporal and spatial pore water pressure distribution surrounding a vertical landfill leachate recirculation well.

    PubMed

    Kadambala, Ravi; Townsend, Timothy G; Jain, Pradeep; Singh, Karamjit

    2011-05-01

    Addition of liquids into landfilled waste can result in an increase in pore water pressure, and this in turn may increase concerns with respect to geotechnical stability of the landfilled waste mass. While the impact of vertical well leachate recirculation on landfill pore water pressures has been mathematically modeled, measurements of these systems in operating landfills have not been reported. Pressure readings from vibrating wire piezometers placed in the waste surrounding a liquids addition well at a full-scale operating landfill in Florida were recorded over a 2-year period. Prior to the addition of liquids, measured pore pressures were found to increase with landfill depth, an indication of gas pressure increase and decreasing waste permeability with depth. When liquid addition commenced, piezometers located closer to either the leachate injection well or the landfill surface responded more rapidly to leachate addition relative to those far from the well and those at deeper locations. After liquid addition stopped, measured pore pressures did not immediately drop, but slowly decreased with time. Despite the large pressures present at the bottom of the liquid addition well, much smaller pressures were measured in the surrounding waste. The spatial variation of the pressures recorded in this study suggests that waste permeability is anisotropic and decreases with depth. PMID:21655145

  18. The change in orientation of subsidiary shears near faults containing pore fluid under high pressure

    USGS Publications Warehouse

    Byerlee, J.

    1992-01-01

    Byerlee, J., 1992. The change in orientation of subsidiary shears near faults containing pore fluid under high pressure. In: T. Mikumo, K. Aki, M. Ohnaka, L.J. Ruff and P.K.P. Spudich (Editors), Earthquake Source Physics and Earthquake Precursors. Tectonophysics, 211: 295-303. The mechanical effects of a fault containing near-lithostatic fluid pressure in which fluid pressure decreases monotonically from the core of the fault zone to the adjacent country rock is considered. This fluid pressure distribution has mechanical implications for the orientation of subsidiary shears around a fault. Analysis shows that the maximum principal stress is oriented at a high angle to the fault in the country rock where the pore pressure is hydrostatic, and rotates to 45?? to the fault within the fault zone where the pore pressure is much higher. This analysis suggests that on the San Andreas fault, where heat flow constraints require that the coefficient of friction for slip on the fault be less than 0.1, the pore fluid pressure on the main fault is 85% of the lithostatic pressure. The observed geometry of the subsidiary shears in the creeping section of the San Andreas are broadly consistent with this model, with differences that may be due to the heterogeneous nature of the fault. ?? 1992.

  19. Solute dispersion under electric and pressure driven flows; pore scale processes

    NASA Astrophysics Data System (ADS)

    Li, Shuai; Raoof, Amir; Schotting, Ruud

    2014-09-01

    Solute dispersion is one of the major mixing mechanisms in transport through porous media, originating from velocity variations at different scales, starting from the pore scale. Different driving forces, such as pressure driven flow (PDF) and electro-osmotic flow (EOF), establish different velocity profiles within individual pores, resulting in different spreading of solutes at this scale. While the velocity profile in PDF is parabolic due to the wall friction effects, the velocity in EOF is typically plug flow, due to the wall charge effects. In this study, we applied a pore network modeling formulation to simulate the velocity field driven by pressure and electric potential to calculate and compare the corresponding average solute dispersivity values. The influence of different driving forces on the hydrodynamic dispersion of a tracer solute is investigated. Applying the pore network modeling, we could capture the velocity variations among different pores, which is the main contribution for the dispersion coefficient. The correlation between pore velocities against pore sizes is found to be different for EOF and PDF, causing different solute dispersion coefficients. The results can provide insight into modeling of electrokinetic remediation for contaminant cleanup in low permeable soils.

  20. Evolution of pore fluid pressures in a stimulated geothermal reservoir inferred from earthquake focal mechanisms

    NASA Astrophysics Data System (ADS)

    Terakawa, T.; Deichmann, N.

    2014-12-01

    We developed an inversion method to estimate the evolution of pore fluid pressure fields from earthquake focal mechanism solutions based on the Bayesian statistical inference and Akaike's Bayesian information criterion (ABIC). This method's application to induced seismicity in the Basel enhanced geothermal system in Switzerland shows the evolution of pore fluid pressures in response to fluid injection experiments. For a few days following the initiation of the fluid injection, overpressurized fluids are concentrated around the borehole and then anisotropically propagate within the reservoir until the bleed-off time. Then, the pore fluid pressure in the vicinity of the borehole drastically decreases, and overpressurized fluids become isolated in a few major fluid pockets. The pore fluid pressure in these pockets gradually decreases with time. The pore fluid pressure in the reservoir is less than the minimum principal stress at each depth, indicating that the hydraulic fracturing did not occur during stimulation. This suggests that seismic events may play an important role to promote the development of permeable channels, particularly southeast of the borehole where the largest seismic event (ML 3.4) occurred. This is not directly related to a drastic decrease in fault strength at the hypocenter, but rather the positive feedback between permeability enhancement and poro-elastic and stress transfer loading from slipping interfaces. These processes likely contribute to this event's nucleation.

  1. Effects of Pore Distributions on Ductility of Thin-Walled High Pressure Die-Cast Magnesium

    SciTech Connect

    Choi, Kyoo Sil; Li, Dongsheng; Sun, Xin; Li, Mei; Allison, John

    2013-06-01

    In this paper, a microstructure-based three-dimensional (3D) finite element modeling method is adopted to investigate the effects of porosity in thin-walled high pressure die-cast (HPDC) Magnesium alloys on their ductility. For this purpose, the cross-sections of AM60 casting samples are first examined using optical microscope and X-ray tomography to obtain the general information on the pore distribution features. The experimentally observed pore distribution features are then used to generate a series of synthetic microstructure-based 3D finite element models with different pore volume fractions and pore distribution features. Shear and ductile damage models are adopted in the finite element analyses to induce the fracture by element removal, leading to the prediction of ductility. The results in this study show that the ductility monotonically decreases as the pore volume fraction increases and that the effect of ‘skin region’ on the ductility is noticeable under the condition of same local pore volume fraction in the center region of the sample and its existence can be beneficial for the improvement of ductility. The further synthetic microstructure-based 3D finite element analyses are planned to investigate the effects of pore size and pore size distribution.

  2. Undrained heating and anomalous pore-fluid pressurization of a hardened cement paste

    NASA Astrophysics Data System (ADS)

    Ghabezloo, S.; Sulem, J.; Saint-Marc, J.

    2009-04-01

    Temperature increase in a fluid-saturated porous material in undrained condition leads to volume change and pore pressure increase due to the discrepancy between the thermal expansion coefficients of the pore fluid and of the pore volume. This increase of the pore fluid pressure induces a reduction of the effective mean stress, and can lead to shear failure or hydraulic fracturing. This phenomenon is important is important in environmental engineering for radioactive (exothermal) waste disposal in deep clay geological formations as well as in geophysics in the studies of rapid fault slip events when shear heating tends to increase the pore pressure and to decrease the effective compressive stress and the shearing resistance of the fault material (Sulem et al. 2007). This is also important in petroleum engineering where the reservoir rock and the well cement lining undergo sudden temperature changes for example when extracting heavy oils by steam injection methods. This rapid increase of temperature could damage cement sheath integrity of wells and lead to loss of zonal isolation. The values of the thermal pressurization coefficient, defined as the pore pressure increase due to a unit temperature increase in undrained condition, is largely dependent upon the nature of the material, the state of stress, the range of temperature change, the induced damage. The large variability of the thermal pressurization coefficient reported in the literature for different porous materials with values from 0.01MPa/°C to 1.5MPa/°C highlights the necessity of laboratory studies. This phenomenon of thermal pressurization is studied experimentally for a fluid-saturated hardened cement paste in an undrained heating test. Careful analysis of the effect of the dead volume of the drainage system of the triaxial cell has been performed based on a simple correction method proposed by Ghabezloo and Sulem (2008, 2009). The drained and undrained thermal expansion coefficients of the hardened

  3. Numerical modelling of pore-pressure measurements in saturated sandy seabed sediments

    SciTech Connect

    Magda, W.

    1995-12-31

    The question of model conditions (i.e., saturation procedure and temporal dewatering of soil model, as well as existence of a geotextile on the top of seabed model and existence of pore-pressure transducers itself in seabed sediments) in large-scale modelling is discussed with respect to the quality of measured pore-pressure values. The meaning of locally unsaturated zones within the seabed model, due to an improper installation procedure or man-made mistake during the testing period, are illustrated by some example computations, based on 2-D finite-element model, the results of which are presented in terms of the momentaneous pore-pressure distribution with depth, induced by surface harmonic waves passing over the seabed.

  4. Fracture propagation, stable sliding and stick slip by pore pressurizing a fault gouge analog

    NASA Astrophysics Data System (ADS)

    Schubnel, A.; Thompson, B.; Fortin, J.; Young, R.

    2004-12-01

    Thermal pressurization of pore fluid has recently been proposed as a mechanism for velocity weakening of fault gouge materials (Mase et al., [1984]). Rice [1992] and Miller [2003] have also suggested the earthquake cycle is mainly a pore pressure cycle. A Fontainebleau sandstone sample of 14% porosity was deformed tri-axially at the Laboratoire de Géologie of ENS Paris. A confining pressure of 100 MPa was used, in saturated conditions. Acoutic properties were monitored through 14 compressional wave piezoceramic transducers (PZT) which were directly glued onto the sample cylindrical surface. During the first cycle, differential stress was slowly raised to 250 MPa. Subsequently, an increase in pore pressure induced brittle failure at Pp=72MPa, with a stress drop of 150 MPa. In addition to triggered Acoustic Emissions (AE), the entire conitinuous ultrasonic waveform of the rupture was recorded. Over 10 000 AE were located, demonstrating the evolution of a fracture nucleation patch of order 1cc. Measured permeability showed that the nucleation of a damage/fault zone induced a drastic reduction in permeability, which could explain the many aftershocks that were observed after the main fracture propagation. Elastic wave velocities also show the extent of permanent damage in the rock. During the second cycle, we re-loaded the fractured sample up to a differential stress of 150 MPa. An initial slow pore pressurization induced stable sliding from 65 to 70 MPa. The pore pressure was then reduced, and a fast pore pressure pulse applied, (from 0 to 80 MPa in two seconds) inducing major stick slip (with an associated stress drop of 50 MPa). Again, in this cycle, more than 15 000 AE were located and aftershocks due to pore pressure re-equilibration were observed, post failure. In this preliminary study, we present a non-exhaustive compilation of data obtained during this pore pressure cycling experiment, including AE locations, continuous ultrasonic waveform summaries

  5. Prediction of pore-water pressure response to rainfall using support vector regression

    NASA Astrophysics Data System (ADS)

    Babangida, Nuraddeen Muhammad; Mustafa, Muhammad Raza Ul; Yusuf, Khamaruzaman Wan; Isa, Mohamed Hasnain

    2016-05-01

    Nonlinear complex behavior of pore-water pressure responses to rainfall was modelled using support vector regression (SVR). Pore-water pressure can rise to disturbing levels that may result in slope failure during or after rainfall. Traditionally, monitoring slope pore-water pressure responses to rainfall is tedious and expensive, in that the slope must be instrumented with necessary monitors. Data on rainfall and corresponding responses of pore-water pressure were collected from such a monitoring program at a slope site in Malaysia and used to develop SVR models to predict pore-water pressure fluctuations. Three models, based on their different input configurations, were developed. SVR optimum meta-parameters were obtained using k-fold cross validation and a grid search. Model type 3 was adjudged the best among the models and was used to predict three other points on the slope. For each point, lag intervals of 30 min, 1 h and 2 h were used to make the predictions. The SVR model predictions were compared with predictions made by an artificial neural network model; overall, the SVR model showed slightly better results. Uncertainty quantification analysis was also performed for further model assessment. The uncertainty components were found to be low and tolerable, with d-factor of 0.14 and 74 % of observed data falling within the 95 % confidence bound. The study demonstrated that the SVR model is effective in providing an accurate and quick means of obtaining pore-water pressure response, which may be vital in systems where response information is urgently needed.

  6. Temperature and pore pressure distribution in a concrete slab during the microwave decontamination process

    SciTech Connect

    Li, W.; Ebadian, M.A.; White, T.L.; Grubb, R.G.; Foster, D. Jr.

    1994-10-01

    As an application of microwave engineering, the new technology of concrete decontamination and decommissioning using microwave energy has been recently developed. The temperature and pore pressure within the concrete are studied theoretically in this paper. The heat and mass transfer within the porous concrete, coupled with temperature dependent dielectric property are investigated. The effects of microwave frequency (f), microwave power intensity (Q{sub 0,ave}), concrete porosity ({phi}) on the temperature and pore pressure distributions and their variations are fully discussed. The effects of the variation of complex dielectric permittivity ({epsilon}) and presentation of different steel reinforcements are also illustrated.

  7. Field Observations of Basal Forces and Fluid Pore Pressure in a Debris Flow

    NASA Astrophysics Data System (ADS)

    McArdell, B. W.; Bartelt, P.; Kowalski, J.

    2006-12-01

    The interaction of the soil material and interstitial fluid is central to understanding the dynamics of debris flows, however it has been rarely investigated for natural debris flows. Using results from a large force plate (4 m wide, 2 m long) installed on the bed of the Illgraben torrent channel, Switzerland, we describe measurements of normal, shear, and fluid pore pressure for a naturally-released debris flow with a front speed of 1.4 ms-1 that traveled more than 2 km along a gently-sloping (8 to 10%) channel. Peak values of all parameters were observed near the relatively dry granular flow front (flow depth= 1.05 m, normal stress= 23 kPa, shear stress= 2.8 kPa, basal fluid pore pressure= 15 kPa) and decreased approximately in-phase with the flow depth over the remainder of the flow. Assuming that the depths of the fluid and solid phases are identical after 20 s, as indicated by video recordings, and that a static description of the pressure distribution within the fluid phase is approximately valid, the ratio of effective stress to shear stress yields plausible estimates of the Coulomb basal friction angle near the front of the flow. Large non-lithostatic pressures are not apparent in our data; calculated bulk densities of the flow remaining at about 2200 kgm-3 over the most of the flow. The bulk density of the fluid phase calculated from the measured fluid pore pressure and flow height, assuming a hydrostatic pore pressure distribution, is 1200---1300 kgm-3. An alternative explanation is that the fluid pressure contains both hydrostatic and dynamics components. To explore this idea, we assume that a dynamic pore pressure component is proportional to the strength of the shearing of the solid phase or to the strength of the collisions of the particles comprising the solid phase, which we approximate using data from a geophone installed on the force plate. We find only a weak correlation between the geophone signal and a dynamic pore pressure component for this

  8. Formulas to Correct Excess Pressure and Pressure Shift to be Used in Volume Measurement for Plutonium Nitrate Solution

    SciTech Connect

    Hosoma, Takashi; Aritomi, Masanori; Kawa, Tsunemichi

    2000-02-15

    Excess pressure caused by the bubble and the pressure shift resulting from the air column in a dip-tube pressure measurement are the error sources to be considered for highly accurate density, level, and volume determination of plutonium nitrate solution in a tank. A new approach to estimate the maximum, the minimum, and the average of oscillating excess pressure as a function of tube diameter d, solution density {rho}, and surface tension {sigma} without including height, curvature, and amplitude of the bubble is proposed. This approach can be applied without reducing the rate of downward airflow that is necessary to prevent contamination. When the estimates were compared with the experimental results in a water-ethanol system within the range 3.6 x 10{sup -6} {<=} {sigma}/({rho}g) {<=} 7.4 x 10{sup -6} (m{sup 2}) and 1.8 {<=} d({rho}g/{sigma}){sup 1/2} {<=} 9.6, the mean of the difference was <2 Pa. The estimate for the maximum excess pressure was also compared with the conventional formula, and the difference was <1 Pa. We also proposed an equation to estimate the surface tension of the plutonium nitrate solution. For the pressure shift, a new formula assuming that the air density varies exponentially in the tube is proposed. The measured differential pressure is proportional to the hydrostatic pressure, and the coefficient is nearly independent of the liquid level. These correction factors of excess pressure and pressure shift can practically be given as constants.

  9. Geometrical Properties of Pore Structure in Berea Sandstone under Pressurization with Micro Focus X-Ray CT

    NASA Astrophysics Data System (ADS)

    Takahashi, M.; Urushimatsu, Y.

    2008-12-01

    Three dimensional geometry and connectivity of pore space play a fundamental role in governing fluid transport properties of porous media. Total porosity and pore size distribution have been obtained through mercury intrusion porosimetry and gas absorption method, but the spatial and three dimensional information of pore geometry were difficult to obtain. To visualize in detail the manner of deformation in sedimentary rocks under various confining pressure and pore pressure, we used a micro focus X-ray CT system to obtain three dimensional images with high resolution of 5 micron. A new pressure vessel was developed to simultaneously supply both confining pressure and pore pressure to cylindrical rock specimen. Berea sandstone specimen of 10mm diameter and 20mm length was deformed hydrostatically. The diameters at every 15 degree angle were measured under the various conditions of confining pressure and pore pressures. The average diameter decreased monotonically with increasing effective confining pressure. Sensitive orientation around the specimen diameter with large deformation was recognized under pressurization. In addition, to quantify the flow-relevant geometrical properties of the pore structure, we utilized three dimensional data of Berea sandstone obtained with micro focus X-ray CT. We present measured distributions of pore size, throat size, channel length, coordination number, and of correlations between pore and throat geometry.

  10. Temporal pore pressure induced stress changes during injection and depletion

    NASA Astrophysics Data System (ADS)

    Müller, Birgit; Heidbach, Oliver; Schilling, Frank; Fuchs, Karl; Röckel, Thomas

    2016-04-01

    Induced seismicity is observed during injection of fluids in oil, gas or geothermal wells as a rather immediate response close to the injection wells due to the often high-rate pressurization. It was recognized even earlier in connection with more moderate rate injection of fluid waste on a longer time frame but higher induced event magnitudes. Today, injection-related induced seismicity significantly increased the number of events with M>3 in the Mid U.S. However, induced seismicity is also observed during production of fluids and gas, even years after the onset of production. E.g. in the Groningen gas field production was required to be reduced due to the increase in felt and damaging seismicity after more than 50 years of exploitation of that field. Thus, injection and production induced seismicity can cause severe impact in terms of hazard but also on economic measures. In order to understand the different onset times of induced seismicity we built a generic model to quantify the role of poro-elasticity processes with special emphasis on the factors time, regional crustal stress conditions and fault parameters for three case studies (injection into a low permeable crystalline rock, hydrothermal circulation and production of fluids). With this approach we consider the spatial and temporal variation of reservoir stress paths, the "early" injection-related induced events during stimulation and the "late" production induced ones. Furthermore, in dependence of the undisturbed in situ stress field conditions the stress tensor can change significantly due to injection and long-term production with changes of the tectonic stress regime in which previously not critically stressed faults could turn to be optimally oriented for fault reactivation.

  11. Pore pressure in a wind-swept rippled bed below the suspension threshold

    NASA Astrophysics Data System (ADS)

    Musa, R. A.; Takarrouht, S.; Louge, M. Y.; Xu, J.; Berberich, M. E.

    2014-12-01

    Toward elucidating how a wavy porous sand bed perturbs a turbulent flow above its surface, we record pressure within a permeable material resembling the region just below desert ripples, contrasting these delicate measurements with earlier studies on similar impermeable surfaces. We run separate tests in a wind tunnel on two sinusoidal porous ripples with aspect ratio of half crest-to-trough amplitude to wavelength of 3% and 6%. For the smaller ratio, pore pressure is a function of streamwise distance with a single delayed harmonic decaying exponentially with depth and proportional to wind speed squared. The resulting pressure on the porous surface is nearly identical to that on a similar impermeable wave. Pore pressure variations at the larger aspect ratio are greater and more complicated. Consistent with the regime map of Kuzan et al., the flow separates, creating a depression at crests. Unlike flows on impermeable waves, the porous rippled bed diffuses the depression upstream, reduces surface pressure gradients, and gives rise to a slip velocity, thus affecting the turbulent boundary layer. Pressure gradients within the porous material also generate body forces rising with wind speed squared and ripple aspect ratio, partially counteracting gravity around crests, thereby facilitating the onset of erosion, particularly on ripples of high aspect ratio armored with large surface grains. By establishing how pore pressure gradients scale with ripple aspect ratio and wind speed, our measurements quantify the internal seepage flow that draws dust and humidity beneath the porous surface.

  12. A Sequential Dynamic Bayesian Network for Pore Pressure Prediction and Quantification of Uncertainty.

    NASA Astrophysics Data System (ADS)

    Oughton, R. H.; Wooff, D. A.; Hobbs, R. W.; Swarbrick, R. E.

    2014-12-01

    Pore pressure prediction is vital when drilling a well, as unexpected overpressure can cause drilling challenges and uncontrolled hydrocarbon leakage. One cause of overpressure is when pore fluid is trapped during burial and takes on part of the lithostatic load. Predictions often use porosity-based techniques, such as the Eaton Ratio method and equivalent depth method. These rely on an idealised compaction trend and use a single wireline log as a proxy for porosity. Such methods do not account for the many sources of uncertainty, or for the multivariate nature of the system. We propose a sequential dynamic Bayesian network (SDBN) as a solution to these issues. The SDBN models the quantities in the system (such as pressures, porosity, lithology, wireline logs, fluid properties and so on) using conditional probability distributions to capture their joint behaviour. A compaction model is central to the SDBN, relating porosity to vertical effective stress, with uncertainty in the relationship, so that the logic is similar to that of the equivalent depth method. The probability distribution for porosity depends on VES and lithology, with much more uncertainty in sandstone-like rocks than in shales to reflect a general lack of understanding of sandstone compaction. The distributions of the wireline logs depend on porosity and lithology, along with other quantities, and so when they are observed the SDBN learns about porosity and lithology and in turn VES and pore pressure, using Bayes theorem. The probability distribution for each quantity in the SDBN is updated in light of any data, so that rather than giving a single-valued prediction for pore pressure, the SDBN gives a prediction with uncertainty that takes into account the whole system, knowledge and data. The dynamic nature of the SDBN enables it to use the bulk density to calculate total vertical stress, and to account for the dissipation of pore pressure. The vertical correlation in the SDBN means it is suited to

  13. Influence of pore pressure on the successive failures of intact slopes

    NASA Astrophysics Data System (ADS)

    Voulgari, Chrysoula; Utili, Stefano

    2016-04-01

    The presence of water can significantly change the stability of a slope and as a result the evolution of a slope in time. In this paper the influence of pore water pressure on the morphological evolution of natural cliffs subject to progressive retreat is investigated. The upper bound theorem of limit analysis is employed to evaluate the stability number and the failure mechanism of successive failures of uniform c, φ slopes with the presence of water. This model extends the existing analytical framework on the evolution of slopes subjected to weathering by accounting for the presence of water. Pore-water pressure is considered in the model by using the coefficient ru, a description of the pore-water pressure distribution that is approximate, but is commonly used in slope stability analyses. To account for the influence of the pore pressure, the work of pore-water pressure on the deformation of the soil along the failure surface had to be included in the model leading to modified analytical expressions of the energy balance equation (the balance between external work and dissipated energy) and as a consequence, of the function whose minimum provides the solution in terms of failure mechanisms and associated values of soil strength. With this model it is possible to relate the evolution of natural slopes with the presence of water by a sequence of rotational sliding block failures to the degradation of material strength properties. Computations were carried out for a wide range of parameters (friction angle φ and initial slope inclination β) and a set of normalized solutions is presented for different values of ru coefficient.

  14. Closing an open system: Pore pressure changes in permeable edifice rock at high strain rates

    NASA Astrophysics Data System (ADS)

    Heap, Michael J.; Wadsworth, Fabian B.

    2016-04-01

    A permeable or open system will react as a closed system if the rocks implicated are deformed on a timescale that precludes fluid movement. Closed system ("undrained") deformation therefore leads to a failure mode dependent change in pore pressure: microcracking (dilatant behaviour) and cataclastic pore collapse (compactant behaviour) will decrease and increase pore pressure, respectively. In the dilatant regime (i.e., in the shallow edifice, < 1 km depth), a decrease in pore pressure will serve to strengthen rock-a process termed dilatancy hardening. However, it is shown here, using undrained triaxial deformation experiments, that the high initial porosity and microcrack density of typical edifice-forming andesites prevent dilatancy hardening. This allows the rock proximal to the magma-filled conduit in the shallow edifice to remain weak during periods of unrest when high magma strain rates could be transferred to the adjacent country rock. Although the propensity for fracturing will likely reduce the structural integrity of the edifice, fracturing of the shallow edifice may improve the outgassing efficiency of the nearby magma-filled conduit. The increase in pore pressure during undrained deformation in the compactant regime (i.e., in the deep edifice, > 1 km depth) could lead to pore pressure embrittlement and fracturing. Indeed, the experiments of this study show that the pore pressure increases during progressive compaction in a closed system. However, the pore pressure is prevented from reaching the critical value required to promote a dilatant response (i.e., fracturing) for two reasons. First, the rate of compaction (i.e., porosity decrease) slows as the sample is deformed at a constant strain rate, a consequence of the decay in effective pressure. Second, the emergence of microcracking as the rock approaches the compactant-dilatant transition acts as a negative feedback and prevents the rock from transiting into the dilatant field. At this point, local

  15. Characterization of pores in high pressure die cast aluminum using active thermography and computed tomography

    NASA Astrophysics Data System (ADS)

    Maierhofer, Christiane; Myrach, Philipp; Röllig, Mathias; Jonietz, Florian; Illerhaus, Bernhard; Meinel, Dietmar; Richter, Uwe; Miksche, Ronald

    2016-02-01

    Larger high pressure die castings (HPDC) and decreasing wall thicknesses are raising the issue of casting defects like pores in aluminum structures. Properties of components are often strongly influenced by inner porosity. As these products are being established more and more in lightweight construction (e.g. automotive and other transport areas), non-destructive testing methods, which can be applied fast and on-site, are required for quality assurance. In this contribution, the application of active thermography for the direct detection of larger pores is demonstrated. The analysis of limits and accuracy of the method are completed by numerical simulation and the method is validated using computed tomography.

  16. The representativeness of pore water samples collected from the unsaturated zone using pressure-vacuum lysimeters

    USGS Publications Warehouse

    Peters, C.A.; Healy, R.W.

    1988-01-01

    Studies have indicated that the chemistry of water samples may be altered by the collection technique, creating concern about the representativeness of the pore water samples obtained. A study using soil water pressure-vacuum lysimeters in outwash sand and glacial till deposits demonstrates that for non-dilute-solution samples the effect of pH of sampling with lysimeters is minimal, and that measured major cation and anion concentrations are representative of the natural pore water; trace-metal concentrations can be significantly altered by collection procedures at low concentrations. -from Authors

  17. Landslide stability: Role of rainfall-induced, laterally propagating, pore-pressure waves

    USGS Publications Warehouse

    Priest, G.R.; Schulz, W.H.; Ellis, W.L.; Allan, J.A.; Niem, A.R.; Niem, W.A.

    2011-01-01

    The Johnson Creek Landslide is a translational slide in seaward-dipping Miocene siltstone and sandstone (Astoria Formation) and an overlying Quaternary marine terrace deposit. The basal slide plane slopes sub-parallel to the dip of the Miocene rocks, except beneath the back-tilted toe block, where it slopes inland. Rainfall events raise pore-water pressure in the basal shear zone in the form of pulses of water pressure traveling laterally from the headwall graben down the axis of the slide at rates of 1-6 m/hr. Infiltration of meteoric water and vertical pressure transmission through the unsaturated zone has been measured at ~50 mm/hr. Infiltration and vertical pressure transmission were too slow to directly raise head at the basal shear zone prior to landslide movement. Only at the headwall graben was the saturated zone shallow enough for rainfall events to trigger lateral pulses of water pressure through the saturated zone. When pressure levels in the basal shear zone exceeded thresholds defined in this paper, the slide began slow, creeping movement as an intact block. As pressures exceeded thresholds for movement in more of the slide mass, movement accelerated, and differential displacement between internal slide blocks became more pronounced. Rainfall-induced pore-pressure waves are probably a common landslide trigger wherever effective hydraulic conductivity is high and the saturated zone is located near the surface in some part of a slide. An ancillary finding is apparently greater accuracy of grouted piezometers relative to those in sand packs for measurement of pore pressures at the installed depth.

  18. Dilatancy and pore pressure effects during fracture and shear of antigorite-rich serpentinite

    NASA Astrophysics Data System (ADS)

    French, M. E.; Zhu, W.

    2015-12-01

    Geophysical observations show evidence of near-lithostatic pore pressure in fault zones that experience episodic slow slip events. In addition, dilatancy hardening is one of several hypotheses proposed to explain the transient self-sustaining nature of slow slip. Thus, pore pressure evolution is possibly an important control on slow slip behavior. Phyllosilicates are abundant in regions of subduction zones and along the deep San Andreas Fault where slow slip is observed, yet previous work on phyllosilicate-bearing rocks indicates that fracture and frictional sliding occur with little dilation of the pore space. We present experimental results of pore pressure effects during fracture and frictional shear of antigorite-rich serpentinite. Triaxial deformation experiments were conducted on intact cores 25.4 mm in diameter and 53.0 mm in length and ~1.5 mm thick gouge zones sandwiched between porous sandstone or steel sawcut forcing blocks. Experiments were conducted at room temperature, confining pressures from 50 to 100 MPa, pore pressure from 0 to 95 MPa, and axial displacement rates from 0.016 to 4.0 μm/s (shear rates from 0.02 to 5 μm/s). Foliated and macroscopically isotropic intact serpentinite samples were tested; fabric orientation is strongly correlated with both strength and dilatancy. When foliation is oriented parallel to σ1, strength and dilatancy are greatest and similar to those for crystalline rocks. When foliation is oriented 45 ° to σ1, however, dilatancy and strength are both greatly reduced. During frictional shear we observe a transition from rate-strengthening to rate-weakening behavior at ~0.5 μm/s, which is within range of typical slow slip rates and consistent with previous studies. This transition occurs concurrently with a transition from slip-induced compaction to dilation. Higher pore pressure correlates with overall higher friction coefficient, and also with lower compaction rates and higher dilation rates in the rate

  19. Transient pore pressure response to confining stress excursions in Berea sandstone flooded with an aqueous solution of CO2

    NASA Astrophysics Data System (ADS)

    Crews, Jackson B.; Cooper, Clay A.

    2014-06-01

    We measured the pore pressure response due to carbon dioxide (CO2) gas bubble nucleation and growth in a Berea sandstone core flooded with an initially subsaturated aqueous solution of CO2, in response to a rapid drop in confining stress, under conditions representative of a confined aquifer. A portion of the CO2 in the Earth's crust, derived from volcanic, magmatic, and biogenic sources, dissolves in groundwater. Sudden reductions in confining stress in the Earth's crust occur due to dilational strain generated by the propagation of seismic Rayleigh and P waves, or aseismic slip in the near field of earthquakes. A drop in confining stress produces a proportional drop in pore fluid pressure. When the pore fluid contains dissolved CO2, the pore pressure responds to a drop in confining stress like it does in the dissolved gas-free case, until the pore pressure falls below the bubble pressure. Gas bubble nucleation and diffusive growth in the pore space trigger spontaneous, transient buildup of the pore fluid pressure, and reduction of effective stress. We measured the rate of pore fluid pressure buildup in the 100 s immediately following the confining stress drop, as a function of the saturation with respect to CO2 at the lowest pore pressure realized during the confining stress drop, using five different CO2 partial pressures. The rate scales with the saturation with respect to dissolved CO2, from 10 kPa/min at 1.25 to 166 kPa/min at 1.8. The net pore pressure rise was as large as 0.7 MPa (100 psi) over 5 h.

  20. Estimating the hydraulic properties of an aquitard from in situ pore pressure measurements

    NASA Astrophysics Data System (ADS)

    Smerdon, Brian D.; Smith, Laura A.; Harrington, Glenn A.; Gardner, W. Payton; Piane, Claudio Delle; Sarout, Joel

    2014-12-01

    A workflow is described to estimate specific storage ( S s) and hydraulic conductivity ( K) from a profile of vibrating wire piezometers embedded into a regional aquitard in Australia. The loading efficiency, compressibility and S s were estimated from pore pressure response to atmospheric pressure changes, and K was estimated from the earliest part of the measurement record following grouting. Results indicate that S s and K were, respectively, 8.8 × 10-6 to 1.2 × 10-5 m-1 and 2 × 10-12 m s-1 for a claystone/siltstone, and 4.3 × 10-6 to 9.6 × 10-6 m-1 and 1 × 10-12 to 5 × 10-12 m s-1 for a thick mudstone. K estimates from the pore pressure response are within one order of magnitude when compared to direct measurement in a laboratory and inverse modelled flux rates determined from natural tracer profiles. Further analysis of the evolution and longevity of the properties of borehole grout (e.g. thermal and chemical effects) may help refine the estimation of formation hydraulic properties using this workflow. However, the convergence of K values illustrates the benefit of multiple lines of evidence to support aquitard characterization. An additional benefit of in situ pore pressure measurement is the generation of long-term data to constrain groundwater flow models, which provides a link between laboratory scale data and the formation scale.

  1. Pore-by-pore capillary pressure measurements using X-ray microtomography at reservoir conditions: Curvature, snap-off, and remobilization of residual CO2

    NASA Astrophysics Data System (ADS)

    Andrew, Matthew; Bijeljic, Branko; Blunt, Martin J.

    2014-11-01

    X-ray microtomography was used to image the shape and size of residual ganglia of supercritical CO2 at resolutions of 3.5 and 2 μm and at representative subsurface conditions of temperature and pressure. The capillary pressure for each ganglion was found by measuring the curvature of the CO2-brine interface, while the pore structure was parameterized using distance maps of the pore space. The formation of the residual clusters by snap-off was examined by comparing the ganglion capillary pressure to local pore topography. The capillary pressure was found to be inversely proportional to the radius of the largest restriction (throat) surrounding the ganglion, which validates the imbibition mechanisms used in pore-network modeling. The potential mobilization of residual ganglia was assessed using a reformulation of both the capillary (Ncmacro) and Bond numbers (Nbmacro), rigorously based on a balance of pore-scale forces, with the majority of ganglia remobilized at Ncmacro around 1. Buoyancy forces were found to be small in this system (Nbmacro << 1), meaning the gravitational remobilization of CO2 after residual trapping would be extremely difficult.

  2. Experimental Studies of Dynamic Fault Weakening Due to Thermal Pore-Fluid Pressurization

    NASA Astrophysics Data System (ADS)

    Goldsby, D. L.; Tullis, T. E.; Okazaka, K.; Platt, J. D.; Mitchell, T. M.

    2014-12-01

    Thermal pressurization is a co-seismic weakening mechanism driven by the thermal expansion of native pore fluids, which leads to elevated pore pressures and significant co-seismic weakening. While thermal pressurization has been studied theoretically for many decades, and has been invoked in recent earthquake simulations, its activation in laboratory experiments has remained elusive. Several high-speed friction experiments yield indirect evidence for thermal pressurization, yet none have directly linked with existing theoretical models or the relevant physical parameters -- such as permeability, slip, and slip rate - that control the weakening rate. We are conducting thermal pressurization experiments on fluid-saturated, low-permeability rocks (primarily Fredrick diabase; also SAFOD gouge) at slip rates up to ~5 mm/s, with constant confining pressures in the range 21-149 MPa and initial pore pressures in the range 10-25 MPa. The impractically low permeability of the diabase, ~10-23 m2, is increased prior to the friction test by thermally cracking the samples, yielding measured permeabilities in the range 1.3*10-18 to 6.1*10-19 m2. These permeabilites are high enough to allow sample saturation over one to several days, but also low enough to confine pore pressure rises during rapid sliding and allow thermal pressurization to occur. In recent experiments we also embed a thermocouple ~1-2 mm from the sliding surface, and use the resulting data to calibrate a finite element model that calculates the sliding surface temperature. One experiment revealed a rapid decay of shear stress by ~25% following a step-change in velocity from 10 μm/s to 4.8 mm/s. For the first 28 mm of slip the experimentally measured shear stress agrees closely with the theoretical solution for slip on a plane (Rice [2006]) with an inferred slip weakening distance of ~500 mm, which is in the range predicted by inserting laboratory determined rock and fluid properties into the formula for L* from

  3. Gender-related differences in the excess pressure component of central aortic pressure waveform of healthy young.

    PubMed

    Cymberknop, Leandro; Bia, Daniel; Zócalo, Yanina; Farro, Ignacio; Torrado, Juan; Farro, Federico; Pessana, Franco; Armentano, Ricardo L

    2011-01-01

    Gender-related difference in cardiovascular diseases is one of the most investigated and still unsolved issues. Finding an explanation to this topic might have important implications for the understanding of the differences between men and women in diseases and possibly lead to the development of gender-specific strategies for its management. Recent studies have proposed that the capacitive or reservoir function of the aorta and large elastic arteries plays a major role in determining the pulse wave morphology. The pressure waveform can be explained in terms of a reservoir pressure related to arterial compliance and an "excess" or wave-related pressure associated with traveling waves. Gender-differences in the ascending aorta pressure waveform reservoir and excess components are to be characterized. The aim of this study was to evaluate, by means of a mathematical approach, gender-related differences in the central aortic pressure waveform components. Central aortic pressure waveform was non-invasively obtained in 22 healthy subjects (Age: 20 years old; 11 female). Males and females showed differences in the level and time to maximal excess pressure component, but no gender-related differences were found in the reservoir one. PMID:22254286

  4. Estimation of upper limit of pore pressure by fault stability analysis

    NASA Astrophysics Data System (ADS)

    Chen, Zijian; Deng, Jingen; Yu, Baohua; Zhang, Yanan; Chen, Zhuo

    2016-06-01

    Generally, the pore pressure for a pre-drill well is predicted using empirical parameters, which are regressed from the drilled well's data. However, for areas with large geological differences, empirical parameters which are obtained using traditional methods may fail because intense tectonic movement would result in huge differences between the pre-drill well and drilled well. Firstly, in order to overcome this problem, the method of fault stability analysis is introduced. Analysis indicates that when abnormal overpressure exceeds a certain value, the fault ruptures and the overpressured fluid escapes, so that there is an upper limit of pore pressure (ULPP) for the stable fault. Secondly, the influences of fault angle, formation Poisson ratio and modulus of elasticity on the ULPP are discussed further. The results show that the ULPP of a fault with angle of 65.2° is the minimum, and the critical angle increases with the increase of internal friction coefficient. For reverse faults and strike faults, the influences of Poisson ratio and modulus of elasticity are small, but for normal faults these are significant. Finally, three kinds of ULPP for these different faults are proposed, respectively. The application of this method in the Xihu Sag in the East China Sea has proved that reference to ULPP can verify and correct regressed empirical parameters, so as to improve pore pressure prediction accuracy.

  5. Characterization of pore structure in cement-based materials using pressurization-depressurization cycling mercury intrusion porosimetry (PDC-MIP)

    SciTech Connect

    Zhou Jian; Ye Guang; Breugel, Klaas van

    2010-07-15

    Numerous mercury intrusion porosimetry (MIP) studies have been carried out to investigate the pore structure in cement-based materials. However, the standard MIP often results in an underestimation of large pores and an overestimation of small pores because of its intrinsic limitation. In this paper, an innovative MIP method is developed in order to provide a more accurate estimation of pore size distribution. The new MIP measurements are conducted following a unique mercury intrusion procedure, in which the applied pressure is increased from the minimum to the maximum by repeating pressurization-depressurization cycles instead of a continuous pressurization followed by a continuous depressurization. Accordingly, this method is called pressurization-depressurization cycling MIP (PDC-MIP). By following the PDC-MIP testing sequence, the volumes of the throat pores and the corresponding ink-bottle pores can be determined at every pore size. These values are used to calculate pore size distribution by using the newly developed analysis method. This paper presents an application of PDC-MIP on the investigation of the pore size distribution in cement-based materials. The experimental results of PDC-MIP are compared with those measured by standard MIP. The PDC-MIP is further validated with the other experimental methods and numerical tool, including nitrogen sorption, backscanning electron (BSE) image analysis, Wood's metal intrusion porosimetry (WMIP) and the numerical simulation by the cement hydration model HYMOSTRUC3D.

  6. A pore-pressure diffusion model for estimating landslide-inducing rainfall

    USGS Publications Warehouse

    Reid, M.E.

    1994-01-01

    Many types of landslide movement are induced by large rainstorms, and empirical rainfall intensity/duration thresholds for initiating movement have been determined for various parts of the world. In this paper, I present a simple pressure diffusion model that provides a physically based hydrologic link between rainfall intensity/duration at the ground surface and destabilizing pore-water pressures at depth. The model approximates rainfall infiltration as a sinusoidally varying flux over time and uses physical parameters that can be determined independently. Using a comprehensive data set from an intensively monitored landslide, I demonstrate that the model is capable of distinguishing movement-inducing rainstorms. -Author

  7. Age-related changes in reservoir and excess components of central aortic pressure in asymptomatic adults.

    PubMed

    Bia, Daniel; Cymberknop, Leandro; Zócalo, Yanina; Farro, Ignacio; Torrado, Juan; Farro, Federico; Pessana, Franco; Armentano, Ricardo L

    2011-01-01

    Study of humans aging has presented difficulties in separating the aging process from concomitant disease and/or in defining normality and abnormality during its development. In accordance with this, aging associates structural and functional changes evidenced in variations in vascular parameters witch suffer alterations during atherosclerosis and have been proposed as early markers of the disease. The absence of adequate tools to differentiate the expected (normal) vascular changes due to aging from those related with a vascular disease is not a minor issue. For an individual, an early diagnosis of a vascular disease should be as important as the diagnosis of a healthy vascular aging. Recent studies have proposed that the capacitive or reservoir function of the aorta and large elastic arteries plays a major role in determining the pulse wave morphology. The arterial pressure waveform can be explained in terms of a reservoir pressure, related to the arterial system compliance, and an "excess" or wave-related pressure, associated with the traveling waves. The aim of this study was to evaluate, by means of a mathematical approach, age-related changes in measured, reservoir and excess central aortic pressure in order to determine if age-related changes are concentrated in particular decades of life. Central aortic pressure waveform was non-invasively obtained in healthy subjects (age range: 20-69 years old). Age-related profiles in measured, reservoir and excess pressure were calculated. PMID:22255816

  8. Elucidating the mechanical effects of pore water pressure increase on the stability of unsaturated soil slopes

    NASA Astrophysics Data System (ADS)

    Buscarnera, G.

    2012-12-01

    The increase of the pore water pressure due to rain infiltration can be a dominant component in the activation of slope failures. This paper shows an application of the theory of material stability to the triggering analysis of this important class of natural hazards. The goal is to identify the mechanisms through which the process of suction removal promotes the initiation of mechanical instabilities. The interplay between increase in pore water pressure, and failure mechanisms is investigated at material point level. In order to account for multiple failure mechanisms, the second-order work criterion is used and different stability indices are devised. The paper shows that the theory of material stability can assess the risk of shear failure and static liquefaction in both saturated and unsaturated contexts. It is shown that the combined use of an enhanced definition of second-order work for unsaturated porous media and a hydro-mechanical constitutive framework enables to retrieve bifurcation conditions for water-infiltration processes in unsaturated deposits. This finding discloses the importance of the coupling terms that incorporate the interaction between the solid skeleton and the pore fluids. As a consequence, these theoretical results suggest that some material properties that are not directly associated with the shearing resistance (e.g., the potential for wetting compaction) can play an important role in the initiation of slope failures. According to the proposed interpretation, the process of pore pressure increase can be understood as a trigger of uncontrolled strains, which at material point level are reflected by the onset of bifurcation conditions.

  9. Distribution of physical properties and pore pressure of sediments off Costa Rica: IODP Expedition 344

    NASA Astrophysics Data System (ADS)

    Saiki, A.; Hashimoto, Y.

    2014-12-01

    Evolution of physical properties in subduction zone is a key to understand lithification processes, location of decollement, stress distribution. In this study, we examined the physical properties of sediments using on-board data and laboratory experimental data on sediments obtained off Costa Rica margin to understand the distribution of compaction states. Target sites are in the Integrate Ocean Drilling Program (IODP) Expedition 344 off Costa Rica, including reference sites (U1381 and U1414), frontal prism site (U1412), mid-slope site (U1380) and upper-slope site (U1413). Laboratory experiments for velocity and porosity measurements were conducted with variation of effective pressure. Porosity ranges from about 80% to about 53% during experiments. P-wave velocity ranges from about 1.4 to about 1.7 km/s. Velocity-porosity relationships from on-board data and from laboratory experiments are comparable nicely. This comparable trend in Vp-porosity relationship suggests that the relationship between porosity and effective pressure can be applied to most of sediments. The porosity-effective pressure curves under isotropic condition were converted to the curves under uniaxial condition (Teeuw, 1971). Using the normal consolidation curves under isotropic and uniaxial stress conditions, we converted the on-board porosity to effective pressure and fluid pressure. For U1381 Unit I, hydrostatic fluid pressure was estimated as expected as a reference site. For U1414 in another reference site, hydrostatic pressure was observed in Unit I, but lower fluid pressure than hydrostatic pressure was estimated in the upper part of Unit II. Below that, the pore pressure returned along hydrostatic pressure. This boundary can be weakened by higher fluid pressure below the boundary, suggesting that this boundary is likely a precursor of decollement. For Unit 1412 in frontal prism, pore fluid pressure is lower than hydrostatic pressure, suggesting that they have lower porosity possibly

  10. Friction experiments of halite in brittle-ductile transition with high pore pressure

    NASA Astrophysics Data System (ADS)

    Noda, H.; Takahashi, M.; Katayama, I.

    2015-12-01

    Flow stress of rock (τ) approximately linearly depends on normal stress on a shear zone (σn) minus pore pressure (p) in a brittle regime, and insensitive to σn in a fully plastic regime where pores are isolated and filled with fluid of high pressure comparable to the mean stress, like oil drops in water. How p affects τ in the transitional regime is not fully understood, although it is a key to understanding many important geological problems such as role of fluids in deformation mechanism, stress and strength profile of the crust, seismogenic depth range, and so on. The effective normal stress σe is often given by σe = σn - α p (α: a constant around 1 in the brittle regime), and frictional resistance, by τ = f σe (f: friction coefficient). Recently, Hirth and Beeler [2015] proposed a model of the effective stress law in the transitional regime. Because of increasing ratio of real area of contact to nominal area of frictional interface, α may decrease to zero towards fully plastic regime, causing a sharper peak in the strength profile than a conventional Brace-Goetze strength profile which is sometimes referred to as "Christmas tree". We investigated this idea by means of friction experiments at high temperature and pore pressure. We used halite as an analogue material which undergoes a transition from brittle to fully plastic regime under convenient conditions [Shimamoto, 1986]. We conducted friction experiments of a pre-cut sliding interface filled with halite gouge with gas-medium triaxial apparatus in Hiroshima University, at 150 MPa confining pressure, from room temperature to 210 °C, and from atmospheric pressure to more than 100 MPa fluid (argon gas) pressure in a reservoir. Our preliminary result shows that the sharp peak in the flow stress is probably absent. A phenomenological smooth connection proposed by Shimamoto and Noda [2014] based on friction experiments without a jacket (i.e. atmospheric pore pressure) may work in explaining the

  11. A New Mechanism for Pore Pressure Changes Induced by Distant Earthquakes

    NASA Astrophysics Data System (ADS)

    Brodsky, E. E.; Roeloffs, E.; Woodcock, D.; Gall, I.; Manga, M.

    2001-12-01

    Observations during the Mw=7.3 1992 Landers earthquake, Mw=7.4 Izmit earthquake and Mw=7.2 Hector Mine earthquake suggest that seismicity is triggered hundreds of kilometers from a mainshock epicenter. This puzzling phenomenon is not explained by traditional elastic models of seismic stresses. The fact that the triggered sites are often geothermal or magmatic suggests that fluids may be an important part of the triggering process. Rapid changes in pore pressure either reduce the effective stress on faults locally or prompt hydrofracturing to initiate local earthquakes. The challenge is to discover how the seismic waves generate a change in pore fluid pressure. We constrain a mechanism for seismically-induced pore pressure changes by studying coseismic water level drops at a well in Grants Pass, Oregon. Water level drops at the site have been associated with earthquakes for nearly 20 years. High-sample rate (up to 1 Hz) digital water level data is available for the two coseismic drops that have occurred since 1994. The approach of this study is to use the amplification of the seismic waves in the well to constrain variations of the aquifer properties during the water level drops. We find that the amplification of the seismic waves in the well is consistent with standard theory for 7 digitally recorded events without drops, but during an earthquake with a drop a dramatic change in amplification occurs during the passage of the Rayleigh waves. The change in amplification indicates that the transmissivity increases by a factor of 50 during the 11 cm coseismic water level drop accompanying the 1999 Mw=7.5 1999 Oaxaca, Mexico earthquake. Based on these observations, we propose a new model for coseismic pore pressure changes. Drops occur if an earthquake occurs when the well has become temporarily clogged by a solid precipitate or sediment. The seismic shaking induces a flow which removes the obstruction. Once a barrier is removed, water flows rapidly to generate dramatic

  12. Pore-lining composition and capillary breakthrough pressure of mudstone caprocks : sealing efficiency of geologic CO2 storage sites.

    SciTech Connect

    Petrusak, Robin; Heath, Jason E.; McPherson, Brian J. O. L.; Dewers, Thomas A.; Kotula, Paul Gabriel

    2010-08-01

    Subsurface containment of CO2 is predicated on effective caprock sealing. Many previous studies have relied on macroscopic measurements of capillary breakthrough pressure and other petrophysical properties without direct examination of solid phases that line pore networks and directly contact fluids. However, pore-lining phases strongly contribute to sealing behavior through interfacial interactions among CO2, brine, and the mineral or non-mineral phases. Our high resolution (i.e., sub-micron) examination of the composition of pore-lining phases of several continental and marine mudstones indicates that sealing efficiency (i.e., breakthrough pressure) is governed by pore shapes and pore-lining phases that are not identifiable except through direct characterization of pores. Bulk X-ray diffraction data does not indicate which phases line the pores and may be especially lacking for mudstones with organic material. Organics can line pores and may represent once-mobile phases that modify the wettability of an originally clay-lined pore network. For shallow formations (i.e., < {approx}800 m depth), interfacial tension and contact angles result in breakthrough pressures that may be as high as those needed to fracture the rock - thus, in the absence of fractures, capillary sealing efficiency is indicated. Deeper seals have poorer capillary sealing if mica-like wetting dominates the wettability.

  13. Pore-lining composition and capillary breakthrough pressure of mudstone caprocks : sealing efficiency at geologic CO2 storage sites.

    SciTech Connect

    Heath, Jason E.; Nemer, Martin B.; McPherson, Brian J. O. L.; Dewers, Thomas A.; Kotula, Paul Gabriel

    2010-12-01

    Subsurface containment of CO2 is predicated on effective caprock sealing. Many previous studies have relied on macroscopic measurements of capillary breakthrough pressure and other petrophysical properties without direct examination of solid phases that line pore networks and directly contact fluids. However, pore-lining phases strongly contribute to sealing behavior through interfacial interactions among CO2, brine, and the mineral or non-mineral phases. Our high resolution (i.e., sub-micron) examination of the composition of pore-lining phases of several continental and marine mudstones indicates that sealing efficiency (i.e., breakthrough pressure) is governed by pore shapes and pore-lining phases that are not identifiable except through direct characterization of pores. Bulk X-ray diffraction data does not indicate which phases line the pores and may be especially lacking for mudstones with organic material. Organics can line pores and may represent once-mobile phases that modify the wettability of an originally clay-lined pore network. For shallow formations (i.e., < {approx}800 m depth), interfacial tension and contact angles result in breakthrough pressures that may be as high as those needed to fracture the rock - thus, in the absence of fractures, capillary sealing efficiency is indicated. Deeper seals have poorer capillary sealing if mica-like wetting dominates the wettability. We thank the U.S. Department of Energy's National Energy Technology Laboratory and the Office of Basic Energy Sciences, and the Southeast and Southwest Carbon Sequestration Partnerships for supporting this work.

  14. Predicting the Influence of Pore Characteristics on Ductility of Thin-Walled High Pressure Die Casting Magnesium

    SciTech Connect

    Sun, Xin; Choi, Kyoo Sil; Li, Dongsheng

    2013-06-10

    In this paper, a two-dimensional microstructure-based finite element modeling method is adopted to investigate the effects of porosity in thin-walled high pressure die casting Mg materials on their ductility. For this purpose, the cross-sections of AM50 and AM60 casting samples are first examined using optical microscope to obtain the overall information on the pore characteristics. The experimentally quantified pore characteristics are then used to generate a series of synthetic microstructures with different pore sizes, pore volume fractions and pore size distributions. Pores are explicitly represented in the synthetic microstructures and meshed out for the subsequent finite element analysis. In the finite element analysis, an intrinsic critical strain value is used for the Mg matrix material, beyond which work-hardening is no longer permissible. With no artificial failure criterion prescribed, ductility levels are predicted for the various microstructures in the form of strain localization. Mesh size effect study is also conducted, from which a mesh size dependent critical strain curve is determined. A concept of scalability of pore size effects is then presented and examined with the use of the mesh size dependent critical strain curve. The results in this study show that, for the regions with lower pore size and lower volume fraction, the ductility generally decreases as the pore size and pore volume fraction increase whereas, for the regions with larger pore size and larger pore volume fraction, other factors such as the mean distance between the pores begin to have some substantial influence on the ductility. The results also indicate that the pore size effects may be scalable for the models with good-representative pore shape and distribution with the use of the mesh size dependent critical strain curve.

  15. The effects of pressure, temperature, and pore water on velocities in Westerly granite. [for seismic wave propagation

    NASA Technical Reports Server (NTRS)

    Spencer, J. W., Jr.; Nur, A. M.

    1976-01-01

    A description is presented of an experimental assembly which has been developed to conduct concurrent measurements of compressional and shear wave velocities in rocks at high temperatures and confining pressures and with independent control of the pore pressure. The apparatus was used in studies of the joint effects of temperature, external confining pressure, and internal pore water on sonic velocities in Westerly granite. It was found that at a given temperature, confining pressure has a larger accelerating effect on compressional waves in dry rock, whereas at a given confining pressure, temperature has a larger retarding effect on shear waves.

  16. Quantification of in situ pore pressure and stress in regions of low frequency earthquakes and anomalously low seismic velocity at the Nankai Trough

    NASA Astrophysics Data System (ADS)

    Kitajima, H.; Saffer, D. M.

    2012-12-01

    LVZ's are at shear failure defined by a critical state stress condition, we estimate that effective vertical stress in the LVZ ranges from 15 MPa at 13 km landward of the trench, to 41 MPa at a distance of 55 km. The maximum horizontal effective stress ranges from 41-124 MPa over this region. Excess pore fluid pressure ranges from 15-81 MPa, corresponding to modified pore pressure ratios, λ* of 0.44-0.73. If LVZ is composed dominantly of sandstones, both the effective vertical and horizontal stresses would be lower, and the excess pore pressure would be higher, with pore pressure ratios λ* = 0.31-0.90. Our results suggest that the sediments have been loaded under poorly drained conditions, and that pore fluids support ≥~53-91 % of the overburden stress along the base of the accretionary wedge across the outer forearc. The low effective stress should lead to a mechanically weak plate boundary, and is spatially correlated with well-located low-frequency earthquakes in the outer accretionary wedge. The heterogeneous distribution of inferred pore pressure also suggests that fluid sources and drainage are localized and possibly transient.

  17. Earthquake Fracture Energies and Weakening of Faults by Thermal Pressurization of Pore Fluid

    NASA Astrophysics Data System (ADS)

    Rice, J. R.

    2003-12-01

    Seismic inferences of fracture energy G constrain how fault strength degrades during slip and allow testing of candidate physical mechanisms. Recently G has been estimated by interpreting parameters from seismic slip inversions within a self-healing rupture model (Rice, Sammis and Parsons, 2003), and by studying the scaling of radiated energy and stress drop with earthquake size (Abercrombie and Rice, 2003). Those and earlier studies suggest that for larger events (slip > 0.1 m), G ranges from 0.1 to 10 MJ/m2 with average of 2-4 MJ/m2. There is a clear trend for G to increase with slip over the broad range from mm to m slip. Sibson-Lachenbruch thermal pressurization of pore water is examined as a possible general fault weakening mechanism for large crustal events. For adiabatic and undrained conditions, with strength given by the effective stress law with a constant friction coefficient f, the thermal properties of water in this context (Lachenbruch, 1980; Mase and Smith, 1988) lead to G = 1.7 (σ n - po) (1 + r) h. Here h is shearing zone thickness, σ n is normal stress, assumed constant during slip, po is ambient pore pressure, and r is the ratio fractional volume change of pore space per unit pore pressure increase divided by the compressibility of the pore fluid. Dilatancy is neglected; if confined to only the early phases of slip, it decreases po from ambient and so increases G, but the effect may be modest. The model predicts exponential decay of strength with slip, with e-folding slip distance 1.7 (1 + r) h / f. The total temperature rise in K is ≈ 0.6 (1 + r) (σ n - po) where the latter factor is in MPa. Estimating r = 1-2 and evaluating σ n - po as overburden minus hydrostatic pore pressure at 7 km as a representative centroidal depth for large crustal events, we obtain G ≈ 1-6 MJ/m2 for h = 2 to 10 mm. Shear zone thicknesses towards the lower end of such a range are suggested by recent field studies (Chester and Chester, 1998), which identify a

  18. Relations between hydrology and velocity of a continuously moving landslide-evidence of pore-pressure feedback regulating landslide motion?

    USGS Publications Warehouse

    Schulz, W.H.; McKenna, J.P.; Kibler, J.D.; Biavati, G.

    2009-01-01

    We measured displacement, pore-water pressure, and climatic conditions for 3 years at the continuously moving Slumgullion landslide in Colorado, USA. The landslide accelerated when pore-water pressure increased within the landslide body, but this occurred as pore-water pressure decreased along the landslide margin. The decrease probably occurred in response to shear-induced soil dilation at rates greater than pore-pressure diffusion and likely increased resistance to shear displacement and resulted in landslide deceleration. This dilative strengthening has been experimentally observed and explained theoretically, but not previously identified during field studies. Although landslide displacement should have exceeded that required to achieve critical-state density of shear boundaries, observed relocation of these boundaries indicates that shearing is episodic at fixed locations, so it permits renewed dilative strengthening when "fresh" soil is sheared. Thus, dilatant strengthening may be a considerable mechanism controlling landslide velocity, even for landslides that have continuously moved great distances. ?? Springer-Verlag 2009.

  19. Modeling strain and pore pressure associated with fluid extraction: The Pathfinder Ranch experiment

    NASA Astrophysics Data System (ADS)

    Barbour, Andrew J.; Wyatt, Frank K.

    2014-06-01

    Strainmeters can be subject to hydrologic effects from pumping of nearby water wells, depending on the state of the local rock. Strain signals associated with hydrology are generally not used and regarded as troublesome because they are much larger than most tectonic signals (e.g., tides or slow slip episodes in Cascadia), but here we show that fluid extraction leads to detectable strain and pore pressure signals, which we use to constrain valuable material properties of the rock, namely the hydraulic diffusivity and elastic shear modulus. We collected multiple years of pump activity at two active water wells near a pair of Plate Boundary Observatory borehole strainmeters in southern California. These data demonstrate clearly the connection between fluid extraction and deformation: the onset of transient strains and pore pressures is strongly correlated with both the onset of fluid extraction, and the sizes of the transient signals are strongly correlated with cumulative extraction volumes. These data also suggest that the instruments are a possible tool for remote monitoring of fluid injection and withdrawal. Based on poroelastic modeling, we find estimates of hydraulic diffusivity (0.061 m2s-1 to 0.126 m2s-1) which are consistent with data for fractured igneous rock, and estimates of shear modulus (39.7 MPa to 101 MPa) which are comparable to data for shallow granodiorite—expected to be weak from weathering, and other sources of damage (e.g., faulting). We infer that crustal rock in this region is drained at shallow depths by pervasive, hydraulically conductive fractures: as a result of changes in applied stress, fluid flow will occur rather than a sustained change in pore fluid pressure.

  20. Analysis of pore pressure conditions leading to slope instability in Tuscany (Italy)

    NASA Astrophysics Data System (ADS)

    Dapporto, S.; Tofani, V.; Vannocci, P.; Casagli, N.

    2003-04-01

    Complex landslides, originated as rotational or planar slides that transform into flows, are frequent in the Italian landscape. Triggering mechanisms of such landslides are still poorly understood. The objective of this study is to investigate pore water pressure changes (negative and positive) during a rainfall event and their effect on slope stability. Two events that occurred on June 1996 and November 2000 respectively in Versilia and near Pescia (Tuscany), having different characteristics in terms of rainfall intensity, stratigraphy, vegetative cover, and geometry of failure, were analysed. A detailed topographic investigation of slope profiles in pre- and post-failure conditions was performed using a GPS. The geotechnical and hydrological properties of the materials involved were then investigated with a series of in situ (Borehole Shear Tests and Amoozemeter Tests) and laboratory tests (grain size analyses, Atterberg limits, phase relationship analyses, direct shear tests). The evaluation of the potential for slope failure during the event was performed with an analysis of infiltration, seepage, and instability mechanisms. First, the infiltration rate at the surface was predicted by modifying the Chu approach for the Green and Ampt equations in case of unsteady rainfall together with a water balance at the surface. Changes in positive and negative pore pressures during the event were then modelled by a finite element analysis of water flow in transient conditions, using as boundary condition for the nodes along the slope surface the computed infiltration rate. Finally, a slope stability analysis was conducted applying the limit equilibrium method (Morgenstern-Price), using pore water pressure distributions obtained in the different time steps by the seepage analysis as input data for the calculation of the factor of safety. The followed approach allows the detailed reconstruction of changes in the factor of safety during the event and the determination of the

  1. An evaluation of factors influencing pore pressure in accretionary complexes: Implications for taper angle and wedge mechanics

    USGS Publications Warehouse

    Saffer, D.M.; Bekins, B.A.

    2006-01-01

    At many subduction zones, accretionary complexes form as sediment is off-scraped from the subducting plate. Mechanical models that treat accretionary complexes as critically tapered wedges of sediment demonstrate that pore pressure controls their taper angle by modifying basal and internal shear strength. Here, we combine a numerical model of groundwater flow with critical taper theory to quantify the effects of sediment and de??collement permeability, sediment thickness, sediment partitioning between accretion and underthrusting, and plate convergence rate on steady state pore pressure. Our results show that pore pressure in accretionary wedges can be viewed as a dynamically maintained response to factors which drive pore pressure (source terms) and those that limit flow (permeability and drainage path length). We find that sediment permeability and incoming sediment thickness are the most important factors, whereas fault permeability and the partitioning of sediment have a small effect. For our base case model scenario, as sediment permeability is increased, pore pressure decreases from near-lithostatic to hydrostatic values and allows stable taper angles to increase from ??? 2.5?? to 8??-12.5??. With increased sediment thickness in our models (from 100 to 8000 m), increased pore pressure drives a decrease in stable taper angle from 8.4??-12.5?? to 15?? to <4??) with increased sediment thickness (from <1 to 7 km). One key implication is that hydrologic properties may strongly influence the strength of the crust in a wide range of geologic settings. Copyright 2006 by the American Geophysical Union.

  2. Estimation of the pore pressure distribution from three dimensional groundwater flow model at mine sites in Korea

    NASA Astrophysics Data System (ADS)

    Kang, Sangsoo; Jang, Myounghwan; Kim, Gyoungman; Kim, Donghui; Kim, Daehoon; Baek, Hwanjo

    2016-04-01

    Mining activities continually change the groundwater flow and associated pore pressure distributions within the rockmass around the mine openings or the open-pit bench during the operational periods. As the pore pressure distributions may substantially affect the mechanical behaviour or stability of the rockmass, it is important to monitor the variation of pore pressure incurred by mining operation. The pore pressure distributions within the rockmass can be derived using a two- or three-dimensional finite element groundwater flow model, adopted to simulate the groundwater flow. While the groundwater inflow at mines has generally been dealt with respect to the working environment, detailed case studies on the distribution of pore water pressure related to the stability analysis of mine openings have been relatively rare in Korea. Recently, however, as the health and safety problems are emerged for sustainable mining practice, these issues are of the major concerns for the mining industries. This study aims to establish a three dimensional groundwater flow model to estimate the pore pressure distributions in order to employ as an input parameter for numerical codes such as the FLAC 3D. Also, the groundwater flow simulated can be used for de-watering design at a mine site. The MINEDW code, a groundwater flow model code specifically developed to simulate the complicated hydro-geologic conditions related to mining, has mainly been used in this study. Based on the data collected from field surveys and literature reviews, a conceptual model was established and sensitivity analysis was performed.

  3. Hydromechanical Rock Mass Fatigue in Deep-Seated Landslides Accompanying Seasonal Variations in Pore Pressures

    NASA Astrophysics Data System (ADS)

    Preisig, Giona; Eberhardt, Erik; Smithyman, Megan; Preh, Alexander; Bonzanigo, Luca

    2016-06-01

    The episodic movement of deep-seated landslides is often governed by the presence of high pore pressures and reduced effective stresses along active shear surfaces. Pore pressures are subject to cyclic fluctuation under seasonal variations of groundwater recharge, resulting in an intermittent movement characterized by acceleration-deceleration phases. However, it is not always clear why certain acceleration phases reach alarming levels without a clear trigger (i.e., in the absence of an exceptional pore pressure event). This paper presents a conceptual framework linking hydromechanical cycling, progressive failure and fatigue to investigate and explain the episodic behavior of deep-seated landslides using the Campo Vallemaggia landslide in Switzerland as a case study. A combination of monitoring data and advanced numerical modeling is used. The principal processes forcing the slope into a critical disequilibrium state are analyzed as a function of rock mass damage and fatigue. Modeling results suggest that during periods of slope acceleration, the rock slope experiences localized fatigue and gradual weakening through slip along pre-existing natural fractures and yield of critically stressed intact rock bridges. At certain intervals, pockets of critically weakened rock may produce a period of enhanced slope movement in response to a small pore pressure increase similar to those routinely experienced each year. Accordingly, the distribution and connectivity of pre-existing permeable planes of weakness play a central role. These structures are often related to the rock mass's tectonic history or initiate (and dilate) in response to stress changes that disturb the entire slope, such as glacial unloading or seismic loading via large earthquakes. The latter is discussed in detail in a companion paper to this (Gischig et al., Rock Mech Rock Eng, 2015). The results and framework presented further demonstrate that episodic movement and progressive failure of deep

  4. Experimental Studies of Dynamic Fault Weakening Due to Thermal Pressurization of Pore Fluids

    NASA Astrophysics Data System (ADS)

    Goldsby, David; Tullis, Terry; Platt, John; Okazaki, Keishi

    2016-04-01

    High-velocity friction experiments and geophysical observations suggest that mature faults weaken dramatically during seismic slip. However, while many coseismic weakening mechanisms have been proposed, it is still unclear which mechanisms are most important or how the efficiency of weakening varies within the seismogenic zone. Thermal pressurization is one possible coseismic weakening mechanism driven by the thermal expansion of native pore fluids, which leads to elevated pore pressures and significant coseismic weakening. While thermal pressurization has been studied theoretically for many decades, and invoked in recent earthquake simulations, its activation in laboratory experiments has remained elusive. Several high-speed friction studies have yielded indirect evidence for thermal pressurization, yet none has directly linked with existing theoretical models or the relevant physical parameters, such as permeability, slip, and slip rate, that control the weakening rate. To fill this gap, we are conducting thermal pressurization experiments on fluid-saturated, low-permeability rocks (Frederick diabase) at slip rates up to ~5 mm/s, at constant confining pressures in the range 21-149 MPa and initial imposed pore pressures in the range 10-25 MPa. The impractically low permeability of the as-is diabase, ~10-23 m2, is increased prior to the test by thermal cracking, yielding measured permeabilities in the range 1.3*10-18 to 6.1*10-19 m2. These values of permeability are high enough to allow sample saturation over one to several days, but low enough to confine the elevated pore pressures generated by frictional heating during rapid sliding. Our experiments reveal a rapid decay of shear stress following a step-change in velocity from 10 μm/s to 4.8 mm/s. In one test, the decrease in shear stress of ~25% over the first 28 mm of slip at 4.8 mm/s agrees closely with the theoretical solution for slip on a plane (Rice [2006]), with an inferred slip-weakening distance of ~500

  5. Coupling of Pore Pressure and Ground Motion: Further Studies using Data Recorded at the NEES@UCSB Wildlife Station

    NASA Astrophysics Data System (ADS)

    Seale, S. H.; Lavallee, D.; Archuleta, R. J.; Steidl, J. H.

    2012-12-01

    Pore pressure built up during an earthquake and the hazard associated with soil liquefaction present a major challenge for our society, as has been dramatically illustrated by recent large events (e.g. the 2011 Tohoku-oki, Japan, earthquake). There is consensus among scientists that a better assessment of the liquefaction risk requires a better understanding of the coupling between pore pressure and ground motion time histories. There is a basic need to investigate coupling as a function of the frequency content of the ground motion. The 2010 M7.2 El Mayor-Cucapah event has provided a remarkable opportunity to investigate and model the coupling. The event was well recorded at the NEES@UCSB Wildlife station located 110 km from the hypocenter. The station is equipped with three-component strong-motion accelerometers at the surface and in boreholes at various depths and with pore pressure transducers located in a saturated, liquefiable layer. The recorded pore pressure and ground motion time histories both have frequency content that is a function of time. We have applied a wavelet decomposition technique to the El Mayor ground motion and pore pressure data, looking for a linear relationship between the signals. The analysis shows that the early P-wave accelerations (vertical component) initiate pore pressure response. However, the pore pressure records contain a low-frequency component that dominates the signal with no corresponding low-frequency component in the ground motion signals recorded near-by. Although uncommon, a similar behavior has been also reported in the literature for pore pressure signals recoded during the 1980 Mammoth Lakes, California, earthquake. We have extended this work to the analysis of 4 other seismic events that have induced an increase in pore pressure at WLA. As the response of pore pressure is potentially a local phenomenon, we have restricted our analysis to recordings from the same site. These events include the M5.8 Ocotillo

  6. Influence of pressure, temperature, and pore fluid on the frequency-dependent attenuation of elastic waves in Berea sandstone

    NASA Astrophysics Data System (ADS)

    O'hara, Stephen G.

    1985-07-01

    The effects of pore fluid, effective stress, pore fluid pressure, and temperature on the frequency dependence of elastic wave attenuation in Berea sandstone are interrelated in a series of systematic experiments. The attenuation of both the extensional and torsional modes of cylindrical samples of the sandstone is measured on the frequency range 3-30 kHz. To simulate conditions within the earth, the sandstone is subjected to confining stress to 70.0 MPa and temperature from 24.0 °C to 120.0 °C. Confining pressure and pore fluid pressure are varied independently. Data for two different pore fluids, brine and n-heptane, suggest that a scaling law exists for the pressure and temperature dependence of the attenuation in terms of the pore fluid. The logarithmic decrement of the sandstone is almost frequency independent in a vacuum evacuated sample, but shows a linear frequency dependence, once the sample is saturated. Extrapolation of this linear trend to low frequencies suggests that the decrement in fluid-filled sandstone is effectively frequency independent at seismic frequencies (<100 Hz). The frequency dependence becomes more pronounced as either the effective stress or the temperature is decreased. When the difference between the external stress on the sandstone and the pore fluid pressure is large, the attenuation depends only on the effective stress and is relatively temperature independent. But at low effective stress, the attenuation increases linearly with increasing pore fluid pressure and decreases linearly with increasing temperature. While a specific model is lacking, the attenuation process is apparently influenced most strongly by chemical processes at the pore fluid-matrix interface accompanied by subtle changes in the sandstone matrix dimensions.

  7. Modeling wave-induced pore pressure and effective stress in a granular seabed

    NASA Astrophysics Data System (ADS)

    Scholtès, Luc; Chareyre, Bruno; Michallet, Hervé; Catalano, Emanuele; Marzougui, Donia

    2014-08-01

    The response of a sandy seabed under wave loading is investigated on the basis of numerical modeling using a multi-scale approach. To that aim, the discrete element method is coupled to a finite volume method specially enhanced to describe compressible fluid flow. Both solid and fluid phase mechanics are upscaled from considerations established at the pore level. Model's predictions are validated against poroelasticity theory and discussed in comparison with experiments where a sediment analog is subjected to wave action in a flume. Special emphasis is put on the mechanisms leading the seabed to liquefy under wave-induced pressure variation on its surface. Liquefaction is observed in both dilative and compactive regimes. It is shown that the instability can be triggered for a well-identified range of hydraulic conditions. Particularly, the results confirm that the gas content, together with the permeability of the medium are key parameters affecting the transmission of pressure inside the soil.

  8. Modeling wave-induced pore pressure and effective stress in a granular seabed

    NASA Astrophysics Data System (ADS)

    Scholtès, Luc; Chareyre, Bruno; Michallet, Hervé; Catalano, Emanuele; Marzougui, Donia

    2015-01-01

    The response of a sandy seabed under wave loading is investigated on the basis of numerical modeling using a multi-scale approach. To that aim, the discrete element method is coupled to a finite volume method specially enhanced to describe compressible fluid flow. Both solid and fluid phase mechanics are upscaled from considerations established at the pore level. Model's predictions are validated against poroelasticity theory and discussed in comparison with experiments where a sediment analog is subjected to wave action in a flume. Special emphasis is put on the mechanisms leading the seabed to liquefy under wave-induced pressure variation on its surface. Liquefaction is observed in both dilative and compactive regimes. It is shown that the instability can be triggered for a well-identified range of hydraulic conditions. Particularly, the results confirm that the gas content, together with the permeability of the medium are key parameters affecting the transmission of pressure inside the soil.

  9. Tremor-tide correlations and near-lithostatic pore pressure on the deep San Andreas fault.

    PubMed

    Thomas, Amanda M; Nadeau, Robert M; Bürgmann, Roland

    2009-12-24

    Since its initial discovery nearly a decade ago, non-volcanic tremor has provided information about a region of the Earth that was previously thought incapable of generating seismic radiation. A thorough explanation of the geologic process responsible for tremor generation has, however, yet to be determined. Owing to their location at the plate interface, temporal correlation with geodetically measured slow-slip events and dominant shear wave energy, tremor observations in southwest Japan have been interpreted as a superposition of many low-frequency earthquakes that represent slip on a fault surface. Fluids may also be fundamental to the failure process in subduction zone environments, as teleseismic and tidal modulation of tremor in Cascadia and Japan and high Poisson ratios in both source regions are indicative of pressurized pore fluids. Here we identify a robust correlation between extremely small, tidally induced shear stress parallel to the San Andreas fault and non-volcanic tremor activity near Parkfield, California. We suggest that this tremor represents shear failure on a critically stressed fault in the presence of near-lithostatic pore pressure. There are a number of similarities between tremor in subduction zone environments, such as Cascadia and Japan, and tremor on the deep San Andreas transform, suggesting that the results presented here may also be applicable in other tectonic settings. PMID:20033046

  10. Along-fault pore-pressure evolution during a slow-slip event in Guerrero, Mexico

    NASA Astrophysics Data System (ADS)

    Frank, W. B.; Shapiro, N. M.; Husker, A. L.; Kostoglodov, V.; Bhat, H. S.; Campillo, M.

    2015-03-01

    Slow earthquakes are important constituents of the seismic cycle and are involved in the stress transfer between the viscously slipping portion of the plate interface and the seismogenic zone. Their occurrence is likely associated with the near-lithostatic pore pressure in the slow earthquake source region, where fluids might modify fault friction and whose presence is indicated by high ratios of compressional (P)-wave velocity to shear (S)-wave velocity observed at the interface between the subducting plate and the overlying crust. Here we compare two slow earthquake phenomena observed in the Guerrero region of the Mexican subduction zone: low-frequency earthquakes (LFEs) and a slow-slip event (SSE) recorded by GPS. We observe variations of the LFE occurrence rates over month-long time scales during a large SSE that we interpret as a manifestation of transient changes in the fault shear strength. We argue that these transient changes are caused by a pore pressure fluctuation that migrates updip along the subduction interface. This mechanism suggests that fluids do not only passively weaken the plate interface but also play an active role in slow earthquake source regions.

  11. Pore Structure and Limit Pressure of Gas Slippage Effect in Tight Sandstone

    PubMed Central

    You, Lijun; Xue, Kunlin; Kang, Yili; Liao, Yi

    2013-01-01

    Gas slip effect is an important mechanism that the gas flow is different from liquid flow in porous media. It is generally considered that the lower the permeability in porous media is, the more severe slip effect of gas flow will be. We design and then carry out experiments with the increase of backpressure at the outlet of the core samples based on the definition of gas slip effect and in view of different levels of permeability of tight sandstone reservoir. This study inspects a limit pressure of the gas slip effect in tight sandstones and analyzes the characteristic parameter of capillary pressure curves. The experimental results indicate that gas slip effect can be eliminated when the backpressure reaches a limit pressure. When the backpressure exceeds the limit pressure, the measured gas permeability is a relatively stable value whose range is less than 3% for a given core sample. It is also found that the limit pressure increases with the decreasing in permeability and has close relation with pore structure of the core samples. The results have an important influence on correlation study on gas flow in porous medium, and are beneficial to reduce the workload of laboratory experiment. PMID:24379747

  12. Pore structure and limit pressure of gas slippage effect in tight sandstone.

    PubMed

    You, Lijun; Xue, Kunlin; Kang, Yili; Liao, Yi; Kong, Lie

    2013-01-01

    Gas slip effect is an important mechanism that the gas flow is different from liquid flow in porous media. It is generally considered that the lower the permeability in porous media is, the more severe slip effect of gas flow will be. We design and then carry out experiments with the increase of backpressure at the outlet of the core samples based on the definition of gas slip effect and in view of different levels of permeability of tight sandstone reservoir. This study inspects a limit pressure of the gas slip effect in tight sandstones and analyzes the characteristic parameter of capillary pressure curves. The experimental results indicate that gas slip effect can be eliminated when the backpressure reaches a limit pressure. When the backpressure exceeds the limit pressure, the measured gas permeability is a relatively stable value whose range is less than 3% for a given core sample. It is also found that the limit pressure increases with the decreasing in permeability and has close relation with pore structure of the core samples. The results have an important influence on correlation study on gas flow in porous medium, and are beneficial to reduce the workload of laboratory experiment. PMID:24379747

  13. Effect of Pore Pressure on Slip Failure of an Impermeable Fault: A Coupled Micro Hydro-Geomechanical Model

    NASA Astrophysics Data System (ADS)

    Yang, Z.; Juanes, R.

    2015-12-01

    The geomechanical processes associated with subsurface fluid injection/extraction is of central importance for many industrial operations related to energy and water resources. However, the mechanisms controlling the stability and slip motion of a preexisting geologic fault remain poorly understood and are critical for the assessment of seismic risk. In this work, we develop a coupled hydro-geomechanical model to investigate the effect of fluid injection induced pressure perturbation on the slip behavior of a sealing fault. The model couples single-phase flow in the pores and mechanics of the solid phase. Granular packs (see example in Fig. 1a) are numerically generated where the grains can be either bonded or not, depending on the degree of cementation. A pore network is extracted for each granular pack with pore body volumes and pore throat conductivities calculated rigorously based on geometry of the local pore space. The pore fluid pressure is solved via an explicit scheme, taking into account the effect of deformation of the solid matrix. The mechanics part of the model is solved using the discrete element method (DEM). We first test the validity of the model with regard to the classical one-dimensional consolidation problem where an analytical solution exists. We then demonstrate the ability of the coupled model to reproduce rock deformation behavior measured in triaxial laboratory tests under the influence of pore pressure. We proceed to study the fault stability in presence of a pressure discontinuity across the impermeable fault which is implemented as a plane with its intersected pore throats being deactivated and thus obstructing fluid flow (Fig. 1b, c). We focus on the onset of shear failure along preexisting faults. We discuss the fault stability criterion in light of the numerical results obtained from the DEM simulations coupled with pore fluid flow. The implication on how should faults be treated in a large-scale continuum model is also presented.

  14. Ontogenesis Of Hydrofracturing: Pore Pressure Diffusion And Its Implications For Stress Dependant Matrix Permeability Stimulation

    NASA Astrophysics Data System (ADS)

    Ghani, I.; koehn, D.; Toussaint, R.

    2012-04-01

    Hydrofracturing is a common and important geological process that engineers different structures of varying scales in a variety of geological settings in the upper Crust. Many natural examples of joint and vein networks in layered rocks manifest porosity-effective stress relationships during deformation processes that are principally led by transient pore fluid overpressure. Local stimulation of extreme pore pressure by certain fluid expansion mechanisms in reservoirs tenders the evolution of effective stress, which has been postulated to be highly sensitive to the reservoir's permeability. Changes in effective stress introduce appreciable poro-elastic response of the matrix inducing new fractures or opening/closing existing faults and fractures. In this contribution, we investigate three aspects of time dependant dynamic mechanisms of hydro-fracturing at micro scale: (1) evolution of local effective stress by pore pressure, (2) permeability enhancement with respect to elastic deformation of host rock and (3) fracture propagation as long as fluid pressure heads the tensile strength of the rock. The numerical scheme is a 2d coupled hydro-mechanical model, which integrates DEM and a supplementary continuum description. It resides two overlapping areas in physical space, where one represents the solid media, which constitutes a small-scale triangular discrete spring network of the software 'Latte' (Elle) and is hybridized with the other large-scale (fixed) square lattice of continuum description. A general form of the macroscopic diffusion equation of pressure is given by the compressible Navier-Stokes equation that is derived by ensuring conservation of mass of the fluid and solid media along with local Darcy's Law. Finite difference ADI method is implemented on the square lattice for the pressure discretization (hydrodynamic) in order to acquire pressure diffusion. The hydraulic head then contributes to the net force on each particle in the elastic lattice through a

  15. Pore Pressure prediction in shale gas reservoirs using neural network and fuzzy logic with an application to Barnett Shale.

    NASA Astrophysics Data System (ADS)

    Aliouane, Leila; Ouadfeul, Sid-Ali; Boudella, Amar

    2015-04-01

    The main goal of the proposed idea is to use the artificial intelligence such as the neural network and fuzzy logic to predict the pore pressure in shale gas reservoirs. Pore pressure is a very important parameter that will be used or estimation of effective stress. This last is used to resolve well-bore stability problems, failure plan identification from Mohr-Coulomb circle and sweet spots identification. Many models have been proposed to estimate the pore pressure from well-logs data; we can cite for example the equivalent depth model, the horizontal model for undercompaction called the Eaton's model…etc. All these models require a continuous measurement of the slowness of the primary wave, some thing that is not easy during well-logs data acquisition in shale gas formtions. Here, we suggest the use the fuzzy logic and the multilayer perceptron neural network to predict the pore pressure in two horizontal wells drilled in the lower Barnett shale formation. The first horizontal well is used for the training of the fuzzy set and the multilayer perecptron, the input is the natural gamma ray, the neutron porosity, the slowness of the compression and shear wave, however the desired output is the estimated pore pressure using Eaton's model. Data of another horizontal well are used for generalization. Obtained results clearly show the power of the fuzzy logic system than the multilayer perceptron neural network machine to predict the pore pressure in shale gas reservoirs. Keywords: artificial intelligence, fuzzy logic, pore pressure, multilayer perecptron, Barnett shale.

  16. Pore water pressure variations in Subpermafrost groundwater : Numerical modeling compared with experimental modeling

    NASA Astrophysics Data System (ADS)

    Rivière, Agnès.; Goncalves, Julio; Jost, Anne; Font, Marianne

    2010-05-01

    Development and degradation of permafrost directly affect numerous hydrogeological processes such as thermal regime, exchange between river and groundwater, groundwater flows patterns and groundwater recharge (Michel, 1994). Groundwater in permafrost area is subdivided into two zones: suprapermafrost and subpermafrost which are separated by permafrost. As a result of the volumetric expansion of water upon freezing and assuming ice lenses and frost heave do not form freezing in a saturated aquifer, the progressive formation of permafrost leads to the pressurization of the subpermafrost groundwater (Wang, 2006). Therefore disappearance or aggradation of permafrost modifies the confined or unconfined state of subpermafrost groundwater. Our study focuses on modifications of pore water pressure of subpermafrost groundwater which could appear during thawing and freezing of soil. Numerical simulation allows elucidation of some of these processes. Our numerical model accounts for phase changes for coupled heat transport and variably saturated flow involving cycles of freezing and thawing. The flow model is a combination of a one-dimensional channel flow model which uses Manning-Strickler equation and a two-dimensional vertically groundwater flow model using Richards equation. Numerical simulation of heat transport consisted in a two dimensional model accounting for the effects of latent heat of phase change of water associated with melting/freezing cycles which incorporated the advection-diffusion equation describing heat-transfer in porous media. The change of hydraulic conductivity and thermal conductivity are considered by our numerical model. The model was evaluated by comparing predictions with data from laboratory freezing experiments. Experimental design was undertaken at the Laboratory M2C (Univesité de Caen-Basse Normandie, CNRS, France). The device consisted of a Plexiglas box insulated on all sides except on the top. Precipitation and ambient temperature are

  17. In-situ stress, pore pressure, and hydrocarbon migration and accumulation in sedimentary basins

    NASA Astrophysics Data System (ADS)

    Finkbeiner, Thomas

    1999-11-01

    An important concept for understanding fluid flow in hydrocarbon fields is that dynamic mechanisms governed by the stress state present drive oil and gas migration and accumulation. The principal goals in this dissertation are to constrain the full in-situ stress tensor and reservoir pore pressure conditions, identify hydrocarbon migration pathways, and test dynamic processes controlling fluid flow and rock deformation. For this purpose I analyze various types of downhole measurements from two hydrocarbon producing sedimentary basins. In the Santa Maria Basin, on- and offshore California, stress orientations derived from borehole breakouts and inversion of earthquake focal plane mechanisms indicate a rather uniform stress field consistent with the regional trend. Analysis of borehole wall images reveal ubiquitous fractures and faults that exhibit great variations in orientation and occurrence. These variations can be correlated with changes of lithology and physical properties. Permeability appears to be enhanced in the vicinity of fractures and faults that are active and optimally oriented for failure in the current stress field. In the South Eugene Island 330 field, Gulf of Mexico, drilling induced borehole breakouts, reveal least principal horizontal stress orientations, that are predominantly perpendicular to active normal faults. Minimum principal stress magnitudes show significant scatter revealing fracture gradients that cannot be correlated with previously published models from this area. Reservoir pore pressures are highly variable and range from hydrostatic to severely overpressured indicating compartmentalization and production induced depletion. Reservoir depletion, pore pressures, and hydrocarbon column heights in individual reservoirs appear to be a function of stratigraphy. Shallow sands are hydrostatically pressured, well drained, and normally compacted. Oil and gas columns are long and controlled by a spill point. At intermediate stratigraphic

  18. Understanding North Texas Seismicity: A Joint Analysis of Seismic Data and 3D Pore Pressure Modeling

    NASA Astrophysics Data System (ADS)

    DeShon, H. R.; Hornbach, M. J.; Ellsworth, W. L.; Oldham, H. R.; Hayward, C.; Stump, B. W.; Frohlich, C.; Olson, J. E.; Luetgert, J. H.

    2014-12-01

    In November 2013, a series of earthquakes began along a mapped ancient fault system near Azle, Texas. The Azle events are the third felt earthquake sequence in the Fort Worth (Barnett Shale) Basin since 2008, and several production and injection wells in the area are drilled to depths near the recent seismic activity. Understanding if and/or how injection and removal of fluids in the crystalline crust reactivates faults have important implications for seismology, the energy industry, and society. We assessed whether the Azle earthquakes were induced using a joint analysis of the earthquake data, subsurface geology and fault structure, and 3D pore pressure modeling. Using a 12-station temporary seismic deployment, we have recorded and located >300 events large enough to be recorded on multiple stations and 1000s of events during periods of swarm activity. High-resolution locations and focal mechanisms indicate that events occurred on NE-SW trending, steeply dipping normal faults associated with the southern end of the Newark East Fault Zone with hypocenters between 2-8 km depth. We considered multiple causes that might have changed stress along this system. Earthquakes resulting from natural processes, though perhaps unlikely in this historically inactive region, can be neither ruled out nor confirmed due to lack of information on the natural stress state of these faults. Analysis of lake and groundwater variations near Azle showed that no significant stress changes occurred prior to or during the earthquake sequence. In contrast, analysis of pore-pressure models shows that the combination of formation water production and wastewater injection near the fault could have caused pressure increases that induced earthquakes on near-critically stressed faults.

  19. Irreversible xenon insertion into a small-pore zeolite at moderate pressures and temperatures.

    PubMed

    Seoung, Donghoon; Lee, Yongmoon; Cynn, Hyunchae; Park, Changyong; Choi, Kwang-Yong; Blom, Douglas A; Evans, William J; Kao, Chi-Chang; Vogt, Thomas; Lee, Yongjae

    2014-09-01

    Pressure drastically alters the chemical and physical properties of materials and allows structural phase transitions and chemical reactions to occur that defy much of our understanding gained under ambient conditions. Particularly exciting is the high-pressure chemistry of xenon, which is known to react with hydrogen and ice at high pressures and form stable compounds. Here, we show that Ag16Al16Si24O8·16H2O (Ag-natrolite) irreversibly inserts xenon into its micropores at 1.7 GPa and 250 °C, while Ag(+) is reduced to metallic Ag and possibly oxidized to Ag(2+). In contrast to krypton, xenon is retained within the pores of this zeolite after pressure release and requires heat to desorb. This irreversible insertion and trapping of xenon in Ag-natrolite under moderate conditions sheds new light on chemical reactions that could account for the xenon deficiency relative to argon observed in terrestrial and Martian atmospheres. PMID:25143221

  20. Irreversible xenon insertion into a small-pore zeolite at moderate pressures and temperatures

    DOE PAGESBeta

    Seoung, Donghoon; Cynn, Hyunchae; Park, Changyong; Choi, Kwang -Yong; Blom, Douglas A.; Evans, William J.; Kao, Chi -Chang; Vogt, Thomas; Lee, Yongjae

    2014-09-01

    Pressure drastically alters the chemical and physical properties of materials and allows structural phase transitions and chemical reactions to occur that defy much of our understanding gained under ambient conditions. Particularly exciting is the high-pressure chemistry of xenon, which is known to react with hydrogen and ice at high pressures and form stable compounds. Here, we show that Ag16Al16Si24O8·16H2O (Ag-natrolite) irreversibly inserts xenon into its micropores at 1.7 GPa and 250 °C, while Ag+ is reduced to metallic Ag and possibly oxidized to Ag2+. In contrast to krypton, xenon is retained within the pores of this zeolite after pressure releasemore » and requires heat to desorb. This irreversible insertion and trapping of xenon in Ag-natrolite under moderate conditions sheds new light on chemical reactions that could account for the xenon deficiency relative to argon observed in terrestrial and Martian atmospheres.« less

  1. Irreversible xenon insertion into a small-pore zeolite at moderate pressures and temperatures

    SciTech Connect

    Seoung, Donghoon; Cynn, Hyunchae; Park, Changyong; Choi, Kwang -Yong; Blom, Douglas A.; Evans, William J.; Kao, Chi -Chang; Vogt, Thomas; Lee, Yongjae

    2014-09-01

    Pressure drastically alters the chemical and physical properties of materials and allows structural phase transitions and chemical reactions to occur that defy much of our understanding gained under ambient conditions. Particularly exciting is the high-pressure chemistry of xenon, which is known to react with hydrogen and ice at high pressures and form stable compounds. Here, we show that Ag16Al16Si24O8·16H2O (Ag-natrolite) irreversibly inserts xenon into its micropores at 1.7 GPa and 250 °C, while Ag+ is reduced to metallic Ag and possibly oxidized to Ag2+. In contrast to krypton, xenon is retained within the pores of this zeolite after pressure release and requires heat to desorb. This irreversible insertion and trapping of xenon in Ag-natrolite under moderate conditions sheds new light on chemical reactions that could account for the xenon deficiency relative to argon observed in terrestrial and Martian atmospheres.

  2. Monitoring and Analysis of Transient Pore Water Pressures in Large Suspended Rock Slides near Poschiavo, CH

    NASA Astrophysics Data System (ADS)

    de Palézieux, Larissa; Loew, Simon; Zwahlen, Peter

    2016-04-01

    Many mountain slopes in the Alps exhibit large compound rock slides or Deep Seated Gravitational Slope Deformations. Due to the basal rupture plane geometry and the cumulative displacement magnitude such landslide bodies are often strongly deformed, highly fractured and - at least locally - very permeable. This can lead to high infiltration rates and low phreatic groundwater tables. This is also the situation in the studied mountain slopes southwest of Poschiavo, where large suspended rockslides occur, with very little surface runoff at high elevations, and torrents developing only at the elevation of the basal rupture planes. Below the landslide toes, at altitudes below ca. 1700 m a.s.l., groundwater appears forming spring lines or distributed spring clusters. Within the scope of the design of a hydropower pump storage plant in the Poschiavo valley by Lagobianco SA (Repower AG), numerous cored and deep boreholes (of 50 to 300 m depth) have been drilled along the planned pressure tunnel alignement at elevations ranging from 963 to 2538 m a.s.l. in the years 2010 and 2012. In several boreholes Lugeon and transient pressure tests were executed and pore water pressure sensors installed in short monitoring sections at various depths. Most of these boreholes intersect deep rockslides in crystalline rocks and limestones, showing highly fragmented rock masses and cohesionless cataclastic shear zones of several tens of meters thickness. This study explores these borehole observations in landslides and adjacent stable slopes and links them to the general hydrologic and hydrogeologic framework. The analysis of the pore water pressure data shows significant variability in seasonal trends and short-term events (from snow melt and summer rain storms) and remarkable pressure differences over short horizontal and vertical distances. This reflects rock mass damage within landslide bodies and important sealing horizons at their base. Based on water balances, the estimated effective

  3. Exercise excess pressure and exercise-induced albuminuria in patients with type 2 diabetes mellitus.

    PubMed

    Climie, Rachel E D; Srikanth, Velandai; Keith, Laura J; Davies, Justin E; Sharman, James E

    2015-05-01

    Exercise-induced albuminuria is common in patients with type 2 diabetes mellitus (T2DM) in response to maximal exercise, but the response to light-moderate exercise is unclear. Patients with T2DM have abnormal central hemodynamics and greater propensity for exercise hypertension. This study sought to determine the relationship between light-moderate exercise central hemodynamics (including aortic reservoir and excess pressure) and exercise-induced albuminuria. Thirty-nine T2DM (62 ± 9 yr; 49% male) and 39 nondiabetic controls (53 ± 9 yr; 51% male) were examined at rest and during 20 min of light-moderate cycle exercise (30 W; 50 revolutions/min). Albuminuria was assessed by the albumin-creatinine ratio (ACR) at rest and 30 min postexercise. Hemodynamics recorded included brachial and central blood pressure (BP), aortic stiffness, augmented pressure (AP), aortic reservoir pressure, and excess pressure integral (Pexcess). There was no difference in ACR between groups before exercise (P > 0.05). Exercise induced a significant rise in ACR in T2DM but not controls (1.73 ± 1.43 vs. 0.53 ± 1.0 mg/mol, P = 0.002). All central hemodynamic variables were significantly higher during exercise in T2DM (i.e., Pexcess, systolic BP and AP; P < 0.01 all). In T2DM (but not controls), exercise Pexcess was associated with postexercise ACR (r = 0.51, P = 0.002), and this relationship was independent of age, sex, body mass index, heart rate, aortic stiffness, antihypertensive medication, and ambulatory daytime systolic BP (β = 0.003, P = 0.003). Light-moderate exercise induced a significant rise in ACR in T2DM, and this was independently associated with Pexcess, a potential marker of vascular dysfunction. These novel findings suggest that Pexcess could be important for appropriate renal function in T2DM. PMID:25724495

  4. 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.

  5. Dual simulations of fluid flow and seismic wave propagation in a fractured network: effects of pore pressure on seismic signature

    NASA Astrophysics Data System (ADS)

    Vlastos, S.; Liu, E.; Main, I. G.; Schoenberg, M.; Narteau, C.; Li, X. Y.; Maillot, B.

    2006-08-01

    Fluid flow in the Earth's crust plays an important role in a number of geological processes. In relatively tight rock formations such flow is usually controlled by open macrofractures, with significant implications for ground water flow and hydrocarbon reservoir management. The movement of fluids in the fractured media will result in changes in the pore pressure and consequently will cause changes to the effective stress, traction and elastic properties. The main purpose of this study is to numerically examine the effect of pore pressure changes on seismic wave propagation (i.e. the effects of pore pressures on amplitude, arrival time, frequency content). This is achieved by using dual simulations of fluid flow and seismic propagation in a common 2-D fracture network. Note that the dual simulations are performed separately as the coupled simulations of fluid flow and seismic wave propagations in such fracture network is not possible because the timescales of fluid flow and wave propagation are considerably different (typically, fluid flows in hours, whereas wave propagation in seconds). The flow simulation updates the pore pressure at consecutive time steps, and thus the elastic properties of the rock, for the seismic modelling. In other words, during each time step of the flow simulations, we compute the elastic response corresponding to the pore pressure distribution. The relationship between pore pressure and fractures is linked via an empirical relationship given by Schoenberg and the elastic response of fractures is computed using the equivalent medium theory described by Hudson and Liu. Therefore, we can evaluate the possibility of inferring the changes of fluid properties directly from seismic data. Our results indicate that P waves are not as sensitive to pore pressure changes as S and coda (or scattered) waves. The increase in pore pressure causes a shift of the energy towards lower frequencies, as shown from the spectrum (as a result of scattering

  6. Excess Weight, Anthropometric Variables and Blood Pressure in Schoolchildren aged 10 to 18 years

    PubMed Central

    Schommer, Vânia Ames; Barbiero, Sandra Mari; Cesa, Cláudia Ciceri; Oliveira, Rosemary; Silva, Anelise Damiani; Pellanda, Lucia Campos

    2014-01-01

    Background The prevalence of hypertension among children and adolescents is estimated to range between 1% and 13%. Excess weight and central obesity are related to blood pressure levels in adults, and may be important in the early pathogenesis of SH when present in childhood. Objectives To study the association between anthropometric variables and blood pressure levels in schoolchildren from the 5th and 8th grades, and to identify which parameter was more strongly correlated with blood pressure levels. Methods Contemporary cross-sectional study with probabilistic population-based cluster sampling of schoolchildren enrolled from the 5th to the 8th grades in public elementary schools of Porto Alegre. Data on familial risk factors and anthropometry were collected. Statistical analysis included correlations and cluster-adjusted confidence intervals. Results The mean age of participants was 12.57 (± 1.64) years, and 55.2% of them were females. Abnormal blood pressure levels were found in 11.3% of the sample and borderline values, in 16.2%. Among the anthropometric variables analyzed, hip circumference was the one with the strongest correlation with increased blood pressure (r = 0.462, p < 0.001), followed by waist circumference (r = 0.404, p < 0.001) and abdominal skinfold (r = 0.291, p < 0.001). Conclusion We observed an association of waist circumference and skinfolds with increased blood pressure levels in the schoolchildren of the sample. Therefore, it is of the utmost importance that early measurements of blood pressure, and waist and hip circumferences become a routine in health services in order to prevent this condition. PMID:24676224

  7. The signature of devolatisation: excess 40Ar in high pressure rocks

    NASA Astrophysics Data System (ADS)

    Smye, A.; Warren, C. J.; Bickle, M. J.; Holland, T.

    2012-12-01

    The presence of excess 40Ar in (ultra-)high pressure ((U)HP) metamorphic rocks shows that the assumption of open system argon exchange between the source mineral and the grain boundary is not valid. Typically, phengites from (U)HP metasediments have apparent 40Ar/39Ar ages <50% in excess of the age of peak (U)HP conditions, whereas cogenetic mafic eclogites yield ages up to 700% older, despite lower bulk-rock K2O concentrations. Given the highly incompatible behaviour of argon, the fraction of protolith-derived 40Ar that is retained by mica on equilibration under (U)HP conditions reflects the extent to which the rock has behaved as an open or closed system to volatile-loss during subduction. This has not previously been quantified for (U)HP rocks. A model is developed that calculates excess argon age fractions as a function of variable mica—fluid KD, bulk K2O and porosity under closed system conditions. Using two recently-published single-grain 40Ar/39Ar datasets from the Tauern Window [1] and Omani [2] HP terranes, measured excess argon concentrations in mafic eclogites are reproduced only when porosities are <10-4 volume fraction, showing that mafic protoliths operate as closed systems to advective solute transport during subduction. Porosities in eclogite-facies metapelites are >10-3, reflecting loss of significant volumes of lattice-bound H2O relative to mafic rocks during subduction. These results are supported by phase equilibria calculations of H2O loss during progade metamorphism of a MORB and pelitic rock composition: pelites lose H2O continuously along subduction geotherms, whereas MORB compositions require hydration, or, liberate small quantities of structurally bound H2O. Violation of the model assumptions by loss of argon, or transiently higher porosities will lower the excess argon age. Accordingly, the porosity estimates provide a limiting case to examine the effects of fluid availability, permeability and argon diffusivity on the accumulation of

  8. Pore pressure evolution and induced seismicity within the Permian Basin, Southeast New Mexico USA

    NASA Astrophysics Data System (ADS)

    Person, M. A.; Zhang, Y.; Mozley, P.; Broadhead, R.; Bilek, S.; Edel, S.

    2015-12-01

    We used three-dimensional hydrologic modeling to assess the potential linkages between crystalline basement seismicity (up to M3.2) beneath the Dagger Draw oil field in response to saline water reinjection. Production began in 2004 and preceded an increase in seismicity by about 5 years. Reinjection of produced brines occurred within the basal Ellenberger Group carbonate reservoir (yellow square). Published core permeability measurements for the Ellenberger vary between about 10-15 to 10-12 m2. Evidence for seismicity being triggered by injection include observations that the largest injection rates (> 106 barrels/month) occurred within wells closest to the induced seismicity (red circle about 15 km to the west of the injection well in A-C). Arguing against triggered seismicity is the apparent lack of temporal correlation between peak injection and felt seismicity as well as the extreme depth of the earthquakes (about 10-12 km below land surface). We conducted a numerical sensitivity study in which we varied the permeability of the basal reservoir as well as the crystalline basement rocks over several orders of magnitude. Assuming a crystalline basement permeability of 10-16 m2 and a basal reservoir permeability of 10-13 m2 produced about 50 m of excess heads in the seismogenic crust about 1900 days (D) after injection started. Prior studies suggest that excess heads of only a few meters could induce failure along critically stressed faults. The lag between injection and seismicity can be explained by the time required for the pressure envelope to propagate laterally 15 km and downward into the crystalline basement 11 km. Peak injection occurred 1900 days before recent increases in seismicity were observed. Future work will include assessing the potential role of relatively permeable Proterozoic faults in transmitting high fluid pressures into the crystalline basement.

  9. Slow slip pulses driven by thermal pressurization of pore fluid: theory and observational constraints

    NASA Astrophysics Data System (ADS)

    Garagash, D.

    2012-12-01

    We discuss recently developed solutions for steadily propagating self-healing slip pulses driven by thermal pressurization (TP) of pore fluid [Garagash, 2012] on a fault with a constant sliding friction. These pulses are characterized by initial stage of undrained weakening of the fault (when fluid/heat can not yet escape the frictionally heated shear zone), which gives way to partial restrengthening due to increasing hydrothermal diffusion under conditions of diminished rate of heating, leading to eventual locking of the slip. The rupture speed of these pulses is decreasing function of the thickness (h) of the principal shear zone. We find that "thick" shear zones, h >> hdyna, where hdyna = (μ/τ0) (ρc/fΛ)(4α/cs), can support aseismic TP pulses propagating at a fraction hdyna/h of the shear wave speed cs, while "thin" shear zones, h˜hdyna or thinner, can only harbor seismic slip. (Here μ - shear modulus, τ0 - the nominal fault strength, f - sliding friction, ρc - the heat capacity of the fault gouge, Λ - the fluid thermal pressurization factor, α - hydrothermal diffusivity parameter of the gouge). For plausible range of fault parameters, hdyna is between 10s to 100s of micrometers, suggesting that slow slip transients propagating at 1 to 10 km/day may occur in the form of a TP slip pulse accommodated by a meter-thick shear zone. We verify that this is, indeed, a possibility by contrasting the predictions for aseismic, small-slip TP pulses operating at seismologically-constrained, near-lithostatic pore pressure (effective normal stress ≈ 3 to 10 MPa) with the observations (slip duration at a given fault location ≈ week, propagation speed ≈ 15 km/day, and the inferred total slip ≈ 2 to 3 cm) for along-strike propagation of the North Cascadia slow slip events of '98-99 [Dragert et al., 2001, 2004]. Furthermore, we show that the effect of thermal pressurization on the strength of the subduction interface is comparable to or exceeds that of the rate

  10. Laser-Doppler acoustic probing of granular media with in-depth property gradient and varying pore pressures

    SciTech Connect

    Bodet, L.; Dhemaied, A.; Mourgues, R.; Tournat, V.; Rejiba, F.

    2012-05-24

    Non-contacting ultrasonic techniques recently proved to be efficient in the physical modeling of seismic-wave propagation at various application scales, as for instance in the context of geological analogue and seismic modeling. An innovative experimental set-up is proposed here to perform laser-Doppler acoustic probing of unconsolidated granular media with varying pore pressures. The preliminary experiments presented here provide reproducible results and exploitable data, thus validating both the proposed medium preparation and pressure gradient generation procedure.

  11. Grain boundary excess volume and defect annealing of copper after high-pressure torsion

    PubMed Central

    Oberdorfer, Bernd; Setman, Daria; Steyskal, Eva-Maria; Hohenwarter, Anton; Sprengel, Wolfgang; Zehetbauer, Michael; Pippan, Reinhard; Würschum, Roland

    2014-01-01

    The release of excess volume upon recrystallization of ultrafine-grained Cu deformed by high-pressure torsion (HPT) was studied by means of the direct technique of high-precision difference dilatometry in combination with differential scanning calorimetry (DSC) and scanning electron microscopy. From the length change associated with the removal of grain boundaries in the wake of crystallite growth, a structural key quantity of grain boundaries, the grain boundary excess volume or expansion eGB=(0.46±0.11)×10-10 m was directly determined. The value is quite similar to that measured by dilatometry for grain boundaries in HPT-deformed Ni. Activation energies for crystallite growth of 0.99±0.11 and 0.96±0.06eV are derived by Kissinger analysis from dilatometry and DSC data, respectively. In contrast to Ni, substantial length change proceeds in Cu at elevated temperatures beyond the regime of dominant crystallite growth. In the light of recent findings from tracer diffusion and permeation experiments, this is associated with the shrinkage of nanovoids at high temperatures. PMID:24748848

  12. Analysis of Pore Pressure and Stress Distribution around a Wellbore Drilled in Chemically Active Elastoplastic Formations

    NASA Astrophysics Data System (ADS)

    Roshan, Hamid; Rahman, S. S.

    2011-09-01

    Drilling in low-permeable reactive shale formations with water-based drilling mud presents significant challenges, particularly in high-pressure and high-temperature environments. In previous studies, several models were proposed to describe the thermodynamic behaviour of shale. Most shale formations under high pressure are expected to undergo plastic deformation. An innovative algorithm including work hardening is proposed in the framework of thermo-chemo-poroelasticity to investigate the effect of plasticity on stresses around the wellbore. For this purpose a finite-element model of coupled thermo-chemo-poro-elastoplasticity is developed. The governing equations are based on the concept of thermodynamics of irreversible processes in discontinuous systems. In order to solve the plastic problem, a single-step backward Euler algorithm containing a yield surface-correction scheme is used to integrate the plastic stress-strain relation. An initial stress method is employed to solve the non-linearity of the plastic equation. In addition, super convergent patch recovery is used to accurately evaluate the time-dependent stress tensor from nodal displacement. The results of this study reveal that thermal and chemical osmosis can significantly affect the fluid flow in low-permeable shale formations. When the salinity of drilling mud is higher than that of pore fluid, fluid is pulled out of the formation by chemical osmotic back flow. Similar results are observed when the temperature of drilling mud is lower than that of the formation fluid. It is found that linear elastic approaches to wellbore stability analysis appear to overestimate the tangential stress around the wellbore and produce more conservative stresses compared to the results of field observation. Therefore, the drilling mud properties obtained from the elastoplastic wellbore stability in shales provide a safer mud weight window and reduce drilling cost.

  13. Spatial heterogeneities of deviatoric stress and pore-pressure in Kyushu, Japan, and their implication for seismic activity

    NASA Astrophysics Data System (ADS)

    Matsumoto, Satoshi; Chikura, Hiromi; Ohkura, Takahiro; Miyazaki, Masahiro; Shimizu, Hiroshi; Abe, Yuki; Inoue, Hiroyuki; Yoshikawa, Shin; Yamashita, Yusuke

    2013-04-01

    We investigated the spatial variation in stress fields and pore fluid pressures on Kyushu Island, southwestern Japan. High seismic activity is found not only along active faults in Kyushu Island (southwestern Japan) but also in the central area of the island where there are active volcanoes. We consider the focal mechanisms of the shallow earthquakes on Kyushu Island to determine the relative deviatoric stress field and pore fluid factor. Generally, the stress field corresponds to a strike slip regime in this area. A decline in the maximum principal compressional stress is found in the western part of the high seismicity area, in the middle of Kyushu Island; this may be caused by a thickening of the seismogenic zone, as estimated from D90 analysis. At thin seismogenic layer, strike slip faulting dominates and strain rate from GPS study is high. In the active fault zone, seismic activity along the fault is high, and the pore pressure within the zone is higher than the values observed elsewhere, suggesting a mechanism explained by the fault valve model of Sibson [1992]. The pore pressure in the high seismic area with scattered hypocenter distribution in the middle part is lower than that in the active fault zones.

  14. Influence of Pore-Fluid Pressure on Elastic Wave Velocity and Electrical Conductivity in Water-Saturated Rocks

    NASA Astrophysics Data System (ADS)

    Higuchi, A.; Watanabe, T.

    2013-12-01

    Pore-fluid pressure in seismogenic zones can play a key role in the occurrence of earthquakes (e.g., Sibson, 2009). Its evaluation via geophysical observations can lead to a good understanding of seismic activities. The evaluation requires a thorough understanding of the influence of the pore-fluid pressure on geophysical observables like seismic velocity and electrical conductivity. We have studied the influence of pore-fluid pressure on elastic wave velocity and electrical conductivity in water-saturated rocks. Fine grained (100-500μm) biotite granite (Aji, Kagawa pref., Japan) was used as rock samples. The density is 2.658-2.668 g/cm3, and the porosity 0.68-0.87%. The sample is composed of 52.8% plagioclase, 36.0% Quartz, 3.0% K-feldspar, 8.2% biotite. SEM images show that a lot of grain boundaries are open. Few intracrystalline cracks were observed. Following the method proposed by David and Zimmerman (2012), the distribution function of crack aspect ratio was evaluated from the pressure dependence of compressional and shear wave velocities in a dry sample. Cylindrical sample has dimensions of 25 mm in diameter and 30 mm in length, and saturated with 0.01 mol/l KCl aqueous solution. Compressional and shear wave velocities were measured with the pulse transmission technique (PZT transducers, f=2 MHz), and electrical conductivity the two-electrode method (Ag-AgCl electrodes, f=1 Hz-100 kHz). Simultaneous measurements of velocities and conductivity were made using a 200 MPa hydrostatic pressure vessel, in which confining and pore-fluid pressures can be separately controlled. The pore-fluid is electrically insulated from the metal work of the pressure vessel by using a newly designed plastic device (Watanabe and Higuchi, 2013). The confining pressure was progressively increased up to 25 MPa, while the pore-fluid pressure was kept at 0.1 MPa. It took five days or longer for the electrical conductivity to become stationary after increasing the confining pressure

  15. Modeling the space-time evolution of pore pressure in layered shallow covers

    NASA Astrophysics Data System (ADS)

    Salciarini, Diana; Cuomo, Sabatino; Castorino, Giuseppe; Fanelli, Giulia; Tamagnini, Claudio

    2015-04-01

    In most of the available models for the prediction of shallow landslide susceptibility, the potentially unstable soil cover is considered uniform and homogeneous, over an impervious underlying bedrock (see, e.g., Baum et al. 2008; Salciarini et al. 2006, 2012). However, in several case studies, this was proven to be unlikely, for example in the case of pyroclastic soil covers, where two clearly separated layers are detectable (Cascini et al., 2008, 2011). The possibility of taking into account the detailed configuration of the soil cover allows having a more accurate estimate of the potentially unstable volumes, which significantly modify the intensity of the considered phenomena. To take into account the possibility of having layers in the soil cover with different permeability, the existing routines of the TRIGRS code (Baum et al. 2008) devoted to the hydrologic process modeling have been modified. The closed-form solution by Srivastava & Yeh (1991) implemented into TRIGRS was substituted with the numerical solution of the mass balance equation governing the infiltration process. A parametric analysis was carried out by varying the permeability ratio between the two layers, with the aim of examining the influence of such parameter on the pore-pressure distribution along the vertical profile. As expected, as the permeability ratio increases, the underlying layer tends to behave as an impervious boundary. This increases the chance that only the most superficial soil layer fails. An analysis of the routine performance and efficiency was also done to investigate the response of the model with different tolerances and different time steps of the integration procedure, and different spatial discretizations along the vertical profile.

  16. [Investigation of high pore fluid pressure in the Uinta Basin, Utah]. Final report

    SciTech Connect

    1998-11-01

    High pore fluid pressures, approaching lithostatic, are observed in the deepest sections of the Uinta basin, Utah. The authors analyzed the cause of the anomalous overpressures with a 3-dimensional, numerical model of the evolution of the basin, including compaction disequilibrium and hydrocarbon generation as possible mechanisms. The numerical model builds the basin through time, coupling the structural, thermal and hydrodynamic evolution, and includes in situ hydrocarbon generation and migration. They used the evolution model to evaluate overpressure mechanisms and oil migration patterns for different possible conceptual models of the geologic history. Model results suggest that observed overpressures in the Uinta basin are probably caused by ongoing oil generation in strata with specific conditions of permeability, relative permeability, TOC content, and oil viscosity. They conducted a sensitivity analysis that suggests for oil generation to cause overpressures, the necessary conditions are: oil viscosity is {approximately}0.05 cP or higher, intrinsic permeability is {approximately}5 {times} 10{sup {minus}18} m{sup 2} or lower, and source rock TOC values are {approximately}0.5% or higher. The authors also analyzed hydrocarbon migration patterns in the basin and how they are affected by the basin`s structural history. Oil migration patterns produced by the model are consistent with published oil production maps: oil moves from the deep Altamont source rocks toward Redwash, the eastern Douglas Creek Arch area, and southward towards the Sunnyside tar-sands and Book Cliffs. Peak oil generation occurs from the time of maximum burial in the mid-Tertiary ({approximately}35 to {approximately}30 Ma). Most differential uplift of the basin`s flanks probably occurs well after this time, and most oil migration to the basin`s southern and eastern flanks occurs prior to uplift of these flanks. Model results show that if the basin`s flanks are uplifted too soon, reduced

  17. Kerogen to oil conversion in source rocks. Pore-pressure build-up and effects on seismic velocities

    NASA Astrophysics Data System (ADS)

    Pinna, Giorgia; Carcione, José M.; Poletto, Flavio

    2011-08-01

    The aim of this work is to obtain a model for source rocks relating to kerogen-oil conversion and pore pressure to seismic velocity and anisotropy. The source rock is described by a porous transversely isotropic medium composed of illite/smectite and organic matter. The rock has a very low permeability and pore-pressure build-up occurs. We consider a basin-evolution model with constant sedimentation rate and geothermal gradient. Kerogen-oil conversion starts at a given depth in a volume whose permeability is sufficiently low so that the increase in pressure due to oil generation greatly exceeds the dissipation of pressure by flow. Assuming a first-order kinetic reaction, with a reaction rate satisfying the Arrhenius equation, the kerogen-oil conversion fraction is calculated. Pore-pressure changes affect the dry-rock stiffnesses, which have an influence on seismic velocities. The properties of the kerogen-oil mixture are obtained with the Kuster and Toksöz model, assuming that oil is the inclusion in a kerogen matrix. We use Gassmann's equations generalized to the anisotropic case to obtain the seismic velocities of the source rock as a function of depth, pressure and oil saturation. The procedure is to obtain the dry-rock stiffnesses by assuming a Poisson medium for the mineral material constrained by the physical stability conditions at the calibration confining pressures. The example considers a sample of the North-Sea Kimmeridge shale. At a given depth, the conversion increases with increasing geothermal gradient and decreasing sedimentation rate, and the porosity increases with depth due to the conversion. As expected, the horizontal velocities are greater than the vertical velocities and the degree of anisotropy increases with depth. The analysis reveals that the vertical P-wave velocity is the main indicator of overpressure.

  18. An evaluation of pore pressure diffusion into a shale overburden and sideburden induced by production-related changes in reservoir fluid pressure

    NASA Astrophysics Data System (ADS)

    Ricard, Ludovic P.; MacBeth, Colin; HajNasser, Yesser; Schutjens, Peter

    2012-06-01

    It is commonplace in the simulation of reservoir fluid flow induced by hydrocarbon production to regard shales as barriers to flow. Whilst this appears correct for fluid exchange, this is not the case for the fluid pressure component of this process. Indeed, the authors observe that pore pressure reduction due to reservoir depletion can propagate significant distances into the shale overburden or sideburden over the production time scale. Shales may deplete their pore pressures by more than 10% of that experienced in the reservoir sand for distances of tens of metres to kilometres into the shale, depending on the production history, duration and the specific shale properties. An important factor controlling these results is heterogeneity of the shale sediments, and the pressure diffusion process can be considerably enhanced by the presence of silt laminations and streaks. These results suggest a possible risk to drillers when advancing towards the top of a depleting reservoir or when drilling a well alongside an already depleted reservoir. Our analyses conclude that pore pressure diffusion should be considered as a factor in geomechanical and fluid flow reservoir modelling, and in mud weight determination during infill drilling.

  19. In situ stress and pore pressure in the Kumano Forearc Basin, offshore SW Honshu from downhole measurements during riser drilling

    NASA Astrophysics Data System (ADS)

    Saffer, D. M.; Flemings, P. B.; Boutt, D.; Doan, M.-L.; Ito, T.; McNeill, L.; Byrne, T.; Conin, M.; Lin, W.; Kano, Y.; Araki, E.; Eguchi, N.; Toczko, S.

    2013-05-01

    situ stress and pore pressure are key parameters governing rock deformation, yet direct measurements of these quantities are rare. During Integrated Ocean Drilling Program (IODP) Expedition #319, we drilled through a forearc basin at the Nankai subduction zone and into the underlying accretionary prism. We used the Modular Formation Dynamics Tester tool (MDT) for the first time in IODP to measure in situ minimum stress, pore pressure, and permeability at 11 depths between 729.9 and 1533.9 mbsf. Leak-off testing at 708.6 mbsf conducted as part of drilling operations provided a second measurement of minimum stress. The MDT campaign included nine single-probe (SP) tests to measure permeability and in situ pore pressure and two dual-packer (DP) tests to measure minimum principal stress. Permeabilities defined from the SP tests range from 6.53 × 10-17 to 4.23 × 10-14 m2. Pore fluid pressures are near hydrostatic throughout the section despite rapid sedimentation. This is consistent with the measured hydraulic diffusivity of the sediments and suggests that the forearc basin should not trap overpressures within the upper plate of the subduction zone. Minimum principal stresses are consistently lower than the vertical stress. We estimate the maximum horizontal stress from wellbore failures at the leak-off test and shallow MDT DP test depths. The results indicate a normal or strike-slip stress regime, consistent with the observation of abundant active normal faults in the seaward-most part of the basin, and a general decrease in fault activity in the vicinity of Site C0009.

  20. Differential equations governing slip-induced pore-pressure fluctuations in a water-saturated granular medium

    USGS Publications Warehouse

    Iverson, R.M.

    1993-01-01

    Macroscopic frictional slip in water-saturated granular media occurs commonly during landsliding, surface faulting, and intense bedload transport. A mathematical model of dynamic pore-pressure fluctuations that accompany and influence such sliding is derived here by both inductive and deductive methods. The inductive derivation shows how the governing differential equations represent the physics of the steadily sliding array of cylindrical fiberglass rods investigated experimentally by Iverson and LaHusen (1989). The deductive derivation shows how the same equations result from a novel application of Biot's (1956) dynamic mixture theory to macroscopic deformation. The model consists of two linear differential equations and five initial and boundary conditions that govern solid displacements and pore-water pressures. Solid displacements and water pressures are strongly coupled, in part through a boundary condition that ensures mass conservation during irreversible pore deformation that occurs along the bumpy slip surface. Feedback between this deformation and the pore-pressure field may yield complex system responses. The dual derivations of the model help explicate key assumptions. For example, the model requires that the dimensionless parameter B, defined here through normalization of Biot's equations, is much larger than one. This indicates that solid-fluid coupling forces are dominated by viscous rather than inertial effects. A tabulation of physical and kinematic variables for the rod-array experiments of Iverson and LaHusen and for various geologic phenomena shows that the model assumptions commonly are satisfied. A subsequent paper will describe model tests against experimental data. ?? 1993 International Association for Mathematical Geology.

  1. Pressure and temperature dependence of excess enthalpies of methanol + tetraethylene glycol dimethyl ether and methanol + polyethylene glycol dimethyl ether 250

    SciTech Connect

    Lopez, E.R.; Coxam, J.Y.; Fernandez, J.; Grolier, J.P.E.

    1999-12-01

    The excess molar enthalpies at 323.15 K, 373.15 K, and 423.15 K, at 8 MPa, are reported for the binary mixtures methanol + tetraethylene glycol dimethyl ether (TEGDME) and methanol + poly(ethylene glycol) dimethyl ether 250 (PEGDME 250). Excess molar enthalpies were determined with a Setaram C-80 calorimeter equipped with a flow mixing cell. For both systems, the excess enthalpies are positive over the whole composition range, increasing with temperature. The H{sup E}(x) curves are slightly asymmetrical, and their maxima are skewed toward the methanol-rich region. The excess enthalpies slightly change with the pressure, the sign of this change being composition-dependent. In the case of mixtures with TEGDME, the experimental H{sup E} values have been compared with those predicted with the Gmehling et al. version of UNIFAC (Dortmund) and the Nitta-Chao and DISQUAC group contribution models.

  2. Evaluation of two-phase relative permeability and capillary pressure relations for unstable displacements in a pore network

    SciTech Connect

    Dehoff, Karl J.; Oostrom, Martinus; Zhang, Changyong; Grate, Jay W.

    2012-10-29

    A series of displacement experiments was conducted using five wetting-nonwetting immiscible fluid pairs in a homogenous and uniform pore network. The micromodel was initially saturated with either polyethylene glycol 200 (PEG) or water as a wetting fluid, which was subsequently displaced by a nonwetting fluid (dodecane, hexadecane, or mineral oil) at different flow rates. The experiments were designed to allow determinations of nonwetting fluid relative permeabilities ( ), fluid saturations ( ), and capillary pressure heads ( ). In the displacements, nonwetting fluid saturations increased with increasing flow rates for all five fluid pairs, and viscous fingering, capillary fingering, and stable displacement were observed. Viscous fingering occurred when PEG was displaced by either dodecane or hexadecane. For the water displacements, capillary fingers were observed at low capillary numbers. Due to unstable fingering phenomena, values for the PEG displacements were smaller than for the water displacements. A fitting exercise using the Brooks-Corey (1964) relationship showed that the fitted entry pressure heads are reasonably close to the computed entry pressure head. The fitted pore geometry factor, Sn values for the displacements are considerably lower than what is expected for displacements in homogeneous, highly uniform, porous systems, demonstrating the impact of unstable displacement on the apparent value of Sn. It was shown that a continuum-based multiphase model could be used to predict the average behavior for wetting fluid drainage in a pore network as long as independently fitted - and - relations are used. The use of a coupled approach through the Brooks-Corey pore geometry factor underpredicts observed values.

  3. Pore water pressure assessment in a forest watershed: Simulations and distributed field measurements related to forest practices

    NASA Astrophysics Data System (ADS)

    Dhakal, Amod S.; Sidle, Roy C.

    2004-02-01

    A distributed shallow groundwater model related to slope stability is described to assess the spatial distribution of pore water pressure in steep forested terrain in British Columbia. Additionally, effects of timber harvesting and roads on measured changes in pressure head during rainstorms were evaluated for the first time to assess the need for incorporating different hydrological components in the event-driven distributed model. Although explicit spatial quantification of pore water pressure requires many measurements for accurate prediction, model performance using average parameter values was reasonable when compared with pressure heads measured at nine spatially distributed sites. Increases in maximum pressure head (varying from 9 to 28 cm) between preharvesting (after road construction) and postharvesting rainstorm events were observed in seven of nine sites. The remaining two sites showed either a small decrease (≈5 cm) or similar peak pressure heads following harvesting. Peak pressure head evaluated at one piezometer located 46 m downslope of the road decreased substantially (≈50 cm) after road construction during moderate rainstorms and then recovered following harvesting. Piezometric responses in sites upslope of the road were not affected by road construction but did increase after harvesting. Moderate storms caused the largest relative increases in pressure head between preharvesting (after roads) and postharvesting conditions; such increases were small during large storms, lending support to the idea that timber harvesting in temperate forests enhances hydrologic response only during small and moderate storms. Since landslides in coastal Pacific Northwest are typically caused by large winter rainstorms, it appears more justified to include better spatial representation of soil physical and engineering parameters in the distributed shallow groundwater model compared to specifying evapotranspiration; road hydrology may, however, need to be included.

  4. Pore pressure evolution at the plate interface along the Cascadia subduction zone from the trench to the ETS transition zone

    NASA Astrophysics Data System (ADS)

    Skarbek, R. M.; Rempel, A. W.; Schmidt, D. A.

    2010-12-01

    Pore fluid pressures in subduction zones are a primary control on fault strength and slip dynamics. Numerous studies document elevated pore pressures in the outer wedge along several margins. Seismic observations and the occurrence of non-volcanic tremor provide additional evidence for the presence of near-lithostatic pore pressures at the plate interface far down-dip from the trench (~35 km depth). Here we use numerical models in one and two dimensions to evaluate the pore pressure and compaction state of sediments on the subducting Juan de Fuca plate in Cascadia from the trench to the ETS zone. 2-D models allow pressure to diffuse vertically and also laterally normal to strike of the megathrust; 1-D models simulate only vertical diffusion. Model parameters are chosen with reference to two strike-normal profiles: one through central Oregon and one through the Olympic Peninsula of Washington. We examine temporal variations in sediment input to the trench and consider implications for fault strength and permeability as well as the down-dip extent to which compactive dewatering can be considered a significant fluid source. In 1-D, we use a general and fully nonlinear model of sediment compaction derived without making any assumptions regarding stress-strain or porosity-permeability relations and allowing finite strains. In contrast, most previous models of fluid flow in subduction zones have used linear models of diffusion that rely on assumptions of constant sediment permeability and infinitesimal strains for their formulation. Our nonlinear finite-strain model remains valid at greater depths, where stresses and strains are large. Boundary conditions in 1-D are constrained by pore pressure estimates along the megathrust fault that are based on seismic velocities (e.g. Tobin and Saffer, 2010) and data from consolidation tests conducted on sediments gathered during ODP Leg 204 (Tan, 2001). Initial conditions rely on input sediment thickness; while sediment thickness

  5. 10+ years of ACORK: Continuous pore pressure record from the decollement zone at Nankai Trough off Muroto

    NASA Astrophysics Data System (ADS)

    Kinoshita, M.; Davis, E. E.; Becker, K.; Miyazaki, J.; Hulme, S.; Mendrum, R.; Toki, T.; Wheat, C. G.; Kasaya, T.

    2012-12-01

    Pore pressure and hydrological properties play key roles in governing coupling and slip behavior along the subducting plate interface. During the KR22-12 cruise, three dives were completed using ROV KAIKO onboard R/V KAIREI during Dec. 20-25, 2011, to retrieve pore pressure data and interstitial fluid samples from ACORKs at ODP Holes 808I and 1173B situated landward and seaward of the deformation front in the Nankai Trough off Cape Muroto. With 3-year-long and a 4-year-long new data records from Holes 808I and 1173B, respectively, we now have over 10-year-long continuous pressure records since June 2001 at both sites. Data from most monitoring depths show systematic variations in average pressure, and in formation pressure response to seafloor tidal loading. In 2005 and 2009, we observed significant decrease in the amplitudes of pressure response to semi-diurnal tidal loading at Hole 808I. Transient changes were observed at the time of several nearby earthquakes, including the 2011 Mar. 11 Tohoku earthquake, followed by long-lasting pressure changes in both holes starting on Mar. 23, 2011. Gas-tight fluid sampling operations were successfully carried out from the hydraulic port attached to the swellable packer inserted within the ACORK head at Hole 808I. The swellable packer was set in order to isolate the décollement zone that lies roughly 20 m below the bottom of casing at 922 m below the seafloor. We observed shimmering water venting through the port, and the flow rate was measured using a ball-type flowmeter. Fluid samples looked muddy, probably as a result of staining from the casing steel. We believe that the packer seal at the ACORK head is set properly, although the pore pressure at 922 m does not seem to have increased up to 2011. Still, the observed fluid seepage suggests a significant amount of fluid evacuated from the décollement zone since ACORK installation, which may have changed its hydrogeological condition.

  6. In-situ method for determining pore size distribution, capillary pressure and permeability

    SciTech Connect

    Vinegar, H.J.; Waxman, M.H.

    1987-02-17

    A method is described for determining the pore sizes entered by the oil phase in an oil-bearing formation, comprising: logging the formation of interest with an induced polarization logging tool having at least one source electrode; computing from the induced polarization measurements obtained by the logging tool a normalized induced polarization response function; obtaining core material from the formation of interest; extracting the water and hydrocarbons from the core material; resaturating the core material with formation brine; measuring the normalized induced polarization response function for the core material; and determining the pore sizes containing oil in the formation by comparing the normalized induced polarization response function from the formation with the normalized induced polarization response function of the core.

  7. Prospecting and developing carbonate reservoirs under excessive pressures in fields of preCaspian depression taken as an example

    SciTech Connect

    Leonard, R.; Perepelichenko, V.; Shilin, A.

    1996-08-01

    All large sub-salt hydrocarbon fields of the PreCaspian depression are connected with carbonate reservoirs and are characterized by abnormally high reservoir pressures of different origin. Exploratory drilling in fields under excessive pressures is very much complicated. To reduce the probability of disastrous absorptions and blowouts there has been developed special drilling-in technology with constant bottom-hole pressure control. To avoid fractures healing, to provide hydrocarbon phase state control, and to achieve maximum oil recovery there has been worked out a new technology of oil field development. According to this technology oil should be recovered first from the lower peripheral parts of the pool. This technology (taking into account the abnormally high reservoir pressures) provides gradual decreasing of reservoir pressure in the process of field development.

  8. Slip-weakening zone sizes at nucleation of catastrophic subaerial and submarine landslides by gradually increasing pore pressure

    NASA Astrophysics Data System (ADS)

    Viesca, R. C.; Rice, J. R.

    2011-12-01

    We address the nucleation of dynamic landslide rupture in response to gradual pore pressure increases. Nucleation marks the onset of acceleration of the overlying slope mass due to the suddenly rapid enlargement of a sub-surface zone of shear failure, previously deforming quasi-statically. We model that zone as a planar surface undergoing initially linear slip-weakening frictional failure within a bordering linear-elastic medium. The results are also relevant to earthquake nucleation. The sub-surface rupture zone considered runs parallel to the free surface of a uniform slope, under a 2D plane-strain deformation state. We show results for ruptures with friction coefficients following linear slip weakening (i.e., the residual friction is not yet reached). For spatially broad increases in pore pressure, the nucleation length depends on a ratio of depth to a cohesive zone length scale. In the very broad-increase limit, a direct numerical solution for nucleation lengths compares well with solutions to a corresponding eigenvalue problem (similar to Uenishi and Rice [JGR '03]), in which spatial variations in normal stress are neglected. We estimate nucleation lengths for subaerial and submarine conditions using data [e.g., Bishop et al., Géotech. '71; Stark et al., JGGE '05] from ring-shear tests on sediments (peak friction fp = 0.5, frictional slip-weakening rate within the range w = -df/d(slip) = 0.1/cm-1/cm). We assume that only pre-stresses, and not material properties, vary with depth. With such fp and w, we find for a range of subsurface depths and shear moduli μ that nucleation lengths are typically several hundred meters long for shallow undersea slopes, and up to an order of magnitude less for steeper slopes on the Earth's surface. In the submarine case, this puts nucleation lengths in a size range comparable to observed pore-pressure-generated seafloor disturbances as pockmarks [e.g., Gay et al., MG '06].

  9. Influence of slope angle on pore pressure generation and kinematics of pyroclastic flows: insights from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Chédeville, Corentin; Roche, Olivier

    2015-11-01

    The influence of slope angle on pore pressure generation and kinematics of fines-rich pyroclastic flows was investigated through laboratory experiments. Granular flows were generated by the release of a column of fine glass beads ( d = 0.08 mm) in an inclined channel (0-30°). The granular column could be fluidized while the channel base was either smooth or made rough by glued beads of 3 mm diameter. Pore pressure measurements reveal that the degree of autofluidization, caused by air escaping from the substrate interstices into which flow particles settled, was high at all slope angles. Flow runout increase due to autofluidization, however, was reduced at slope angle higher than ˜12° because of the occurrence of a strong deceleration phase that limited the flow duration. This is probably caused by the combination of flow head thinning at increased slope angle and settling of particles into the substrate interstices until the flow ran out of mass. Analysis of high-speed videos suggests that ingestion of ambient air at the flow front did not occur, even on steep slopes of 30°. Experiments at inclinations close to (25°) or slightly higher (30°) than the repose angle of the granular material (28.5°) revealed the formation of a thin basal deposit that was then eroded as the flow thickness and velocity gradually decreased. Our study suggests that air escape from substrate interstices in nature can be a significant external cause of pore pressure generation that favors low energy dissipation and long runout distances of pyroclastic flows on moderate topographies.

  10. Evaluation of Displacement and Pore Pressure change Due to the Injections of Fluid in Geological Formations and Mineralization

    NASA Astrophysics Data System (ADS)

    Chang, C.; Hsu, K.

    2011-12-01

    Cap rock plays an important role in the geological sequestration of carbon dioxide capture and storage. It indicates the effectiveness of the storage formation and controls the leakance of carbon dioxide and serves the need for geological repair and restoration. In this study, analytical solutions were devived based on the poroelastic theory. The effects of properties geological formation and mineralization were investigated on the change of pore pressure and the displacement of caprock. The results can be used for monitoring the geological sequestration of carbon dioxide.

  11. Characterization of Gas-Hydrate Sediment: In Situ Evaluation of Hydrate Saturation in Pores of Pressured Sedimental Samples

    NASA Astrophysics Data System (ADS)

    Jin, Y.; Konno, Y.; Kida, M.; Nagao, J.

    2014-12-01

    Hydrate saturation of gas-hydrate bearing sediment is a key of gas production from natural gas-hydrate reservoir. Developable natural gas-hydrates by conventional gas/oil production apparatus almost exist in unconsolidated sedimental layer. Generally, hydrate saturations of sedimental samples are directly estimated by volume of gas generated from dissociation of gas hydrates in pore spaces, porosity data and volume of the sediments. Furthermore, hydrate saturation can be also assessed using velocity of P-wave through sedimental samples. Nevertheless, hydrate saturation would be changed by morphological variations (grain-coating, cementing and pore-filling model) of gas hydrates in pore spaces. Jin et al.[1,2] recently observed the O-H stretching bands of H2O molecules of methane hydrate in porous media using an attenuated total reflection IR (ATR-IR) spectra. They observed in situ hydrate formation/dissociation process in sandy samples (Tohoku Keisya number 8, grain size of ca. 110 μm). In this presentation, we present IR spectroscopy approach to in situ evaluation of hydrate saturation of pressured gas-hydrate sediments. This work was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan. [1] Jin, Y.; Konno, Y.; Nagao, J. Energy Fules, 2012, 26, 2242-2247. [2] Jin, Y.; Oyama, H.; Nagao, J. Jpn. J. Appl. Phys. 2009, 48, No. 108001.

  12. Role of pore pressure gradients in sustaining frontal particle entrainment in eruption currents: The case of powder snow avalanches

    NASA Astrophysics Data System (ADS)

    Louge, M. Y.; Carroll, C. S.; Turnbull, B.

    2011-12-01

    We present a model that underscores the role played by the porous snow cover in sustaining large, rapid, dilute powder avalanches over weakly cohesive snow. The model attributes massive localized material injection into the avalanche head to synergistic pressure gradients established within the porous cover by the very static pressure field that this influx induces along the pack surface. Treating massive frontal snow entrainment as a source of fluid, we show that static pressure time-histories recorded at the Vallée de la Sionne (Switzerland) conform to the classical two-dimensional Rankine half-body flow field. We calculate pore pressure within the snow cover and, from the resulting pressure gradient, find stresses on a vertical failure plane. After inferring an upper bound for snow cohesion from pressure records, we derive a sufficient condition for steady failure that sets the depth through which the cover changes from porous solid to fluidized suspension. Fluidization of the top surface imposes another relation among maximum density, internal friction and cohesion of the pack, maximum cloud size and minimum avalanche speed. Altogether, these conditions dictate which snow covers can produce powder snow avalanches. We suggest how similar "eruption currents" sustained by massive frontal entrainment may be relevant to other fluid-particle suspensions.

  13. Development of a New Analog Test System Capable of Modeling Tectonic Deformation Incorporating the Effects of Pore Fluid Pressure

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Nakajima, H.; Takeda, M.; Aung, T. T.

    2005-12-01

    Understanding and predicting the tectonic deformation within geologic strata has been a very important research subject in many fields such as structural geology and petroleum geology. In recent years, such research has also become a fundamental necessity for the assessment of active fault migration, site selection for geological disposal of radioactive nuclear waste and exploration for methane hydrate. Although analog modeling techniques have played an important role in the elucidation of the tectonic deformation mechanisms, traditional approaches have typically used dry materials and ignored the effects of pore fluid pressure. In order for analog models to properly depict the tectonic deformation of the targeted, large-prototype system within a small laboratory-scale configuration, physical properties of the models, including geometry, force, and time, must be correctly scaled. Model materials representing brittle rock behavior require an internal friction identical to the prototype rock and virtually zero cohesion. Granular materials such as sand, glass beads, or steel beads of dry condition have been preferably used for this reason in addition to their availability and ease of handling. Modeling protocols for dry granular materials have been well established but such model tests cannot account for the pore fluid effects. Although the concept of effective stress has long been recognized and the role of pore-fluid pressure in tectonic deformation processes is evident, there have been few analog model studies that consider the effects of pore fluid movement. Some new applications require a thorough understanding of the coupled deformation and fluid flow processes within the strata. Taking the field of waste management as an example, deep geological disposal of radioactive waste has been thought to be an appropriate methodology for the safe isolation of the wastes from the human environment until the toxicity of the wastes decays to non-hazardous levels. For the

  14. On the analyses of mixture vapor pressure data: the hydrogen peroxide/water system and its excess thermodynamic functions.

    PubMed

    Manatt, Stanley L; Manatt, Margaret R R

    2004-12-01

    Reported here are some aspects of the analysis of mixture vapor pressure data using the model-free Redlich-Kister approach that have heretofore not been recognized. These are that the pure vapor pressure of one or more components and the average temperature of the complex apparatuses used in such studies can be obtained from the mixture vapor pressures. The findings reported here raise questions regarding current and past approaches for analyses of mixture vapor pressure data. As a test case for this analysis approach the H2O2-H2O mixture vapor pressure measurements reported by Scatchard, Kavanagh, and Tickner (G. Scatchard, G. M. Kavanagh, L. B. Ticknor, J. Am. Chem. Soc. 1952, 74, 3715-3720; G. M. Kavanagh, PhD. Thesis, Massachusetts Institute of Technology (USA), 1949) have been used; there is significant recent interest in this system. It was found that the original data is fit far better with a four-parameter Redlich-Kister excess energy expansion with inclusion of the pure hydrogen peroxide vapor pressure and the temperature as parameters. Comparisons of the present results with the previous analyses of this suite of data exhibit significant deviations. A precedent for consideration of iteration of temperature exists from the little-known work of Uchida, Ogawa, and Yamaguchi (S. Uchida, S. Ogawa, M. Yamaguchi, Japan Sci. Eng. Sci. 1950, 1, 41-49) who observed significant variations of temperature from place to place within a carefully insulated apparatus of the type traditionally used in mixture vapor pressure measurements. For hydrogen peroxide, new critical constants and vapor pressure-temperature equations needed in the analysis approach described above have been derived. Also temperature functions for the four Redlich-Kister parameters were derived, that allowed calculations of the excess Gibbs energy, excess entropy, and excess enthalpy whose values at various temperatures indicate the complexity of H2O2-H2O mixtures not evident in the original analyses

  15. Propagation of pore pressure diffusion waves in saturated dual-porosity media (II)

    NASA Astrophysics Data System (ADS)

    Yang, Duoxing; Li, Qi; Zhang, Lianzhong

    2016-04-01

    A mechanism has been established for pressure diffusion waves in dual-porosity media. Pressure diffusion waves are heavily damped with relatively low velocities and short wavelengths. The characteristic frequency dominates the attenuation behavior of pressure diffusions and separates wave fields into two asymptotic regimes: relaxed and unrelaxed. Characteristic delay times control the pressure diffusion between the matrix and the fractures. The transition zones in wavelength and attenuation peak shift toward high frequencies when the characteristic delay time decreases. In contrast, the transition zones in both phase and group velocity shift toward low frequencies as the characteristic time of the delay increases. In a spatially dependent diffusivity field, the pressure diffusion waves in dual-porosity media obey an accumulation-depletion law.

  16. Comparison between monitored and modeled pore water pressure and safety factor in a slope susceptible to shallow landslides

    NASA Astrophysics Data System (ADS)

    Bordoni, Massimiliano; Meisina, Claudia; Zizioli, Davide; Valentino, Roberto; Bittelli, Marco; Chersich, Silvia

    2014-05-01

    Shallow landslides can be defined as slope movements affecting superficial deposits of small thicknesses which are usually triggered due to extreme rainfall events, also very concentrated in time. Shallow landslides are hazardous phenomena: in particular, if they happen close to urbanized areas they could cause significant damages to cultivations, structures, infrastructures and, sometimes, human losses. The triggering mechanism of rainfall-induced shallow landslides is strictly linked with the hydrological and mechanical responses of usually unsaturated soils to rainfall events. For this reason, it is fundamental knowing the intrinsic hydro-mechanical properties of the soils in order to assess both susceptibility and hazard of shallow landslide and to develop early-warning systems at large scale. The hydrological data collected by a 20 months monitoring on a slope susceptible to shallow landslides in an area of the North -Eastern Oltrepo Pavese (Northern Apennines, Italy) were used to identify the hydrological behaviors of the investigated soils towards rainfall events. Field conditions under different rainfall trends have also been modeled by using both hydrological and physically-based stability models for the evaluation of the slope safety factor . The main objectives of this research are: (a) to compare the field measured pore water pressures at different depths with results of hydrological models, in order to evaluate the efficiency of the tested models and to determine how precipitations affect pore pressure development; (b) to compare the time trends of the safety factor that have been obtained by applying different stability models; (c) to evaluate, through a sensitivity analysis, the effects of soil hydrological properties on modeling pore water pressure and safety factor. The test site slope where field measurements were acquired is representative of other sites in Northern Apennines affected by shallow landslides and is characterized by medium

  17. Revisiting the Hubbert-Rubey pore pressure model for overthrust faulting: Inferences from bedding-parallel detachment surfaces within Middle Devonian gas shale, the Appalachian Basin, USA

    NASA Astrophysics Data System (ADS)

    Aydin, Murat G.; Engelder, Terry

    2014-12-01

    Both bedding-parallel slickensides and cleavage duplexes are forms of mesoscopic-scale detachment faulting populating black (Marcellus and Geneseo/Burket) and intervening gray (Mahantango) shales of the Middle Devonian, a section known for abnormal pore pressure below the Appalachian Plateau. The abundance and the orientation of slickensides and cleavage duplexes in the more organic-rich black shale relative to gray shale suggests that maturation-related abnormal pore pressure facilitates detachment, a mesoscopic manifestation of the Hubbert-Rubey pore pressure model for overthrust faulting. The former are discrete slip surfaces whereas the latter consists of nested, anastomosing slip surfaces, either cutting through bedding or on disrupted bedding surfaces stacked as mesoscopic versions of thrust duplexes. Cleavage duplexes are between a few cm and over 1 m thick with their hanging walls commonly transported toward the Appalachian foreland, regardless of local limb dip. Cleavage duplexes are most common near the stratigraphic maximum flooding surface, the organic-rich section most prone to develop maturation-related pore pressure in the Middle Devonian gas shales. Bedding-parallel slickensides are somewhat more evenly distributed in the black shale but also found in overlying gray shale. In both black and gray shales, slickensides are more abundant on the limbs of folds, an indication of pore-pressure-related flexural-slip folding. On the macroscopic scale, the Pine Mountain Block of the Southern Appalachian Mountains was enabled by a basal detachment cutting along the Upper Devonian Chattanooga black shale which has a thermal maturity sufficient for the generation of abnormal pore pressure. The Pine Mountain block is a large-scale overthrust showing little evidence of collapse of the hinterland side, a credible example of a pore-pressure-aided overthrust fault block of the type envisioned by the Hubbert-Rubey model.

  18. A fault constitutive relation accounting for thermal pressurization of pore fluid

    USGS Publications Warehouse

    Andrews, D.J.

    2002-01-01

    The heat generated in a slip zone during an earthquake can raise fluid pressure and thereby reduce frictional resistance to slip. The amount of fluid pressure rise depends on the associated fluid flow. The heat generated at a given time produces fluid pressure that decreases inversely with the square root of hydraulic diffusivity times the elapsed time. If the slip velocity function is crack-like, there is a prompt fluid pressure rise at the onset of slip, followed by a slower increase. The stress drop associated with the prompt fluid pressure rise increases with rupture propagation distance. The threshold propagation distance at which thermally induced stress drop starts to dominate over frictionally induced stress drop is proportional to hydraulic diffusivity. If hydraulic diffusivity is 0.02 m2/s, estimated from borehole samples of fault zone material, the threshold propagation distance is 300 m. The stress wave in an earthquake will induce an unknown amount of dilatancy and will increase hydraulic diffusivity, both of which will lessen the fluid pressure effect. Nevertheless, if hydraulic diffusivity is no more than two orders of magnitude larger than the laboratory value, then stress drop is complete in large earthquakes.

  19. Carbonate pore system evaluation using the velocity-porosity-pressure relationship, digital image analysis, and differential effective medium theory

    NASA Astrophysics Data System (ADS)

    Lima Neto, Irineu A.; Misságia, Roseane M.; Ceia, Marco A.; Archilha, Nathaly L.; Oliveira, Lucas C.

    2014-11-01

    Carbonate reservoirs exhibit heterogeneous pore systems and a wide variety of grain types, which affect the rock's elastic properties and the reservoir parameter relationships. To study the Albian carbonates in the Campos Basin, a methodology is proposed to predict the amount of microporosity and the representative aspect ratio of these inclusions. The method assumes three pore-space scales in two representative inclusion scenarios: 1) a macro-mesopore median aspect ratio from the thin-section digital image analysis (DIA) and 2) a microporosity aspect ratio predicted based on the measured P-wave velocities. Through a laboratory analysis of 10 grainstone core samples of the Albian age, the P- and S-wave velocities (Vp and Vs) are evaluated at effective pressures of 0-10 MPa. The analytical theories in the proposed methodology are functions of the aspect ratios from the differential effective medium (DEM) theory, the macro-mesopore system recognized from the DIA, the amount of microporosity determined by the difference between the porosities estimated from laboratorial helium-gas and the thin-section petrographic images, and the P-wave velocities under dry effective pressure conditions. The DIA procedure is applied to estimate the local and global parameters, and the textural implications concerning ultrasonic velocities and image resolution. The macro-mesopore inclusions contribute to stiffer rocks and higher velocities, whereas the microporosity inclusions contribute to softer rocks and lower velocities. We observe a high potential for this methodology, which uses the microporosity aspect ratio inverted from Vp to predict Vs with a good agreement. The results acceptably characterize the Albian grainstones. The representative macro-mesopore aspect ratio is 0.5, and the inverted microporosity aspect ratio ranges from 0.01 to 0.07. The effective pressure induced an effect of slight porosity reduction during the triaxial tests, mainly in the microporosity inclusions

  20. Near-field stress and pore pressure observations along the Carrizo Plain segment of the San Andreas fault in California

    SciTech Connect

    Castillo, D.A.; Hickman, S.H.

    1996-12-31

    Preliminary observations of wellbore breakouts from 9 wells drilled to depths approaching 5 km and located within 3-10 km of the San Andreas fault in the Carrizo Plain area indicate maximum principal stress orientations (SHmax) 30-40{degrees} from the fault trend, consistent with high shear stress resolved unto the fault. Analysis of stress orientation data from additional wells located >10 km from the fault confirm previous observations that SHmax stresses are at high angles to the fault trend, consistent with low shear stress on the San Andreas. We suggest that the overall variation in shear stresses resolved onto the fault may be depth dependent, with greater shear stress at shallower depths. Alternatively, these stress rotations observed in the vicinity of the San Andreas might also reflect the influence of local secondary faulting and folding, variations in lithology and/or slip heterogeneties associated with the 1857 M8+ Fort Tejon earthquake. Estimates of crustal pore pressure inferred from drilling mud-weights and drill-stem tests from wells in the vicinity (<10 km) of the San Andreas fault indicate near-hydrostatic conditions to depths of about 5 km. However, 20-30 km from the San Andreas fault and within the central portions of the southern San Joaquin Valley, crustal pore pressures approach 60% of the lithostatic load starting at about 3.5 km depth. Thus, our data close to the fault suggests that elevated fluid pressures within the fault zone, as proposed to explain the long-term low-strength of the San Andreas, either do not penetrate far into the adjacent crust and/or are confined largely to deeper portions of the fault zone.

  1. Near-field stress and pore pressure observations along the Carrizo Plain segment of the San Andreas fault in California

    SciTech Connect

    Castillo, D.A. ); Hickman, S.H. )

    1996-01-01

    Preliminary observations of wellbore breakouts from 9 wells drilled to depths approaching 5 km and located within 3-10 km of the San Andreas fault in the Carrizo Plain area indicate maximum principal stress orientations (SHmax) 30-40[degrees] from the fault trend, consistent with high shear stress resolved unto the fault. Analysis of stress orientation data from additional wells located >10 km from the fault confirm previous observations that SHmax stresses are at high angles to the fault trend, consistent with low shear stress on the San Andreas. We suggest that the overall variation in shear stresses resolved onto the fault may be depth dependent, with greater shear stress at shallower depths. Alternatively, these stress rotations observed in the vicinity of the San Andreas might also reflect the influence of local secondary faulting and folding, variations in lithology and/or slip heterogeneties associated with the 1857 M8+ Fort Tejon earthquake. Estimates of crustal pore pressure inferred from drilling mud-weights and drill-stem tests from wells in the vicinity (<10 km) of the San Andreas fault indicate near-hydrostatic conditions to depths of about 5 km. However, 20-30 km from the San Andreas fault and within the central portions of the southern San Joaquin Valley, crustal pore pressures approach 60% of the lithostatic load starting at about 3.5 km depth. Thus, our data close to the fault suggests that elevated fluid pressures within the fault zone, as proposed to explain the long-term low-strength of the San Andreas, either do not penetrate far into the adjacent crust and/or are confined largely to deeper portions of the fault zone.

  2. Pore geometry of Berea sandstone and numerical simulation of fluid flow by LBM under pressurization

    NASA Astrophysics Data System (ADS)

    Takahashi, M.; Sato, M.

    2012-12-01

    The Berea sandstone has a clear bedding plane and not clear cross lamina in cm size specimen, which is mainly caused by grain orientation and void space in microscopic scale. During the confined triaxial compression test, we measured permeability of Berea sandstone by constant head test for three mutually perpendicular directions under effective confining pressure and increasing differential axial stress. In general, the permeability of Berea sandstones decreased slightly with increasing the effective confining pressure and axial differential stress. Permeability anisotropy was also observed in the normal and two parallel directions to the bedding planes. We introduced the three-dimensional medial axis (3DMA) method of Lindquist et al. (2000) to quantify the flow-relevant geometric properties of the voids structure in Berea sandstone. Using these data, we also evaluated the number of connecting path between two faces, tortuosity and the shortest path distribution within an arbitrary region of Berea sandstone specimen. Geometrical information on the number of connecting path in an arbitrary volume CT data shows reasonable correlation between permeability anisotropy and mutually perpendicular directions normal and parallel to bedding planes. In addition, we introduced numerical simulation of fluid flow of pressurized Berea sandstone by LBM, to discuss the permeability reduction caused by pressurization. We obtained the detail distributions of fluid pressure, fluid velocity and its vector distribution in rather narrow voids space more than 10 μm. It is confirmed that pressurization caused decrease of the connecting path and the shortest path between arbitrary faces, and then caused a complex condition of on fluid pressure and fluid velocity.

  3. Excess of low frequency vibrational modes and glass transition: A molecular dynamics study for soft spheres at constant pressure

    NASA Astrophysics Data System (ADS)

    Flores-Ruiz, Hugo M.; Naumis, Gerardo G.

    2009-10-01

    Using molecular dynamics at constant pressure, the relationship between the excess of low frequency vibrational modes (known as the boson peak) and the glass transition is investigated for a truncated Lennard-Jones potential. It is observed that the quadratic mean displacement is enhanced by such modes, as predicted using a harmonic Hamiltonian for metastable states. As a result, glasses loose mechanical stability at lower temperatures than the corresponding crystal, since the Lindemann criteria are observed, as is also deduced from density functional theory. Finally, we found that the average force and elastic constant are reduced in the glass due to such excess of modes. The ratio between average elastic constants can be approximated using the 2/3 rule between melting and glass transition temperatures.

  4. Effects Of Bedrock Shape And Hillslope Gradient On The Pore-Water Pressure Development: Implication For Slope Stability

    NASA Astrophysics Data System (ADS)

    Lanni, Cristiano; McDonnell, Jeff

    2010-05-01

    Shallow Landslides are one of the most important causes of loss of human life and socio-economic damage related to the hydro-geological risk issues. The danger of these phenomena is related to their speed of development, the diffculty of foreseeing their location, and the high density of individual phenomena, whose downhill trajectories have a relevant probability of interfering with urbanized areas. Research activity on precipitation-induced landslides has focused mainly on developing predictive understanding of where and when landslides are likely to occur. Nevertheless, some major aspects that may be related to activation of landslides have been poorly investigated. For instance, landslide susceptibility zones are generally predicted assuming constant thickness of soil over an impervious bedrock layer. Nevertheless, recent studies showed subsurface topography could be a first order control for subsurface water-flow dynamics, because of the effects of its own irregular shape. Tromp-van Meerveld and McDonnell (2006) argued that connectivity of patches of transient saturation were a necessary prerequisite for exceeding the rainfall threshold necessary to drive lateral flow. Connectivity - "how the hillslope architecture controls the filling and spilling of isolated patches of saturation" (Hopp and McDonnell, 2009) - appears to be a possible unifying concept and theoretical platform for moving hillslope and watershed hydrology forward. Connectivity could also have important implications on triggering of shallow landslides, because the particular shape of bedrock may limit the water-flow downhill. Here we present a number of virtual numerical experiments performed to investigate the role of bedrock shape and hillslope gradient on pore-water pressure development. On this purpose, our test is represented by the subsurface topography of the Panola Experiment Hillslope (PEH). That is because scientific literature on PEH provides substantial documentation about the role

  5. Pore Pressure Diffusion as a possible mechanism for the Ag. Ioanis 2001 earthquake swarm activity (Gulf of Corinth, Central Greece).

    NASA Astrophysics Data System (ADS)

    Vallianatos, F.; Michas, G.; Papadakis, G.; Sammonds, P.

    2012-04-01

    The Gulf of Corinth rift (Central Greece) is one of the most seismotectonically active areas in Europe (Ambraseys and Jackson, 1990; 1997), with an important continental N-S extension of about 13 mm/yr and 6 mm/yr at the west and east part respectively (Clarke et al., 1997a). The seismicity of the area includes 5 main earthquakes of magnitude greater than 5.8 since 1960. In the western part of the rift, where the extension reaches its maximum value, earthquake swarms are often being observed (Bourouis and Cornet, 2009). Such an earthquake crisis has been occurred on 2001 at the southern margin of the west part of the rift. The crisis lasted about 100 days with a major event the Ag. Ioanis earthquake (4.3 Mw) on 8th of April 2001 (Pacchiani and Lyon-Caen, 2010). The possible relation between fluids flow and the observed earthquake swarms at the west part of the Gulf of Corinth rift has been discussed in the works of Bourouis and Cornet (2009) and Pacchiani and Lyon-Caen (2010). In the present work we examine the spatiotemporal properties of the Ag. Ioanis 2001 earthquake swarm, using data from the CRL network (http://crlab.eu/). We connect these properties to a mechanism due to pore pressure diffusion (Shapiro et al., 1997) and we estimate the hydraulic diffusivity and the permeability of the surrounding rocks. A back front of the seismicity (Parotidis et al., 2004) is also been observed, related to the migration of seismicity and the development of a quiescence region near the area of the initial pore pressure perturbation. Moreover, anisotropy of the hydraulic diffusivity has been observed, revealing the heterogeneity of the surrounding rocks and the fracture systems. This anisotropy is consistent in direction with the fault zone responsible for the Ag. Ioanis earthquake (Pacchiani and Lyon-Caen, 2010). Our results indicate that fluids flow and pore pressure perturbations are possible mechanisms for the initiation and the evolution of the Ag. Ioanis 2001

  6. High pressure effects on the properties and reactions of excess electrons in hydrocarbons

    SciTech Connect

    Holroyd, R. ); Nishikawa, Masaru . Dept. of Pure and Applied Sciences)

    1990-01-01

    These studies, utilizing high pressure, have provided considerable insight into the mechanism of electron transport and electron reactions in hydrocarbon liquids. Electrostriction leads to a significant negative volume change (about {minus}20 cm{sup 3}/mol) for electron trapping in alkanes. Electrostriction around an ion is even greater ({minus}100 to {minus}200 cm{sup 3}/mol). This effect and the fact that the energy level of the electron increases with pressure both contribute to shifts in electron attachment equilibria to favor ions at high pressure. Considerable effort has gone into studies of the mobility, properties and reactions of electrons in nonpolar liquids at or near normal pressures. Only recently have studies been undertaken of the effect of high pressure (up to 3 kbar) on electron behavior in such liquids. Pressures of this magnitude change the electron mobility in both alkane and aromatic liquids, and affect the ground state energy of electrons and stability of ions, which cause changes in the rates of electron reactions. 19 refs., 2 figs., 2 tabs.

  7. A two-phase debris-flow model that includes coupled evolution of volume fractions, granular dilatancy, and pore-fluid pressure

    USGS Publications Warehouse

    George, David L.; Iverson, Richard M.

    2011-01-01

    Pore-fluid pressure plays a crucial role in debris flows because it counteracts normal stresses at grain contacts and thereby reduces intergranular friction. Pore-pressure feedback accompanying debris deformation is particularly important during the onset of debrisflow motion, when it can dramatically influence the balance of forces governing downslope acceleration. We consider further effects of this feedback by formulating a new, depth-averaged mathematical model that simulates coupled evolution of granular dilatancy, solid and fluid volume fractions, pore-fluid pressure, and flow depth and velocity during all stages of debris-flow motion. To illustrate implications of the model, we use a finite-volume method to compute one-dimensional motion of a debris flow descending a rigid, uniformly inclined slope, and we compare model predictions with data obtained in large-scale experiments at the USGS debris-flow flume. Predictions for the first 1 s of motion show that increasing pore pressures (due to debris contraction) cause liquefaction that enhances flow acceleration. As acceleration continues, however, debris dilation causes dissipation of pore pressures, and this dissipation helps stabilize debris-flow motion. Our numerical predictions of this process match experimental data reasonably well, but predictions might be improved by accounting for the effects of grain-size segregation.

  8. Pore pressure regime leading to shallow failures in a mountain slope: monitoring and interpretation by soil-atmosphere coupled model.

    NASA Astrophysics Data System (ADS)

    Vaunat, Jean; Hürlimann, Marcel; Luna, Boris

    2016-04-01

    The study deals with the onset of debris flows in the "El Rebaixader" basin, located in South Central Pyrenees. The initiation area of debris flows is located on a lateral moraine with a thickness of tens of meters, in which torrential processes and other shallow mass movements have generated a large scarp with steep slopes. To follow slope evolution towards shallow failure, different sensors have been installed to monitor meteorological data and hydraulic variables at shallow depths (positive and negative pore pressure, water content). Measurements are interpreted by means of a thermo-hydro-mechanical coupled Finite Element code provided with a specific boundary condition to model water mass and heat flux exchanged between the ground and the atmosphere, including infiltration, evaporation, sensible heat and solar radiation. Results evidence the different modes of pore regime variation imposed, on the one hand, by surface infiltration and evaporation and, on the other hand, by the settlement of a slope parallel flow in a loose layer at some decimetres depth. As a conclusion, the analysis highlights the strong dependency of slope stability to the water regime taking place in slightly more permeable horizons connected to the top of the catchment area rather than to surficial climatic input. On this basis, some keys about debris flow mitigation are finally put forward.

  9. Bubble snap-off and capillary-back pressure during counter-current spontaneous imbibition into model pores.

    PubMed

    Unsal, Evren; Mason, Geoffrey; Morrow, Norman R; Ruth, Douglas W

    2009-04-01

    A previous paper (Unsal, E.; Mason, G.; Ruth, D. W.; Morrow, N. R. J. Colloid Interface Sci. 2007, 315, 200-209) reported experiments involving counter-current spontaneous imbibition into a model pore system consisting of a rod in an angled slot covered by a glass plate. Such an arrangement gives two tubes with different cross-sections (both size and shape) with an interconnection through the gap between the rod and the plate. In the previous experiments, the wetting phase advanced in the small tube and nonwetting phase retreated in the large tube. No bubbles were formed. In this paper, we study experimentally and theoretically the formation of bubbles at the open end of the large tube and their subsequent snap-off. Such bubbles reduce the capillary back pressure produced by the larger tube and can thus have an effect on the local rate of imbibition. In the model pore system, the rod was either in contact with the glass, forming two independent tubes, or the rod was spaced from the glass to allow cross-flow between the tubes. For small gaps, there were three distinct menisci. The one with the highest curvature was between the rod and the plate. The next most highly curved was in the smaller tube, and the least highly curved meniscus was in the large tube and this was the tube from which the bubbles developed. The pressure in the dead end of the system was recorded during imbibition. Once the bubble starts to form outside of the tube, the pressure drops rapidly and then steadies. After the bubble snaps off, the pressure rises to almost the initial value and stays essentially constant until the next bubble starts to form. After snap-off, the meniscus in the large tube appears to invade the large tube for some distance. The snap-off is the result of capillary instability; it takes place significantly inside the large tube with flow of wetting phase moving in the angular corners. As imbibition into the small tube progresses, the rate of imbibition decreases and the

  10. Pore Characterization of Shale Rock and Shale Interaction with Fluids at Reservoir Pressure-Temperature Conditions Using Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Ding, M.; Hjelm, R.; Watkins, E.; Xu, H.; Pawar, R.

    2015-12-01

    Oil/gas produced from unconventional reservoirs has become strategically important for the US domestic energy independence. In unconventional realm, hydrocarbons are generated and stored in nanopores media ranging from a few to hundreds of nanometers. Fundamental knowledge of coupled thermo-hydro-mechanical-chemical (THMC) processes that control fluid flow and propagation within nano-pore confinement is critical for maximizing unconventional oil/gas production. The size and confinement of the nanometer pores creates many complex rock-fluid interface interactions. It is imperative to promote innovative experimental studies to decipher physical and chemical processes at the nanopore scale that govern hydrocarbon generation and mass transport of hydrocarbon mixtures in tight shale and other low permeability formations at reservoir pressure-temperature conditions. We have carried out laboratory investigations exploring quantitative relationship between pore characteristics of the Wolfcamp shale from Western Texas and the shale interaction with fluids at reservoir P-T conditions using small-angle neutron scattering (SANS). We have performed SANS measurements of the shale rock in single fluid (e.g., H2O and D2O) and multifluid (CH4/(30% H2O+70% D2O)) systems at various pressures up to 20000 psi and temperature up to 150 oF. Figure 1 shows our SANS data at different pressures with H2O as the pressure medium. Our data analysis using IRENA software suggests that the principal changes of pore volume in the shale occurred on smaller than 50 nm pores and pressure at 5000 psi (Figure 2). Our results also suggest that with increasing P, more water flows into pores; with decreasing P, water is retained in the pores.

  11. Effect of pore pressure on the elastic moduli, porosity and permeability of Berea sandstone and Leuders limestone

    SciTech Connect

    Thompson, T.W.; Kelkar, S.M.; Gray, K.E.

    1983-02-01

    The behavior of Berea sandstone and Leuders limestone under atmospheric and elevated pore pressures is reported. The porosity and the permeability changes, along with the static and dynamic moduli for these rocks have been determined under various conditions. The existing theoretical background pertinent to the study is reviewed along with the previous experimental work. The detailed descriptions and the discussions on the experimental procedure involved and the equipment utilized are presented. A discussion on the sources of experimental errors is included. It also includes the error propagation equations and relevant discussions on the data acquisition and analysis. The findings are summarized together with a discussion of the results. The conclusions drawn from these results are included. The bulk of the data acquired and the results computed from it are presented.

  12. MONITORING OF PORE WATER PRESSURE AND WATER CONTENT AROUND A HORIZONTAL DRIFT THROUGH EXCAVATION - MEASUREMENT AT THE 140m GALLERY IN THE HORONOBE URL -

    NASA Astrophysics Data System (ADS)

    Yabuuchi, Satoshi; Kunimaru, Takanori; Kishi, Atsuyasu; Komatsu, Mitsuru

    Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. Pore water pressure and water content around a horizontal drift in the URL have been monitored for over 18 months since before the drift excavation was started. During the drift excavation, both pore water pressure and water content were decreasing. Pore water pressure has been still positive though it continued to decrease with its gradient gradually smaller after excavation, while water content turned to increase about 6 months after the completion of the excavation. It turned to fall again about 5 months later. An unsaturated zone containing gases which were dissolved in groundwater may have been formed around the horizontal drift.

  13. Orbital-free molecular dynamics simulations of a warm dense mixture: Examination of the excess-pressure matching rule

    SciTech Connect

    Danel, J-F.; Kazandjian, L.; Zerah, G.

    2009-06-15

    A form of the linear mixing rule involving the equality of excess pressures is tested with various mole fractions and various types of orbital-free molecular dynamics simulations. For all the cases considered, this mixing rule yields, within statistical error, the pressure of a mixture of helium and iron obtained by a direct simulation. In an attempt to interpret the robustness of the mixing rule, we show that it can be derived from thermodynamic stability if the system is regarded as a mixture of independent effective average atoms. The success of the mixing rule applied with equations of state including various degrees of approximation leads us to suggest its use in the thermodynamic domain where quantum molecular dynamics can be implemented.

  14. Note: Molecular diffusivity in a small pore zeolite measured by a variable pressure (piezometric) uptake method

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Kobayashi, Yasukazu; Muhammad, Usman; Wang, Dezheng; Wang, Yao

    2016-03-01

    The use of numerical analysis to solve the diffusion equation in the uptake method allowed the measurement of molecular diffusivity in a zeolite with a variable pressure around it. The diffusivity was obtained from the data in the measurement of the adsorption isotherm, which means that the diffusivity measurement now needs neither a special instrument nor procedure. The diffusivities of all the gases are readily available from the measurement of their adsorption isotherms and these data include how the diffusivity changes versus adsorbed concentration. The modeling introduced can also be used for a zeolite with a surface barrier.

  15. Pore pressure diffusion and the hydrologic response of nearly saturated, thin landslide deposits of rainfall

    SciTech Connect

    Haneberg, W.C. )

    1991-11-01

    Previous workers have correlated slope failures during rainstorms with rainfall intensity, rainfall duration, and seasonal antecedent rainfall. This note shows how such relationships can be interpreted using a periodic steady-state solution to the well-known linear pressure diffusion equation. Normalization of the governing equation yields a characteristic response time that is a function of soil thickness, saturated hydraulic conductivity, and pre-storm effective porosity, and which is analogous to the travel time of a piston wetting front. The effects of storm frequency and magnitude are also successfully quantified using dimensionless attenuation factors and lag times.

  16. Shear Veins Under High Pore Pressure Condition Along Subduction Interface: Yokonami Mélange, Cretaceous Shimanto Belt, Shikoku, Southwest Japan

    NASA Astrophysics Data System (ADS)

    Hashimoto, Y.; Eida, M.

    2013-12-01

    subducting plate in the Yokonami mélange was about 50-60Ma from the difference of depositional ages between chert and black shale. The geothermal gradient estimated from the slab age is consistent with from fluid pressure ratio and fluid inclusion analysis. This suggests that the low effective frictional coefficient and high fluid pressure ratio estimated from geological evidences are reasonable values for the formation of shear veins. Kitajima and Saffer (2012) revealed that very low frequency earthquakes (VLFs) occur in the high pore pressure area. Saito et al. (2013) found the quartz cemented fault rocks represent velocity weakening behavior and suggested that the quartz-rich shear veins in shallow accretionary complex might be a geological evidence of VLFs. Our result in this study can support this idea as a shear veins with high fluid pressure at the time of their formation.

  17. Excessive pediatric fasciitis necrotisans due to Pseudomonas aeruginosa infection successfully treated with negative pressure wound therapy.

    PubMed

    Szabó, Levente; Szegedi, István; Kiss, Csongor; Szikszay, Edit; Remenyik, Éva; Csízy, István; Juhász, István

    2015-01-01

    The case of a 10-year old female child is described with a history of myeloproliferative disorder having skin, bone and visceral involvement. Bone marrow biopsy revealed histiocytosis X. During chemotherapy necrotizing fasciitis of the lower abdominal wall was diagnosed. Multiple microbiological cultures taken from the wound base revealed Pseudomonas aeruginosa infection. Surgical necrectomy and application of negative pressure wound therapy (NPWT) was started together with intensive care treatment for sepsis. As both wound and general condition of the patient improved, autologous split thickness skin grafting was carried out in two sitting under continuing NPWT application. The applied skin grafts showed excellent take, the perilesional subcutaneous recesses resolved and complete healing was achieved after 28 days of NPWT treatment. Proper dermatological diagnosis and immediate escharectomy complemented with application of NPWT can be life-saving in the treatment of necrotizing fasciitis. PMID:26032296

  18. Effect of unstable layer depth on the pore pressure distribution, case study of the Slano Blato landslide (Slovenia)

    NASA Astrophysics Data System (ADS)

    Askarinejad, Amin; Secchi, Bandar; Macek, Matej; Petkovsek, Ana; Springman, Sarah

    2013-04-01

    The Slano Blato landslide is one of the largest landslides in Slovenia with a volume of more than 1 mio m3 of moving debris. The landslide is located at the border of Triassic limestone and Eocene flysch formations. Flysch is composed of layers of marls and sandstones. The sliding mass consists mainly of clay and clayey gravel of highly weathered and deteriorated flysch, while a minor part represents grains and blocks of limestones. (Petkovšek et al., 2009). The first documentation of an instability event dates back to 1789 and the landslide was reactivated during a heavy rain period in November 2000. Since then, the ground surface level above the unstable material on the upper zones of the landslide is significantly decreasing so that the current slope surface is now more than 10 m below the terrain surveyed in 1998. The new landslide topography results in different pore pressure distributions in the slope, which were anticipated to have a detrimental effect on the stability and movement regime of the slope. The main goal of this work is to investigate the effect of the overlying debris depth on the pore water pressure distribution during a predefined precipitation scenario. The behaviour of the unsaturated soil and the effects of fissures in the bedrock are also considered in the analysis. Hydro-mechanical simulations were performed using 2D finite element software (PLAXIS) and numerical results are compared with results from analytical models, which use a 1D steady state formulation for the hydraulic part and a 2D limit equilibrium approach to calculate the safety factors. The numerical studies show significant change in the pore water pressure distribution in the landslide body with variation of the debris depth. An increase in the debris depth leads to higher suction due to the deeper location of the water table. Higher suction increases landslide stability due to: i) increase of the effective stress and hence the shear strength of the material and ii

  19. The electrical conductivity of CO2-bearing pore waters at elevated pressure and temperature: a laboratory study and its implications in CO2 storage monitoring and leakage detection

    NASA Astrophysics Data System (ADS)

    Börner, Jana H.; Herdegen, Volker; Repke, Jens-Uwe; Spitzer, Klaus

    2015-11-01

    The electrical rock conductivity is a sensitive indicator for carbon dioxide (CO2) injection and migration processes. For a reliable balancing of the free CO2 in pore space with petrophysical models such as Archie's law or for the detection of migrating CO2, detailed knowledge of the pore water conductivity during interaction with CO2 is essential but not available yet. Contrary to common assumptions, pore water conductivity cannot be assumed constant since CO2 is a reactive gas that dissolves into the pore water in large amounts and provides additional charge carriers due to the dissociation of carbonic acid. We consequently carried out systematic laboratory experiments to quantify and analyse the changes in saline pore water conductivity caused by CO2 at thermodynamic equilibrium. Electrical conductivity is measured on pore water samples for pressures up to 30 MPa and temperatures up to 80 °C. The parameter range covers the gaseous, liquid and supercritical state of the CO2 involved. Pore water salinities from 0.006 up to 57.27 g L-1 sodium chloride were investigated as well as selective other ion species. At the same time, the CO2 concentration in the salt solution was determined by a wet-chemical procedure. A two-regime behaviour appears: for small salinities, we observe an increase of up to more than factor 3 in the electrical pore water conductivity, which strongly depends on the solution salinity (low-salinity regime). This is an expected behaviour, since the additional ions originating from the dissociation of carbonic acid positively contribute to the solution conductivity. However, when increasing salinities are considered this effect is completely diminished. For highly saline solutions, the increased mutual impeding causes the mobility of all ions to decrease, which may result in a significant reduction of conductivity by up to 15 per cent despite the added CO2 (high-salinity regime). We present the data set covering the pressure, temperature, salinity

  20. Densities and excess molar volumes of binary mixtures containing propylene carbonate + chlorohydrocarbons at 298.15 K and atmospheric pressure

    SciTech Connect

    Comelli, F.; Francesconi, R.

    1995-11-01

    Densities and excess molar volumes, V{sub m}{sup E}, for binary mixtures containing propylene carbonate + 10 chlorohydrocarbons (dichloromethane, 1,2-dichloroethane, 1,3-dichloropropane, 1,4-dichlorobuthane, 1,6-dichlorohexane, 1,10-dichlorodecane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trans-1,2-dichloroethene, and trichloroethene) have been measured at 298.15 K and at atmospheric pressure using an Anton Paar digital vibrating tube density meter. The results are fitted to the Redlich-Kister equation. The values of V{sub m}{sup E} for the mixtures containing dichloroalkanes show an increasing trend with the increase of the chain length and vary from a minimum of {minus}0.24 cm{sup 3}/mol for dichloromethane up to a maximum of +0.31 cm{sup 3}/mol for 1,10-dichlorodecane. The excess molar volumes for the other mixtures are negative over the entire range of composition. Results are qualitatively discussed in terms of molecular interactions.

  1. Excess heart rate and systolic blood pressure during psychological stress in relation to metabolic demand in adolescents.

    PubMed

    Lambiase, Maya J; Dorn, Joan; Chernega, Nicholas J; McCarthy, Thomas F; Roemmich, James N

    2012-09-01

    Cardiovascular responses during exercise are matched to the increased metabolic demand, but this may not be the case during psychological stress. No studies to date have tested this hypothesis in youth. Fifty-four youth, ages 13-16 years completed two visits. Heart rate (HR), systolic blood pressure (SBP), and oxygen (O(2)) consumption were measured during a graded exercise test on one day and during psychological stress reactivity (star tracing, speech) on another day. Predicted HR and SBP values during psychological stress were calculated based on HR-O(2) and SBP-O(2) relationships calculated during graded exercise. At a given O(2) consumption, actual HR was greater (p<0.02) than predicted for all stress tasks. Actual SBP was greater (p<0.001) than predicted for all stress tasks. This was the first study to demonstrate that cardiovascular responses were in excess of what would be expected based on metabolic demand in youth. PMID:22634388

  2. Application of a drainage film reduces fibroblast ingrowth into large-pored polyurethane foam during negative-pressure wound therapy in an in vitro model.

    PubMed

    Wiegand, Cornelia; Springer, Steffen; Abel, Martin; Wesarg, Falko; Ruth, Peter; Hipler, Uta-Christina

    2013-01-01

    Negative-pressure wound therapy (NPWT) is an advantageous treatment option in wound management to promote healing and reduce the risk of complications. NPWT is mainly carried out using open-cell polyurethane (PU) foams that stimulate granulation tissue formation. However, growth of wound bed tissue into foam material, leading to disruption of newly formed tissue upon dressing removal, has been observed. Consequently, it would be of clinical interest to preserve the positive effects of open-cell PU foams while avoiding cellular ingrowth. The study presented analyzed effects of NPWT using large-pored PU foam, fine-pored PU foam, and the combination of large-pored foam with drainage film on human dermal fibroblasts grown in a collagen matrix. The results showed no difference between the dressings in stimulating cellular migration during NPWT. However, when NPWT was applied using a large-pored PU foam, the fibroblasts continued to migrate into the dressing. This led to significant breaches in the cell layers upon removal of the samples after vacuum treatment. In contrast, cell migration stopped at the collagen matrix edge when fine-pored PU foam was used, as well as with the combination of PU foam and drainage film. In conclusion, placing a drainage film between collagen matrix and the large-pored PU foam dressing reduced the ingrowth of cells into the foam significantly. Moreover, positive effects on cellular migration were not affected, and the effect of the foam on tissue surface roughness in vitro was also reduced. PMID:23937617

  3. Numerical modelling of pore pressure variations due to time varying loads using a hybrid technique: the case of the Itoiz reservoir (Northern Spain)

    NASA Astrophysics Data System (ADS)

    Luzón, Francisco; García-Jerez, Antonio; Santoyo, Miguel A.; Sánchez-Sesma, Francisco J.

    2010-01-01

    In this work, we present a hybrid technique to estimate the pore pressure variations at the neighbourhood of dams due to time varying water loads in their reservoirs. When considering flow boundary conditions, the solution of the equations of the problem can be obtained as the superposition of (1) the part computed from a homogeneous diffusion equation with the Dirichlet boundary condition (this is due to the pore pressure diffusion) and (2) the solution of an initial value problem in an inhomogeneous diffusion equation in which the inhomogeneous term is related with the stress variations due to the water loads (the solution due to the compression in the medium). Here, two different techniques are joined to calculate each one of these partial solutions: the pore pressure diffusion term is obtained by using the Green's function of the problem, whereas the second contribution due to stress time changes is computed with a finite difference method. This hybrid technique has been used to compute the pore pressure variations produced by the initial impounding of the Itoiz reservoir, northern Spain. The possible relation between the reservoir and a close seismic series occurred on 2004 September, 8 months after the beginning of its impounding, is investigated. We pay special attention to the pore pressure changes at the hypocentre location of the main shock (with magnitude Mw = 4.5), and also evaluate the change of the Coulomb Failure Stress (ΔCFS) produced by the water loads in the reservoir over the fault responsible of this main shock, obtaining a maximum change of 0.5 kPa in the best of the cases. Accordingly, it seems that the role of the impounding of the reservoir to the main shock was marginal, and that the main load on the origin of the triggered seismicity could well be related to the regional state of stresses of the Pyrenees range and adjacent zones.

  4. Size of seismic events during borehole injections: the effects of source mechanisms, stress and pore pressure distribution

    NASA Astrophysics Data System (ADS)

    Fischer, T.; Ondovcin, T.; Zhao, P.

    2012-12-01

    and space-time distributions, source mechanisms and stress analyses on the available data to shed light on these questions. Our inversion for moment tensors of the Basel injection-induced seismicity shows that the microearthquakes had higher non-DC components during injection than after shut-in. This could be related to the higher stress drops found during injection. We model the pore pressure distribution and out-flow from the well the numerically solving the diffusion equation for the shut-in and open-well conditions. We compare the results of seismicity analysis with the models of pore pressure distribution during and after the injection to test the relevancy of several hypotheses of the occurrence of large events. We find that their anomalous occurrence during the shut-in phase is most-likely caused by the transient effects during the stop of injection. The anomalous space occurrence of large events is probably also related to the unequal distribution of faults in the vicinity of the injection well.

  5. Studying the Hydrology of Landslides: Pore Water Pressure, Preferential Flow and Feedbacks Between Slope Displacement and Hillslope Hydrology

    NASA Astrophysics Data System (ADS)

    Bogaard, T.; Greco, R.

    2014-12-01

    Hydrology is one of the most important triggering factors for slope destabilization. When a slope becomes unstable, cracks and fissures develop during slope deformation. These discontinuities affect both geotechnical and hydrological conditions of the slope. The crucial role of water flow, and especially the important role of preferential flow in unstable slopes, is generally recognized. However, in hydrological modelling, the unstable slope is characterized using static subsurface properties. The dynamic feedback between slope deformation and slope hydrology, being positive or negative depending on other geotechnical conditions, is not taken into account although it influences the pore pressure distribution and as such the overall stability. This research aims to highlight and quantify the dynamic nature of the subsurface hydrological conditions in unstable slopes. We focus on the role preferential flow has on slope destabilization and more specifically on the feedbacks between differential displacement and hydrological behaviour of the subsurface in natural slopes. We will present examples of field experimental work where we measured the hydrological influence of fissures, theoretical analysis and case study modelling of combined hydrology and slope stability, including feedbacks. The results show the subtle trade-off of increased infiltration and storage capacity in a slope and the increased drainage capacity of well connected preferential flow paths. We will furthermore highlight the current status of our knowledge as well as identify the knowledge gaps we face and the importance of cross- and multidisciplinary approach to better understand the internal dynamics of slope deformation and hillslope hydrology.

  6. Extraction of pore-morphology and capillary pressure curves of porous media from synchrotron-based tomography data

    DOE PAGESBeta

    Yang, Feifei; Hingerl, Ferdinand F.; Xiao, Xianghui; Liu, Yijin; Wu, Ziyu; Benson, Sally M.; Toney, Michael F.

    2015-06-03

    The elevated level of atmospheric carbon dioxide (CO2) has caused serious concern of the progression of global warming. Geological sequestration is considered as one of the most promising techniques for mitigating the damaging effect of global climate change. Investigations over wide range of length-scales are important for systematic evaluation of the underground formations from prospective CO2 reservoir. Understanding the relationship between the micro morphology and the observed macro phenomena is even more crucial. Here we show Synchrotron based X-ray micro tomographic study of the morphological buildup of Sandstones. We present a numerical method to extract the pore sizes distribution ofmore » the porous structure directly, without approximation or complex calculation. We have also demonstrated its capability in predicting the capillary pressure curve in a mercury intrusion porosimetry (MIP) measurement. The method presented in this work can be directly applied to the morphological studies of heterogeneous systems in various research fields, ranging from Carbon Capture and Storage, and Enhanced Oil Recovery to environmental remediation in the vadose zone.« less

  7. Extraction of pore-morphology and capillary pressure curves of porous media from synchrotron-based tomography data

    SciTech Connect

    Yang, Feifei; Hingerl, Ferdinand F.; Xiao, Xianghui; Liu, Yijin; Wu, Ziyu; Benson, Sally M.; Toney, Michael F.

    2015-06-03

    The elevated level of atmospheric carbon dioxide (CO2) has caused serious concern of the progression of global warming. Geological sequestration is considered as one of the most promising techniques for mitigating the damaging effect of global climate change. Investigations over wide range of length-scales are important for systematic evaluation of the underground formations from prospective CO2 reservoir. Understanding the relationship between the micro morphology and the observed macro phenomena is even more crucial. Here we show Synchrotron based X-ray micro tomographic study of the morphological buildup of Sandstones. We present a numerical method to extract the pore sizes distribution of the porous structure directly, without approximation or complex calculation. We have also demonstrated its capability in predicting the capillary pressure curve in a mercury intrusion porosimetry (MIP) measurement. The method presented in this work can be directly applied to the morphological studies of heterogeneous systems in various research fields, ranging from Carbon Capture and Storage, and Enhanced Oil Recovery to environmental remediation in the vadose zone.

  8. Extraction of pore-morphology and capillary pressure curves of porous media from synchrotron-based tomography data.

    PubMed

    Yang, Feifei; Hingerl, Ferdinand F; Xiao, Xianghui; Liu, Yijin; Wu, Ziyu; Benson, Sally M; Toney, Michael F

    2015-01-01

    The elevated level of atmospheric carbon dioxide (CO2) has caused serious concern of the progression of global warming. Geological sequestration is considered as one of the most promising techniques for mitigating the damaging effect of global climate change. Investigations over wide range of length-scales are important for systematic evaluation of the underground formations from prospective CO2 reservoir. Understanding the relationship between the micro morphology and the observed macro phenomena is even more crucial. Here we show Synchrotron based X-ray micro tomographic study of the morphological buildup of Sandstones. We present a numerical method to extract the pore sizes distribution of the porous structure directly, without approximation or complex calculation. We have also demonstrated its capability in predicting the capillary pressure curve in a mercury intrusion porosimetry (MIP) measurement. The method presented in this work can be directly applied to the morphological studies of heterogeneous systems in various research fields, ranging from Carbon Capture and Storage, and Enhanced Oil Recovery to environmental remediation in the vadose zone. PMID:26039795

  9. Extraction of pore-morphology and capillary pressure curves of porous media from synchrotron-based tomography data

    PubMed Central

    Yang, Feifei; Hingerl, Ferdinand F.; Xiao, Xianghui; Liu, Yijin; Wu, Ziyu; Benson, Sally M.; Toney, Michael F.

    2015-01-01

    The elevated level of atmospheric carbon dioxide (CO2) has caused serious concern of the progression of global warming. Geological sequestration is considered as one of the most promising techniques for mitigating the damaging effect of global climate change. Investigations over wide range of length-scales are important for systematic evaluation of the underground formations from prospective CO2 reservoir. Understanding the relationship between the micro morphology and the observed macro phenomena is even more crucial. Here we show Synchrotron based X-ray micro tomographic study of the morphological buildup of Sandstones. We present a numerical method to extract the pore sizes distribution of the porous structure directly, without approximation or complex calculation. We have also demonstrated its capability in predicting the capillary pressure curve in a mercury intrusion porosimetry (MIP) measurement. The method presented in this work can be directly applied to the morphological studies of heterogeneous systems in various research fields, ranging from Carbon Capture and Storage, and Enhanced Oil Recovery to environmental remediation in the vadose zone. PMID:26039795

  10. The role of pore pressure during hydraulic fracturing and implications for groundwater outbursts in mining and tunnelling

    NASA Astrophysics Data System (ADS)

    Yang, Tianhong; Zhu, Wancheng; Yu, Qinglei; Liu, Honglei

    2011-08-01

    Water outbursts from the floor during underground mining, and those from the surrounding rock mass of tunnels, involve the basic principle of hydraulic fracturing. Based on the hydraulic-fracturing mechanism, considered to be dependent on the coupling between seepage and damage, it is deemed that the variation of the pore-fluid pressure coefficient must be taken into account during this coupled process, in order to correctly establish the crack propagation mechanism during hydraulic fracturing. The coupled seepage-damage model is validated using numerical simulations of hydraulic fracturing around one hole and three holes; the model may also enable scientific and reasonable explanation of the dominance of hydraulic gradient on the crack propagation path in permeable rock. Finally, the water outburst from the floor at a coal mining site in Hebei Province, China, is numerically simulated, and the coupled seepage and damage mechanism during the mining-induced rock failure is clarified. The numerical simulation implies that the seepage-damage is the main mechanism for controlling the water outburst. Therefore this mechanism should be considered in the numerical simulation to understand the essence of water outburst induced in mines.

  11. Contrasting velocity-porosity relationships in differing tectonic regimes, Nankai Trough subduction zone, Japan: implications for pore pressure and effective stress estimation

    NASA Astrophysics Data System (ADS)

    Tudge, J.; Webb, S. I.; Tobin, H. J.

    2012-12-01

    across the splay fault a smaller porosity contrast is observed. Using a single Vp-porosity transform on a single extracted seismic velocity trace there is a porosity increase of 4 - 9%, in contrast to an increase of 2 - 7% when domain-specific estimates are used. From this preliminary porosity estimate, in-situ pore pressure can be determined if the porosity-effective stress relationship is also constrained. This important in trying to understand the fluid flow dynamics, and fault strength within the Nankai Trough subduction zone. Since excess pore pressure results in fluid migration, which affects the overall strength of the sediments and may suppress stick-slip behavior of faults by reducing the effective normal stress. By constraining the Vp-porosity relationship in the undisturbed Shikoku Basin sediments with we can potentially gain more insights into the controls on fluid migration in the Nankai Trough, and constrain further the up-dip limit of the seismogenic zone.

  12. Variations of absolute gravity accompanying earthquake-induced changes in subsurface pore water pressure at the Mizunami Underground Research Institute construction site, central Japan

    NASA Astrophysics Data System (ADS)

    Tanaka, T.; Salden, W.; Martin, A. J.; Saegusa, H.; Asai, Y.; Fujita, Y.; Aoki, H.

    2006-03-01

    The Tono Research Institute of Earthquake Science has been measuring gravity using an FG5 absolute gravimeter located at the Mizunami Geoscience Academy (MGA) in central Japan since January 2004. Measured gravity decreased immediately following the 2004 earthquake off the Kii peninsula (MJMA 7.4) by about 6 μGal. Here, we investigate the empirical relationship between pore water pressure change in a borehole near the MGA and gravity change measured at the MGA. We reveal that (1) gravity change correlates inversely with pore water pressure change at 81 m below the surface at a particular borehole and (2) several different sets of conversion coefficients from pressure head to gravity can be used to explain 60-70% of gravity variations with less than 2 μGal uncertainty. These newly identified relationships may suggest that an absolute gravimeter alone could be used to observe the change of groundwater quantity.

  13. Studies on deformation/pore pressure coupling processes at Japanese URLs and the development of ultra-high resolution FBG strain sensors for rock mechanics (Invited)

    NASA Astrophysics Data System (ADS)

    Tokunaga, T.; Matsui, H.; Zuyuan, H.; Kashiwai, Y.

    2009-12-01

    Generic, purpose-build underground research laboratories have been under construction in Japan. The objective for the construction is to conduct integrated studies on geology, geophysics, hydrogeology, rock mechanics, hydro-geochemistry, etc., to better understand the behavior and long-term stability of subsurface environments and subsurface openings. The Japan Atomic Energy Agency is responsible for the construction and selected two sites, i.e., Mizunami in central Japan and Horonobe in northern tip of Hokkaido, each representing granitic/crystalline rock environment and sedimentary formations, respectively. The construction of the Mizunami URL site began in July 2003, and the shafts reached to 400 m below ground level as of August 2009. The URL is situated in granitic rock masses including highly altered, fractured and faulted zones which are typical in Japan. The Main Shaft is situated at the fault which strikes to NNW while the Ventilation Shaft at the intact granitic rock. Sub-stages, which connect two shafts were constructed every 100 m depth interval, and several boreholes were drilled and are planned to be drilled from the shafts and the galleries for sampling rocks, groundwater, and for continuous monitoring of pore pressures. During the construction, we observed transient pore pressure responses caused by the excavation and dewatering/flooding of the shafts and boreholes. Here, we present one example of the spatio-temporal pore pressure responses caused by the rapid discharge of groundwater of which amount was 0.5 tons per minute from one pilot borehole. Pore pressure responses showed two distinct patterns, one continuous decline and the other transient increase and subsequent decline. The former pattern was observed at the locations where pore pressure transducers were set in the granitic rocks and were situated in the same block with discharge points with respect to the fault with NNW strike, while the latter in sedimentary formations and in the granite

  14. Coupling of Pore Pressure and Ground Motion Data Recorded During the 2010 El Mayor-Cucapah (Baja California) Earthquake at the NEES@UCSB Wildlife Station

    NASA Astrophysics Data System (ADS)

    Lavallee, D.; Seale, S. H.; Steidl, J. H.

    2011-12-01

    Pore pressure built up during an earthquake and the hazard associated with soil liquefaction present a major challenge for our society, as was dramatically displayed during the 2011 Higashi Nihon Daishinsai (Tohoku-oki, Japan) earthquake. Currently, there is a consensus among scientists that a better assessment of the risk associated with liquefaction requires a better understanding of the coupling between pore pressure time histories and ground motion time histories. Specifically, there is a basic need to investigate the coupling as a function of the frequency content of the ground motion. The 2010 El Mayor-Cucapah (Baja California) earthquake (M 7.2) provides a remarkable opportunity to undertake such an investigation and lay the basis to model the coupling. The event was well recorded at the NEES@UCSB Wildlife station located 110 km from the hypocenter. The station is equipped with three-component strong-motion accelerometers at the surface and in boreholes at various depths and with pore pressure transducers located in a saturated, liquefiable layer. The recorded pore pressure and ground motion time histories are both characterized by a frequency content that is a function of time. A wavelet representation is a natural approach to investigate non-stationary time histories. To study the coupling between two signals we use the following procedure: We first compute the wavelet coefficients associated with the two signals. Then we compute the correlation between the wavelet coefficients of the two signals as a function of the frequency. Correlation coefficients provide information about the degree of linear dependence between the two signals. To account for the presence of multiplicative constants relating the wavelet coefficients of the first signal to the wavelet coefficients of the second signal, we compare the square norm of the wavelet coefficients of the two signals for the available frequency range. Additionally, investigating the distribution of the square

  15. Creating extra pores in microporous carbon via a template strategy for a remarkable enhancement of ambient-pressure CO2 uptake.

    PubMed

    Li, Baiyan; Zhang, Yiming; Ma, Dingxuan; Zhu, Liangkui; Zhang, Daliang; Chrzanowski, Matthew; Shi, Zhan; Ma, Shengqian

    2015-05-21

    In this work, we illustrate a template strategy to create extra pores in microporous carbon for enhancing ambient-pressure CO2 uptake, as exemplified in the context of carbonizing the silicon-containing POP, PPN-4, followed by removal of the silicon template. The resultant PPN-4/C600 demonstrates a remarkable enhancement of CO2 uptake capacity at 295 K and 1 bar by a factor of 2.3 compared to the parent PPN-4. PMID:25907601

  16. Syn-eruptive, soft-sediment deformation of dilute pyroclastic density current deposits: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

    NASA Astrophysics Data System (ADS)

    Douillet, Guilhem Amin; Kueppers, Ulrich; Taisne, Benoit; Tsang-Hin-Sun, Ève; Müller, Sebastian K.; Dingwell, Donald B.

    2015-04-01

    Dilute pyroclastic density currents (PDCs) represent peculiar transport mechanisms sharing similarities with turbidity currents, wind-blown transport and granular flows. Outcrops of syn-eruptive, soft-sediment deformation are compiled from seven volcanic centers in order to provide a broad perspective on the variety of structures: Ubehebe craters (USA), Tungurahua (Ecuador), Soufrière Hills (Montserrat), Laacher See (Germany), Lago di Albano (Italy), Tower Hill and Purrumbete lake (both Australia). The interpretation of the variety of triggers enlightens the understanding of the sedimentary environment and basal boundary processes for PDCs: 1/ Isolated, cm-scale, overturned beds with vortex forms have been interpreted to be the signature of shear instabilities occurring at the boundary of two granular media. They may represent the frozen record of granular, pseudo Kelvin-Helmholtz instabilities. 2/ The occurrence of degassing pipes together with basal intrusive dikes suggest fluidization during flow stages. This, in turn, can facilitate the development of Kelvin-Helmholtz structures. The occurrence of injection dikes at the base of flow units in some outcrops compared with suction-driven local uplifts in others indicates the role of dynamic pore pressure and local changes between depletive and accumulative dynamics of flows. 3/ Isolated slumps as well as sinking pseudonodules are driven by their excess weight and occur after deposition but penecontemporaneous to the eruption. 4/ Impact of ballistic blocks can trigger local displacement or liquefaction. Based on the deformation depth, these can yield precise insights into depositional unit boundaries. Such impact structures may also be at the origin of some of the steep truncation planes visible at the base of the so-called "chute and pool" structures. 5/ Finally, the passage of shock waves emanating from the vent may be preserved in the form of trains of isolated, fine-grained overturned beds, which may disturb

  17. Syn-eruptive, soft-sediment deformation of dilute pyroclastic density current deposits: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

    NASA Astrophysics Data System (ADS)

    Douillet, G. A.; Taisne, B.; Tsang-Hin-Sun, È.; Müller, S. K.; Kueppers, U.; Dingwell, D. B.

    2014-12-01

    Soft-sediment deformation produces intriguing sedimentary structures and can occur in diverse environments and from a variety of triggers. From the observation of such structures and their interpretation in terms of trigger mechanisms, valuable information can be extracted about former conditions. Here we document examples of syn-eruptive deformation in dilute pyroclastic density current deposits. Outcrops from 6 different volcanoes have been compiled in order to provide a broad perspective on the variety of structures: Ubehebe craters (USA), Tungurahua (Ecuador), Soufrière Hills (Montserrat), Laacher See (Germany), Tower Hill and Purrumbete lake (both Australia). Isolated slumps as well as sinking pseudonodules are driven by their excess weight and occur after deposition but penecontemporaneous to the eruption. Isolated, cm-scale, overturned beds with vortex forms have been interpreted to be the signature of shear instabilities occurring at the boundary of two granular media. They may represent the frozen record of granular, pseudo Kelvin-Helmholtz instabilities. Their recognition can be a diagnostic for flows with a granular basal boundary layer. The occurrence of degassing pipes together with basal intrusive dikes suggest fluidization during flow stages, and can facilitate the development of Kelvin-Helmholtz structures. The occurrence at the base of flow units of injection dikes in some outcrops compared with suction-driven local uplifts in others indicates the role of dynamic pore pressure. Variations of the latter are possibly related to local changes between depletive and accumulative dynamics of flows. Ballistic impacts can trigger unconventional sags producing local displacement or liquefaction. Based on the deformation depth, these can yield precise insights into depositional unit boundaries. Such impact structures may also be at the origin of some of the steep truncation planes visible at the base of the so-called "chute and pool" structures. Finally

  18. Syn-eruptive, soft-sediment deformation of deposits from dilute pyroclastic density current: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

    NASA Astrophysics Data System (ADS)

    Douillet, G. A.; Taisne, B.; Tsang-Hin-Sun, E.; Muller, S. K.; Kueppers, U.; Dingwell, D. B.

    2015-05-01

    Soft-sediment deformation structures can provide valuable information about the conditions of parent flows, the sediment state and the surrounding environment. Here, examples of soft-sediment deformation in deposits of dilute pyroclastic density currents are documented and possible syn-eruptive triggers suggested. Outcrops from six different volcanoes have been compiled in order to provide a broad perspective on the variety of structures: Soufriere Hills (Montserrat), Tungurahua (Ecuador), Ubehebe craters (USA), Laacher See (Germany), and Tower Hill and Purrumbete lakes (both Australia). The variety of features can be classified in four groups: (1) tubular features such as pipes; (2) isolated, laterally oriented deformation such as overturned or oversteepened laminations and vortex-shaped laminae; (3) folds-and-faults structures involving thick (>30 cm) units; (4) dominantly vertical inter-penetration of two layers such as potatoids, dishes, or diapiric flame-like structures. The occurrence of degassing pipes together with basal intrusions suggest fluidization during flow stages, and can facilitate the development of other soft-sediment deformation structures. Variations from injection dikes to suction-driven, local uplifts at the base of outcrops indicate the role of dynamic pore pressure. Isolated, centimeter-scale, overturned beds with vortex forms have been interpreted to be the signature of shear instabilities occurring at the boundary of two granular media. They may represent the frozen record of granular, pseudo Kelvin-Helmholtz instabilities. Their recognition can be a diagnostic for flows with a granular basal boundary layer. Vertical inter-penetration and those folds-and-faults features related to slumps are driven by their excess weight and occur after deposition but penecontemporaneous to the eruption. The passage of shock waves emanating from the vent may also produce trains of isolated, fine-grained overturned beds that disturb the surface bedding

  19. Effects of pressure on pore characteristics and permeability of porous rocks as estimated from seismic wave velocities in cores from TCDP Hole-A

    NASA Astrophysics Data System (ADS)

    Kitamura, Keigo; Takahashi, Miki; Mizoguchi, Kazuo; Masuda, Koji; Ito, Hisao; Song, Sheng-Rong

    2010-09-01

    Changes in Vp/Vs (Poisson's ratio) around a fault are related to changes in the fluid transport properties of rocks, which play a significant role in seismogenic processes. Here we report a notable relationship between Vp/Vs and the permeability of porous fault-related rocks (Chelungpu fault, Taiwan) by direct and simultaneous measurement of elastic wave velocities (Vp and Vs) and permeability under increasing effective confining pressure (Peff) up to 25 MPa. Vp and Vs for all samples increased with Peff in the range up to 20 MPa, then were nearly constant as Peff increased to 25 MPa. Most silty sandstones with large proportions of fine-grained material showed positive correlations between Vp/Vs and permeability with rising pressure. On the other hand, well-sorted sandstones showed only slight changes in permeability with respect to Vp/Vs with rising pressure. We infer that grain size distributions, in particular the amount of silt- and clay-size grains, are responsible for the change in permeability with pressure as small particles clog pore networks with increasing Peff, causing the decrease in permeability. These findings may be useful to explain changes in permeability and pore pressure in the deep crust.

  20. Best Practices for Mudweight Window Generation and Accuracy Assessment between Seismic Based Pore Pressure Prediction Methodologies for a Near-Salt Field in Mississippi Canyon, Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Mannon, Timothy Patrick, Jr.

    Improving well design has and always will be the primary goal in drilling operations in the oil and gas industry. Oil and gas plays are continuing to move into increasingly hostile drilling environments, including near and/or sub-salt proximities. The ability to reduce the risk and uncertainly involved in drilling operations in unconventional geologic settings starts with improving the techniques for mudweight window modeling. To address this issue, an analysis of wellbore stability and well design improvement has been conducted. This study will show a systematic approach to well design by focusing on best practices for mudweight window projection for a field in Mississippi Canyon, Gulf of Mexico. The field includes depleted reservoirs and is in close proximity of salt intrusions. Analysis of offset wells has been conducted in the interest of developing an accurate picture of the subsurface environment by making connections between depth, non-productive time (NPT) events, and mudweights used. Commonly practiced petrophysical methods of pore pressure, fracture pressure, and shear failure gradient prediction have been applied to key offset wells in order to enhance the well design for two proposed wells. For the first time in the literature, the accuracy of the commonly accepted, seismic interval velocity based and the relatively new, seismic frequency based methodologies for pore pressure prediction are qualitatively and quantitatively compared for accuracy. Accuracy standards will be based on the agreement of the seismic outputs to pressure data obtained while drilling and petrophysically based pore pressure outputs for each well. The results will show significantly higher accuracy for the seismic frequency based approach in wells that were in near/sub-salt environments and higher overall accuracy for all of the wells in the study as a whole.

  1. The influence of Se pressure on the electronic properties of CuInSe{sub 2} grown under Cu-excess

    SciTech Connect

    Deprédurand, Valérie; Bertram, Tobias; Regesch, David; Henx, Benjamin; Siebentritt, Susanne

    2014-10-27

    Standard Cu-poor Cu(In,Ga)Se{sub 2} solar cell absorbers are usually prepared under high Se excess since the electronic properties of the absorbers are better if prepared under high Se pressure. However, in CuInSe{sub 2}, grown under Cu-excess, it was found that solar cell properties improve with lowering the Se pressure, mostly because of reduced tunnel contribution to the recombination path. Lower Se pressure during Cu-rich growth leads to increased (112) texture of the absorber films, to better optical film quality, as seen by increased excitonic luminescence and to lower net doping levels, which explains the reduced tunnelling effect. These findings show an opposite trend from the one observed in Cu-poor Cu(In,Ga)Se{sub 2}.

  2. Advanced Technologies for Monitoring CO2 Saturation and Pore Pressure in Geologic Formations: Linking the Chemical and Physical Effects to Elastic and Transport Properties

    SciTech Connect

    Mavko, G.; Vanorio, T.; Vialle, S.; Saxena, N.

    2014-03-31

    Ultrasonic P- and S-wave velocities were measured over a range of confining pressures while injecting CO2 and brine into the samples. Pore fluid pressure was also varied and monitored together with porosity during injection. Effective medium models were developed to understand the mechanisms and impact of observed changes and to provide the means for implementation of the interpretation methodologies in the field. Ultrasonic P- and S-wave velocities in carbonate rocks show as much as 20-50% decrease after injection of the reactive CO2-brine mixture; the changes were caused by permanent changes to the rock elastic frame associated with dissolution of mineral. Velocity decreases were observed under both dry and fluid-saturated conditions, and the amount of change was correlated with the initial pore fabrics. Scanning Electron Microscope images of carbonate rock microstructures were taken before and after injection of CO2-rich water. The images reveal enlargement of the pores, dissolution of micrite (micron-scale calcite crystals), and pitting of grain surfaces caused by the fluid- solid chemical reactivity. The magnitude of the changes correlates with the rock microtexture – tight, high surface area samples showed the largest changes in permeability and smallest changes in porosity and elastic stiffness compared to those in rocks with looser texture and larger intergranular pore space. Changes to the pore space also occurred from flow of fine particles with the injected fluid. Carbonates with grain-coating materials, such as residual oil, experienced very little permanent change during injection. In the tight micrite/spar cement component, dissolution is controlled by diffusion: the mass transfer of products and reactants is thus slow and the fluid is expected to be close to thermodynamical equilibrium with the calcite, leading to very little dissolution, or even precipitation. In the microporous rounded micrite and macropores, dissolution is controlled by

  3. Absence of dynamic triggering inside the Coso geothermal field following the 1992 Mw7.3 Landers earthquake: an indication of low pore pressure?

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Lin, G.; Zhan, Z.

    2013-12-01

    Geothermal fields are often considered to be susceptible to dynamic triggering because they are likely to be at near-critical stress state and involved with fluid movement in tectonically active extensional regimes. The 1992 Mw7.3 Landers earthquake dynamically triggered widespread earthquakes, especially at active geothermal areas, such as Long Valley, the Geysers and Coso (Hill et al., 1993). Dynamic triggering in Coso, southern California, is often referred to the broad area around the geothermal field. In this study, we investigate the spatial distribution of triggered events in Coso following the Landers earthquake and find no triggered events inside the geothermal field. The Coso geothermal production area is around 6*10 km2, confined between the Coso Hot Springs and the Sugarloaf Mountain. We estimate the b-value and completeness magnitude from a relocation catalog in the geothermal field to be 1.09 and M1.0, respectively. Based on the relocations for events above magnitude 1.0, we select seven small areas to compare the seismicity rate before and after the Landers earthquake. No seismicity was detected inside the geothermal field within 30 days after the Landers earthquake, whereas the surrounding fault zones outside of the geothermal field display strong elevated seismicity rate, including a segment of the Airport Lake Fault zone where the background seismicity was low before the Landers earthquake. The production area lacking of triggered events correlates with strong subsidence from the InSAR study by Fialko and Simons (2000), which may indicate low pore pressure in the area. This observation is further supported by the low Vp/Vs ratios from our recent 3D tomography model since Vp/Vs ratio decreases with pore pressure reduction (Ito et al., 1979, Christensen, 1984). Our results imply that the geothermal production of hot water and steam in Coso may have decreased the pore pressure and brought the stress state away from the critical state.

  4. Measurement of hydraulic properties in deep lake sediments using a tethered pore pressure probe: Applications in the Hamilton Harbour, western Lake Ontario

    NASA Astrophysics Data System (ADS)

    Harvey, F. Edwin; Rudolph, David L.; Frape, Shaun K.

    1997-08-01

    Estimates of groundwater seepage flux in lake bottom sediments require knowledge of the hydraulic gradient at the sediment-surface water interface and the hydraulic conductivity of the lake-bottom materials. In deep waters, in situ measurement of these parameters can be accomplished through the use of piezometer probes lowered and monitored remotely from a surface vessel. In this research work a new tethered piezometer probe was developed and tested for use in collecting hydraulic property data in deep-lake bottom sediments. The probe uses a variable-reluctance transducer to measure the differential sediment pore pressure between two ports spaced 100 cm apart. The dissipation of pore pressure transients that develop during rapid emplacement of the probe were extrapolated in time to estimate equilibrium hydraulic gradients. In addition, various data analysis techniques were evaluated for determining sediment hydraulic conductivity and specific storage through interpretation of the pore-pressure dissipation data. The probe was used to estimate groundwater seepage in the bottom sediments of the Hamilton Harbour, at the western end of Lake Ontario. Upward gradients were measured at nine locations within the harbor ranging from 0.010 to 0.425 and a downward gradient of -0.015 was recorded at one site along the harbor's eastern boundary. Hydraulic conductivities determined from pore-pressure dissipation over time ranged from 6.9 × 10-9to 4.8 × 10-7 m/s. Specific storage values ranged from 0.08 to 0.19 m-1. Calculated average linear seepage velocities ranged from 4.3 × 10-8 to -8.5 × 10-9 m/s. The groundwater contribution to the harbor through the deeper, fine-grained sediments was estimated to be 9.1 × 10-2 m3/s, or 2.9 × 106 m3/yr. This represents approximately 1.0% of the harbor basin's total volume, 15% of precipitation's contribution, 1.2% of the contribution of surface inflows (excluding the Burlington ship canal) and 0.22% of the total surface outflow passing

  5. Applications of probabilistic methods in geotechnical engineering. Part 2. Analysis of documented case histories using a stochastic model for seismically generated pore pressure and shear strain potential

    SciTech Connect

    Kavazanjian, E. Jr.; Chameau, J.L.; Clough, G.W.; Hadk-Hamou, T.

    1983-09-01

    This report presents the basics of a new stochastic model for seismically-generated pore pressure and shear strain potential and illustrates its use for documented case histories. Model parameters are chosen according to available information on the variability of soil properties, and it is applied to sites where liquefaction was observed and where no evidence of liquefaction was observed and where no evidence of liquefaction was observed after major seismic events. Results of the analysis are in substantial agreement with observed field behavior, indicating that this model can be used in a predictive capacity if parameters are chosen correctly. An application of the model to a comprehensive risk analysis of seismically induced initial liquefaction is also briefly described. An example using available seismic information for a hypothetical soil site near San Francisco is presented to illustrate the use of this type of model. Two models are applied to documented case histories to demonstrate their applicability and to illustrate how the probabilistic design parameters are chosen. The probabilistic pore pressure model developed by Chameau (1980) and the probabilistic shear strain model developed by Hadj Hamou (1982) are used herein to analyze the behavior of three sites where liquefaction did and did not occur during earthquakes.

  6. Pressure-Induced Amorphization of Small Pore Zeolites—the Role of Cation-H2O Topology and Anti-glass Formation

    NASA Astrophysics Data System (ADS)

    Chan Hwang, Gil; Joo Shin, Tae; Blom, Douglas A.; Vogt, Thomas; Lee, Yongjae

    2015-10-01

    Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li+, Na+, K+, Rb+, Cs+ allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NATII) in closer proximity to the aluminosilicate framework. We show that NATI materials have a lower onset pressure of PIA than the NATII materials containing Rb and Cs as EFC. The onset pressure of amorphization (PA) of NATII materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced—this opens a new way to form anti-glass structures.

  7. Pressure-Induced Amorphization of Small Pore Zeolites-the Role of Cation-H2O Topology and Anti-glass Formation.

    PubMed

    Chan Hwang, Gil; Joo Shin, Tae; Blom, Douglas A; Vogt, Thomas; Lee, Yongjae

    2015-01-01

    Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li(+), Na(+), K(+), Rb(+), Cs(+) allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NATII) in closer proximity to the aluminosilicate framework. We show that NATI materials have a lower onset pressure of PIA than the NATII materials containing Rb and Cs as EFC. The onset pressure of amorphization (PA) of NATII materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced-this opens a new way to form anti-glass structures. PMID:26455345

  8. Pressure-Induced Amorphization of Small Pore Zeolites—the Role of Cation-H2O Topology and Anti-glass Formation

    PubMed Central

    Chan Hwang, Gil; Joo Shin, Tae; Blom, Douglas A.; Vogt, Thomas; Lee, Yongjae

    2015-01-01

    Systematic studies of pressure-induced amorphization of natrolites (PIA) containing monovalent extra-framework cations (EFC) Li+, Na+, K+, Rb+, Cs+ allow us to assess the role of two different EFC-H2O configurations within the pores of a zeolite: one arrangement has H2O molecules (NATI) and the other the EFC (NATII) in closer proximity to the aluminosilicate framework. We show that NATI materials have a lower onset pressure of PIA than the NATII materials containing Rb and Cs as EFC. The onset pressure of amorphization (PA) of NATII materials increases linearly with the size of the EFC, whereas their initial bulk moduli (P1 phase) decrease linearly. Only Cs- and Rb-NAT reveal a phase separation into a dense form (P2 phase) under pressure. High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM) imaging shows that after recovery from pressures near 25 and 20 GPa long-range ordered Rb-Rb and Cs-Cs correlations continue to be present over length scales up to 100 nm while short-range ordering of the aluminosilicate framework is significantly reduced—this opens a new way to form anti-glass structures. PMID:26455345

  9. Experimental Pore-scale Study on the Dynamic Response of Blobs in Porous Media to Pressure Gradients

    NASA Astrophysics Data System (ADS)

    Hsu, S.; Hilpert, M.

    2012-12-01

    The dynamic response of blobs, which are trapped in porous media due to capillary forces, to applied pressure gradients is of interest to petroleum reservoir detection, enhanced oil recovery, and groundwater remediation. By performing planar laser-induced fluorescence experiments, we visualized the dynamics of blobs subject to steady and oscillatory pressure gradients in porous media. By analyzing blob images, we measured the 2D/3D contact angles and mean curvatures of the liquid-liquid interfaces and furthermore quantified the effects of contact angle hysteresis on blob mobilization. Once a blob was mobilized, the subsequent movement and interface behavior, such as contact line pinning, contact line slipping, and snap off, depended very much on the magnitude of the applied pressure gradient. We also revealed the flow patterns inside moving blobs by performing particle image velocimetry experiments. For an oscillatory pressure gradient, we showed that a trapped blob can exhibit resonance which can be exploited to enhance blob mobilization by seismic waves.

  10. Non-disturbing characterization of natural organic matter (NOM) contained in clay rock pore water by mass spectrometry using electrospray and atmospheric pressure chemical ionization modes.

    PubMed

    Huclier-Markai, Sandrine; Landesman, Catherine; Rogniaux, Hélène; Monteau, Fabrice; Vinsot, Agnes; Grambow, Bernd

    2010-01-01

    We have investigated the composition of the mobile natural organic matter (NOM) present in Callovo-Oxfodian pore water using electrospray ionization mass spectrometry (ESI-MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and emission-excitation matrix (EEM) spectroscopy. The generation of knowledge of the composition, structure and size of mobile NOM is necessary if one wants to understand the interactions of these compounds with heavy metals/radionuclides, in the context of environmental studies, and particularly how the mobility of these trace elements is affected by mobile NOM. The proposed methodology is very sensitive in unambiguously identifying the in situ composition of dissolved NOM in water even at very low NOM concentration, due to innovative non-disturbing water sampling and ionization (ESI/APCI-MS) techniques. It was possible to analyze a quite exhaustive inventory of the small organic compounds of clay pore water without proceeding to any chemical treatment at naturally occurring concentration levels. The structural features observed were mainly acidic compounds and fatty acids as well as aldehydes and amino acids. PMID:20013952

  11. How changes in pore pressure affect fluid circulation in volcanoes: three examples from Vulcano Island, Mt. Etna and Mt Vesuvius (Italy)

    NASA Astrophysics Data System (ADS)

    Federico, C.; Madonia, P.; Capasso, G.; D'Alessandro, W.; Bellomo, S.; Brusca, L.; Cusano, P.; Longo, M.; Paonita, A.; Petrosino, S.

    2013-05-01

    Fluids circulating in volcanic edifices are attracting increasing interest from scientists, mostly because their role in triggering flank instability, phreatic explosions, and eruptions has been documented in several cases worldwide [Newhall et al. 2001, Thomas et al. 2004]. Fluid pore pressure can change as an effect of either external (meteoric recharge, variation of the stress field), or endogenous causes (e.g. internal pressurization of magmatic volatiles and hydrothermal systems). The reciprocal roles of tectonics and magmatic/hydrothermal activity are still under investigation [Gottsman et al. 2007, Roeloffs et al. 2003]. We discuss the results of decennial data records collected in the aquifers of Mt Etna, Vulcano Island and Mt Vesuvius, and get insights on the role of tectonics and volcanic activity on the observed variations of water level and chemical composition. In Vulcano Island, the shallow thermal aquifer is deeply concerned by deep volcanic fluids. The most significant variations were observed during the 1988-96 crisis, due to the large input of steam and acidic gases from depth. In addition, the record of the water table elevation provided remarkable insights on the pressure of the volcano-hydrothermal system, which can be envisaged as the cause for the onset of the phase of higher vapor output in the fumarolic field in late 2004. On Mt. Vesuvius, the geochemical behavior of the aquifer appears strictly controlled by the input of volcanic gases and variations in the stress field. These latter, which were responsible for the seismic crisis of 1999, and the almost simultaneous increased input of CO2-rich vapor, significantly affected water chemistry and temperature, until 2006. The recent observations of low salinity, temperature, and dissolved carbon contents in groundwater provide strong evidence for reduced pressure in the volcano-hydrothermal system. The record of water chemistry available on Mt. Etna since 1994 shows coeval changes in almost all

  12. Veins in Paleo-reservoir as a Natural Indication of Coupled Changes in Pore Pressure and Stress, Salt Wash Graben of SE Utah, USA

    NASA Astrophysics Data System (ADS)

    Gwon, S.; Edwards, P.; Kim, Y. S.

    2015-12-01

    Hydrofracturing associated with elevated fluid pressure coupled with changes in stress has been crucial in enhancing the production and recovery of hydrocarbons. Furthermore, it is also an important issue to access the efficiency and stability of long-term CO2 geologic storage reservoirs. Veins are mineral-filled extension fractures developed along the plane of σ1-σ2 and perpendicular to σ3, and the fluid pressure must exceed σ3applied to the plane when the vein opens. Therefore, vein is a well-known natural analogue for fluid migration in a paleo-reservoir. In the Salt Wash Graben of SE Utah, CO2-charged vein systems hosted in the bleached Entrada Formation are well developed and examined to understand the conditions of fluid pressure and stress during the injections of CO2-charged fluid. Based on color and relative cross-cutting relationship in the field, veins are subdivided into two sets; sub-vertical black mineral-rich veins and orthogonal calcite veins that have previously been described as 'grid-lock fractures'. The vein distribution and fluid leakage along through-going fractures in mechanic units allow us to determine the stress regime and driving stress condition through 3D-Mohr circle reconstruction. The results of this statistical analysis for the veins show that the orthogonal veins indicate a 'stress transition' with maximum principal stress direction changing from vertical to NNW-SSE sub-horizontal which coincides with the current regional stress regime. The possible causes of the stress transition can be considered. The process of repeated sealing, reactivation and localization of veins within the bleached zone is a natural indication of a coupled change in pore pressure and stress in the reservoir. Thus, an understanding of the effect of stress changes due to the volumetric injection of CO2 in the subsurface as well as a knowledge of how pre-existing fractures affect fluid flow with respect to elevated pore pressures in layered rocks are

  13. Land subsidence, seismicity and pore pressure monitoring: the new requirements for the future development of oil and gas fields in Italy

    NASA Astrophysics Data System (ADS)

    Macini, P.; Mesini, E.; Panei, L.; Terlizzese, F.

    2015-11-01

    The Emilia earthquake of 2012 (Italy) stimulated a controversial debate concerning the possibility that the event could have been induced or triggered by underground fluids production. The public discussion led the Italian Government to issue a protocol of guidelines for the monitoring of microseismic activity, ground deformation and reservoir pore pressure. The guidelines will be put into operation as soon as practicable when licensing is being considered, and all data provided by mining operators must be made available to the relevant Authorities. The implementation of an outreach and communication program to local residents and administrative authorities is prescribed, so that the civil and scientific community at large can gain confidence that operations are being managed optimally.

  14. The 2003-2004 seismic swarm in the western Corinth rift: Evidence for a multiscale pore pressure diffusion process along a permeable fault system

    NASA Astrophysics Data System (ADS)

    Duverger, Clara; Godano, Maxime; Bernard, Pascal; Lyon-Caen, Hélène; Lambotte, Sophie

    2015-09-01

    Microseismic multiplets occurring in the western Corinth rift, Greece, during a large swarm are analyzed to retrieve their spatiotemporal characteristics. These multiplets activated small subfaults at depth (˜7 km), up to 1 km long, at the root of two parallel active normal faults. The swarm migrates westward nearly horizontally over 10 km at an average velocity of 50 m/d with a diffusivity of 0.5 m2 s-1. It successively activates the Aigion fault, a relay zone in its hanging wall, and the Fassouleika fault. Within each multiplet, hypocenters also migrate with diffusivities ranging from 0.001 to 0.4 m2 s-1. The largest internal diffusivities appear at the core of the layer defined by the clusters. These results are interpreted as a hydroshear process caused by pore pressure migration within permeable corridors resulting from the intersection of the major faults with a brittle geological layer inherited from the Hellenic nappe stack.

  15. Regional pore-fluid pressures in the active western Taiwan thrust belt: A test of the classic Hubbert-Rubey fault-weakening hypothesis

    NASA Astrophysics Data System (ADS)

    Yue, Li-Fan; Suppe, John

    2014-12-01

    We document regional pore-fluid pressures in the active Taiwan thrust belt using 55 deep boreholes to test the classic Hubbert-Rubey hypothesis that high static fluid pressures (depth normalized as λ = Pf/ρrgz) account for the extreme weakness of thrust faults, since effective friction μf∗ =μf(1 - λ) . Taiwan fluid pressures are dominated by disequilibrium compaction, showing fully compacted sediments with hydrostatic fluid pressures at shallow depths until the fluid-retention depth zFRD ≈ 3 km, below which sediments are increasingly undercompacted and overpressured. The Hubbert-Rubey fault weakening coefficient is a simple function of depth (1 - λ) ≈ 0.6zFRD/z. We map present-day and pre-erosion fluid pressures and weakening (1 - λ) regionally and show that active thrusts are too shallow relative to zFRD for the classic Hubbert-Rubey mechanism to be important, which requires z ≥ ˜4zFRD ≈ 12 km to have the required order-of-magnitude Hubbert-Rubey fault weakening of (1 - λ) ≤ ˜0.15. The best-characterized thrust is the Chelungpu fault that slipped in the 1999 (Mw = 7.6) Chi-Chi earthquake, which has a low effective friction μf∗ ≈ 0.08- 0.12 , yet lies near the base of the hydrostatic zone at depths of 1-5 km with a modest Hubbert-Rubey weakening of (1 - λ) ≈ 0.4-0.6. Overpressured Miocene and Oligocene detachments at 5-7 km depth have (1 - λ) ≈ 0.3. Therefore, other mechanisms of fault weakening are required, such as the dynamical mechanisms documented for the Chi-Chi earthquake.

  16. Direct measurements of pore fluid density by vibrating tube densimetry.

    PubMed

    Gruszkiewicz, Miroslaw S; Rother, Gernot; Wesolowski, David J; Cole, David R; Wallacher, Dirk

    2012-03-20

    The densities of pore-confined fluids were measured for the first time by means of vibrating tube densimetry (VTD). A custom-built high-pressure, high-temperature vibrating tube densimeter was used to measure the densities of propane at subcritical and supercritical temperatures (between 35 and 97 °C) and carbon dioxide at supercritical temperatures (between 32 and 50 °C) saturating hydrophobic silica aerogel (0.2 g/cm(3), 90% porosity) synthesized inside Hastelloy U-tubes. Additionally, supercritical isotherms of excess adsorption for CO(2) and the same porous solid were measured gravimetrically using a precise magnetically coupled microbalance. Pore fluid densities and total adsorption isotherms increased monotonically with increasing density of the bulk fluid, in contrast to excess adsorption isotherms, which reached a maximum and then decreased toward zero or negative values above the critical density of the bulk fluid. The isotherms of confined fluid density and excess adsorption obtained by VTD contain additional information. For instance, the maxima of excess adsorption occur below the critical density of the bulk fluid at the beginning of the plateau region in the total adsorption, marking the end of the transition of pore fluid to a denser, liquidlike pore phase. Compression of the confined fluid significantly beyond the density of the bulk fluid at the same temperature was observed even at subcritical temperatures. The effect of pore confinement on the liquid-vapor critical temperature of propane was less than ~1.7 K. The results for propane and carbon dioxide showed similarity in the sense of the principle of corresponding states. Good quantitative agreement was obtained between excess adsorption isotherms determined from VTD total adsorption results and those measured gravimetrically at the same temperature, confirming the validity of the vibrating tube measurements. Thus, it is demonstrated that vibrating tube densimetry is a novel experimental

  17. Computation of time-dependent subsurface pore pressure variations and stresses due to time varying water loads at the Itoiz reservoir (Northern Spain), and their relation with near seismicity

    NASA Astrophysics Data System (ADS)

    Luzón, F.; García-Jerez, A.; Santoyo, M. A.

    2009-04-01

    In this work we study the seismicity produced near the newly constructed Itoiz reservoir in the western Pyrenees (northern Spain). We computed the evolution of the stress changes in the subsoil due to the time water load distribution and relate it with the main seismicity occurred after the beginning of impoundment in 2004. We also computed the pore pressure variations produced around Itoiz dam using a hybrid technique which take into account the time varying water loads in the reservoir. In this methodology, two different techniques are joined to calculate each one of the partial solutions evolved: the pore pressure diffusion term is obtained by using the Green functions of the problem, whereas the second term due to stress time changes is computed with a Finite Difference Method (FDM). We pay special attention to the pore pressure changes at the hypocenter location of the mainshock (with magnitude mb = 4.6) occurred on September 2004, 8 months after the beginning of its impounding. After this, we compute the coseismic and postseismic stress changes produced by the main events of the seismic series and study its influence on the triggering of the aftershocks by means of the Coulomb Failure Stress criterion (ΔCFS). Results show that at the time of occurrence of the main earthquake the pore pressure change was of about 1000 Pa at the hypocenter. However, the pore pressure variation exceeded 1000 Pa at other earlier times and at many different positions near Itoiz dam without the occurrence of earlier earthquakes. Thus, the origin of the September 18, 2004 earthquake (mb = 4.6) can be explained when considering the pore pressure perturbation at a pre-existent fault in the hypocenter location with more aptitude to fail than other sites, together with the assumption of regional pre-existing stress field. At last we found, a large positive influence over most of the aftershocks of the seismic series due to the stress changes produced by the largest events.

  18. Relationships between pore pressure, stresses, and present-day geodynamics in the Scotian Shelf, offshore eastern Canada

    SciTech Connect

    Yassir, N.A.; Bell, J.S.

    1994-12-01

    A geomechanical study of the Mesozoic and Tertiary sediments beneath the Scotian Shelf shows that two major weak layers exist at depth: the over-pressured unit at 4000 m and the basal Argo salt, which is ductile and diapiric. A consistent relationships is observed between the overpressures and the stress state in the basin. First, the smaller horizontal principal stress increases dramatically just above the onset of overpressuring, and secondly, borehole breakouts, indicators of stress anisotropy-decrease in abundance within the overpressure zone. Neither tectonic shear nor rapid burial can explain these observations; however, overpressuring by fluid generation will result in horizontal stress increase and eventually lead to an isotropic stress state. Compelling evidence is found for hydrocarbon generation being a key cause of overpressuring in the Scotian Shelf.

  19. Hypoadiponectinemia and aldosterone excess are associated with lack of blood pressure control in subjects with resistant hypertension.

    PubMed

    de Faria, Ana P C; Demacq, Caroline; Figueiredo, Valéria N; Moraes, Carolina H; Santos, Rodrigo C; Sabbatini, Andréa R; Barbaro, Natália R; Boer-Martins, Leandro; Fontana, Vanessa; Moreno, Heitor

    2013-12-01

    Obesity, arterial stiffness and high aldosterone levels can interact to cause resistant hypertension (RHTN). Lower adiponectin (APN) levels may be significantly associated with hypertension. However, the importance of hypoadiponectinemia as a complicating factor in the lack of blood pressure (BP) control in individuals with RHTN has not been demonstrated. Ninety-six RHTN patients were classified into uncontrolled (UCRHTN, n = 44) and controlled (CRHTN, n = 52) subgroups. Their APN and aldosterone levels, office and ambulatory BP (ABPM) measurements, endothelium-dependent brachial artery responses (flow-mediated dilation (FMD)), left ventricular mass index (LVMI) and pulse wave velocity (PWV) were evaluated. The UCRHTN subgroup had increased aldosterone levels, as well as higher LVMI and PWV. In addition, lower APN levels and impaired FMD response were found in this subgroup. The brachial and ABPM pulse pressures were inversely associated with the APN levels (r = -0.45, P = 0.002; r = -0.33, P = 0.03, respectively), as were the aldosterone levels and the PWV (r = -0.38, P = 0.01; r = -0.36, P = 0.02, respectively) in UCRHTN patients. The PWV was only significantly influenced by the APN level in the UCRHTN subgroup in the multivariate regression analysis. None of the correlations mentioned above were observed in the CRHTN subgroup. Hypoadiponectinemia and high aldosterone levels may therefore be implicated in resistance to antihypertensive therapy related to arterial stiffness. PMID:23966059

  20. Correlation between pore fluid pressures and DInSAR post-seismic deformation of the May 20, 2012 Emilia-Romagna (Italy) earthquake

    NASA Astrophysics Data System (ADS)

    Moro, M.; Stramondo, S.; Albano, M.; Barba, S.; Solaro, G.; Saroli, M.; Bignami, C.

    2015-12-01

    The present work focuses on the detection and analysis of the postseismic surface deformations following the two earthquakes that hit the Emilia Romagna region (Italy) on May 20 and 29, 2012. The 2012 Emilia earthquake sequence struck the central sector of the Ferrara arc, which represents the external fold-and-thrust system of the Northern Apennines thrust belt buried below the Po plain. The May 20 event occurred on the Ferrara basal thrust at depth, at about 6-7 km, while, during the May 29 event, the rupture jumped on an inner splay of the Ferrara system. The analysis of the postseismic displacements was carried out thanks to a dataset of SAR COSMO­ SkyMed images covering a time span of about one year (May 20, 2012 - May 11, 2013) after the May 20 event. The DInSAR results revealed the presence of two deformation patches: the first one is located in the area that experienced the coseismic uplift. Here the postseismic displacements point out a further ground uplift occurring along the first three months after the 20 May event. The second deformation patch is located in the villages of San Carlo and Mirabello, where ground subsidence lasting about four months was detected. We hypothesized that both the observed phenomena are related to the pore pressure perturbation caused by the coseismic deformation. In particular, the ground uplift is due to the deep crustal deformations caused by the pore fluid diffusion at depth to re-establish the initial hydrostatic stresses. Instead, the ground subsidence is related to the compaction of the shallow sandy layers caused by the liquefaction phenomena, which widely affected the San Carlo and Mirabello area. Preliminary numerical analyses performed with the Finite Element Method and empirical relations confirmed our hypothesis.

  1. Multi-Layer, Sharp-Interface Models of Pore Pressure Buildup within the Illinois Basin due to Basin-Wide CO2 Injection

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Person, M. A.; Gable, C. W.; Celia, M. A.; Nordbotten, J. M.; Bandilla, K.; Elliot, T. R.; Rupp, J.; Ellett, K. M.; Bowen, B.; Pickett, W.; Woolsey, E. E.

    2011-12-01

    We recently developed and applied a new parallel, multi-layer, finite-element model to the Illinois Basin in order to assess the spatial extent and magnitude of pore pressure increases resulting from the annual projected injection of 100 million metric tons of CO2. One focus of this work is to assess the potential for inducing a seismic event associated with low effective stress conditions around CO2 injection wells in the southern Illinois Basin where Mt Simon permeability is relatively low (< 50 mD). We used a sharp-interface formulation to represent a CO2, freshwater, and brine transport within each layer. A simple parallelization scheme was used in which fluid transport in each layer is solved on a separate processor. The layers are linked at the after each time step through vertical fluxes of fresh and saline water across their respective confining units. This model was validated, in part, by comparison to computed pore pressure distributions from a published 8-layer test case. Our Illinois Basin model represents spatial variations in porosity using a modified form of Athy's law. Permeability is logarithmically related to porosity so that permeability. Principal reservoirs represented in our model include the Mt. Simon Formation, the Knox Dolomite, Ordovician carbonates, Silurian-Devonian and Mississippian-Pennsylvanian sandstone/carbonates units. Key confining unit represented include the Eau Claire, Maquoketa, and New Albany Shales. A limited number of low-permeability faults were also included in the model. The permeability of fault elements were set to between 10-100 times lower than surrounding sediments. We calibrated our model using historical freshwater pumping data from the Chicago area (128 million gallons per day of H2O) as well as the salinity distribution across the Illinois Basin. We found that incorporating a stream network which included the Rock River near Chicago was important in reproducing pre-development head patterns in the Cambro

  2. Pore Fluid Pressure and State of Stress Above the Plate Interface from Observations in a 3 Kilometer Deep Borehole: IODP Site C0002, Nankai Trough Subduction Zone

    NASA Astrophysics Data System (ADS)

    Tobin, H. J.; Saffer, D. M.; Hirose, T.; Castillo, D. A.; Kitajima, H.; Sone, H.

    2014-12-01

    During IODP Expedition 348 from October 2013 to January 2014, Site C0002 was drilled to more than 3000 meters' depth into the inner accretionary wedge at the Nankai Trough, setting a new depth record for scientific ocean drilling. It is the first hole to access the deep interior of an active convergent margin. Site C0002 is part of the NanTroSEIZE project off the Kii-Kumano region of Japan, designed to shed light on plate boundary fault zone processes near the up-dip edge of seismogenic locking and slip. The zone from 865 - 3056 meters below the sea floor was sampled via logging-while-drilling measurements, continuous sampling of drill cuttings, and limited coring. This interval was composed of lithified middle to late Miocene hemipelagic sediments and turbidites that are markedly deformed and dip steeply. P-wave speeds from sonic logs increase with depth to ~ 1600 meters, but are constant to slightly decreasing with depth from 1600 to 3050 meters. We hypothesize that this change in trend indicates the onset of elevated pore fluid pressure, but structural and lithologic factors may also play a role. We explore several methods for quantitative estimation of sonic-derived fluid pressure conditions in the inner wedge. A borehole leak-off test (LOT) and a series of borehole pressurization and injection tests were also performed, which we synthesize to estimate the least principal stress, or Shmin. Furthermore, downhole pressure while drilling (PWD) measurements recorded during borehole packoff events provide information on the maximum principal stress, SHmax. Taken together, the LOT and PWD observations suggest that the inner wedge at ~ 2000 meters depth is currently in a strike-slip stress regime, despite its position as the hanging wall of a main plate boundary thrust. This may be a transitional stress regime between shallow normal and deep thrust, controlled by depth-dependent magnitude of the tectonic convergence-related principal stress. Our results document for

  3. The impact of splay faults on fluid flow, solute transport, and pore pressure distribution in subduction zones: A case study offshore the Nicoya Peninsula, Costa Rica

    NASA Astrophysics Data System (ADS)

    Lauer, Rachel M.; Saffer, Demian M.

    2015-04-01

    Observations of seafloor seeps on the continental slope of many subduction zones illustrate that splay faults represent a primary hydraulic connection to the plate boundary at depth, carry deeply sourced fluids to the seafloor, and are in some cases associated with mud volcanoes. However, the role of these structures in forearc hydrogeology remains poorly quantified. We use a 2-D numerical model that simulates coupled fluid flow and solute transport driven by fluid sources from tectonically driven compaction and smectite transformation to investigate the effects of permeable splay faults on solute transport and pore pressure distribution. We focus on the Nicoya margin of Costa Rica as a case study, where previous modeling and field studies constrain flow rates, thermal structure, and margin geology. In our simulations, splay faults accommodate up to 33% of the total dewatering flux, primarily along faults that outcrop within 25 km of the trench. The distribution and fate of dehydration-derived fluids is strongly dependent on thermal structure, which determines the locus of smectite transformation. In simulations of a cold end-member margin, smectite transformation initiates 30 km from the trench, and 64% of the dehydration-derived fluids are intercepted by splay faults and carried to the middle and upper slope, rather than exiting at the trench. For a warm end-member, smectite transformation initiates 7 km from the trench, and the associated fluids are primarily transmitted to the trench via the décollement (50%), and faults intercept only 21% of these fluids. For a wide range of splay fault permeabilities, simulated fluid pressures are near lithostatic where the faults intersect overlying slope sediments, providing a viable mechanism for the formation of mud volcanoes.

  4. Deformation T-Cup: A new Kawai-style deformation device capable of controlled strain-rate deformation at pressures in excess of 20 GPa

    NASA Astrophysics Data System (ADS)

    Hunt, S. A.; Dobson, D. P.; Santangeli, J. R.; McCormack, R.; Li, L.; Whitaker, M. L.; Vaughan, M. T.; Weidner, D. J.

    2012-12-01

    A significant proportion of our understanding of the rheological properties of mantle minerals is gained by analysing the data from, both offline and synchrotron based, controlled strain-rate deformation experiments. However, controlled strain-rate deformation experiments at in-situ conditions have been limited by the current generation of deformation apparatus (the deformation-DIA and the Rotational Drickamer) to about 15 GPa. Being limited to 15 GPa means that in situ deformation experiments are limited to phases stable in the upper mantle and the upper parts of the transition-zone. Therefore, deformation experiments on mantle composition ringwoodite and majorite have not been performed in significant numbers and there are no measurements at controlled strain-rates of the lower-mantle perovskites. Here, we report the capabilities of a new device the DT-cup or deformation T-Cup, which is capable for deformation experiments at pressures in excess of 20 GPa, and with continued development in excess of 25 GPa. The two instances of the DT-Cup press at University College London and the X17B2 beamline at the NSLS, consist of 400 tonne, Paris-Edinburgh style, load frames into which split-cylinder 6-8 multi-anvil tooling is inserted, with the <111> axis of the inner cube set aligned with the action of the press. The 'top' and 'bottom' anvils of the cube set are replaced by hexagonal rods, cut so the end of the rods are the same shape as the inner faces of the 10 (X17B2 device) or 14 mm (UCL device) edge length cubes they replace. Controlled strain-rate deformation of the sample is undertaken by differential pistons pushing on the two hexagonal rams and advancing the two anvils along the aligned <111> axis of the inner cube set. As the pistons advance the main ram adjusts in order that the confining pressure exerted on the sample remains constant. The differences between the standard Kawai-style split cylinder devices and the DT-Cup are analogous to the differences between

  5. Evaluation of Pore Networks in Caprocks at Geologic Storage Sites: A Combined Study using High Temperature and Pressure Reaction Experiments, Small Angle Neutron Scattering, and Focused Ion Beam-Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Mouzakis, K. M.; Sitchler, A.; Wang, X.; McCray, J. E.; Kaszuba, J. P.; Rother, G.; Dewers, T. A.; Heath, J. E.

    2011-12-01

    Low permeability rock units, often shales or mudstones, that overlie geologic formations under consideration for CO2 sequestration will help contain injected CO2. CO2 that does flow through these rocks will dissolve into the porewaters, creating carbonic acid lowering the pH. This perturbation of the system may result in mineral dissolution or precipitation, which can change the pore structure and impact the flow properties of the caprocks. In order to investigate the impacts that reaction can have on caprock pore structure, we performed a combination of high pressure high temperature reaction experiments, small angle neutron scattering (SANS) experiments and high resolution focused ion beam-scanning electron microscope (FIB-SEM) imaging on samples from the Gothic shale and Marine Tuscaloosa Group. Small angle neutron scattering was performed on unreacted and reacted caprocks at the High Flux Isotope Reactor at Oak Ridge National Laboratory. New precipitates and pores are observed in high-resolution images of the reacted samples. The precipitates have been preliminarily identified as gypsum or anhydrite, and sulfide minerals. Results from small angle neutron scattering, a technique that provides information about pores and pore/mineral interfaces at scales ~ 5 to 300 nm, show an increased porosity and specific surface area after reaction with brine and CO2. However, there appear to be differences in how the pore networks change between the two samples that are related to sample mineralogy and original pore network structure. Changes to pores and formation of new pores may lead to different capillary sealing behavior and permeability. This combination of controlled laboratory experiments, neutron scattering and high-resolution imaging provides detailed information about the geochemical processes that occur at the pore scale as CO2 reacts with rocks underground. Such information is integral to the evaluation of large-scale CO2 sequestration as a feasible technology

  6. Accounting for pore water pressure and confined aquifers in assessing the stability of slopes: a Limit Equilibrium analysis carried out through the Minimum Lithostatic Deviation method

    NASA Astrophysics Data System (ADS)

    Ausilia Paparo, Maria; Tinti, Stefano

    2015-04-01

    The model we introduce is an implementation of the Minimum Lithostatic Deviation (MLD) method, developed by Tinti and Manucci (Tinti and Manucci 2006; 2008), that makes use of the limit equilibrium (LE) theory to estimate the stability of a slope. The main purpose here is to analyse the role of a confined aquifer on the value of the Safety Factor (F), the parameter that in the LE is used to determine if a slope is stable or unstable. The classical LE methods treat unconfined aquifers by including the water pore pressure in the Mohr-Coulomb failure formula: since the water decreases the friction shear strength, the soil above the sliding surface turns out to be more prone to instability. In case of a confined aquifer, however, due to a presence of impermeable layers, the water is not free to flow into the matrix of the overlying soil. We consider here the assumption of a permeable soil sliding over an impermeable layer, which is an occurrence that is found in several known landslide cases (e.g. Person, 2008; Strout and Tjeltja, 2008; Morgan et al., 2010 for offshore slides; and Palladino and Peck, 1972; Miller and Sias, 1998; Jiao et al. 2005; Paparo et al., 2013 for slopes in proximity of artificial or natural water basins) where clay beds form the potential sliding surface: the water, confined below, pushes along these layers and acts on the sliding body as an external bottom load. We modify the MLD method equations in order to take into account the load due to a confined aquifer and apply the new model to the Vajont case, where many have hypothesised the contribution of a confined aquifer to the failure. Our calculations show that the rain load i) infiltrating directly into the soil body and ii) penetrating into the confined aquifer below the clay layers, in addition with the lowering of the reservoir level, were key factors of destabilization of the Mt Toc flank and caused the disastrous landslide.

  7. Role of pore fluid pressure on transient strength changes and fabric development during serpentine dehydration at mantle conditions: Implications for subduction-zone seismicity

    NASA Astrophysics Data System (ADS)

    Proctor, Brooks; Hirth, Greg

    2015-07-01

    To further investigate the dehydration embrittlement hypothesis and its possible link to subduction-zone seismicity, we conducted deformation experiments on antigorite serpentinite in a Griggs-type apparatus at conditions below and above antigorite stability. Temperature ramps (crossing the antigorite thermal stability) were used in conjunction with a new experimental method that allows fluid produced during dehydration reactions to be drained, partially drained or undrained. During temperature ramps, weakening coupled with transient slip initiated at ˜ 650 °C, coincident with the predicted phase transition of antigorite to olivine and talc at ˜ 1 GPa. The weakening-rate and steady-state strength were dependent on drainage conditions; undrained samples weakened over a few minutes and supported the lowest shear stress (˜ 50 MPa), while drained samples weakened over a few hours and supported the highest shear stress (˜ 210 MPa). The coefficient of friction (shear stress over normal stress) in drained samples decreased from ˜0.4 to ˜0.16 after the temperature ramp. The strengths of samples that were first annealed at 700 °C for ˜ 12 h, then deformed, were similar to those observed in the temperature ramp experiments. Strain localization along fractures occurred in all samples during temperature ramping, regardless of the drainage conditions. However, microstructural observations indicate deformation by ductile mechanisms at higher strain under both undrained and drained conditions. The rheology and microstructures suggest dehydrating serpentinite deforms via semibrittle flow with grain-scale ductile deformation more active at high pore fluid pressures. Our results suggest that earthquakes in serpentinized mantle do not nucleate as a direct result of unstable frictional sliding along fractures generated at the onset of dehydration reactions.

  8. Excess flow shutoff valve

    DOEpatents

    Kiffer, Micah S.; Tentarelli, Stephen Clyde

    2016-02-09

    Excess flow shutoff valve comprising a valve body, a valve plug, a partition, and an activation component where the valve plug, the partition, and activation component are disposed within the valve body. A suitable flow restriction is provided to create a pressure difference between the upstream end of the valve plug and the downstream end of the valve plug when fluid flows through the valve body. The pressure difference exceeds a target pressure difference needed to activate the activation component when fluid flow through the valve body is higher than a desired rate, and thereby closes the valve.

  9. Does Extension Play a Role in Ionian Tectonics? Potential Effects of Preexisting Bounding Faults, Local Brittle Failure, and Sulfur Pore Pressure on Crustal Stresses

    NASA Astrophysics Data System (ADS)

    McKinnon, William B.; Kirchoff, M.; Bland, M.

    2013-10-01

    The majority of mountains observed on Io are tectonic, upthrusted blocks. Their formation is generally thought to be related to Io’s heat-pipe volcanism, crustal subsidence, and accompanying lateral confinement. In previous work, we demonstrated that compressional thermal stresses from sustained local or regional shut down of Io’s heat-pipe volcanism could also play a vital role in mountain formation, and help explain the anticorrelation between Io’s mountains and volcanic centers [Kirchoff and McKinnon 2009, Formation of mountains on Io: Variable volcanism and thermal stresses, Icarus 201, 598-614; Kirchoff et al. 2011, Global distribution of volcanoes and mountains on Io: Control by asthenospheric heating and implications for mountain formation, Earth Planet. Sci. Lett. 301, 22-30]. Here we refine our previous model by using an “unconfined” horizontal boundary condition (zero average lateral stress), including brittle failure (crustal plasticity), and adding sulfur to our rheological model. The unconfined horizontal boundary condition accounts for stresses released on preexisting, more distant faults; including crustal plasticity allows us to more realistically represent stresses that would exceed the brittle failure limit otherwise, and addition of sulfur to the model composition of Io’s crust further improves the rheological model of the crust. Heated and melted at depth, liquid sulfur creates pore pressure in the lower crust and profoundly reduces the brittle failure limit. Including these modifications when the volcanic eruption rate decreases introduces a region of tensional failure in the upper crust and increases the size of the region in compressional failure in the lower crust. Finite element models show that increasing compression at depth imparts substantial bending stresses, which can drive surface faulting and block rotation. Such conditions further facilitate mountain formation at the surface, and highlight the difference between Io

  10. The Association between the Phenotype of Excessive Daytime Sleepiness and Blood Pressure in Patients with Obstructive Sleep Apnea-Hypopnea Syndrome

    PubMed Central

    Wang, Qimin; Zhang, Cheng; Jia, Peng; Zhang, Jing; Feng, Liping; Wei, Shumin; Luo, Yiping; Su, Li; Zhao, Can; Dong, Hui; Ma, Jing; Wang, Guangfa

    2014-01-01

    Objective Investigate the clinical features and the blood pressure (BP) pattern of the phenotype of excessive daytime sleepiness (EDS) in OSAHS. Methods A total of 508 Chinese adults with suspected OSAHS were referred to our sleep laboratory from October 2009 to May 2012. On the same night of polysomnography (PSG), the levels of blood pressure were measured before sleeping (bedtime BP) and immediately after waking up in the next morning (morning BP). EDS was recognized as Epworth Sleepiness Scale (ESS)≥9. Subjects were classified into four groups based on the apnea-hypopnea index (AHI) from PSG as follows: control (simple snoring) group (control, n=104) with AHI<5; mild group (mild, n=89) with AHI≥5 and <15; moderate group (moderate, n=70) with AHI≥15 and<30; and severe group (severe, n=245) with AHI ≥30. The differences and correlations between BP and PSG parameters in EDS and non-EDS group of OSAHS patients were analyzed. Results In all subjects, ESS was positively correlated with morning diastolic blood pressure (DBP), Mean arterial pressure (MAP) and bedtime DBP (r=0.144, 0.102 and 0.114, respectively, each P value<0.05). In OSAHS patients, ESS was only positively correlated with morning DBP (r=0.137, P<0.05). OSAHS patients with EDS phenotype were younger and were more likely to have the symptom of waking up feeling tired (36.1% vs. 23.2%, p=0.023), who had lower MSaO2, longer SIT90 (the ratio of time of SpO2 below 90% in total sleep time) and higher DBP (bedtime as well as morning). In patients with AHI≥15, ESS was correlated positively with both bedtime and morning DBP after controlling the confounding effects of age, sex, BMI, AHI and nadir nocturnal oxygen saturation( r=0.126,0.143, respectively, both P values<0.05). And in OSAHS patients of EDS phenotype, the bedtime DBP, bedtime MAP, morning DBP, and morning MAP were 3~5 mm Hg higher than that in patients of non-EDS phenotype(P<0.05). In the moderate and severe OSAHS group, patients with EDS

  11. Effect of Pore Fluid Salinity on Compressibility and Shear Strength Development of Clayey Soils

    NASA Astrophysics Data System (ADS)

    van Paassen, Leon A.; Gareau, Laurent F.

    Investigations of shear strength, compressibility and moisture content of a recent marine clay in the Caspian Sea showed soil profiles with a lower shear strength and higher moisture content, than expected for a normally consolidated soil. Further, measured preconsolidation pressures were lower than the calculated in-situ effective stress, suggesting that the deposit was underconsolidated. The pore fluid salinity was also measured and showed an increase with depth up to saturation concentration. A research project was carried out to study the effect of pore fluid salinity on shear strength and compressibility of remoulded clays. Results of this study showed that increasing pore fluid salinity caused a decrease of the moisture content for a normally consolidated clayey soil of high plasticity. The remoulded shear strength corresponded with the measured moisture contents. The observed compressive behaviour of these clays is explained using the modified effective stress concept, which considers not only (excess) pore pressure and effective pressure, but also the electrochemical repulsive and attractive forces between the clay particles. The laboratory tests on remoulded clays show opposite results to the measurements on the natural soils. The effects of soil structure are used to explain the differences for the measurements of moisture content, undrained shear strength and preconsolidation pressure. The oedometer test procedure was reviewed and additional tests were performed on natural clay samples from this site. Results showed that the measured pre-consolidation pressure depends largely on the salinity of the permeating fluid used in the oedometer apparatus and suggest that when testing marine clays with very high pore fluid salinity, using a brine solution that closely resembles the pore fluid chemistry yields a measured preconsolidation pressure closer to the known geological stress history.

  12. Electrolyte pore/solution partitioning by expanded grand canonical ensemble Monte Carlo simulation

    SciTech Connect

    Moucka, Filip; Bratko, Dusan Luzar, Alenka

    2015-03-28

    Using a newly developed grand canonical Monte Carlo approach based on fractional exchanges of dissolved ions and water molecules, we studied equilibrium partitioning of both components between laterally extended apolar confinements and surrounding electrolyte solution. Accurate calculations of the Hamiltonian and tensorial pressure components at anisotropic conditions in the pore required the development of a novel algorithm for a self-consistent correction of nonelectrostatic cut-off effects. At pore widths above the kinetic threshold to capillary evaporation, the molality of the salt inside the confinement grows in parallel with that of the bulk phase, but presents a nonuniform width-dependence, being depleted at some and elevated at other separations. The presence of the salt enhances the layered structure in the slit and lengthens the range of inter-wall pressure exerted by the metastable liquid. Solvation pressure becomes increasingly repulsive with growing salt molality in the surrounding bath. Depending on the sign of the excess molality in the pore, the wetting free energy of pore walls is either increased or decreased by the presence of the salt. Because of simultaneous rise in the solution surface tension, which increases the free-energy cost of vapor nucleation, the rise in the apparent hydrophobicity of the walls has not been shown to enhance the volatility of the metastable liquid in the pores.

  13. Electrolyte pore/solution partitioning by expanded grand canonical ensemble Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Moucka, Filip; Bratko, Dusan; Luzar, Alenka

    2015-03-01

    Using a newly developed grand canonical Monte Carlo approach based on fractional exchanges of dissolved ions and water molecules, we studied equilibrium partitioning of both components between laterally extended apolar confinements and surrounding electrolyte solution. Accurate calculations of the Hamiltonian and tensorial pressure components at anisotropic conditions in the pore required the development of a novel algorithm for a self-consistent correction of nonelectrostatic cut-off effects. At pore widths above the kinetic threshold to capillary evaporation, the molality of the salt inside the confinement grows in parallel with that of the bulk phase, but presents a nonuniform width-dependence, being depleted at some and elevated at other separations. The presence of the salt enhances the layered structure in the slit and lengthens the range of inter-wall pressure exerted by the metastable liquid. Solvation pressure becomes increasingly repulsive with growing salt molality in the surrounding bath. Depending on the sign of the excess molality in the pore, the wetting free energy of pore walls is either increased or decreased by the presence of the salt. Because of simultaneous rise in the solution surface tension, which increases the free-energy cost of vapor nucleation, the rise in the apparent hydrophobicity of the walls has not been shown to enhance the volatility of the metastable liquid in the pores.

  14. Poring over two-pore channel pore mutants

    PubMed Central

    Penny, Christopher J.; Patel, Sandip

    2016-01-01

    Two-pore channels are members of the voltage-gated ion channel superfamily. They localise to the endolysosomal system and are likely targets for the Ca2+ mobilising messenger NAADP. In this brief review, we relate mutagenesis of the TPC pore to a recently published homology model and discuss how pore mutants are informing us of TPC function. Molecular physiology of these ubiquitous proteins is thus emerging. PMID:27226934

  15. Development of a numerical workflow based on μ-CT imaging for the determination of capillary pressure-saturation-specific interfacial area relationship in 2-phase flow pore-scale porous-media systems: a case study on Heletz sandstone

    NASA Astrophysics Data System (ADS)

    Peche, Aaron; Halisch, Matthias; Bogdan Tatomir, Alexandru; Sauter, Martin

    2016-05-01

    In this case study, we present the implementation of a finite element method (FEM)-based numerical pore-scale model that is able to track and quantify the propagating fluid-fluid interfacial area on highly complex micro-computed tomography (μ-CT)-obtained geometries. Special focus is drawn to the relationship between reservoir-specific capillary pressure (pc), wetting phase saturation (Sw) and interfacial area (awn). The basis of this approach is high-resolution μ-CT images representing the geometrical characteristics of a georeservoir sample. The successfully validated 2-phase flow model is based on the Navier-Stokes equations, including the surface tension force, in order to consider capillary effects for the computation of flow and the phase-field method for the emulation of a sharp fluid-fluid interface. In combination with specialized software packages, a complex high-resolution modelling domain can be obtained. A numerical workflow based on representative elementary volume (REV)-scale pore-size distributions is introduced. This workflow aims at the successive modification of model and model set-up for simulating, such as a type of 2-phase problem on asymmetric μ-CT-based model domains. The geometrical complexity is gradually increased, starting from idealized pore geometries until complex μ-CT-based pore network domains, whereas all domains represent geostatistics of the REV-scale core sample pore-size distribution. Finally, the model can be applied to a complex μ-CT-based model domain and the pc-Sw-awn relationship can be computed.

  16. Sublithostatic pore fluid pressure in the brittle-ductile transition zone of Mesozoic Yingxiu-Beichuan fault and its implication for the 2008 Mw 7.9 Wenchuan earthquake

    NASA Astrophysics Data System (ADS)

    Han, Liang; Zhou, Yongsheng; He, Changrong; Li, Haibing

    2016-03-01

    In order to understand the mechanism for occurrence of large earthquakes in the Longmen Shan region, we indirectly estimated the flow stress and pore fluid pressure in the brittle-ductile transition zone by studying exhumed granitic rocks which experienced Mesozoic ductile deformation, and constructed rheological profiles for the brittle regime and transition zone. The samples were collected from a small pluton that includes granites and deformed granitic rocks overthrust at an outcrop along the southern segment of the Yingxiu-Beichuan fault. The outcrop profile consists of granitic gneiss, protomylonite and mylonite. We observed that heterogeneous ductile deformation occurred in the brittle-ductile transition zone, and that the flow stress ranges from 15 to 80 MPa. Moreover, the fault in that zone experienced a temporary brittle deformation, which might indicate a high strain rate during the co-seismic process and early post-seismic creep. Secondary fluid inclusions were found and measured to define the possible range of the capture temperature and fluid pressure. Sublithostatic pore fluid pressure was determined at the capture temperatures of 330-350 °C during the process of filling and/or healing of microcracks. According to constructed rheological profiles and related mechanisms, high, sublithostatic pore fluid pressure is likely to significantly weaken the fault and to be related to inception of a brittle fault slip above the brittle-ductile transition zone. A high strain rate driven by the coseismic slip in the brittle regime may lead to a brittle fault slip in the brittle-ductile transition zone, and then plastic deformation in the transition zone may resume gradually during post-seismic creep. The focal depth of the 2008 Mw 7.9 Wenchuan earthquake may be controlled by a velocity weakening to velocity strengthening transition in frictional slip (brittle regime) of granite around a temperature of 350 °C.

  17. Pore Velocity Estimation Uncertainties

    NASA Astrophysics Data System (ADS)

    Devary, J. L.; Doctor, P. G.

    1982-08-01

    Geostatistical data analysis techniques were used to stochastically model the spatial variability of groundwater pore velocity in a potential waste repository site. Kriging algorithms were applied to Hanford Reservation data to estimate hydraulic conductivities, hydraulic head gradients, and pore velocities. A first-order Taylor series expansion for pore velocity was used to statistically combine hydraulic conductivity, hydraulic head gradient, and effective porosity surfaces and uncertainties to characterize the pore velocity uncertainty. Use of these techniques permits the estimation of pore velocity uncertainties when pore velocity measurements do not exist. Large pore velocity estimation uncertainties were found to be located in the region where the hydraulic head gradient relative uncertainty was maximal.

  18. Resolving pore-space characteristics by rate-controlled porosimetry

    SciTech Connect

    Yuan, H.H.; Swanson, B.F.

    1989-03-01

    By monitoring the mercury capillary pressure in rate-controlled porosimetry (intrusion) experiments, new information regarding the pore space of a rock sample has been obtained. With this technique, called an apparatus for pore examination (APEX), it is now possible to resolve the pore space of a rock sample into two interconnected parts. One part identifies the individual pore systems (pore bodies), which are low-energy sumps or regions of low capillarity. The other part corresponds to the pore throats that interconnect with pore systems. New capillary-pressure curves have been obtained by partitioning the total capillary-pressure curve (normal capillary-pressure curve) into two subcurves: the subison capillary-pressure curve, which details the distribution of pore bodies, and the rison capillary-pressure curve, which details the distribution of pore throats. The authors present APEX data on Berea sandstone and San Andres dolomite that show the volume distribution of low-capillarity regions within the pore space of these rocks. These regions of low capillarity are the principal pore-space regions that trap the residual nonwetting phase upon imbibition of a strongly wetting fluid, as measured by toluene/air systems. The residual nonwetting-phase saturations as determined by the APEX method and by the toluene/air method are in excellent agreement. Thus, the detailed volume distribution of pore systems responsible for trapped nonwetting-phase saturation is determined from APEX measurements, which can have important implications for EOR.

  19. Demonstration of fuel hot-spot pressure in excess of 50 Gbar for direct-drive, layered deuterium-tritium implosions on OMEGA

    DOE PAGESBeta

    Regan, S. P.; Goncharov, V. N.; Igumenshchev, I. V.; Sangster, T. C.; Betti, R.; Bose, A.; Boehly, T. R.; Bonino, M. J.; Campbell, E. M.; Cao, D.; et al

    2016-07-07

    A record fuel hot-spot pressure Phs = 56±7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium–tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility (NIF), these implosions achieved a Lawson parameter ~60% of the value required for ignition [A. Bose et al., Phys. Rev. E (in press)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is ~40%more » lower. Furthermore, three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.« less

  20. Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA

    NASA Astrophysics Data System (ADS)

    Regan, S. P.; Goncharov, V. N.; Igumenshchev, I. V.; Sangster, T. C.; Betti, R.; Bose, A.; Boehly, T. R.; Bonino, M. J.; Campbell, E. M.; Cao, D.; Collins, T. J. B.; Craxton, R. S.; Davis, A. K.; Delettrez, J. A.; Edgell, D. H.; Epstein, R.; Forrest, C. J.; Frenje, J. A.; Froula, D. H.; Gatu Johnson, M.; Glebov, V. Yu.; Harding, D. R.; Hohenberger, M.; Hu, S. X.; Jacobs-Perkins, D.; Janezic, R.; Karasik, M.; Keck, R. L.; Kelly, J. H.; Kessler, T. J.; Knauer, J. P.; Kosc, T. Z.; Loucks, S. J.; Marozas, J. A.; Marshall, F. J.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Michel, D. T.; Myatt, J. F.; Obenschain, S. P.; Petrasso, R. D.; Radha, P. B.; Rice, B.; Rosenberg, M. J.; Schmitt, A. J.; Schmitt, M. J.; Seka, W.; Shmayda, W. T.; Shoup, M. J.; Shvydky, A.; Skupsky, S.; Solodov, A. A.; Stoeckl, C.; Theobald, W.; Ulreich, J.; Wittman, M. D.; Woo, K. M.; Yaakobi, B.; Zuegel, J. D.

    2016-07-01

    A record fuel hot-spot pressure Phs=56 ±7 Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ˜60 % of the value required for ignition [A. Bose et al., Phys. Rev. E 93, LM15119ER (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance.

  1. Evolution of pore-fluid pressure during folding and basin contraction in overpressured reservoirs assessed by combined fracture analysis and calcite twinning paleopiezometry

    NASA Astrophysics Data System (ADS)

    Beaudoin, Nicolas; Lacombe, Olivier; Bellahsen, Nicolas; Amrouch, Khalid; Daniel, Jean-Marc

    2014-05-01

    Reconstructing the evolution of paleofluid (over)pressure in sedimentary basins during deformation is a challenging problem, especially when no hydrocarbon-bearing fluid inclusions are available to provide barometric constraints on the fluid system. This contribution reports the application to a natural case (the Bighorn Basin) of recent methodological advance to access fluid (over)pressure level prevailing in strata during sub-seismic fracture development. The fluid pressure evolution in the Mississippian-Permian Madison-Phosphoria carbonate reservoir is tentatively reconstructed from the early Sevier Layer Parallel Shortening to the Laramide folding in two basement-cored folds: the Sheep Mountain Anticline and the Rattlesnake Mountain Anticline, located on both edges of the Bighorn Basin. This reconstruction is based on a combination of stress inversion of fault slip data, calcite twins paleopiezometry and rock mechanics. Results point out that supra-hydrostatic pressure values prevail in the carbonate reservoir during most of its whole Sevier-Laramide history, and a coeval evolution between fluid overpressure and differential stress build-up is also emphasized. In each fold, a maximum value of 30-35 MPa for overpressure (i.e. above hydrostatic value) is recorded, just before Laramide folding, while minimum values of 0 MPa or 7 MPa are recorded during Sevier foreland flexure/forebulge and Laramide folding, respectively. After normalization to the same depth for both folds of differential stress magnitudes obtained from calcite twins paleopiezometry, the reconstructed values for the two folds can be compared and this comparison provides an image of the evolution fluid pressure levels at the basin scale. Until folding, the evolution of the fluid overpressure during deformation can be interpreted as reflecting large-scale fluid migrations in a laterally connected reservoir. The drop of fluid overpressure recorded in both folds during folding illustrates the

  2. An integral-free expression for short-term changes in fault stability due to pore pressure induced when a point load is placed on the pervious boundary of a porous elastic half space containing a fault

    NASA Astrophysics Data System (ADS)

    Chander, Ramesh; Tomar, S. K.

    2014-10-01

    A concentrated load with step-function time behaviour is placed normal to the planar, pervious boundary of a porous elastic half space (PEHS) with compressible constituents. A planar fault exists in the PEHS in such a way that the poroelastic behaviour of the medium is unhindered. We derive an approximate but integral-free expression for CFSCPP, i.e., changes in fault stability due to changes in pore pressure, at a point not too far off the line along which the load acts. But, in the interest of simplicity, the main discussion is focussed on a consideration of CFSCPP at a point P located on the fault at depth z directly beneath the load. It is convenient to introduce dimensionless time t D directly proportional to real time t. The constant of proportionality is 4 c/ z 2, where c is hydraulic diffusivity. The derived approximate expression gives results with an accuracy of greater than 99% for limited values of t D after the load is imposed. We learn from the derived expression that, for a given z, fault stability undergoes an initial sudden decrease commensurate with the undrained pore pressure induced in the PEHS. This is followed by a more gradual decrease in fault stability with increasing t D until a minimum is reached. The real time t to minimum fault stability increases with z. The magnitude of CFSCPP decreases with z as z -2 for a given t D in the permissible range. The derived expression and the inferences based on it should be useful during earth science investigations of the possible hazards due to reactivation of a pre-existing shallow fault when a civil engineering project involving imposition of a heavy load on the earth's surface is to be executed nearby. They should be useful also for investigations if a shallow earthquake occurs near such a project soon after its execution.

  3. Continuous borehole strain and pore pressure in the near field of the 28 September 2004 M 6.0 parkfield, California, earthquake: Implications for nucleation, fault response, earthquake prediction and tremor

    USGS Publications Warehouse

    Johnston, M.J.S.; Borcherdt, R.D.; Linde, A.T.; Gladwin, M.T.

    2006-01-01

    Near-field observations of high-precision borehole strain and pore pressure, show no indication of coherent accelerating strain or pore pressure during the weeks to seconds before the 28 September 2004 M 6.0 Parkfield earthquake. Minor changes in strain rate did occur at a few sites during the last 24 hr before the earthquake but these changes are neither significant nor have the form expected for strain during slip coalescence initiating fault failure. Seconds before the event, strain is stable at the 10-11 level. Final prerupture nucleation slip in the hypocentral region is constrained to have a moment less than 2 ?? 1012 N m (M 2.2) and a source size less than 30 m. Ground displacement data indicate similar constraints. Localized rupture nucleation and runaway precludes useful prediction of damaging earthquakes. Coseismic dynamic strains of about 10 microstrain peak-to-peak were superimposed on volumetric strain offsets of about 0.5 microstrain to the northwest of the epicenter and about 0.2 microstrain to the southeast of the epicenter, consistent with right lateral slip. Observed strain and Global Positioning System (GPS) offsets can be simply fit with 20 cm of slip between 4 and 10 km on a 20-km segment of the fault north of Gold Hill (M0 = 7 ?? 1017 N m). Variable slip inversion models using GPS data and seismic data indicate similar moments. Observed postseismic strain is 60% to 300% of the coseismic strain, indicating incomplete release of accumulated strain. No measurable change in fault zone compliance preceding or following the earthquake is indicated by stable earth tidal response. No indications of strain change accompany nonvolcanic tremor events reported prior to and following the earthquake.

  4. Demonstration of Fuel Hot-Spot Pressure in Excess of 50 Gbar for Direct-Drive, Layered Deuterium-Tritium Implosions on OMEGA.

    PubMed

    Regan, S P; Goncharov, V N; Igumenshchev, I V; Sangster, T C; Betti, R; Bose, A; Boehly, T R; Bonino, M J; Campbell, E M; Cao, D; Collins, T J B; Craxton, R S; Davis, A K; Delettrez, J A; Edgell, D H; Epstein, R; Forrest, C J; Frenje, J A; Froula, D H; Gatu Johnson, M; Glebov, V Yu; Harding, D R; Hohenberger, M; Hu, S X; Jacobs-Perkins, D; Janezic, R; Karasik, M; Keck, R L; Kelly, J H; Kessler, T J; Knauer, J P; Kosc, T Z; Loucks, S J; Marozas, J A; Marshall, F J; McCrory, R L; McKenty, P W; Meyerhofer, D D; Michel, D T; Myatt, J F; Obenschain, S P; Petrasso, R D; Radha, P B; Rice, B; Rosenberg, M J; Schmitt, A J; Schmitt, M J; Seka, W; Shmayda, W T; Shoup, M J; Shvydky, A; Skupsky, S; Solodov, A A; Stoeckl, C; Theobald, W; Ulreich, J; Wittman, M D; Woo, K M; Yaakobi, B; Zuegel, J D

    2016-07-01

    A record fuel hot-spot pressure P_{hs}=56±7  Gbar was inferred from x-ray and nuclear diagnostics for direct-drive inertial confinement fusion cryogenic, layered deuterium-tritium implosions on the 60-beam, 30-kJ, 351-nm OMEGA Laser System. When hydrodynamically scaled to the energy of the National Ignition Facility, these implosions achieved a Lawson parameter ∼60% of the value required for ignition [A. Bose et al., Phys. Rev. E 93, 011201(R) (2016)], similar to indirect-drive implosions [R. Betti et al., Phys. Rev. Lett. 114, 255003 (2015)], and nearly half of the direct-drive ignition-threshold pressure. Relative to symmetric, one-dimensional simulations, the inferred hot-spot pressure is approximately 40% lower. Three-dimensional simulations suggest that low-mode distortion of the hot spot seeded by laser-drive nonuniformity and target-positioning error reduces target performance. PMID:27447511

  5. Local pressure components and interfacial tensions of a liquid film in the vicinity of a solid surface with a nanometer-scale slit pore obtained by the perturbative method

    SciTech Connect

    Fujiwara, K.; Shibahara, M.

    2015-03-07

    A classical molecular dynamics simulation was conducted for a liquid-solid interfacial system with a nanometer-scale slit pore in order to reveal local thermodynamic states: local pressure components and interfacial tensions of a liquid film in the vicinity of the slit. The simulation also examined the transition mechanism between the two states of the liquid film: (a) liquid film on the slit and (b) liquid film in the slit, based on the local thermodynamic quantities from a molecular point of view. An instantaneous expression of the local pressure components and interfacial tensions, which is based on a volume perturbation, was presented to investigate time-dependent phenomena in molecular dynamics simulations. The interactions between the particles were described by the 12-6 Lennard-Jones potential, and effects of the fluid-solid interaction intensity on the local pressure components and interfacial tensions of the fluid in the vicinity of the slit were examined in detail by the presented perturbative method. The results revealed that the local pressure components tangential to the solid surface in the vicinity of the 1st fluid layer from the solid surface are different in a two dimensional plane, and the difference became pronounced in the vicinity of the corner of the slit, for cases where the fluid-solid interaction intensities are relatively strong. The results for the local interfacial tensions of the fluid inside the slit suggested that the local interfacial tensions in the vicinity of the 2nd and 3rd layers of the solid atoms from the entrance of the slit act as a trigger for the transition between the two states under the influence of a varying fluid-solid interaction.

  6. Pressure Dependent Mass Fraction in Noble Gas Mass Spectrometers: A Possible Explanation for the Excessive Dispersion in the EARTHTIME Fish Canyon/Alder Creek Inter-Calibration Experiment

    NASA Astrophysics Data System (ADS)

    Turrin, B. D.; Swisher, C. C.; Mana, S.

    2011-12-01

    Mass spectrometer fractionation bias (mass discrimination) is a ubiquitous phenomenon in noble gas mass spectroscopy and must be corrected for in order to obtain accurate-high precision isotopic ratios that are used in isotopic age calculations. Temporal variations in mass fractionation are well known phenomena and have been reported in several studies (eg. Turrin et al., 2010 and references therein). Here we report on the pressure dependency on mass spectrometer fractionation bias. In our experiment, we varied by a factor of five the signal size of aliquots of atmospheric argon delivered from an automated air pipette system. The measured mass discrimination difference (MD) as determined by the 40Ar/36Ar ratio between the 1-fold and 5-fold air pipette shots is ~5%. The air 40Ar/36Ar aliquots were measured using a MAP 215-50 operating in pulse counting mode. The air measurements were interspersed with measurements of Alder Creek (AC) sanidine and Fish Canyon (FC) sanidine that were co-irradiated for 0.75 hours. The grain sizes for the two mineral standards were chosen such that the AC sample yielded 40Ar signals of about 50 kcps, similar to that delivered by a single aliquot delivered by the air pipette. The FC grains were about 5-10 times greater (150-600 kcps) than the single air aliquot. Following the analyses, we applied the MD correction to both the FC and AC analyses. When the MD as determined from the single pipette data (which matches 40Ar beam intensity of the AC sample) is applied to both the AC and FC data a "J" of 1.579±0.001x10-4 is obtained from the FC data and an age of 1183 ±4 ka for AC. However, when the MD as determined from the multiple aliquot pipette data (with an 40Ar beam similar to that of the FC analyses) is applied to the FC data a "J" of 1.588±0.001x10-4 is obtained and an AC age of 1189 ±4 ka the same age at the 95% confidence level, the reported age for AC. We conclude that variation in MD over signal sizes typically analyzed in 40Ar

  7. Gas hydrate dissociation in sediments: Pressure-temperature evolution

    NASA Astrophysics Data System (ADS)

    Kwon, Tae-Hyuk; Cho, Gye-Chun; Santamarina, J. Carlos

    2008-03-01

    Hydrate-bearing sediments may destabilize spontaneously as part of geological processes, unavoidably during petroleum drilling/production operations or intentionally as part of gas extraction from the hydrate itself. In all cases, high pore fluid pressure generation is anticipated during hydrate dissociation. A comprehensive formulation is derived for the prediction of fluid pressure evolution in hydrate-bearing sediments subjected to thermal stimulation without mass transfer. The formulation considers pressure- and temperature-dependent volume changes in all phases, effective stress-controlled sediment compressibility, capillarity, and the relative solubilities of fluids. Salient implications are explored through parametric studies. The model properly reproduces experimental data, including the PT evolution along the phase boundary during dissociation and the effect of capillarity. Pore fluid pressure generation is proportional to the initial hydrate fraction and the sediment bulk stiffness; is inversely proportional to the initial gas fraction and gas solubility; and is limited by changes in effective stress that cause the failure of the sediment. When the sediment stiffness is high, the generated pore pressure reflects thermal and pressure changes in water, hydrate, and mineral densities. Comparative analyses for CO2 and CH4 highlight the role of gas solubility in excess pore fluid pressure generation. Dissociation in small pores experiences melting point depression due to changes in water activity, and lower pore fluid pressure generation due to the higher gas pressure in small gas bubbles. Capillarity effects may be disregarded in silts and sands, when hydrates are present in nodules and lenses and when the sediment experiences hydraulic fracture.

  8. Excessive Sweating (Hyperhidrosis)

    MedlinePlus

    ... and rashes clinical tools newsletter | contact Share | Excessive Sweating (Hyperhidrosis) Information for adults A A A Profusely ... palms. Overview Hyperhidrosis, the medical name for excessive sweating, involves overactive sweat glands, usually of a defined ...

  9. Pore space morphology analysis using maximal inscribed spheres

    NASA Astrophysics Data System (ADS)

    Silin, Dmitriy; Patzek, Tad

    2006-11-01

    A new robust algorithm analyzing the geometry and connectivity of the pore space of sedimentary rock is based on fundamental concepts of mathematical morphology. The algorithm distinguishes between the “pore bodies” and “pore throats,” and establishes their respective volumes and connectivity. The proposed algorithm also produces a stick-and-ball diagram of the rock pore space. The tests on a pack of equal spheres, for which the results are verifiable, confirm its stability. The impact of image resolution on the algorithm output is investigated on the images of computer-generated pore space. One of distinctive features of our approach is that no image thinning is applied. Instead, the information about the skeleton is stored through the maximal inscribed balls or spheres (MIS) associated with each voxel. These maximal balls retain information about the entire pore space. Comparison with the results obtained by a thinning procedure preserving some topological properties of the pore space shows that our method produces more realistic estimates of the number and shapes of pore bodies and pore throats, and the pore coordination numbers. The distribution of maximal inscribed spheres makes possible simulation of mercury injection and computation of the corresponding dimensionless capillary pressure curve. It turns out that the calculated capillary pressure curve is a robust descriptor of the pore space geometry and, in particular, can be used to determine the quality of computer-based rock reconstruction.

  10. Evaluation of the Long-Term Performance of Titanate Ceramics for Immobilization of Excess Weapons Plutonium: Results from Pressurized Unsaturated Flow and Single Pass Flow-Through Testing

    SciTech Connect

    BP McGrail; HT Schaef; JP Icenhower; PF Martin; RD Orr; VL Legore

    1999-09-13

    This report summarizes our findings from pressurized unsaturated flow (PUF) and single-pass flow-through (SPFT) experiments to date. Results from the PUF test of a Pu-bearing ceramic with enclosing surrogate high-level waste glass show that the glass reacts rapidly to alteration products. Glass reaction causes variations in the solution pH in contact with the ceramic materials. We also document variable concentrations of Pu in solution, primarily in colloidal form, which appear to be related to secular variations in solution composition. The apparent dissolution rate of the ceramic waste form, based on Ba concentrations in the effluent, is estimated at {le} 10{sup {minus}5} g/(m{sup 2} {center_dot} d). Pu-bearing colloids were recovered in the size range of 0.2 to 2 {micro}m, but it is not clear that such entities would be transported in a system that is not advective-flow dominated. Results from SPFT experiments give information on the corrosion resistance of two surrogate Pu-ceramics (Ce-pyrochlore and Ce-zirconolite) at 90 C over a pH range of 2 to 12. The two ceramics were doped with minor quantities ({approximately}0.1 mass%) of MoO{sub 3}, so that concentrations of Mo in the effluent solution could be used to monitor the reaction behavior of the materials. The data obtained thus far from experiments with durations up to 150 d do not conclusively prove that the solid-aqueous solution systems have reached steady-state conditions. Therefore, the dissolution mechanism cannot be determined. Apparent dissolution rates of the two ceramic materials based on Ce, Gd, and Mo concentrations in the effluent solutions from the SPFT are nearly identical and vary between 1.1 to 8.5 x 10{sup {minus}4} g/(m{sup 2} {center_dot} d). In addition, the data reveal a slightly amphoteric dissolution behavior, with a minimum apparent rate at pH = 7 to 8, over the pH range examined. Results from two related ceramic samples suggest that radiation damage can have a measurable effect on

  11. Problems of Excess Capacity

    NASA Technical Reports Server (NTRS)

    Douglas, G.

    1972-01-01

    The problems of excess capacity in the airline industry are discussed with focus on the following topics: load factors; fair rate of return on investment; service-quality rivalry among airlines; pricing (fare) policies; aircraft production; and the impacts of excess capacity on operating costs. Also included is a discussion of the interrelationships among these topics.

  12. Excessive acquisition in hoarding.

    PubMed

    Frost, Randy O; Tolin, David F; Steketee, Gail; Fitch, Kristin E; Selbo-Bruns, Alexandra

    2009-06-01

    Compulsive hoarding (the acquisition of and failure to discard large numbers of possessions) is associated with substantial health risk, impairment, and economic burden. However, little research has examined separate components of this definition, particularly excessive acquisition. The present study examined acquisition in hoarding. Participants, 878 self-identified with hoarding and 665 family informants (not matched to hoarding participants), completed an Internet survey. Among hoarding participants who met criteria for clinically significant hoarding, 61% met criteria for a diagnosis of compulsive buying and approximately 85% reported excessive acquisition. Family informants indicated that nearly 95% exhibited excessive acquisition. Those who acquired excessively had more severe hoarding; their hoarding had an earlier onset and resulted in more psychiatric work impairment days; and they experienced more symptoms of obsessive-compulsive disorder, depression, and anxiety. Two forms of excessive acquisition (buying and free things) each contributed independent variance in the prediction of hoarding severity and related symptoms. PMID:19261435

  13. Excessive Acquisition in Hoarding

    PubMed Central

    Frost, Randy O.; Tolin, David F.; Steketee, Gail; Fitch, Kristin E.; Selbo-Bruns, Alexandra

    2009-01-01

    Compulsive hoarding (the acquisition of and failure to discard large numbers of possessions) is associated with substantial health risk, impairment, and economic burden. However, little research has examined separate components of this definition, particularly excessive acquisition. The present study examined acquisition in hoarding. Participants, 878 self-identified with hoarding and 665 family informants (not matched to hoarding participants), completed an internet survey. Among hoarding participants who met criteria for clinically significant hoarding, 61% met criteria for a diagnosis of compulsive buying and approximately 85% reported excessive acquisition. Family informants indicated that nearly 95% exhibited excessive acquisition. Those who acquired excessively had more severe hoarding; their hoarding had an earlier onset and resulted in more psychiatric work impairment days; and they experienced more symptoms of obsessive-compulsive disorder, depression, and anxiety. Two forms of excessive acquisition (buying and free things) each contributed independent variance in the prediction of hoarding severity and related symptoms. PMID:19261435

  14. MRI and PGSE NMR Studies of Long-range, Pore-pore Interaction Effects in Gas Adsorption

    NASA Astrophysics Data System (ADS)

    Hitchcock, Iain; Rigby, Sean; Chudek, John; Holt, Liz; Lowe, John

    2011-03-01

    In this work MRI and PGSE NMR have been used to directly study the advanced condensation effect during water adsorption in a macroscopically heterogeneous sol-gel silica pellet. It has been found that capillary condensation will occur at unexpectedly lower pressures in regions of much larger pores that lie in close proximity to smaller pores.

  15. Pore networks in continental and marine mudstones: Characteristics and controls on sealing behavior

    USGS Publications Warehouse

    Heath, J.E.; Dewers, T.A.; McPherson, B.J.O.L.; Petrusak, R.; Chidsey, T.C.; Rinehart, A.J.; Mozley, P.S.

    2011-01-01

    Mudstone pore networks are strong modifiers of sedimentary basin fluid dynamics and have a critical role in the distribution of hydrocarbons and containment of injected fluids. Using core samples from continental and marine mudstones, we investigate properties of pore types and networks from a variety of geologic environments, together with estimates of capillary beam- scanning electron microscopy, suggest seven dominant mudstone pore types distinguished by geometry and connectivity. A dominant planar pore type occurs in all investigated mudstones and generally has high coordination numbers (i.e., number of neighboring connected pores). Connected networks of pores of this type contribute to high mercury capillary pressures due to small pore throats at the junctions of connected pores and likely control most matrix transport in these mudstones. Other pore types are related to authigenic (e.g., replacement or pore-lining precipitation) clay minerals and pyrite nodules; pores in clay packets adjacent to larger, more competent clastic grains; pores in organic phases; and stylolitic and microfracture-related pores. Pores within regions of authigenic clay minerals often form small isolated networks (<3 ??m). Pores in stringers of organic phases occur as tubular pores or slit- and/or sheet-like pores. These form short, connected lengths in 3D reconstructions, but appear to form networks no larger than a few microns in size. Sealing efficiency of the studied mudstones increases with greater distal depositional environments and greater maximum depth of burial. ?? 2011 Geological Society of America.

  16. Pore structure analysis of American coals

    SciTech Connect

    Gallegos, D.P.; Smith, D.M.; Stermer, D.L.

    1987-01-01

    The pore structure of 19 American coals, representing a wide range of rank and geographic origin, has been studied via gas adsorption, mercury porosimetry, helium displacement and NMR spin-lattice relaxation measurements. Nitrogen adsorption at 77 K was used to determine surface area in the pore range of r/sub p/ > approx. = 1nm and carbon dioxide adsorption at 273 K was used to obtain the total surface area. Porosimetry results were complicated by inter-particle void filling, surface roughness/porosity and sample compression. By employing a range of particle sizes, information concerning the relative magnitude of these mechanisms was ascertained as a function of pressure. Spin-lattice relaxation measurements of water contained in saturated coal were used to find pore size distributions over a broad range of T/sub 1/, the spin-lattice relaxation time. Good qualitative agreement was obtained between these measurements and gas adsorption/condensation results. 13 refs., 3 figs., 1 tab.

  17. Excessive Blinking in Children

    MedlinePlus

    ... scratch on the front surface of the eye), conjunctivitis (pink eye), foreign body in the eye, or ... is excessive blinking treated? If an abrasion or conjunctivitis is diagnosed, eye drops or ointment may be ...

  18. Electrokinetic induced solute dispersion in porous media; pore network modeling

    NASA Astrophysics Data System (ADS)

    Li, Shuai; Schotting, Ruud; Raoof, Amir

    2013-04-01

    Electrokinetic flow plays an important role in remediation process, separation technique, and chromatography. The solute dispersion is a key parameter to determine transport efficiency. In this study, we present the electrokinetic effects on solute dispersion in porous media at the pore scale, using a pore network model. The analytical solution of the electrokinetic coupling coefficient was obtained to quantity the fluid flow velocity in a cylinder capillary. The effect of electrical double layer on the electrokinetic coupling coefficient was investigated by applying different ionic concentration. By averaging the velocity over cross section within a single pore, the average flux was obtained. Applying such single pore relationships, in the thin electrical double layer limit, to each and every pore within the pore network, potential distribution and the induced fluid flow was calculated for the whole domain. The resulting pore velocities were used to simulate solute transport within the pore network. By averaging the results, we obtained the breakthrough curve (BTC) of the average concentration at the outlet of the pore network. Optimizing the solution of continuum scale advection-dispersion equation to such a BTC, solute dispersion coefficient was estimated. We have compared the dispersion caused by electrokinetic flow and pure pressure driven flow under different Peclet number values. In addition, the effect of microstructure and topological properties of porous media on fluid flow and solute dispersion is presented, mainly based on different pore coordination numbers.

  19. Modelling multiphase dynamics during infiltration using a pore network model

    NASA Astrophysics Data System (ADS)

    Tzavaras, Jannis; Arns, Ji-Youns; Max, Koehne; Hans-Joerg, Vogel

    2013-04-01

    We present an implementation of water infiltration into a pore network model where the local water pressures is continuously updated during the transient process. The network geometry is designed to represent structured soil which is different from simple granular porous media in some respect: Pores are more elongated and less isometric and the pore size distribution is much wider and structured hierarchically. To reproduce these properties, the classical concept of pore-bodies and throats is replaced by direct measurements of pore topology and the pores below the minimal pore size of the network model are represented by a continuous network of water saturated micro pores. The latter ensures that the water phase is always continuous which affects the propagation of the water potential during infiltration. The network model is based on cylindrical pores and considers capillary and gravitational forces. The propagation of interfaces is calculated for each time step by repeatedly solving the complete set of linear equation arising from Kirchhoff's law based on mass balance at each node of the network. This is done using the public domain package ITPack. The successive overrelaxation (SOR) and the Jacobi conjugate gradient (JCG) method proved to be more robust and faster than other solvers tested for the complex topology. The model accounts for entrapped air which is assumed to be incompressible. We present first results demonstrating the impact of external forcing (i.e infiltration rate) and pore topology on the dynamics of water-gas interfaces, the volume of entrapped air and hysteresis.

  20. Process of inducing pores in membranes by melittin

    PubMed Central

    Lee, Ming-Tao; Sun, Tzu-Lin; Hung, Wei-Chin; Huang, Huey W.

    2013-01-01

    Melittin is a prototype of the ubiquitous antimicrobial peptides that induce pores in membranes. It is commonly used as a molecular device for membrane permeabilization. Even at concentrations in the nanomolar range, melittin can induce transient pores that allow transmembrane conduction of atomic ions but not leakage of glucose or larger molecules. At micromolar concentrations, melittin induces stable pores allowing transmembrane leakage of molecules up to tens of kilodaltons, corresponding to its antimicrobial activities. Despite extensive studies, aspects of the molecular mechanism for pore formation remain unclear. To clarify the mechanism, one must know the states of the melittin-bound membrane before and after the process. By correlating experiments using giant unilamellar vesicles with those of peptide-lipid multilayers, we found that melittin bound on the vesicle translocated and redistributed to both sides of the membrane before the formation of stable pores. Furthermore, stable pores are formed only above a critical peptide-to-lipid ratio. The initial states for transient and stable pores are different, which implies different mechanisms at low and high peptide concentrations. To determine the lipidic structure of the pore, the pores in peptide–lipid multilayers were induced to form a lattice and examined by anomalous X-ray diffraction. The electron density distribution of lipid labels shows that the pore is formed by merging of two interfaces through a hole. The molecular property of melittin is such that it adsorbs strongly to the bilayer interface. Pore formation can be viewed as the bilayer adopting a lipid configuration to accommodate its excessive interfacial area. PMID:23940362

  1. The pore space scramble

    NASA Astrophysics Data System (ADS)

    Gormally, Alexandra; Bentham, Michelle; Vermeylen, Saskia; Markusson, Nils

    2015-04-01

    Climate change and energy security continue to be the context of the transition to a secure, affordable and low carbon energy future, both in the UK and beyond. This is reflected in for example, binding climate policy targets at the EU level, the introduction of renewable energy targets, and has also led to an increasing interest in Carbon Capture and Storage (CCS) technology with its potential to help mitigate against the effects of CO2 emissions from fossil fuel burning. The UK has proposed a three phase strategy to integrate CCS into its energy system in the long term focussing on off-shore subsurface storage (DECC, 2014). The potential of CCS therefore, raises a number of challenging questions and issues surrounding the long-term storage of CO2 captured and injected into underground spaces and, alongside other novel uses of the subsurface, contributes to opening a new field for discussion on the governance of the subsurface. Such 'novel' uses of the subsurface have lead to it becoming an increasingly contested space in terms of its governance, with issues emerging around the role of ownership, liability and property rights of subsurface pore space. For instance, questions over the legal ownership of pore space have arisen with ambiguity over the legal standpoint of the surface owner and those wanting to utilise the pore space for gas storage, and suggestions of whether there are depths at which legal 'ownership' becomes obsolete (Barton, 2014). Here we propose to discuss this 'pore space scramble' and provide examples of the competing trajectories of different stakeholders, particularly in the off-shore context given its priority in the UK. We also propose to highlight the current ambiguity around property law of pore space in the UK with reference to approaches currently taken in different national contexts. Ultimately we delineate contrasting models of governance to illustrate the choices we face and consider the ethics of these models for the common good

  2. Magnetic-resonance pore imaging of nonsymmetric microscopic pore shapes

    NASA Astrophysics Data System (ADS)

    Hertel, Stefan Andreas; Wang, Xindi; Hosking, Peter; Simpson, M. Cather; Hunter, Mark; Galvosas, Petrik

    2015-07-01

    Imaging of the microstructure of porous media such as biological tissue or porous solids is of high interest in health science and technology, engineering and material science. Magnetic resonance pore imaging (MRPI) is a recent technique based on nuclear magnetic resonance (NMR) which allows us to acquire images of the average pore shape in a given sample. Here we provide details on the experimental design, challenges, and requirements of MRPI, including its calibration procedures. Utilizing a laser-machined phantom sample, we present images of microscopic pores with a hemiequilateral triangular shape even in the presence of NMR relaxation effects at the pore walls. We therefore show that MRPI is applicable to porous samples without a priori knowledge about their pore shape and symmetry. Furthermore, we introduce "MRPI mapping," which combines MRPI with conventional magnetic resonance imaging (MRI). This enables one to resolve microscopic pore sizes and shapes spatially, thus expanding the application of MRPI to samples with heterogeneous distributions of pores.

  3. Soils, Pores, and NMR

    NASA Astrophysics Data System (ADS)

    Pohlmeier, Andreas; Haber-Pohlmeier, Sabina; Haber, Agnes; Sucre, Oscar; Stingaciu, Laura; Stapf, Siegfried; Blümich, Bernhard

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 < 5 ms. Moreover, the dependence of the relaxation rate on magnetic field strength allows the identification of 2D diffusion at the interfaces as the mechanism which governs the relaxation process (Pohlmeier et al. 2009). T2 relaxation curves are frequently measured for the rapid characterization of soils by means of the CPMG echo train. Basically, they contain the same information about the pore systems like T1 curves, since mostly the overall relaxation is dominated by surface relaxivity and the surface/volume ratio of the pores. However, one must be aware that T2 relaxation is additionally affected by diffusion in internal gradients, and this can be overcome by using sufficiently short echo times and low magnetic fields (Stingaciu et al. 2009). Second, the logic continuation of conventional relaxation measurements is the 2-dimensional experiment, where prior to the final detection of the CPMG echo train an encoding period is applied. This can be T1-encoding by an inversion pulse, or T2 encoding by a sequence of 90 and 180° pulses. During the following evolution time the separately encoded signals can mix and this reveals information about

  4. Mechanical and transport properties of rocks at high temperatures and pressures. Task II. Fracture permeability of crystalline rocks as a function of temperature, pressure, and hydrothermal alteration. Final report

    SciTech Connect

    Johnson, B.

    1985-11-01

    Pore-fluid chemical interactions on both short and long time scales can significantly change the permeability of a rock. Measurement of the permeability variations requires adaption and modification on standard measurement systems, with special attention given to pore-fluid flow rates and metal corrosion of system components. In this report, system requirements and capabilities are reviewed, analyzed, and recommendations made. Special attention is given to the choice of corrosion resistant metals, fluid-flow systems, back-pressure systems, jacketing materials, and flow-rate measurement. On the basis of this study, an economical, highly flexible, permeability system was designed and built. The system allows measurement of permeability over the darcy to nanodarcy range, using geologically meaningful, chemically reactive, pore fluids under constant volume flow rates as small as 0.2 ml/day at temperatures in excess of 300C, fluid pressures to 20 MPa, and confining pressures to 100 MPa. 7 refs., 3 figs., 1 tab.

  5. Ion transport and dehydration in sub-nanoscale pores

    NASA Astrophysics Data System (ADS)

    Sahu, Subin; di Ventra, Massimiliano; Zwolak, Michael

    Ions in solution develop tightly bound layers of water - hydration layers - which stabilize disassociation and enable ionic currents to flow. Sub-nanometer pores in a membrane enable ions to pass provided that they shed their hydration shell. This process has an associated large energy penalty that is predicted to give rise to ''quantized'' steps in the ionic conductance. Using all-atom molecular dynamics simulation, we demonstrate that the ionic current begins to show nonlinear behavior as the radius of the pore is reduced to the sub-nanometer scale. This nonlinear behavior is seen as a sharp rise in the pore resistance and excess noise in the current. Our work sheds light on basic mechanism of ion transport through sub-nanoscale pores. S. Sahu acknowledges support by UMD/CNST Cooperative Research Agreement, Award 70NANB10H193 through University of Maryland.

  6. Pore facies analysis: incorporation of rock properties into pore geometry based classes in a Permo-Triassic carbonate reservoir in the Persian Gulf

    NASA Astrophysics Data System (ADS)

    Rahimpour-Bonab, H.; Aliakbardoust, E.

    2014-06-01

    Pore facies analysis is a useful method for the classification of reservoir rocks according to pore geometry characteristics. The importance of this method is related to the dependence of the dynamic behaviour of the reservoir rock on the pore geometry. In this study, pore facies analysis was performed by the quantification and classification of the mercury injection capillary pressure (MICP) curves applying the multi-resolution graph-based clustering (MRGC) method. Each pore facies includes a limited variety of rock samples with different depositional fabrics and diagenetic histories, which are representative of one type of pore geometry. The present pore geometry is the result of the interaction between the primary rock fabric and its diagenetic overprint. Thus the variations in petrographic properties can be correlated with the pore geometry characteristics. Accordingly, the controlling parameters in the pore geometry characteristics were revealed by detailed petrographic analysis in each pore facies. The reservoir rock samples were then classified using the determined petrographic properties which control the pore system quality. This method is proposed for the classification of reservoir rocks in complicated carbonate reservoirs, in order to reduce the incompatibility of traditional facies analysis with pore system characteristics. The method is applicable where enough capillary pressure data is not available.

  7. Molecular Dynamics Simulations of Hydrophilic Pores in Lipid Bilayers

    PubMed Central

    Leontiadou, Hari; Mark, Alan E.; Marrink, Siewert J.

    2004-01-01

    Hydrophilic pores are formed in peptide free lipid bilayers under mechanical stress. It has been proposed that the transport of ionic species across such membranes is largely determined by the existence of such meta-stable hydrophilic pores. To study the properties of these structures and understand the mechanism by which pore expansion leads to membrane rupture, a series of molecular dynamics simulations of a dipalmitoylphosphatidylcholine (DPPC) bilayer have been conducted. The system was simulated in two different states; first, as a bilayer containing a meta-stable pore and second, as an equilibrated bilayer without a pore. Surface tension in both cases was applied to study the formation and stability of hydrophilic pores inside the bilayers. It is observed that below a critical threshold tension of ∼38 mN/m the pores are stabilized. The minimum radius at which a pore can be stabilized is 0.7 nm. Based on the critical threshold tension the line tension of the bilayer was estimated to be ∼3 × 10−11 N, in good agreement with experimental measurements. The flux of water molecules through these stabilized pores was analyzed, and the structure and size of the pores characterized. When the lateral pressure exceeds the threshold tension, the pores become unstable and start to expand causing the rupture of the membrane. In the simulations the mechanical threshold tension necessary to cause rupture of the membrane on a nanosecond timescale is much higher in the case of the equilibrated bilayers, as compared with membranes containing preexisting pores. PMID:15041656

  8. Reducing Excessive Television Viewing.

    ERIC Educational Resources Information Center

    Jason, Leonard A.; Rooney-Rebeck, Patty

    1984-01-01

    A youngster who excessively watched television was placed on a modified token economy: earned tokens were used to activate the television for set periods of time. Positive effects resulted in the child's school work, in the amount of time his family spent together, and in his mother's perception of family social support. (KH)

  9. HIV Excess Cancers JNCI

    Cancer.gov

    In 2010, an estimated 7,760 new cancers were diagnosed among the nearly 900,000 Americans known to be living with HIV infection. According to the first comprehensive study in the United States, approximately half of these cancers were in excess of what wo

  10. Finite Element and Experimental Analysis of Closure and Contact Bonding of Pores During Hot Rolling of Steel

    NASA Astrophysics Data System (ADS)

    Joo, Soo-Hyun; Jung, Jaimyun; Chun, Myung Sik; Moon, Chang Ho; Lee, Sunghak; Kim, Hyoung Seop

    2014-08-01

    The closure and contact bonding behavior of internal pores in steel slabs during hot rolling was studied using experiments and the finite element method (FEM). Effects of pore size and shape were investigated, and three different cases of pore closure results were observed: no closure, partial closure, and full closure. The FEM results well reproduced various closure events. Bonding strengths of unsuccessfully closed pores, measured by tensile tests, showed critical effects. Also, there was a difference in bonding strengths of several fully closed pores. Fracture surfaces showed that welded regions could be divided into three (not, partially, and perfectly) welded regions. The pressure-time curves obtained from the FEM results indicate that pore surface contact time and deformed surface length are important parameters in pore welding. Pore size, pore shape, time of pressure contact, and deformed surface length should be considered to completely eliminate pores in final products.

  11. Dependence of hydrogen permeabilities of isotropic graphites on the pore structure

    NASA Astrophysics Data System (ADS)

    Yamawaki, M.; Yamaguchi, K.; Suzuki, Y.; Tanaka, S.

    1991-03-01

    The permeation behavior of molecular hydrogen through isotropic graphites is investigated. The observed dependences of the permeation rate on pressure, specimen thickness, temperature and molecular weight suggest that hydrogen permeates by molecular flow, probably through open pores. A simple pore structure model is developed and is compared with the experimental results. It is revealed that hydrogen permeation through isotropic graphites depends not only on the pore size or the porosity, but also on the pore size distribution and tortuosity.

  12. Gaseous Diffusion and Pore Structure in Nuclear Graphites.

    NASA Astrophysics Data System (ADS)

    Mays, Timothy John

    Available from UMI in association with The British Library. With the incentive of providing more information for oxidation and safety studies of graphite components in thermal nuclear reactors, a new method has been developed to determine the gas transport pore structure in nuclear graphites. It involves an analysis of the dependence on pressure of the isobaric, isothermal (room temperature) diffusivity ratios of components in a binary gas mixture flowing through annular graphite samples. A Wicke-Kallenbach apparatus was specially built to measure He-Ar diffusivity ratios at pressures below 100 Torr. The new apparatus incorporates capacitance manometers and servovalves for pressure measurement and control, hot wire meters for flow rate measurements, and a mass spectrometer for gas analysis. As pressure decreased, the diffusivity ratios were observed to decrease non-linearly, indicating that the mechanism of flow in the materials was in the transition region between molecular and Knudsen diffusion. A mathematical model was derived to relate the pressure dependence of the transition diffusivity ratio to gas transport pore structure, and a statistical analysis based on Tikhonov regularisation was developed which gave a good fit of the model to the data, and optimal estimates of the number of model capillary pores, and the distribution of pore sizes. In comparison, the established methods of molecular diffusion and permeation (flow of pure gases) only give mean data on the pore size distribution. Pore structure data from the new method accurately predicted CO_2-Ar molecular diffusivity ratios, but overestimated N_2 permeability coefficients, due, it was assumed, to differences between diffusion and permeation pore structure. The cumulative volume distributions for transport pores from the transition diffusion data were similar in shape to those for open pores from mercury porosimetry, but shifted towards higher pore radii, indicating that diffusion is not so influenced

  13. Pore dynamics in lipid membranes

    NASA Astrophysics Data System (ADS)

    Gozen, I.; Dommersnes, P.

    2014-09-01

    Transient circular pores can open in plasma membrane of cells due to mechanical stress, and failure to repair such pores lead to cell death. Similar pores in the form of defects also exist among smectic membranes, such as in myelin sheaths or mitochondrial membranes. The formation and growth of membrane defects are associated with diseases, for example multiple sclerosis. A deeper understanding of membrane pore dynamics can provide a more refined picture of membrane integrity-related disease development, and possibly also treatment options and strategies. Pore dynamics is also of great importance regarding healthcare applications such as drug delivery, gene or as recently been implied, cancer therapy. The dynamics of pores significantly differ in stacks which are confined in 2D compared to those in cells or vesicles. In this short review, we will summarize the dynamics of different types of pores that can be observed in biological membranes, which include circular transient, fusion and hemi-fusion pores. We will dedicate a section to floral and fractal pores which were discovered a few years ago and have highly peculiar characteristics. Finally, we will discuss the repair mechanisms of large area pores in conjunction with the current cell membrane repair hypotheses.

  14. Pore size engineering applied to starved electrochemical cells and batteries

    NASA Technical Reports Server (NTRS)

    Abbey, K. M.; Thaller, L. H.

    1982-01-01

    To maximize performance in starved, multiplate cells, the cell design should rely on techniques which widen the volume tolerance characteristics. These involve engineering capillary pressure differences between the components of an electrochemical cell and using these forces to promote redistribution of electrolyte to the desired optimum values. This can be implemented in practice by prescribing pore size distributions for porous back-up plates, reservoirs, and electrodes. In addition, electrolyte volume management can be controlled by incorporating different pore size distributions into the separator. In a nickel/hydrogen cell, the separator must contain pores similar in size to the small pores of both the nickel and hydrogen electrodes in order to maintain an optimum conductive path for the electrolyte. The pore size distributions of all components should overlap in such a way as to prevent drying of the separator and/or flooding of the hydrogen electrode.

  15. The otherness of sexuality: excess.

    PubMed

    Stein, Ruth

    2008-03-01

    The present essay, the second of a series of three, aims at developing an experience-near account of sexuality by rehabilitating the idea of excess and its place in sexual experience. It is suggested that various types of excess, such as excess of excitation (Freud), the excess of the other (Laplanche), excess beyond symbolization and the excess of the forbidden object of desire (Leviticus; Lacan) work synergistically to constitute the compelling power of sexuality. In addition to these notions, further notions of excess touch on its transformative potential. Such notions address excess that shatters psychic structures and that is actively sought so as to enable new ones to evolve (Bersani). Work is quoted that regards excess as a way of dealing with our lonely, discontinuous being by using the "excessive" cosmic energy circulating through us to achieve continuity against death (Bataille). Two contemporary analytic thinkers are engaged who deal with the object-relational and intersubjective vicissitudes of excess. PMID:18430702

  16. Extrusion of transmitter, water and ions generates forces to close fusion pore.

    PubMed

    Tajparast, M; Glavinović, M I

    2009-05-01

    During exocytosis the fusion pore opens rapidly, then dilates gradually, and may subsequently close completely, but what controls its dynamics is not well understood. In this study we focus our attention on forces acting on the pore wall, and which are generated solely by the passage of transmitter, ions and water through the open fusion pore. The transport through the charged cylindrical nano-size pore is simulated using a coupled system of Poisson-Nernst-Planck and Navier-Stokes equations and the forces that act radially on the wall of the fusion pore are then estimated. Four forces are considered: a) inertial force, b) pressure, c) viscotic force, and d) electrostatic force. The inertial and viscotic forces are small, but the electrostatic force and the pressure are typically significant. High vesicular pressure tends to open the fusion pore, but the pressure induced by the transport of charged particles (glutamate, ions), which is predominant when the pore wall charge density is high tends to close the pore. The electrostatic force, which also depends on the charge density on the pore wall, is weakly repulsive before the pore dilates, but becomes attractive and pronounced as the pore dilates. Given that the vesicular concentration of free transmitter can change rapidly due to the release, or owing to the dissociation from the gel matrix, we evaluated how much and how rapidly a change of the vesicular K(+)-glutamate(-) concentration affects the concentration of glutamate(-) and ions in the pore and how such changes alter the radial force on the wall of the fusion pore. A step-like rise of the vesicular K(+)-glutamate(-) concentration leads to a chain of events. Pore concentration (and efflux) of both K(+) and glutamate(-) rise reaching their new steady-state values in less than 100 ns. Interestingly within a similar time interval the pore concentration of Na(+) also rises, whereas that of Cl(-) diminishes, although their extra-cellular concentration does not

  17. Pore size and pore throat types in a heterogeneous dolostone reservoir, Devonian Grosmont formation, western Canada sedimentary basin

    SciTech Connect

    Luo, P.; Machel, H. G.

    1995-11-01

    The Devonian Grosmont Formation in northeastern Alberta, Canada, is a giant heavy-oil reservoir. The main reservoir rocks are dolomitized and karstified platform and ramp carbonates, and the best reservoir facies occur in the upper Grosmont (UGM) units 3 and 2. In these units, reservoir properties are highly heterogeneous. Hand specimen, thin section, UV, and SEM petrography, as well as grading scales, mercury capillary pressure curve analysis, and statistics, have been used to characterize reservoir heterogeneity. Our investigation led to a new pore size classification for carbonate reservoirs; this new classification has four pore sizes: microporosity (pore diameters <1 {mu}m), mesoporosity (pore diameters 1-1000 {mu}m), macroporosity (pore diameters 1-256 mm), and megaporosity (pore diameters >256 mm). A combination of microscopic observations and capillary pressure curve characteristics led to the recognition of four pore throat texture types on the microporosity scale, and to five types on the mesoporosity scale. Microporosity pore types include (1) intracrystal dissolution porosity, (2) pervasive intercrystal and intracrystal dissolution porosity, (3) intergranular and/or intercrystal porosity in grainstones, and (4) primary or solution microporosity in mud matrix (only in limestones). Mesoporosity pore types include (1) intercrystal porosity, (2) solution-enhanced intercrystal porosity, (3) oversized porosity, (4) intragranular solution porosity, and (5) intergranular solution porosity. Some of these types are homogeneous (e.g., non-fabric selective dissolution porosity and intercrystal primary porosity), whereas others are heterogeneous. Generally, hydrocarbon recovery efficiency is good in the homogeneous pore throat types, but poor in the heterogeneous types.

  18. Cilia and Nuclear Pore Proteins: Pore No More?

    PubMed

    Obado, Samson O; Rout, Michael P

    2016-09-12

    Nuclear pore proteins at the base of cilia were thought to regulate transport into cilia. In this issue of Developmental Cell, Del Viso et al. (2016) challenge this view, showing instead that pore proteins localize to ciliary basal bodies and that their perturbation leads to congenital heart disease. PMID:27623377

  19. Nanometer-Scale Pore Characteristics of Lacustrine Shale, Songliao Basin, NE China

    PubMed Central

    Wang, Min; Yang, Jinxiu; Wang, Zhiwei; Lu, Shuangfang

    2015-01-01

    In shale, liquid hydrocarbons are accumulated mainly in nanometer-scale pores or fractures, so the pore types and PSDs (pore size distributions) play a major role in the shale oil occurrence (free or absorbed state), amount of oil, and flow features. The pore types and PSDs of marine shale have been well studied; however, research on lacustrine shale is rare, especially for shale in the oil generation window, although lacustrine shale is deposited widely around the world. To investigate the relationship between nanometer-scale pores and oil occurrence in the lacustrine shale, 10 lacustrine shale core samples from Songliao Basin, NE China were analyzed. Analyses of these samples included geochemical measurements, SEM (scanning electron microscope) observations, low pressure CO2 and N2 adsorption, and high-pressure mercury injection experiments. Analysis results indicate that: (1) Pore types in the lacustrine shale include inter-matrix pores, intergranular pores, organic matter pores, and dissolution pores, and these pores are dominated by mesopores and micropores; (2) There is no apparent correlation between pore volumes and clay content, however, a weak negative correlation is present between total pore volume and carbonate content; (3) Pores in lacustrine shale are well developed when the organic matter maturity (Ro) is >1.0% and the pore volume is positively correlated with the TOC (total organic carbon) content. The statistical results suggest that oil in lacustrine shale mainly occurs in pores with diameters larger than 40 nm. However, more research is needed to determine whether this minimum pore diameter for oil occurrence in lacustrine shale is widely applicable. PMID:26285123

  20. Nanometer-Scale Pore Characteristics of Lacustrine Shale, Songliao Basin, NE China.

    PubMed

    Wang, Min; Yang, Jinxiu; Wang, Zhiwei; Lu, Shuangfang

    2015-01-01

    In shale, liquid hydrocarbons are accumulated mainly in nanometer-scale pores or fractures, so the pore types and PSDs (pore size distributions) play a major role in the shale oil occurrence (free or absorbed state), amount of oil, and flow features. The pore types and PSDs of marine shale have been well studied; however, research on lacustrine shale is rare, especially for shale in the oil generation window, although lacustrine shale is deposited widely around the world. To investigate the relationship between nanometer-scale pores and oil occurrence in the lacustrine shale, 10 lacustrine shale core samples from Songliao Basin, NE China were analyzed. Analyses of these samples included geochemical measurements, SEM (scanning electron microscope) observations, low pressure CO2 and N2 adsorption, and high-pressure mercury injection experiments. Analysis results indicate that: (1) Pore types in the lacustrine shale include inter-matrix pores, intergranular pores, organic matter pores, and dissolution pores, and these pores are dominated by mesopores and micropores; (2) There is no apparent correlation between pore volumes and clay content, however, a weak negative correlation is present between total pore volume and carbonate content; (3) Pores in lacustrine shale are well developed when the organic matter maturity (Ro) is >1.0% and the pore volume is positively correlated with the TOC (total organic carbon) content. The statistical results suggest that oil in lacustrine shale mainly occurs in pores with diameters larger than 40 nm. However, more research is needed to determine whether this minimum pore diameter for oil occurrence in lacustrine shale is widely applicable. PMID:26285123

  1. Silicon Pore Optics Technology

    NASA Astrophysics Data System (ADS)

    Beijersbergen, Marco; Collon, M. J.; Günther, R.; Partapsing, R.; Ackermann, M.; Olde Riekerink, M.; Cooper-Jensen, C.; Christensen, F.; Freyberg, M.; Krumrey, M.; Erhard, M.; van Baren, C.; Wallace, K.; Bavdaz, M.

    2009-01-01

    Silicon pore optics have been developed over the last years to enable future astrophysical X-ray telescopes and have now become a candidate mirror technology for the IXO mission. Scientific requirements demand an angular resolution better than 5” and a large effective area of several square meters at photon energies of 1 keV. This paper discusses the performance of the latest generation of these novel light, stiff and modular X-ray optics, based on ribbed plates made from commercial high grade 12” silicon wafers. Stacks with several tens of silicon plates have been assembled in the course of an ESA technology development program, by bending the plates into an accurate shape and directly bonding them on top of each other. Several mirror modules, using two stacks each, have been aligned and integrated to form the conical approximation of a Wolter-I design. This paper presents the status of the technology, addresses and discusses a number of activities in the ongoing ESA technology development and shows the latest results of full area measurements at the long-beamline MPE X-ray test facility (PANTER) and the PTB beam line at the BESSY electron storage ring in Berlin.

  2. CO2 Sorption to Subsingle Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction Measurements

    SciTech Connect

    Rother, Gernot; Ilton, Eugene S.; Wallacher, Dirk; Hauβ, Thomas; Schaef, Herbert T.; Qafoku, Odeta; Rosso, Kevin M.; Felmy, Andrew R.; Krukowski, Elizabeth G.; Stack, Andrew G.; Grimm, Nico; Bodnar, Robert J.

    2013-01-02

    Geologic storage of CO2 requires that the caprock sealing the storage rock is highly impermeable to CO2. Swelling clays, which are important components of caprocks, may interact with CO2 leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO2 with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of ≈0.15 g/cm3, followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO2 bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO2 are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO2 in the clay pores is relatively stable over a wide range of CO2 pressures at a given temperature, indicating the formation of a clay-CO2 phase. Finally, at the excess sorption maximum, increasing CO2 sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.

  3. CO2 sorption to subsingle hydration layer montmorillonite clay studied by excess sorption and neutron diffraction measurements.

    PubMed

    Rother, Gernot; Ilton, Eugene S; Wallacher, Dirk; Hauβ, Thomas; Schaef, Herbert T; Qafoku, Odeta; Rosso, Kevin M; Felmy, Andrew R; Krukowski, Elizabeth G; Stack, Andrew G; Grimm, Nico; Bodnar, Robert J

    2013-01-01

    Geologic storage of CO(2) requires that the caprock sealing the storage rock is highly impermeable to CO(2). Swelling clays, which are important components of caprocks, may interact with CO(2) leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO(2) with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO(2) densities of ≈ 0.15 g/cm(3), followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO(2) bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO(2) are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO(2) in the clay pores is relatively stable over a wide range of CO(2) pressures at a given temperature, indicating the formation of a clay-CO(2) phase. At the excess sorption maximum, increasing CO(2) sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence. PMID:22917276

  4. Conical tungsten stamps for the replication of pore arrays in anodic aluminium oxide films

    NASA Astrophysics Data System (ADS)

    LeClere, D. J.; Thompson, G. E.; Derby, B.

    2009-06-01

    A tungsten master stamp has been generated by applying a novel procedure that includes two-step anodizing, followed by sequential anodizing and pore widening to develop nominally funnelled pores. These conical-shaped pores were filled with tungsten by sputter coating to manufacture a master stamp. Under a pressure of 65 MPa, the master stamp successfully embossed the surface of annealed and electropolished aluminium. The embossed surface was then used to control the position of pores created by anodizing under the conditions used to produce the original pore array.

  5. Conical tungsten stamps for the replication of pore arrays in anodic aluminium oxide films.

    PubMed

    LeClere, D J; Thompson, G E; Derby, B

    2009-06-17

    A tungsten master stamp has been generated by applying a novel procedure that includes two-step anodizing, followed by sequential anodizing and pore widening to develop nominally funnelled pores. These conical-shaped pores were filled with tungsten by sputter coating to manufacture a master stamp. Under a pressure of 65 MPa, the master stamp successfully embossed the surface of annealed and electropolished aluminium. The embossed surface was then used to control the position of pores created by anodizing under the conditions used to produce the original pore array. PMID:19468168

  6. Pore destruction resulting from mechanical thermal expression

    SciTech Connect

    Clayton, S.A.; Wheeler, R.A.; Hoadley, A.F.A.

    2007-07-01

    Mechanical thermal expression (MTE) is a dewatering technology ideally suited for the dewatering of internally porous biomaterials. For such materials, the combined application of temperature and compressive force in the MTE process enhances the collapse of the porous structure, resulting in effective water removal. In this article, a comparison of the dewatering of titanium dioxide, which is an ideal incompressible, non-porous material, and lignite, which is a porous plant-based biomaterial, is presented. The comparison is based on the parameters critical to dewatering, namely the material compressibility and the permeability. With the aid of mercury porosimetry results, a detailed discussion of the pore destruction of lignite resulting from MTE processing is presented. It is illustrated that there is a well-defined relationship between the pore size distribution after MTE dewatering and the MTE temperature and pressure. The discussion is extended to an investigation of the effects of MTE processing conditions on the effective and noneffective porosity. The effective porosity is defined as the interconnected porosity, which contributes to flow through the compressed matrix, while the non-effective porosity is the remaining porosity, which does not contribute to flow. It is illustrated that there is a linear relationship in both the effective and non-effective porosity with the total porosity. The linear relationship is independent of the processing conditions. It is also shown that MTE processing collapses the effective and non-effective pores at roughly the same rate.

  7. Numerical Simulation on Hydromechanical Coupling in Porous Media Adopting Three-Dimensional Pore-Scale Model

    PubMed Central

    Liu, Jianjun; Song, Rui; Cui, Mengmeng

    2014-01-01

    A novel approach of simulating hydromechanical coupling in pore-scale models of porous media is presented in this paper. Parameters of the sandstone samples, such as the stress-strain curve, Poisson's ratio, and permeability under different pore pressure and confining pressure, are tested in laboratory scale. The micro-CT scanner is employed to scan the samples for three-dimensional images, as input to construct the model. Accordingly, four physical models possessing the same pore and rock matrix characteristics as the natural sandstones are developed. Based on the micro-CT images, the three-dimensional finite element models of both rock matrix and pore space are established by MIMICS and ICEM software platform. Navier-Stokes equation and elastic constitutive equation are used as the mathematical model for simulation. A hydromechanical coupling analysis in pore-scale finite element model of porous media is simulated by ANSYS and CFX software. Hereby, permeability of sandstone samples under different pore pressure and confining pressure has been predicted. The simulation results agree well with the benchmark data. Through reproducing its stress state underground, the prediction accuracy of the porous rock permeability in pore-scale simulation is promoted. Consequently, the effects of pore pressure and confining pressure on permeability are revealed from the microscopic view. PMID:24955384

  8. Silver speciation in wastewater effluent, surface waters, and pore waters

    SciTech Connect

    Adams, N.W.H.; Kramer, J.R.

    1999-12-01

    Silver, inorganic sulfide, and thiol compounds were measured in municipal wastewater effluent, receiving waters, and pore waters from an anoxic lake sediment in order to predict silver speciation in these systems. The authors found submicromolar concentrations of inorganic sulfide even in fully oxic surface water. This inorganic sulfide is likely to exist in the form of colloidal metal sulfides, which have been shown to be stable under oxidizing conditions for periods of several hours. Inorganic sulfide in both the wastewater effluent and receiving waters was found to be 200 to 300 times in excess of silver concentrations, whereas inorganic sulfide in pore waters was 1,000 to 15,000 times in excess of silver concentrations. With sulfide in excess of silver, the authors predict silver sulfide complexes to dominate silver speciation. Thiols were present at low nanomolar levels in pore waters but were not detectable in wastewater effluent or receiving waters. Thiols do not appear to be important to silver speciation in these freshwater systems. Partitioning of silver into particular, colloidal, and dissolved size fractions showed that a significant proportion of silver is in the colloidal and dissolved phases. Dissolved phase concentrations were relatively constant in the treatment plant effluent and receiving waters, suggesting that silver in the <10-kDa size fraction is strongly complexed by ligands that are not significantly affected by aggregation or sorption processes.

  9. Micro/Nano-pore Network Analysis of Gas Flow in Shale Matrix

    PubMed Central

    Zhang, Pengwei; Hu, Liming; Meegoda, Jay N.; Gao, Shengyan

    2015-01-01

    The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow regimes. The proposed pore network model accounts for the various size distributions and low connectivity of shale pores. The pore size, pore throat size and coordination number obey normal distribution, and the average values can be obtained from shale reservoir data. The gas flow regimes were simulated using an extracted pore network backbone. The numerical results show that apparent permeability is strongly dependent on pore pressure in the reservoir and pore throat size, which is overestimated by low-pressure laboratory tests. With the decrease of reservoir pressure, viscous flow is weakening, then slip flow and Knudsen diffusion are gradually becoming dominant flow regimes. The fingering phenomenon can be predicted by micro/nano-pore network for gas flow, which provides an effective way to capture heterogeneity of shale gas reservoir. PMID:26310236

  10. Micro/Nano-pore Network Analysis of Gas Flow in Shale Matrix

    NASA Astrophysics Data System (ADS)

    Zhang, Pengwei; Hu, Liming; Meegoda, Jay N.; Gao, Shengyan

    2015-08-01

    The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow regimes. The proposed pore network model accounts for the various size distributions and low connectivity of shale pores. The pore size, pore throat size and coordination number obey normal distribution, and the average values can be obtained from shale reservoir data. The gas flow regimes were simulated using an extracted pore network backbone. The numerical results show that apparent permeability is strongly dependent on pore pressure in the reservoir and pore throat size, which is overestimated by low-pressure laboratory tests. With the decrease of reservoir pressure, viscous flow is weakening, then slip flow and Knudsen diffusion are gradually becoming dominant flow regimes. The fingering phenomenon can be predicted by micro/nano-pore network for gas flow, which provides an effective way to capture heterogeneity of shale gas reservoir.

  11. Micro/Nano-pore Network Analysis of Gas Flow in Shale Matrix.

    PubMed

    Zhang, Pengwei; Hu, Liming; Meegoda, Jay N; Gao, Shengyan

    2015-01-01

    The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow regimes. The proposed pore network model accounts for the various size distributions and low connectivity of shale pores. The pore size, pore throat size and coordination number obey normal distribution, and the average values can be obtained from shale reservoir data. The gas flow regimes were simulated using an extracted pore network backbone. The numerical results show that apparent permeability is strongly dependent on pore pressure in the reservoir and pore throat size, which is overestimated by low-pressure laboratory tests. With the decrease of reservoir pressure, viscous flow is weakening, then slip flow and Knudsen diffusion are gradually becoming dominant flow regimes. The fingering phenomenon can be predicted by micro/nano-pore network for gas flow, which provides an effective way to capture heterogeneity of shale gas reservoir. PMID:26310236

  12. Nanoscale Pore Imaging and Pore Scale Fluid Flow Modeling in Chalk

    SciTech Connect

    Tomutsa, Liviu; Silin, Dmitriy

    2004-08-19

    For many rocks of high economic interest such as chalk, diatomite, tight gas sands or coal, nanometer scale resolution is needed to resolve the 3D-pore structure, which controls the flow and trapping of fluids in the rocks. Such resolutions cannot be achieved with existing tomographic technologies. A new 3D imaging method, based on serial sectioning and using the Focused Ion Beam (FIB) technology has been developed. FIB allows for the milling of layers as thin as 10 nanometers by using accelerated Ga+ ions to sputter atoms from the sample surface. After each milling step, as a new surface is exposed, a 2D image of this surface is generated. Next, the 2D images are stacked to reconstruct the 3D pore or grain structure. Resolutions as high as 10 nm are achievable using such a technique. A new robust method of pore-scale fluid flow modeling has been developed and applied to sandstone and chalk samples. The method uses direct morphological analysis of the pore space to characterize the petrophysical properties of diverse formations. Not only petrophysical properties (porosity, permeability, relative permeability and capillary pressures) can be computed but also flow processes, such as those encountered in various IOR approaches, can be simulated. Petrophysical properties computed with the new method using the new FIB data will be presented. Present study is a part of the development of an Electronic Core Laboratory at LBNL/UCB.

  13. Triggered pore-forming agents

    DOEpatents

    Bayley, Hagan; Walker, Barbara J.; Chang, Chung-yu; Niblack, Brett; Panchal, Rekha

    1998-01-01

    An inactive pore-forming agent which is activated to lytic function by a condition such as pH, light, heat, reducing potential, or metal ion concentration, or substance such as a protease, at the surface of a cell.

  14. CO2 Adsorption to Sub-Single Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction

    SciTech Connect

    Rother, Gernot; Ilton, Eugene; Wallacher, Dirk; Hauss, Thomas; Schaef, Herbert; Qafoku, Odeta; Rosso, Kevin M.; Felmy, Andrew; Krukowski, Elizabeth G; Stack, Andrew G; Bodnar, Robert J

    2013-01-01

    Geologic storage of CO2 requires that the caprock sealing the storage rock is highly impermeable by CO2. Swelling clays, which are important components of caprocks, may react with CO2 under volume change, potentially impacting the seal quality. The interactions of scCO2 with Na saturated montmorillonite clay containing a sub-single layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of 0.15 g/cm3, followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO2 bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO2 are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 . The density of CO2 in the clay pores is relatively stable over a wide range of CO2 pressures at a given temperature, indicating the formation of a clay-CO2 phase. At low pressure increasing CO2 adsorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak or no temperature dependence. Supercritical fluids, sorption phenomena, carbon dioxide, carbon sequestration, caprock integrity

  15. Reconciliation of field observations in a North Slope reservoir through pore fluid microvisualizations

    SciTech Connect

    Gamble, I.J.A.; Buller, D.C.; Sinock, K.J.

    1994-12-31

    Log data from a North Slope field indicated particularly high initial water saturations in the major reservoir zone, often in excess of 50%. Despite this, well tests yielded dry oil from the producing intervals, implying that the mobility of the connate water was negligible. A pore fluid microvisualization technique was used to examine the initial distributions of fluids within core samples, in order to reconcile the apparent inconsistencies in the field observations. The amount and distribution of initial water was controlled by the proportion of micro-porosity. Connate water resided primarily within chert, although some was associated with pore-filling kaolinite. This clay mineral was partly water filled and partly oil filled, depending upon the capillary pressure applied to the core sample to acquire S{sub wi}. Very little water was held in a conventional manner as thin films on quartz surfaces. Core flow tests confirmed that mobility of water was essentially zero, even at the highest water saturations. The technique was also used to examine the distributions of fluids at waterflood residual oil saturation. The rock was predominantly water wet in character and classical snap-off of residual oil was observe,d with the oil being trapped as isolated blobs or as multi-pore ganglia. Saturation and distribution of oil after waterflooding was found to depend upon the flow rate and flow regime used. Microvisualizations provide a unique insight into fluid distributions at S{sub wi} and S{sub orw}. For this reservoir renewed confidence in saturations derived from well logs was realized.

  16. Diagenetic facies controls on pore structure and rock electrical parameters in tight gas sandstone

    NASA Astrophysics Data System (ADS)

    Liu, Hongping; Zhao, Yanchao; Luo, Yang; Chen, Zhaoyou; He, Sheng

    2015-08-01

    Rock electrical parameters of tight gas sandstone show large variations in the T2 member in Dingbei Block, Ordos Basin, China. Applying the same rock electrical parameters in water saturation calculations would lead to large errors. Based on casting thin sections, x-ray diffraction, scanning electron microscopy (SEM), cathode luminescence, porosity and permeability, image analysis, and high-pressure mercury intrusion/withdrawal method, identification of the diagenetic facies are first conducted, and then their pore structure and their relationship with rock electrical parameters are investigated. Five diagenetic facies (A-E), which are identified based mainly on pore types and authigenic minerals, have different pore structure and rock electrical parameters. Conceptual models that incorporate the rock properties of each diagenetic facies have been built, before applying the electrical efficiency theory to explain the values of cementation exponent (m) and saturation exponent (n). A conventional network model, a shunt pore model, a netted pore model, and a dotted line model are utilized to mimic the intergranular pores, authigenic kaolinite intercrystal pores, carbonate-cement dissolution pores, and clay-matrix intercrystal pores, respectively. A decrease of the contents of large pores increases electrical efficiency and therefore reduces m. The saturation exponent, which depends on the distribution of water and gas, can be better understood by applying the different pore models. In the shunt and netted pore models, gas displacement starts from the larger pores and smaller pores provide alternative conduction pathways, hence sustaining electrical efficiency and decreasing n. Clay-matrix intercrystal pores are mainly micropores, since the brine in the rocks are isolated after gas displacement, reducing overall electrical efficiency and dramatically increasing the value of n in the diagenetic facies, which is dominated by clay-matrix intercrystal pores.

  17. Construction of Nuclear Envelope Shape by a High-Genus Vesicle with Pore-Size Constraint.

    PubMed

    Noguchi, Hiroshi

    2016-08-23

    Nuclear pores have an approximately uniform distribution in the nuclear envelope of most living cells. Hence, the morphology of the nuclear envelope is a spherical stomatocyte with a high genus. We have investigated the morphology of high-genus vesicles under pore-size constraint using dynamically triangulated membrane simulations. Bending-energy minimization without volume or other constraints produces a circular-cage stomatocyte, where the pores are aligned in a circular line on an oblate bud. As the pore radius is reduced, the circular-pore alignment is more stabilized than a random pore distribution on a spherical bud. However, we have clarified the conditions for the formation of a spherical stomatocyte: a small perinuclear volume, osmotic pressure within nucleoplasm, and repulsion between the pores. When area-difference elasticity is taken into account, the formation of cylindrical or budded tubules from the stomatocyte and discoidal stomatocyte is found. PMID:27558725

  18. Pore-scale Modelling of Capillarity in Swelling Granular Materials

    NASA Astrophysics Data System (ADS)

    Hassanizadeh, S. M.; Sweijen, T.; Nikooee, E.; Chareyre, B.

    2015-12-01

    Capillarity in granular porous media is a common and important phenomenon in earth materials and industrial products, and therefore has been studied extensively. To model capillarity in granular porous media, one needs to go beyond current models which simulate either two-phase flow in porous media or mechanical behaviour in granular media. Current pore-scale models for two-phase flow such as pore-network models are tailored for rigid pore-skeletons, even though in many applications, namely hydro-mechanical coupling in soils, printing, and hygienic products, the porous structure does change during two-phase flow. On the other hand, models such as Discrete Element Method (DEM), which simulate the deformable porous media, have mostly been employed for dry or saturated granular media. Here, the effects of porosity change and swelling on the retention properties was studied, for swelling granular materials. A pore-unit model that was capable to construct the capillary pressure - saturation curve was coupled to DEM. Such that the capillary pressure - saturation curve could be constructed for varying porosities and amounts of absorbed water. The study material was super absorbent polymer particles, which are capable to absorb water 10's to 200 times their initial weight. We have simulated quasi-static primary imbibition for different porosities and amounts of absorbed water. The results reveal a 3 dimensional surface between capillary pressure, saturation, and porosity, which can be normalized by means of the entry pressure and the effective water saturation to a unique curve.

  19. Inexpensive Pressure-Relief Valve

    NASA Technical Reports Server (NTRS)

    Theordore, E. A.

    1985-01-01

    Simple device vents excess low-pressure gas. Inexpensive pressure relief valve built from polyvinylchloride pipe. Valve suitable for low pressure-- 25 to 50 cm of mercury-- and flow rates up to 14 m3/min.

  20. Can ash clog soil pores?

    NASA Astrophysics Data System (ADS)

    Stoof, Cathelijne; Stoof, Cathelijne; Gevaert, Anouk; Gevaert, Anouk; Baver, Christine; Baver, Christine; Hassanpour, Bahareh; Hassanpour, Bahareh; Morales, Veronica; Morales, Veronica; Zhang, Wei; Zhang, Wei; Martin, Deborah; Martin, Deborah; Steenhuis, Tammo; Steenhuis, Tammo

    2015-04-01

    Wildfire can greatly increase a landscape's vulnerability to flooding and erosion events, and ash is thought to play a large role in controlling runoff and erosion processes after wildfire. Although ash can store rainfall and thereby reduce runoff and erosion for a limited period after wildfires, it has also been hypothesized to clog soil pores and reduce infiltration. Several researchers have attributed the commonly observed increase in runoff and erosion after fire to the potential pore-clogging effect of ash. Evidence is however incomplete, as to date, research has solely focused on identifying the presence of ash in the soil, with the actual flow processes associated with the infiltration and pore-clogging of ash remaining a major unknown. In several laboratory experiments, we tested the hypothesis that ash causes pore clogging to the point that infiltration is hampered and ponding occurs. We first visualized and quantified pore-scale infiltration of water and ash in sand of a range of textures and at various infiltration rates, using a digital bright field microscope capturing both photo and video. While these visualization experiments confirm field and lab observation of ash washing into soil pores, we did not observe any clogging of pores, and have not been able to create conditions for which this does occur. Additional electrochemical analysis and measurement of saturated hydraulic conductivity indicate that pore clogging by ash is not plausible. Electrochemical analysis showed that ash and sand are both negatively charged, showing that attachment of ash to sand and any resulting clogging is unlikely. Ash also had quite high saturated conductivity, and systems where ash was mixed in or lying on top of sand had similarly high hydraulic conductivity. Based on these various experiments, we cannot confirm the hypothesis that pore clogging by ash contributes to the frequently observed increase in post-fire runoff, at least for the medium to coarse sands

  1. Geostatistical Modeling of Pore Velocity

    SciTech Connect

    Devary, J.L.; Doctor, P.G.

    1981-06-01

    A significant part of evaluating a geologic formation as a nuclear waste repository involves the modeling of contaminant transport in the surrounding media in the event the repository is breached. The commonly used contaminant transport models are deterministic. However, the spatial variability of hydrologic field parameters introduces uncertainties into contaminant transport predictions. This paper discusses the application of geostatistical techniques to the modeling of spatially varying hydrologic field parameters required as input to contaminant transport analyses. Kriging estimation techniques were applied to Hanford Reservation field data to calculate hydraulic conductivity and the ground-water potential gradients. These quantities were statistically combined to estimate the groundwater pore velocity and to characterize the pore velocity estimation error. Combining geostatistical modeling techniques with product error propagation techniques results in an effective stochastic characterization of groundwater pore velocity, a hydrologic parameter required for contaminant transport analyses.

  2. Protein osmotic pressure gradients and microvascular reflection coefficients.

    PubMed

    Drake, R E; Dhother, S; Teague, R A; Gabel, J C

    1997-08-01

    Microvascular membranes are heteroporous, so the mean osmotic reflection coefficient for a microvascular membrane (sigma d) is a function of the reflection coefficient for each pore. Investigators have derived equations for sigma d based on the assumption that the protein osmotic pressure gradient across the membrane (delta II) does not vary from pore to pore. However, for most microvascular membranes, delta II probably does vary from pore to pore. In this study, we derived a new equation for sigma d. According to our equation, pore-to-pore differences in delta II increase the effect of small pores and decrease the effect of large pores on the overall membrane osmotic reflection coefficient. Thus sigma d for a heteroporous membrane may be much higher than previously derived equations indicate. Furthermore, pore-to-pore delta II differences increase the effect of plasma protein osmotic pressure to oppose microvascular fluid filtration. PMID:9277520

  3. Estimation and modeling of coal pore accessibility using small angle neutron scattering

    DOE PAGESBeta

    Zhang, Rui; Liu, Shimin; Bahadur, Jitendra; Elsworth, Derek; Melnichenko, Yuri; He, Lilin; Wang, Yi

    2015-09-04

    Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. Moreover, a theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. Our results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD4) at low Qmore » values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship.« less

  4. Estimation and modeling of coal pore accessibility using small angle neutron scattering

    SciTech Connect

    Zhang, Rui; Liu, Shimin; Bahadur, Jitendra; Elsworth, Derek; Melnichenko, Yuri; He, Lilin; Wang, Yi

    2015-09-04

    Gas diffusion in coal is controlled by nano-structure of the pores. The interconnectivity of pores not only determines the dynamics of gas transport in the coal matrix but also influences the mechanical strength. In this study, small angle neutron scattering (SANS) was employed to quantify pore accessibility for two coal samples, one of sub-bituminous rank and the other of anthracite rank. Moreover, a theoretical pore accessibility model was proposed based on scattering intensities under both vacuum and zero average contrast (ZAC) conditions. Our results show that scattering intensity decreases with increasing gas pressure using deuterated methane (CD4) at low Q values for both coals. Pores smaller than 40 nm in radius are less accessible for anthracite than sub-bituminous coal. On the contrary, when the pore radius is larger than 40 nm, the pore accessibility of anthracite becomes larger than that of sub-bituminous coal. Only 20% of pores are accessible to CD4 for anthracite and 37% for sub-bituminous coal, where the pore radius is 16 nm. For these two coals, pore accessibility and pore radius follows a power-law relationship.

  5. Neutrons measure phase behavior in pores at Angstrom size

    SciTech Connect

    Bardoel, Agatha A; Melnichenko, Yuri B

    2012-01-01

    Researchers have measured the phase behavior of green house gases in pores at the Angstrom-level, using small angle neutron scattering (SANS) at the Oak Ridge National Laboratory's High Flux Isotope Reactor. Yuri Melnichenko, an instrument scientist on the General Purpose Small Angle Neutron Scattering (GP SANS) Diffractometer at ORNL's High Flux Isotope Reactor, his postdoctoral associate Lilin He and collaborators Nidia Gallego and Cristian Contescu from the Material Sciences Division (ORNL) were engaged in the work. They were studying nanoporous carbons to assess their attractiveness as storage media for hydrogen, with a view to potential use for on-board hydrogen storage for transportation applications. Nanoporous carbons can also serve as electrode material for supercapacitors and batteries. The researchers successfully determined that the most efficiently condensing pore size in a carbon nanoporous material for hydrogen storage is less than one nanometer. In a paper recently published by the Journal of the American Chemical Society, the collaborators used small angle neutron scattering to study how hydrogen condenses in small pores at ambient temperature. They discovered that the surface-molecule interactions create internal pressures in pores that may exceed the external gas pressure by a factor of up to 50. 'This is an exciting result,' Melnichenko said, 'as you achieve extreme densification in pores 'for free', i.e. without spending any energy. These results can be used to guide the development of new carbon adsorbents tailored to maximize hydrogen storage capacities.' Another important factor that defines the adsorption capacity of sub-nanometer pores is their shape. In order to get accurate structural information and maximize sorption capacity, it is important that pores are small and of approximately uniform size. In collaboration with Drexel University's Yury Gogotsi who supplied the samples, Melnichenko and his collaborators used the GP SANS

  6. Restricted Transport in Small Pores

    PubMed Central

    Anderson, John L.; Quinn, John A.

    1974-01-01

    The basic hydrodynamic equations governing transport in submicron pores are reexamined. Conditions necessary for a simplified, one-dimensional treatment of the diffusion/convection process are established. Steric restrictions and Brownian motion are incorporated directly into the resulting model. Currently available fluid mechanical results are used to evaluate an upper limit on hindered diffusion; this limit is valid for small particle-to-pore ratios. Extensions of the analysis are shown to depend on numerical solutions of the related hydrodynamic problem, that of asymmetrical particle motion in a bounded fluid. PMID:4813157

  7. Pore-scale Analysis of the effects of Contact Angle Hysteresis on Blob Mobilization in a Pore Doublet

    NASA Astrophysics Data System (ADS)

    Hsu, Shao-Yiu; Glantz, Roland; Hilpert, Markus

    2011-11-01

    The mobilization of residual oil blobs in porous media is of major interest to the petroleum industry. We studied the Jamin effect, which hampers the blob mobilization, experimentally in a pore doublet model and explain the Jamin effect through contact angle hysteresis. A liquid blob was trapped in one of the tubes of the pore doublet model and then subjected to different pressure gradients. We measured the contact angles (in 2D and 3D) as well as the mean curvatures of the blob. Due to gravity effects and hysteresis, the contact angles of the blob were initially (zero pressure gradient) non-uniform and exhibited a pronounced altitude dependence. As the pressure gradient was increased, the contact angles became more uniform and the altitude dependence of the contact angle decreased. At the same time, the mean curvature of the drainage interface increased, and the mean curvature of the imbibition interface decreased. The pressure drops across the pore model, which we inferred with our theory from the measured contact angles and mean curvatures, were in line with the directly measured pressure data. We not only show that a trapped blob can sustain a finite pressure gradient but also develop methods to measure the contact angles and mean curvatures in 3D.

  8. Mineralocorticoid Excess or Glucocorticoid Insufficiency

    PubMed Central

    Kenyon, Christopher J.; Bailey, Matthew A.; Conway, Bryan R.; Diaz, Mary E.; Mullins, John J.

    2015-01-01

    Obesity and hypertension are 2 major health issues of the 21st century. The syndrome of apparent mineralocorticoid excess is caused by deficiency of 11β-hydroxysteroid dehydrogenase type 2 (Hsd11b2), which normally inactivates glucocorticoids, rendering the mineralocorticoid receptor aldosterone–specific. The metabolic consequences of Hsd11b2 knockout in the rat are investigated in parallel with electrolyte homeostasis. Hsd11b2 was knocked out, by pronuclear microinjection of targeted zinc-finger nuclease mRNAs, and 1 line was characterized for its response to renal and metabolic challenges. Plasma 11-dehydrocorticosterone was below detection thresholds, and Hsd11b2 protein was undetected by Western blot, indicating complete ablation. Homozygotes were 13% smaller than wild-type littermates, and were polydipsic and polyuric. Their kidneys, adrenals, and hearts were significantly enlarged, but mesenteric fat pads and liver were significantly smaller. On a 0.3% Na diet, mean arterial blood pressure was ≈65 mm Hg higher than controls but only 25 mm Hg higher on a 0.03% Na+ diet. Urinary Na/K ratio of homozygotes was similar to controls on 0.3% Na+ diet but urinary albumin and calcium were elevated. Corticosterone and aldosterone levels showed normal circadian variation on both a 0.3% and 0.03% Na+ diet, but plasma renin was suppressed in homozygotes on both diets. Plasma glucose responses to an oral glucose challenge were reduced despite low circulating insulin, indicating much greater sensitivity to insulin in homozygotes. The rat model reveals mechanisms linking electrolyte homeostasis and metabolic control through the restriction of Hsd11b1 substrate availability. PMID:26077568

  9. Measuring Excess Noise in SDL's

    NASA Technical Reports Server (NTRS)

    Katzberg, S. J.; Kowitz, H. R.; Rowland, C. W.; Shull, T. A.; Ruggles, S. L.; Matthews, L. F.

    1983-01-01

    New instrument gives quantitive information on "excess noise" in semiconductor-diode laser (SDL's). By proper selection of detector, instrument tests any SDL from visible wavelengths through thermal infrared. Lasers determine excess noise in SKL source by measuring photocurrent generated in photodetector exposed first to reference laser then to SKL under test.

  10. Transmembrane Pores Formed by Human Antimicrobial Peptide LL-37

    SciTech Connect

    Qian, Shuo

    2011-01-01

    Human LL-37 is a multifunctional cathelicidin peptide that has shown a wide spectrum of antimicrobial activity by permeabilizing microbial membranes similar to other antimicrobial peptides; however, its molecular mechanism has not been clarified. Two independent experiments revealed LL-37 bound to membranes in the {alpha}-helical form with the axis lying in the plane of membrane. This led to the conclusion that membrane permeabilization by LL-37 is a nonpore carpet-like mechanism of action. Here we report the detection of transmembrane pores induced by LL-37. The pore formation coincided with LL-37 helices aligning approximately normal to the plane of the membrane. We observed an unusual phenomenon of LL-37 embedded in stacked membranes, which are commonly used in peptide orientation studies. The membrane-bound LL-37 was found in the normal orientation only when the membrane spacing in the multilayers exceeded its fully hydrated value. This was achieved by swelling the stacked membranes with excessive water to a swollen state. The transmembrane pores were detected and investigated in swollen states by means of oriented circular dichroism, neutron in-plane scattering, and x-ray lamellar diffraction. The results are consistent with the effect of LL-37 on giant unilamellar vesicles. The detected pores had a water channel of radius 2333 {angstrom}. The molecular mechanism of pore formation by LL-37 is consistent with the two-state model exhibited by magainin and other small pore-forming peptides. The discovery that peptide-membrane interactions in swollen states are different from those in less hydrated states may have implications for other large membrane-active peptides and proteins studied in stacked membranes.

  11. Membrane pores induced by magainin.

    PubMed

    Ludtke, S J; He, K; Heller, W T; Harroun, T A; Yang, L; Huang, H W

    1996-10-29

    Magainin, found in the skin of Xenopus laevis, belongs to a broad class of antimicrobial peptides which kill bacteria by permeabilizing the cytoplasmic membrane but do not lyse eukaryotic cells. The 23-residue peptide has been shown to form an amphiphilic helix when associated with membranes. However, its molecular mechanism of action has been controversial. Oriented circular dichroism has detected helical magainin oriented perpendicular to the plane of the membrane at high peptide concentrations, but Raman, fluorescence, differential scanning calorimetry, and NMR all indicate that the peptide is associated with the head groups of the lipid bilayer. Here we show that neutron in-plane scattering detects pores formed by magainin 2 in membranes only when a substantial fraction of the peptide is oriented perpendicular to the membrane. The pores are almost twice as large as the alamethicin pores. On the basis of the in-plane scattering data, we propose a toroidal (or wormhole) model, which differs from the barrel-stave model of alamethicin in that the lipid bends back on itself like the inside of a torus. The bending requires a lateral expansion in the head group region of the bilayer. Magainin monomers play the role of fillers in the expansion region thereby stabilizing the pore. This molecular configuration is consistent with all published magainin data. PMID:8901513

  12. Triggered pore-forming agents

    DOEpatents

    Bayley, H.; Walker, B.J.; Chang, C.Y.; Niblack, B.; Panchal, R.

    1998-07-07

    An inactive pore-forming agent is revealed which is activated to lytic function by a condition such as pH, light, heat, reducing potential, or metal ion concentration, or substance such as a protease, at the surface of a cell. 30 figs.

  13. The Excess Winter Deaths Measure

    PubMed Central

    Gasparrini, Antonio

    2016-01-01

    Background: Excess winter deaths, the ratio between average daily deaths in December–March versus other months, is a measure commonly used by public health practitioners and analysts to assess health burdens associated with wintertime weather. We seek to demonstrate that this measure is fundamentally biased and can lead to misleading conclusions about health impacts associated with current and future winter climate. Methods: Time series regression analysis of 779,372 deaths from natural causes in London over 15 years (1 August 1997–31 July 2012),collapsed by day of death and linked to daily temperature values. The outcome measures were the excess winter deaths index, and daily and annual deaths attributable specifically to cold. Results: Most of the excess winter deaths are driven by cold: The excess winter deaths index decreased from 1.19 to 1.07 after excluding deaths attributable to low temperatures. Over 40% of cold-attributable deaths occurred outside of the December–March period, leading to bias in the excess winter deaths measure. Although there was no relationship between winter severity and annual excess winter deaths, there was a clear correlation with annual cold-attributable deaths. Conclusions: Excess winter deaths is not an appropriate indicator of cold-related health impacts, and its use should be discontinued. We advocate alternative measures. The findings we present bring into doubt previous claims that cold-related deaths in the UK will not reduce in future as a result of climate change. PMID:26986872

  14. Precipitation in pores: A geochemical frontier

    SciTech Connect

    Stack, Andrew G.

    2015-07-29

    (Yoon et al. 2012). An improved ability to synthesize idealized porous media will allow for tailored control of pore distributions, mineralogy and will allow more reproducible results. This in turn may allow us to isolate specific processes without the competing and obfuscatory effects that hinder generalization of observations when working with solely natural samples. It is likely that no one single experiment, or simulation technique will provide the key discoveries: to make substantive progress will require a collaborative effort to understand the interplay between fluid transport and geochemistry. Finally, where rock fracturing and elevated pressures are of concern, an understanding and capability to model geomechanical properties are necessary (Scherer 1999).

  15. Precipitation in pores: A geochemical frontier

    DOE PAGESBeta

    Stack, Andrew G.

    2015-07-29

    velocities (Yoon et al. 2012). An improved ability to synthesize idealized porous media will allow for tailored control of pore distributions, mineralogy and will allow more reproducible results. This in turn may allow us to isolate specific processes without the competing and obfuscatory effects that hinder generalization of observations when working with solely natural samples. It is likely that no one single experiment, or simulation technique will provide the key discoveries: to make substantive progress will require a collaborative effort to understand the interplay between fluid transport and geochemistry. Finally, where rock fracturing and elevated pressures are of concern, an understanding and capability to model geomechanical properties are necessary (Scherer 1999).« less

  16. Pore morphologies of root induced biopores from single pore to network scale investigated by XRCT

    NASA Astrophysics Data System (ADS)

    Peth, Stephan; Wittig, Marlen C.; Uteau Puschmann, Daniel; Pagenkemper, Sebastian; Haas, Christoph; Holthusen, Dörthe; Horn, Rainer

    2015-04-01

    Biopores are assumed to be an important factor for nutrient acquisition by providing biologically highly active soil-root interfaces to re-colonizing roots and controlling oxygen and water flows at the pedon scale and within the rhizosphere through the formation of branching channel networks which potentially enhance microbial turnover processes. Characteristic differences in pore morphologies are to be expected depending on the genesis of biopores which, for example, can be earthworm-induced or root-induced or subsequently modified by one of the two. Our understanding of biophysical interactions between plants and soil can be significantly improved by quantifying 3D biopore architectures across scales ranging from single biopores to pedon scale pore networks and linking pore morphologies to microscale measurements of transport processes (e.g. oxygen diffusion). While a few studies in the past have investigated biopore networks on a larger scale yet little is known on the micro-morphology of root-induces biopores and their associated rhizosphere. Also little data is available on lateral transport of oxygen through the rhizosphere which will strongly influence microbial turnover processes and consequently control the release and uptake of nutrients. This paper highlights results gathered within a research unit on nutrient acquisition from the subsoil. Here we focus on X-ray microtomography (XRCT) studies ranging from large soil columns (70 cm length and 20 cm diameter) to individual biopores and its surrounding rhizosphere. Samples were collected from sites with different preceding crops (fescue, chicory, alfalfa) and various cropping durations (1-3 years). We will present an approach for quantitative image analysis combined with micro-sensor measurements of oxygen diffusion and spatial gradients of O2 partial pressures to relate pore structure with transport functions. Implications of various biopore architectures for the accessibility of nutrient resources in

  17. Kinetics of Diffusion and Convection in 3.2-Å Pores

    PubMed Central

    Levitt, David G.

    1973-01-01

    The kinetics of transport in pores the size postulated for cell membranes has been investigated by direct computer simulation (molecular dynamics). The simulated pore is 11 Å long and 3.2 Å in radius, and the water molecules are modeled by hard, smooth spheres, 1 Å in radius. The balls are given an initial set of positions and velocities (with an average temperature of 313° K) and the computer then calculates their exact paths through the pore. Two different conditions were used at the ends of the pore. In one, the ends are closed and the balls are completely isolated. In the other, the ball density in each end region is fixed so that a pressure difference can be established and a net convective flow produced. The following values were directly measured in the simulated experiments: net and diffusive (oneway) flux; pressure, temperature, and diffusion coefficients in the pore; area available for diffusion; probability distribution of ball positions in the pore; and the interaction between diffusion and convection. The density, viscosity, and diffusion coefficients in the bulk fluid were determined from the theory of hard sphere dense gases. From these values, the “equivalent” pore radius (determined by the same procedure that is used for cell membranes) was computed and compared with the physical pore radius of the simulated pore. PMID:4702015

  18. Network representation of pore scale imagery for percolation models

    NASA Astrophysics Data System (ADS)

    Klise, K. A.; McKenna, S. A.; Read, E.; Karpyn, Z. T.; Celauro, J.

    2012-12-01

    Multiphase flow under capillary dominated flow regimes is driven by an intricate relationship between pore geometry, material and fluid properties. In this research, high-resolution micro-computed tomography (CT) imaging experiments are used to investigate structural and surface properties of bead packs, and how they influence percolation pathways. Coreflood experiments use a mix of hydrophilic and hydrophobic beads to track the influence of variable contact angle on capillary flow. While high-resolution CT images can render micron scale representation of the pore space, data must be upscaled to capture pore and pore throat geometry for use in percolation models. In this analysis, the pore space is upscaled into a network representation based on properties of the medial axis. Finding the medial axis using micron scale images is computationally expensive. Here, we compare the efficiency and accuracy of medial axes using erosion-based and watershed algorithms. The resulting network representation is defined as a ball-and-stick model which represents pores and pore throats. The ball-and-stick model can be further reduced by eliminating sections of the network that fall below a capillary pressure threshold. In a system of mixed hydrophilic and hydrophobic beads, capillary pressure can change significantly throughout the network based on the interaction between surface and fluid properties. The upscaled network representations are used in percolation models to estimate transport pathway. Current results use a basic percolation model that sequentially fills neighboring pores with the highest potential. Future work will expand the percolation model to include additional mechanics, such as trapping, vacating pores, and viscous fingering. Results from the coreflood experiments will be used to validate upscaling techniques and percolation models. Preliminary results show that the relative strength of water-wet and oil-wet surfaces has a significant impact on percolation

  19. Stability of a fluid-fluid interface in a biconical pore segment.

    PubMed

    Hilpert, Markus; Miller, Cass T; Gray, William G

    2003-11-15

    Pore networks that include biconical pore segments are frequently used to model two-phase flow. In this work, we describe in detail the displacement of a fluid-fluid interface in such a pore segment. We assume sharp edges in the throat, inlet, and outlet of the pore segment to be the limiting cases of round edges, the radii of which vanish. We account for interfacial and lineal tensions that cause nonconstant contact angles. For zero lineal tension, we provide analytical solutions for flow induced by changing infinitesimally slowly either capillary pressure or the volume of one fluid. In diverging and converging cones, the common line among the two fluids and the solid phase slides while it is pinned in the throat, inlet, and outlet. We observe hysteresis within the pore segment, and drainage entry pressures deviate from prior work. PMID:14583218

  20. A robust model for pore-water chemistry of clayrock

    NASA Astrophysics Data System (ADS)

    Gaucher, E. C.; Tournassat, C.; Pearson, F. J.; Blanc, P.; Crouzet, C.; Lerouge, C.; Altmann, S.

    2009-11-01

    The chemistry of pore water is an important property of clayrocks being considered as host rocks for long-term storage of radioactive waste. It may be difficult, if not impossible, to obtain water samples for chemical analysis from such rocks because of their low hydraulic conductivity. This paper presents an approach for calculating the pore-water compositions of clayrocks from laboratory-measured properties of core samples, including their leachable Cl and SO 4 concentrations and analysed exchangeable cations, and from mineral and cation exchange equilibria based on the formation mineralogy. New core sampling and analysis procedures are presented that reduce or quantify side reactions such as sample oxidation (e.g. pyrite) and soluble mineral dissolution (celestite, SrSO 4) that affect measured SO 4 concentrations and exchangeable cation distributions. The model considers phase equilibria only with minerals that are observed in the formation including the principal clay phases. The model has been used to calculate the composition of mobile pore water in the Callovo-Oxfordian clayrock and validated against measurements of water chemistry made in an underground research laboratory in that formation. The model reproduces the measured, in situ pore-water composition without any estimated parameters. All required parameters can be obtained from core sample analysis. We highlight the need to consider only those mineral phases which can be shown to be in equilibrium with contacting pore water. The consequence of this is that some conceptual models available in the literature appear not to be appropriate for modelling clayrocks, particularly those considering high temperature and/or high pressure detrital phases as chemical buffers of pore water. The robustness of our model with respect to uncertainties in the log K values of clay phases is also demonstrated. Large uncertainties in log K values for clay minerals have relatively small effects on modelled pore

  1. Ion exclusion by sub-2-nm carbon nanotube pores

    PubMed Central

    Fornasiero, Francesco; Park, Hyung Gyu; Holt, Jason K.; Stadermann, Michael; Grigoropoulos, Costas P.; Noy, Aleksandr; Bakajin, Olgica

    2008-01-01

    Biological pores regulate the cellular traffic of a large variety of solutes, often with high selectivity and fast flow rates. These pores share several common structural features: the inner surface of the pore is frequently lined with hydrophobic residues, and the selectivity filter regions often contain charged functional groups. Hydrophobic, narrow-diameter carbon nanotubes can provide a simplified model of membrane channels by reproducing these critical features in a simpler and more robust platform. Previous studies demonstrated that carbon nanotube pores can support a water flux comparable to natural aquaporin channels. Here, we investigate ion transport through these pores using a sub-2-nm, aligned carbon nanotube membrane nanofluidic platform. To mimic the charged groups at the selectivity region, we introduce negatively charged groups at the opening of the carbon nanotubes by plasma treatment. Pressure-driven filtration experiments, coupled with capillary electrophoresis analysis of the permeate and feed, are used to quantify ion exclusion in these membranes as a function of solution ionic strength, pH, and ion valence. We show that carbon nanotube membranes exhibit significant ion exclusion that can be as high as 98% under certain conditions. Our results strongly support a Donnan-type rejection mechanism, dominated by electrostatic interactions between fixed membrane charges and mobile ions, whereas steric and hydrodynamic effects appear to be less important. PMID:18539773

  2. Postseismic rebound in fault step-overs caused by pore fluid flow

    USGS Publications Warehouse

    Peltzer, G.; Rosen, P.; Rogez, F.; Hudnut, K.

    1996-01-01

    Near-field strain induced by large crustal earthquakes results in changes in pore fluid pressure that dissipate with time and produce surface deformation. Synthetic aperture radar (SAR) interferometry revealed several centimeters of postseismic uplift in pull-apart structures and subsidence in a compressive jog along the Landers, California, 1992 earthquake surface rupture, with a relaxation time of 270 ?? 45 days. Such a postseismic rebound may be explained by the transition of the Poisson's ratio of the deformed volumes of rock from undrained to drained conditions as pore fluid flow allows pore pressure to return to hydrostatic equilibrium.

  3. Tight dual models of pore spaces

    NASA Astrophysics Data System (ADS)

    Glantz, Roland; Hilpert, Markus

    2008-05-01

    The pore throats in a porous medium control permeability, drainage, and straining through their pore scale geometry and through the way they are connected via pore bodies on the macroscale. Likewise, imbibition is controlled through the geometry of the pore bodies (pore scale) and through the way the pore bodies are connected via pore throats on the macroscale. In an effort to account for both scales at the same time we recently introduced an image-based model for pore spaces that consists of two parts related by duality: (1) a decomposition of a polyhedral pore space into polyhedral pore bodies separated by polygonal pore throats and (2) a polygonal pore network that is homotopy equivalent to the pore space. In this paper we stick to the dual concept while amending the definition of the pore throats and, as a consequence, the other elements of the dual model. Formerly, the pore throats consisted of single two-dimensional Delaunay cells, while they now usually consist of more than one two-dimensional Delaunay cell and extend all the way into the narrowing ends of the pore channel cross sections. This is the first reason for naming the amended dual model "tight". The second reason is that the formation of the pore throats is now guided by an objective function that always attains its global optimum (tight optimization). At the end of the paper we report on simulations of drainage performed on tight dual models derived from simulated sphere packings and 3D gray-level images. The C-code for the generation of the tight dual model and the simulation of drainage is publicly available at https://jshare.johnshopkins.edu/mhilper1/public_html/tdm.html.

  4. Defeating the pores of Kohn.

    PubMed

    Ng, Calvin S H; Lau, Rainbow W H; Lau, Kelvin K W; Underwood, Malcolm J; Yim, Anthony P C

    2014-01-01

    In the treatment of emphysema with an endobronchial valve, entire lobar treatment is important in achieving adequate atelectasis. This case illustrates that without treatment of the entire lobe, it can fail to collapse even after several years, leading to treatment failure. Intralobar collateral ventilation through the pores of Kohn is demonstrated in this case, as endobronchial valve blockage of the remaining patent anterior segment resulted in the desired atelectasis and significant improvements in pulmonary function. PMID:24585656

  5. DESIGN INFORMATION ON FINE PORE AERATION SYSTEMS

    EPA Science Inventory

    Field studies were conducted over several years at municipal wastewater treatment plants employing line pore diffused aeration systems. These studies were designed to produce reliable information on the performance and operational requirements of fine pore devices under process ...

  6. Permeability of fault gouge under confining pressure and shear stress.

    USGS Publications Warehouse

    Morrow, C.A.; Shi, L.Q.; Byerlee, J.D.

    1984-01-01

    The permeability of both clay-rich and non-clay gouges, as well as several pure clays, was studied as a function of confining pressures from 5 to 200 MPa and shear strain to 10. Permeability ranged over 4 orders of magnitude, from around 10-22 to 10-18 m2 (1 darcy = 0.987 X 10-12 m2). Grain size was an important factor in determining permeability, particularly for the clay-rich samples. The permeabilities of the non-clay samples were not significantly different than those of the clays. Strength of the saturated samples under drained (low pore pressure) conditions did not correlate with high or low permeability. However, the low permeabilities of these gouges could be a factor in the measured low shear stresses along fault regions if excess pore pressures were created as a result of shearing or compaction, and this pressure was unable to dissipate through a thick section of the material.-from Authors

  7. Pore structure of the activated coconut shell charcoal carbon

    NASA Astrophysics Data System (ADS)

    Budi, E.; Nasbey, H.; Yuniarti, B. D. P.; Nurmayatri, Y.; Fahdiana, J.; Budi, A. S.

    2014-09-01

    The development of activated carbon from coconut shell charcoal has been investigated by using physical method to determine the influence of activation parameters in term of temperature, argon gas pressure and time period on the pore structure of the activated carbon. The coconut shell charcoal was produced by pyrolisis process at temperature of about 75 - 150 °C for 6 hours. The charcoal was activated at various temperature (532, 700 and 868 °C), argon gas pressure (6.59, 15 and 23.4 kgf/cm2) and time period of (10, 60 and 120 minutes). The results showed that the pores size were reduced and distributed uniformly as the activation parameters are increased.

  8. Electron microscopic time-lapse visualization of surface pore filtration on particulate matter trapping process.

    PubMed

    Sanui, Ryoko; Hanamura, Katsunori

    2016-09-01

    A scanning electron microscope (SEM) was used to dynamically visualize the particulate matter (PM) trapping process on diesel particulate filter (DPF) walls at a micro scale as 'time-lapse' images corresponding to the increase in pressure drop simultaneously measured through the DPF. This visualization and pressure drop measurement led to the conclusion that the PM trapping in surface pores was driven by PM bridging and stacking at constricted areas in porous channels. This caused a drastic increase in the pressure drop during PM accumulation at the beginning of the PM trapping process. The relationship between the porous structure of the DPF and the depth of the surface pore was investigated in terms of the porosity distribution and PM penetration depth near the wall surface with respect to depth. The pressure drop calculated with an assumed surface pore depth showed a good correspondence to the measured pressure drop. PMID:26923765

  9. Pore accessibility by methane and carbon dioxide in coal as determined by neutron scattering

    SciTech Connect

    He, Lilin; Melnichenko, Yuri B; Mastalerz, Maria; Sakurovs, Richard; Radlinski, Andrzej Pawell; Blach, Tomasz P

    2012-01-01

    Contrast-matching ultrasmall-angle neutron scattering (USANS) and small-angle neutron scattering (SANS) techniques were used for the first time to determine both the total pore volume and the fraction of the pore volume that is inaccessible to deuterated methane, CD{sub 4}, in four bituminous coals in the range of pore sizes between {approx}10 {angstrom} and {approx}5 {micro}m. Two samples originated from the Illinois Basin in the U.S.A., and the other two samples were commercial Australian bituminous coals from the Bowen Basin. The total and inaccessible porosity were determined in each coal using both Porod invariant and the polydisperse spherical particle (PDSP) model analysis of the scattering data acquired from coals both in vacuum and at the pressure of CD{sub 4}, at which the scattering length density of the pore-saturating fluid is equal to that of the solid coal matrix (zero average contrast pressure). The total porosity of the coals studied ranged from 7 to 13%, and the volume of pores inaccessible to CD{sub 4} varied from {approx}13 to {approx}36% of the total pore volume. The volume fraction of inaccessible pores shows no correlation with the maceral composition; however, it increases with a decreasing total pore volume. In situ measurements of the structure of one coal saturated with CO{sub 2} and CD{sub 4} were conducted as a function of the pressure in the range of 1-400 bar. The neutron scattering intensity from small pores with radii less than 35 {angstrom} in this coal increased sharply immediately after the fluid injection for both gases, which demonstrates strong condensation and densification of the invading subcritical CO{sub 2} and supercritical methane in small pores.

  10. Hydrogen Storage Properties of Rigid Three-Dimensional Hofmann Clathrate Derivatives: The Effects of Pore Size

    SciTech Connect

    Culp, J.T.; Natesakhawat, Sittichai; Smith, M.R.; Bittner, E.; Matranga, C.S.; Bockrath, B.

    2008-05-01

    The effects of pore size on the hydrogen storage properties of a series of pillared layered solids based on the M(L)[M'(CN)4] structural motif, where M ) Co or Ni, L ) pyrazine (pyz), 4,4'-bipyridine (bpy), or 4,4'-dipyridylacetylene (dpac), and M' ) Ni, Pd, or Pt, has been investigated. The compounds all possess slitlike pores with constant in-plane dimensions and similar organic functionality. The pore heights vary as a function of L and provide a means for a systematic investigation of the effects of pore dimension on hydrogen storage properties in porous materials. Hydrogen isotherms were measured at 77 and 87 K up to a pressure of 1 atm. The pyz pillared materials with the smallest pore dimensions store hydrogen at a pore density similar to that of liquid hydrogen. The adsorbed hydrogen density drops by a factor of 2 as the relative pore size is tripled in the dpac material. The decreased storage efficiency diminishes the expected gravimetric gain in capacity for the larger pore materials. The heats of adsorption were found to range from 6 to 8 kJ/mol in the series and weakly correlate with pore size.

  11. METHODS FOR PORE WATER EXTRACTION FROM UNSATURATED ZONE TUFF, YUCCA MOUNTAIN, NEVADA

    SciTech Connect

    K.M. SCOFIELD

    2006-03-22

    Assessing the performance of the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, requires an understanding of the chemistry of the water that moves through the host rock. The uniaxial compression method used to extract pore water from samples of tuffaceous borehole core was successful only for nonwelded tuff. An ultracentrifugation method was adopted to extract pore water from samples of the densely welded tuff of the proposed repository horizon. Tests were performed using both methods to determine the efficiency of pore water extraction and the potential effects on pore water chemistry. Test results indicate that uniaxial compression is most efficient for extracting pore water from nonwelded tuff, while ultracentrifugation is more successful in extracting pore water from densely welded tuff. Pore water splits taken from a single nonwelded tuff core during uniaxial compression tests have shown changes in pore water chemistry with increasing pressure for calcium, chloride, sulfate, and nitrate, while the chemistry of pore water splits from welded and nonwelded tuffs using ultracentrifugation indicates that there is no significant fractionation of solutes.

  12. Measuring kinetic drivers of pneumolysin pore structure.

    PubMed

    Gilbert, Robert J C; Sonnen, Andreas F-P

    2016-05-01

    Most membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins are thought to form pores in target membranes by assembling into pre-pore oligomers before undergoing a pre-pore to pore transition. Assembly during pore formation is into both full rings of subunits and incomplete rings (arcs). The balance between arcs and full rings is determined by a mechanism dependent on protein concentration in which arc pores arise due to kinetic trapping of the pre-pore forms by the depletion of free protein subunits during oligomerization. Here we describe the use of a kinetic assay to study pore formation in red blood cells by the MACPF/CDC pneumolysin from Streptococcus pneumoniae. We show that cell lysis displays two kinds of dependence on protein concentration. At lower concentrations, it is dependent on the pre-pore to pore transition of arc oligomers, which we show to be a cooperative process. At higher concentrations, it is dependent on the amount of pneumolysin bound to the membrane and reflects the affinity of the protein for its receptor, cholesterol. A lag occurs before cell lysis begins; this is dependent on oligomerization of pneumolysin. Kinetic dissection of cell lysis by pneumolysin demonstrates the capacity of MACPF/CDCs to generate pore-forming oligomeric structures of variable size with, most likely, different functional roles in biology. PMID:26906727

  13. Anisotropy of Pore Structure and Permeability in Granite: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Onishi, C. T.; Shimizu, I.; Mizoguchi, K.; Uehara, S.; Shimamoto, T.

    2001-12-01

    The permeability of rocks is sensitive to pore structures. In fault zones where brittle deformation dominates, connectivity of cracks is perhaps the most important factor to control the fluid permeability. The relationship between microstructure, porosity-pore structures and permeability were investigated, using drill core samples from the Toki Granite in Gifu Prefecture, Central Japan. Core samples taken from a borehole penetrating a fault strand of the Tsukiyoshi Fault at the depth of 700 m were used for analysis and measurements. The Toki Granite shows textural variations. For example, away from the fault zone, the granite is fresh, massive biotite granite. Toward the fault the granitic texture is largely destroyed, reflecting deformation due to fault movement, with extensive fracturing and development of calcite veins. The central part of the fault zone constitutes foliated ultra-cataclasites with a fine grained matrix. Microstructural observations indicate that fragmentation of crystals is the cause of grain size reduction in the fault zone and anisotropy in micro-crack development. The effective porosity of bulk samples measured by Helium pycnometer varies from 0.54% for unaltered fresh granite to over 5.4% for foliated cataclasite from the central part of the fault zone. The pore structures of the granite samples were visualized by the Laser Scanning Microscope (LSM). The samples were impregnated with low viscosity fluorescent resin under vacuum condition, and then observed by the LSM. Quasi 3-D images of pore structures were constructed from optical slices (confocal images) of thick sections. Micro-cracks in granites were successfully filled with the fluorescent resin. Micro-cracks were mainly observed at grain boundaries, and the intra and inter granular fractures. Permeability measurements were performed by a High Pressure Temperature (HPT) gas apparatus using the pore oscillation technique. Confining pressure was increased and then decreased in the range

  14. Excessive or unwanted hair in women

    MedlinePlus

    Hypertrichosis; Hirsutism; Hair - excessive (women); Excessive hair in women; Hair - women - excessive or unwanted ... much of this hormone, you may have unwanted hair growth. In most cases, the exact cause is ...

  15. Nondestructive technique for the characterization of the pore size distribution of soft porous constructs for tissue engineering.

    PubMed

    Safinia, Laleh; Mantalaris, Athanasios; Bismarck, Alexander

    2006-03-28

    Polymer scaffolds tailored for tissue engineering applications possessing the desired pore structure require reproducible fabrication techniques. Nondestructive, quantitative methods for pore characterization are required to determine the pore size and its distribution. In this study, a promising alternative to traditional pore size characterization techniques is presented. We introduce a quantitative, nondestructive and inexpensive method to determine the pore size distribution of large soft porous solids based on the on the displacement of a liquid, that spreads without limits though a porous medium, by nitrogen. The capillary pressure is measured and related to the pore sizes as well as the pore size distribution of the narrowest bottlenecks of the largest interconnected pores in a porous medium. The measured pore diameters correspond to the narrowest bottleneck of the largest pores connecting the bottom with the top surface of a given porous solid. The applicability and reproducibility of the breakthrough technique is demonstrated on two polyurethane foams, manufactured using the thermally induced phase separation (TIPS) process, with almost identical overall porosity (60-70%) but very different pore morphology. By selecting different quenching temperatures to induce polymer phase separation, the pore structure could be regulated while maintaining the overall porosity. Depending on the quenching temperature, the foams exhibited either longitudinally oriented tubular macropores interconnected with micropores or independent macropores connected to adjacent pores via openings in the pore walls. The pore size and its distribution obtained by the breakthrough test were in excellent agreement to conventional characterization techniques, such as scanning electron microscopy combined with image analysis, BET technique, and mercury intrusion porosimetry. This technique is suitable for the characterization of the micro- and macropore structure of soft porous solids

  16. Outflows in Sodium Excess Objects

    NASA Astrophysics Data System (ADS)

    Park, Jongwon; Jeong, Hyunjin; Yi, Sukyoung K.

    2015-08-01

    Van Dokkum and Conroy revisited the unexpectedly strong Na i lines at 8200 Å found in some giant elliptical galaxies and interpreted them as evidence for an unusually bottom-heavy initial mass function. Jeong et al. later found a large population of galaxies showing equally extraordinary Na D doublet absorption lines at 5900 Å (Na D excess objects: NEOs) and showed that their origins can be different for different types of galaxies. While a Na D excess seems to be related to the interstellar medium (ISM) in late-type galaxies, smooth-looking early-type NEOs show little or no dust extinction and hence no compelling signs of ISM contributions. To further test this finding, we measured the Doppler components in the Na D lines. We hypothesized that the ISM would have a better (albeit not definite) chance of showing a blueshift Doppler departure from the bulk of the stellar population due to outflow caused by either star formation or AGN activities. Many of the late-type NEOs clearly show blueshift in their Na D lines, which is consistent with the former interpretation that the Na D excess found in them is related to gas outflow caused by star formation. On the contrary, smooth-looking early-type NEOs do not show any notable Doppler components, which is also consistent with the interpretation of Jeong et al. that the Na D excess in early-type NEOs is likely not related to ISM activities but is purely stellar in origin.

  17. USING A NEW FINITE SLIT PORE MODEL FOR NLDFT ANALYSIS OF CARBON PORE STRUCTURE

    SciTech Connect

    Jagiello, Jacek; Kenvin, Jeffrey; Oliver, James P; Lupini, Andrew R; Contescu, Cristian I

    2011-01-01

    In this work, we present a model for analyzing activated carbon micropore structures based on graphene sheet walls of finite thickness and extent. This is a two-dimensional modification of the widely used infinite slit pore model that assumes graphite-like infinitely extended pore walls. The proposed model has two versions: (1) a strip pore constructed with graphene strip walls that have finite length L in the x direction and are infinite in the y direction. Strip pores are open on both sides in the x direction. (2) A channel pore is a strip pore partially closed along one edge by a perpendicularly oriented graphene wall. This more realistic model allows pore termination via both physical pore entrances and pore blockage. The model consequently introduces heterogeneity of the adsorption potential that is reduced near pore entrances and enhanced near corners of pore walls. These energetically heterogeneous structures fill with adsorbate more gradually than homogeneous pores of the same width. As a result, the calculated adsorption isotherms are smoother and less steep for the finite versus the infinite pore model. In the application of this model for carbon characterization it is necessary to make an assumption about the pore length. In this work we made this assumption based on the high resolution scanning transmission electron microscopy (STEM) results. We find the agreement between the experiment and the model significantly better for the finite than for the infinite pore model.

  18. The Presence of Excess Oxygen in Burning Metallic Materials

    NASA Technical Reports Server (NTRS)

    Wilson, D. Bruce; Steinberg, Theodore A.; Stoltzfus, Joel M.; Fries, Joseph (Technical Monitor)

    2000-01-01

    Early work on burning of iron rods under conditions of the ATSM/NASA flammability test showed that there was excess oxygen, that is, above stoichiometric requirements for iron(III) oxide, present in the molten product during burning. Since that work, this phenomenon has been confirmed for burning under microgravity conditions and has been observed for a wide range of metals under burning conditions of a single micro-drop at ambient pressures and 20-second microgravity tests under pressurized oxygen-enriched conditions. This paper reviews these experimental observations and discusses the possible thermodynamic analysis for the metals iron, aluminum, and cobalt. The excess oxygen in the burning molten iron oxide was represented as combined to form a series of ferrite ions. For aluminum the excess oxygen is represented as a bridging species and a similar explanation is postulated for the cobalt system.

  19. In-situ X-ray Synchrotron Microtomography: Real Time Pore Structure Evolution during Olivine Carbonation

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xiao, X.

    2013-12-01

    Mineral carbonation has been proposed as a promising method for long-term, secure sequestration of carbon dioxide. In porous rocks, fluid-rock interactions can significantly alter the pore space and thus exert important controls over the rate and extent of carbonation. We constructed an x-ray transparent pressure cell [Fusseis et al., 2013] to investigate the real time pore structure evolution during mineral carbonation in porous olivine aggregates. In each experiment, a sintered olivine sample was subjected to a confining pressure of 13 MPa and a pore pressure of 10 MPa, with a sodium bicarbonate solution (NaHCO3 at 1.5 M) as pore fluid. At these pressure conditions, the cell was heated to 473 K. Constant pressure and temperature conditions were maintained during the length of the experiments, lasting 72-120 hours. Using a polychromatic beam in the 2-BM upstream hutch at the Advanced Photon Source, 3-dimensional (3-D) microtomography data were collected in 20 seconds with 30-minute interval. A novel phase retrieval reconstruction algorithm [Paganin et al., 2002] was used to reconstruct microtomographic datasets with a voxel size of ~1.1 micron. The microtomography images at different stages of the carbonation process reveal progressive growth of new crystals in the pore space. Integration of a x-ray transparent pressure vessel with flow through capacity and 3-D microtomography provides a novel research direction of studying the coupled chemo-hydro-thermal-mechanical processes in rocks.

  20. Nuclear pores. Architecture of the nuclear pore complex coat.

    PubMed

    Stuwe, Tobias; Correia, Ana R; Lin, Daniel H; Paduch, Marcin; Lu, Vincent T; Kossiakoff, Anthony A; Hoelz, André

    2015-03-01

    The nuclear pore complex (NPC) constitutes the sole gateway for bidirectional nucleocytoplasmic transport. Despite half a century of structural characterization, the architecture of the NPC remains unknown. Here we present the crystal structure of a reconstituted ~400-kilodalton coat nucleoporin complex (CNC) from Saccharomyces cerevisiae at a 7.4 angstrom resolution. The crystal structure revealed a curved Y-shaped architecture and the molecular details of the coat nucleoporin interactions forming the central "triskelion" of the Y. A structural comparison of the yeast CNC with an electron microscopy reconstruction of its human counterpart suggested the evolutionary conservation of the elucidated architecture. Moreover, 32 copies of the CNC crystal structure docked readily into a cryoelectron tomographic reconstruction of the fully assembled human NPC, thereby accounting for ~16 megadalton of its mass. PMID:25745173

  1. Incomplete pneumolysin oligomers form membrane pores.

    PubMed

    Sonnen, Andreas F-P; Plitzko, Jürgen M; Gilbert, Robert J C

    2014-01-01

    Pneumolysin is a member of the cholesterol-dependent cytolysin (CDC) family of pore-forming proteins that are produced as water-soluble monomers or dimers, bind to target membranes and oligomerize into large ring-shaped assemblies comprising approximately 40 subunits and approximately 30 nm across. This pre-pore assembly then refolds to punch a large hole in the lipid bilayer. However, in addition to forming large pores, pneumolysin and other CDCs form smaller lesions characterized by low electrical conductance. Owing to the observation of arc-like (rather than full-ring) oligomers by electron microscopy, it has been hypothesized that smaller oligomers explain smaller functional pores. To investigate whether this is the case, we performed cryo-electron tomography of pneumolysin oligomers on model lipid membranes. We then used sub-tomogram classification and averaging to determine representative membrane-bound low-resolution structures and identified pre-pores versus pores by the presence of membrane within the oligomeric curve. We found pre-pore and pore forms of both complete (ring) and incomplete (arc) oligomers and conclude that arc-shaped oligomeric assemblies of pneumolysin can form pores. As the CDCs are evolutionarily related to the membrane attack complex/perforin family of proteins, which also form variably sized pores, our findings are of relevance to that class of proteins as well. PMID:24759615

  2. Effects of pore volume-transmissivity correlation on transport phenomena

    NASA Astrophysics Data System (ADS)

    Lunati, Ivan; Kinzelbach, Wolfgang; Sørensen, Ivan

    2003-12-01

    The relevant velocity that describes transport phenomena in a porous medium is the pore velocity. For this reason, one needs not only to describe the variability of transmissivity, which fully determines the Darcy velocity field for given source terms and boundary conditions, but also any variability of the pore volume. We demonstrate that hydraulically equivalent media with exactly the same transmissivity field can produce dramatic differences in the displacement of a solute if they have different pore volume distributions. In particular, we demonstrate that correlation between pore volume and transmissivity leads to a much smoother and more homogeneous solute distribution. This was observed in a laboratory experiment performed in artificial fractures made of two plexiglass plates into which a space-dependent aperture distribution was milled. Using visualization by a light transmission technique, we observe that the solute behaviour is much smoother and more regular after the fractures are filled with glass powder, which plays the role of a homogeneous fault gouge material. This is due to a perfect correlation between pore volume and transmissivity that causes pore velocity to be not directly dependent on the transmissivity, but only indirectly through the hydraulic gradient, which is a much smoother function due to the diffusive behaviour of the flow equation acting as a filter. This smoothing property of the pore volume-transmissivity correlation is also supported by numerical simulations of tracer tests in a dipole flow field. Three different conceptual models are used: an empty fracture, a rough-walled fracture filled with a homogeneous material and a parallel-plate fracture with a heterogeneous fault gouge. All three models are hydraulically equivalent, yet they have a different pore volume distribution. Even if piezometric heads and specific flow rates are exactly the same at any point of the domain, the transport process differs dramatically. These

  3. Inertial effects during irreversible meniscus reconfiguration in angular pores

    NASA Astrophysics Data System (ADS)

    Ferrari, Andrea; Lunati, Ivan

    2014-12-01

    In porous media, the dynamics of the invading front between two immiscible fluids is often characterized by abrupt reconfigurations caused by local instabilities of the interface. As a prototype of these phenomena we consider the dynamics of a meniscus in a corner as it can be encountered in angular pores. We investigate this process in detail by means of direct numerical simulations that solve the Navier-Stokes equations in the pore space and employ the Volume of Fluid method (VOF) to track the evolution of the interface. We show that for a quasi-static displacement, the numerically calculated surface energy agrees well with the analytical solutions that we have derived for pores with circular and square cross sections. However, the spontaneous reconfigurations are irreversible and cannot be controlled by the injection rate: they are characterized by the amount of surface energy that is spontaneously released and transformed into kinetic energy. The resulting local velocities can be orders of magnitude larger than the injection velocity and they induce damped oscillations of the interface that possess their own time scales and depend only on fluid properties and pore geometry. In complex media (we consider a network of cubic pores) reconfigurations are so frequent and oscillations last long enough that increasing inertial effects leads to a different fluid distribution by influencing the selection of the next pore to be invaded. This calls into question simple pore-filling rules based only on capillary forces. Also, we demonstrate that inertial effects during irreversible reconfigurations can influence the work done by the external forces that is related to the pressure drop in Darcy's law. This suggests that these phenomena have to be considered when upscaling multiphase flow because local oscillations of the menisci affect macroscopic quantities and modify the constitutive relationships to be used in macro-scale models. These results can be extrapolated to other

  4. Syndromes that Mimic an Excess of Mineralocorticoids.

    PubMed

    Sabbadin, Chiara; Armanini, Decio

    2016-09-01

    Pseudohyperaldosteronism is characterized by a clinical picture of hyperaldosteronism with suppression of renin and aldosterone. It can be due to endogenous or exogenous substances that mimic the effector mechanisms of aldosterone, leading not only to alterations of electrolytes and hypertension, but also to an increased inflammatory reaction in several tissues. Enzymatic defects of adrenal steroidogenesis (deficiency of 17α-hydroxylase and 11β-hydroxylase), mutations of mineralocorticoid receptor (MR) and alterations of expression or saturation of 11-hydroxysteroid dehydrogenase type 2 (apparent mineralocorticoid excess syndrome, Cushing's syndrome, excessive intake of licorice, grapefruits or carbenoxolone) are the main causes of pseudohyperaldosteronism. In these cases treatment with dexamethasone and/or MR-blockers is useful not only to normalize blood pressure and electrolytes, but also to prevent the deleterious effects of prolonged over-activation of MR in epithelial and non-epithelial tissues. Genetic alterations of the sodium channel (Liddle's syndrome) or of the sodium-chloride co-transporter (Gordon's syndrome) cause abnormal sodium and water reabsorption in the distal renal tubules and hypertension. Treatment with amiloride and thiazide diuretics can respectively reverse the clinical picture and the renin aldosterone system. Finally, many other more common situations can lead to an acquired pseudohyperaldosteronism, like the expansion of volume due to exaggerated water and/or sodium intake, and the use of drugs, as contraceptives, corticosteroids, β-adrenergic agonists and FANS. In conclusion, syndromes or situations that mimic aldosterone excess are not rare and an accurate personal and pharmacological history is mandatory for a correct diagnosis and avoiding unnecessary tests and mistreatments. PMID:27251484

  5. Pore Scale Dynamics of Microemulsion Formation.

    PubMed

    Unsal, Evren; Broens, Marc; Armstrong, Ryan T

    2016-07-19

    Experiments in various porous media have shown that multiple parameters come into play when an oleic phase is displaced by an aqueous solution of surfactant. In general, the displacement efficiency is improved when the fluids become quasi-miscible. Understanding the phase behavior oil/water/surfactant systems is important because microemulsion has the ability to generate ultralow interfacial tension (<10(-2) mN m(-1)) that is required for miscibility to occur. Many studies focus on microemulsion formation and the resulting properties under equilibrium conditions. However, the majority of applications where microemulsion is present also involve flow, which has received relatively less attention. It is commonly assumed that the characteristics of an oil/water/surfactant system under flowing conditions are identical to the one under equilibrium conditions. Here, we show that this is not necessarily the case. We studied the equilibrium phase behavior of a model system consisting of n-decane and an aqueous solution of olefin sulfonate surfactant, which has practical applications for enhanced oil recovery. The salt content of the aqueous solution was varied to provide a range of different microemulsion compositions and oil-water interfacial tensions. We then performed microfluidic flow experiments to study the dynamic in situ formation of microemulsion by coinjecting bulk fluids of n-decane and surfactant solution into a T-junction capillary geometry. A solvatochromatic fluorescent dye was used to obtain spatially resolved compositional information. In this way, we visualized the microemulsion formation and the flow of it along with the excess phases. A complex interaction between the flow patterns and the microemulsion properties was observed. The formation of microemulsion influenced the flow regimes, and the flow regimes affected the characteristics of the microemulsion formation. In particular, at low flow rates, slug flow was observed, which had profound

  6. Open-pore polyurethane product

    DOEpatents

    Jefferson, R.T.; Salyer, I.O.

    1974-02-17

    The method is described of producing an open-pore polyurethane foam having a porosity of at least 50% and a density of 0.1 to 0.5 g per cu cm, and which consists of coherent spherical particles of less than 10 mu diam separated by interconnected interstices. It is useful as a filter and oil absorbent. The product is admirably adapted to scavenging of crude oil from the surface of seawater by preferential wicking. The oil-soaked product may then be compressed to recover the oil or burned for disposal. The crosslinked polyurethane structures are remarkably solvent and heat-resistance as compared with known thermoplastic structures. Because of their relative inertness, they are useful filters for gasoline and other hydrocarbon compounds. (7 claims)

  7. Wettability and spontaneous penetration of a water drop into hydrophobic pores.

    PubMed

    Choi, Hyunho; Liang, Hong

    2016-09-01

    The penetration of a water drop into hydrophobic pores reflects its instability on a porous surface. To understand the mechanism of penetration and to predict the behavior of such a drop, an investigation was conducted through experimental study combined theoretical analysis. Water drops with volumes from 0.5 to 15μL were examined on Polydimethylsiloxane (PDMS) substrates containing pores of 800μm and less in diameter. Results showed a critical condition at which a drop starts to penetrate into a certain sized pore. The critical condition presents a parabolic relationship between the volume of a water drop and the size of a hydrophobic pore. This behavior was due to a net force resulting from Laplace pressure, and capillary pressure. This force was found to be affected by the porosity, wetting angle, and there after the critical condition. The finding of this research will be beneficial for future design of structured surfaces. PMID:27267040

  8. Fabrication of porous aluminium with directional pores through thermal decomposition method

    NASA Astrophysics Data System (ADS)

    Nakajima, H.; Y Kim, S.; Park, J. S.

    2009-05-01

    Lotus-type porous metals were fabricated by unidirectional solidification in pressurized gas atmosphere. The elongated pres are evolved by insoluble gas resulted from the solubility gap between liquid and solid when the melt is solidified. Recently we developed a novel fabrication technique, in which gas compounds are used as a source of dissolving gas instead of the high pressure. In the present work this gas compound method was applied to fabrication of lotus aluminium. Hydrogen decomposed from calcium hydroxide, sodium bicarbonate and titanium hydride evolves cylindrical pores in aluminium. The porosity is about 20%. The pore size decreases and the pore number density increases with increasing amount of calcium hydroxide, which is explained by increase in pore nucleation sites.

  9. The one-dimensional compression method for extraction of pore water from unsaturated tuff and effects on pore-water chemistry

    SciTech Connect

    Higgins, J.D.; Burger, P.A.; Yang, L.C.

    1997-12-31

    Study of the hydrologic system at Yucca Mountain, Nevada, requires extraction of pore-water samples from unsaturated tuff bedrock. Two generations of compression cells have been designed and tested for extracting representative, unaltered pore-water samples from unsaturated tuff cores. The one-dimensional compression cell has a maximum compressive stress rating of 552 MPa. Results from 86 tests show that the minimum degree of saturation for successful extraction of pore water was about 14% for non welded tuff and about 61% for densely welded tuff. The high-pressure, one-dimensional compression cell has a maximum compressive stress rating of 827 MPa. Results from 109 tests show that the minimum degree of saturation for successful extraction of pore water was about 7.5% for non welded tuff and about 34% for densely welded tuff. Geochemical analyses show that, in general, there is a decrease in ion concentration of pore waters as extraction pressures increase. Only small changes in pore-water composition occur during the one-dimensional extraction test.

  10. Outflows in Sodium Excess Objects

    NASA Astrophysics Data System (ADS)

    Park, Jongwon; Jeong, Hyunjin; Yi, Sukyoung

    2016-01-01

    van Dokkum and Conroy reported that some giant elliptical galaxies show extraordinarily strong Na I absorption lines and suggested that this is the evidence of unusually bottom-heavy initial mass function. Jeong et al. later studied galaxies with unexpectedly strong Na D absorption lines (Na D excess objects: NEOs) and showed that the origins of NEOs are different for different types of galaxies. According to their study, the origin of Na D excess seems to be related to interstellar medium (ISM) in late-type galaxies, but there seems to be no contributions from ISM in smooth-looking early-type galaxies. In order to test this finding, we measured the Doppler components in Na D lines of NEOs. We hypothesized that if Na D absorption line is related to ISM, the absorption line is more likely to be blueshifted in the spectrum by the motion of ISM caused by outflow. Many of late-type NEOs show blueshifted Na D absorption lines, so their origin seems related to ISM. On the other hand, smooth-looking early-type NEOs do not show Doppler departure and Na D excess in early-type NEOs is likely not related to ISM, which is consistent with the finding of Jeong et al.

  11. The Cosmic Ray Electron Excess

    NASA Technical Reports Server (NTRS)

    Chang, J.; Adams, J. H.; Ahn, H. S.; Bashindzhagyan, G. L.; Christl, M.; Ganel, O.; Guzik, T. G.; Isbert, J.; Kim, K. C.; Kuznetsov, E. N.; Panasyuk, M. I.; Panov, A. D.; Schmidt, W. K. H.; Seo, E. S.; Sokolskaya, N. V.; Watts, J. W.; Wefel, J. P.; Wu, J.; Zatsepin, V. I.

    2008-01-01

    This slide presentation reviews the possible sources for the apparent excess of Cosmic Ray Electrons. The presentation reviews the Advanced Thin Ionization Calorimeter (ATIC) instrument, the various parts, how cosmic ray electrons are measured, and shows graphs that review the results of the ATIC instrument measurement. A review of Cosmic Ray Electrons models is explored, along with the source candidates. Scenarios for the excess are reviewed: Supernova remnants (SNR) Pulsar Wind nebulae, or Microquasars. Each of these has some problem that mitigates the argument. The last possibility discussed is Dark Matter. The Anti-Matter Exploration and Light-nuclei Astrophysics (PAMELA) mission is to search for evidence of annihilations of dark matter particles, to search for anti-nuclei, to test cosmic-ray propagation models, and to measure electron and positron spectra. There are slides explaining the results of Pamela and how to compare these with those of the ATIC experiment. Dark matter annihilation is then reviewed, which represent two types of dark matter: Neutralinos, and kaluza-Kline (KK) particles, which are next explained. The future astrophysical measurements, those from GLAST LAT, the Alpha Magnetic Spectrometer (AMS), and HEPCAT are reviewed, in light of assisting in finding an explanation for the observed excess. Also the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) could help by revealing if there are extra dimensions.

  12. Excess carbon in silicon carbide

    SciTech Connect

    Shen, X; Oxley, Mark P.; Puzyrev, Y; Tuttle, B R; Duscher, Gerd; Pantelides, Sokrates T.

    2010-01-01

    The application of SiC in electronic devices is currently hindered by low carrier mobility at the SiC/SiO{sub 2} interfaces. Recently, it was reported that 4H-SiC/SiO{sub 2} interfaces might have a transition layer on the SiC substrate side with C/Si ratio as high as 1.2, suggesting that carbon is injected into the SiC substrate during oxidation or other processing steps. We report finite-temperature quantum molecular dynamics simulations that explore the behavior of excess carbon in SiC. For SiC with 20% excess carbon, we find that, over short time ({approx} 24 ps), carbon atoms bond to each other and form various complexes, while the silicon lattice is largely unperturbed. These results, however, suggest that at macroscopic times scale, C segregation is likely to occur; therefore a transition layer with 20% extra carbon would not be stable. For a dilute distribution of excess carbon, we explore the pairing of carbon interstitials and show that the formation of dicarbon interstitial cluster is kinetically very favorable, which suggests that isolated carbon clusters may exist inside SiC substrate.

  13. Verification of excess defense material

    SciTech Connect

    Fearey, B.L.; Pilat, J.F.; Eccleston, G.W.; Nicholas, N.J.; Tape, J.W.

    1997-12-01

    The international community in the post-Cold War period has expressed an interest in the International Atomic Energy Agency (IAEA) using its expertise in support of the arms control and disarmament process in unprecedented ways. The pledges of the US and Russian presidents to place excess defense materials under some type of international inspections raises the prospect of using IAEA safeguards approaches for monitoring excess materials, which include both classified and unclassified materials. Although the IAEA has suggested the need to address inspections of both types of materials, the most troublesome and potentially difficult problems involve approaches to the inspection of classified materials. The key issue for placing classified nuclear components and materials under IAEA safeguards is the conflict between these traditional IAEA materials accounting procedures and the US classification laws and nonproliferation policy designed to prevent the disclosure of critical weapon-design information. Possible verification approaches to classified excess defense materials could be based on item accountancy, attributes measurements, and containment and surveillance. Such approaches are not wholly new; in fact, they are quite well established for certain unclassified materials. Such concepts may be applicable to classified items, but the precise approaches have yet to be identified, fully tested, or evaluated for technical and political feasibility, or for their possible acceptability in an international inspection regime. Substantial work remains in these areas. This paper examines many of the challenges presented by international inspections of classified materials.

  14. Atomic Structure of Graphene Subnanometer Pores.

    PubMed

    Robertson, Alex W; Lee, Gun-Do; He, Kuang; Gong, Chuncheng; Chen, Qu; Yoon, Euijoon; Kirkland, Angus I; Warner, Jamie H

    2015-12-22

    The atomic structure of subnanometer pores in graphene, of interest due to graphene's potential as a desalination and gas filtration membrane, is demonstrated by atomic resolution aberration corrected transmission electron microscopy. High temperatures of 500 °C and over are used to prevent self-healing of the pores, permitting the successful imaging of open pore geometries consisting of between -4 to -13 atoms, all exhibiting subnanometer diameters. Picometer resolution bond length measurements are used to confirm reconstruction of five-membered ring projections that often decorate the pore perimeter, knowledge which is used to explore the viability of completely self-passivated subnanometer pore structures; bonding configurations where the pore would not require external passivation by, for example, hydrogen to be chemically inert. PMID:26524121

  15. Pore formation and translocation of melittin.

    PubMed Central

    Matsuzaki, K; Yoneyama, S; Miyajima, K

    1997-01-01

    Melittin, a bee venom, is a basic amphiphilic peptide, which mainly acts on the lipid matrix of membranes, lysing various cells. To elucidate the molecular mechanism, we investigated its interactions with phospholipid vesicles. The peptide formed a pore with a short lifetime in the membrane, as revealed by the release of an anionic fluorescent dye, calcein, from the liposomes. Our new double-labeling method clarified that the pore size increased with the peptide-to-lipid ratio. Upon the disintegration of the pore, a fraction of the peptides translocated across the bilayer. The pore formation was coupled with the translocation, which was proved by three fluorescence experiments recently developed by our laboratory. A novel model for the melittin pore formation was discussed in comparison with other pore-forming peptides. PMID:9251799

  16. Direct pore-to-core up-scaling of displacement processes: Dynamic pore network modeling and experimentation

    NASA Astrophysics Data System (ADS)

    Aghaei, Arash; Piri, Mohammad

    2015-03-01

    We present a new dynamic pore network model that is capable of up-scaling two-phase flow processes from pore to core. This dynamic model provides a platform to study various flow processes in porous media at the core scale using the pore-scale physics. The most critical features of this platform include (1) the incorporation of viscous, capillary, and gravity pressure drops in pore-scale displacement thresholds, (2) wetting-phase corner flow in capillary elements with angular cross-sections, (3) adjustments of corner interfaces between wetting and non-wetting phases based on changes in local capillary pressure, (4) simultaneous injection of wetting and non-wetting phases from the inlet of the medium at constant flow rates that makes the study of steady-state processes possible, (5) heavy parallelization using a three-dimensional domain decomposition scheme that enables the study of two-phase flow at the core scale, and (6) constant pressure boundary condition at the outlet. For the validation of the dynamic model, three two-phase miniature core-flooding experiments were performed in a state-of-the-art micro core-flooding system integrated with a high-resolution X-ray micro-CT scanner. The dynamic model was rigorously validated by comparing the predicted local saturation profiles, fractional flow curves, relative permeabilities, and residual oil saturations against their experimental counterparts. The validated dynamic model was then used to study low-IFT and high-viscosity two-phase flow processes and investigate the effect of high capillary number on relative permeabilities and residual oil saturation.

  17. 12 CFR 925.23 - Excess stock.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 7 2010-01-01 2010-01-01 false Excess stock. 925.23 Section 925.23 Banks and... BANKS Stock Requirements § 925.23 Excess stock. (a) Sale of excess stock. Subject to the restriction in paragraph (b) of this section, a member may purchase excess stock as long as the purchase is approved by...

  18. 34 CFR 300.16 - Excess costs.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 34 Education 2 2010-07-01 2010-07-01 false Excess costs. 300.16 Section 300.16 Education... DISABILITIES General Definitions Used in This Part § 300.16 Excess costs. Excess costs means those costs that... for an example of how excess costs must be calculated.) (Authority: 20 U.S.C. 1401(8))...

  19. 34 CFR 300.16 - Excess costs.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 34 Education 2 2012-07-01 2012-07-01 false Excess costs. 300.16 Section 300.16 Education... DISABILITIES General Definitions Used in This Part § 300.16 Excess costs. Excess costs means those costs that... for an example of how excess costs must be calculated.) (Authority: 20 U.S.C. 1401(8))...

  20. 34 CFR 300.16 - Excess costs.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 34 Education 2 2011-07-01 2010-07-01 true Excess costs. 300.16 Section 300.16 Education... DISABILITIES General Definitions Used in This Part § 300.16 Excess costs. Excess costs means those costs that... for an example of how excess costs must be calculated.) (Authority: 20 U.S.C. 1401(8))...

  1. Nonlinear transport of soft droplets in pore networks

    NASA Astrophysics Data System (ADS)

    Vernerey, Franck; Benet Cerda, Eduard; Koo, Kanghyeon

    A large number of biological and technological processes depend on the transport of soft colloidal particles through porous media; this includes the transport and separation of cells, viruses or drugs through tissues, membranes and microfluidic devices. In these systems, the interactions between soft particles, background fluid and the surrounding pore space yield complex, nonlinear behaviors such as non-Darcy flows, localization and jamming. We devise a computational strategy to investigate the transport of non-wetting and deformable water droplets in a microfluidic device made of a random distribution of cylindrical obstacles. We first derive scaling laws for the entry of the droplet in a single pore and discuss the role of surface tension, contact angle and size in this process. This information is then used to study the transport of multiple droplets in an obstacle network. We find that when the droplet size is close to the pore size, fluid flow and droplet trafficking strongly interact, leading to local redistributions in pressure fields, intermittent clogging and jamming. Importantly, it is found that the overall droplet and fluid transport display three different scaling regimes depending on the forcing pressure, and that these regimes can be related to droplet properties.

  2. Microtomography and pore-scale modeling of two-phase Fluid Distribution

    SciTech Connect

    Silin, D.; Tomutsa, L.; Benson, S.; Patzek, T.

    2010-10-19

    Synchrotron-based X-ray microtomography (micro CT) at the Advanced Light Source (ALS) line 8.3.2 at the Lawrence Berkeley National Laboratory produces three-dimensional micron-scale-resolution digital images of the pore space of the reservoir rock along with the spacial distribution of the fluids. Pore-scale visualization of carbon dioxide flooding experiments performed at a reservoir pressure demonstrates that the injected gas fills some pores and pore clusters, and entirely bypasses the others. Using 3D digital images of the pore space as input data, the method of maximal inscribed spheres (MIS) predicts two-phase fluid distribution in capillary equilibrium. Verification against the tomography images shows a good agreement between the computed fluid distribution in the pores and the experimental data. The model-predicted capillary pressure curves and tomography-based porosimetry distributions compared favorably with the mercury injection data. Thus, micro CT in combination with modeling based on the MIS is a viable approach to study the pore-scale mechanisms of CO{sub 2} injection into an aquifer, as well as more general multi-phase flows.

  3. New general pore size distribution model by classical thermodynamics application: Activated carbon

    USGS Publications Warehouse

    Lordgooei, M.; Rood, M.J.; Rostam-Abadi, M.

    2001-01-01

    A model is developed using classical thermodynamics to characterize pore size distributions (PSDs) of materials containing micropores and mesopores. The thermal equation of equilibrium adsorption (TEEA) is used to provide thermodynamic properties and relate the relative pore filling pressure of vapors to the characteristic pore energies of the adsorbent/adsorbate system for micropore sizes. Pore characteristic energies are calculated by averaging of interaction energies between adsorbate molecules and adsorbent pore walls as well as considering adsorbate-adsorbate interactions. A modified Kelvin equation is used to characterize mesopore sizes by considering variation of the adsorbate surface tension and by excluding the adsorbed film layer for the pore size. The modified-Kelvin equation provides similar pore filling pressures as predicted by density functional theory. Combination of these models provides a complete PSD of the adsorbent for the micropores and mesopores. The resulting PSD is compared with the PSDs from Jaroniec and Choma and Horvath and Kawazoe models as well as a first-order approximation model using Polanyi theory. The major importance of this model is its basis on classical thermodynamic properties, less simplifying assumptions in its derivation compared to other methods, and ease of use.

  4. Modeling the interaction of ultrasound with pores

    NASA Technical Reports Server (NTRS)

    Lu, Yichi; Wadley, Haydn N. G.; Parthasarathi, Sanjai

    1991-01-01

    Factors that affect ultrasonic velocity sensing of density during consolidation of metal powders are examined. A comparison is made between experimental results obtained during the final stage of densification and the predictions of models that assume either a spherical or a spheroidal pore shape. It is found that for measurements made at low frequencies during the final stage of densification, relative density (pore fraction) and pore shape are the two most important factors determining the ultrasonic velocity, the effect of pore size is negligible.

  5. The Effect of Mineralization on Pore-size Distribution Patterns in Sandstone

    NASA Astrophysics Data System (ADS)

    Emmanuel, S.; Ague, J. J.

    2008-12-01

    In geological media, pore-size distributions can strongly influence important physical parameters such as permeability and specific surface area. Mineralization in rock and soil often reduces the overall porosity and can also induce changes in the distribution of pore sizes. However, the way in which mineralization affects pore size is poorly understood, with relatively little data available from field-based studies. Here, we present a high-resolution profile of pore-size distributions from a variably mineralized sandstone section. The samples were obtained from a Barents Sea core in which quartz cement had preferentially precipitated around stylolite (pressure solution) interfaces; pore-size distributions were measured in 15 samples using mercury injection porosimetry. The results demonstrate that mineralization led to a reduction in porosity of around 40% in samples closest to the stylolite. However, this reduction was not uniform over the range of pore-sizes: the greatest level of porosity reduction occurred in the 10-5-10-4 m size range, while there was no discernible change in the porosity associated with smaller pores. A reactive transport model - simulating the dissolution of quartz at the stylolite interface and subsequent reprecipitation in the rock matrix - was used to predict the evolution of the porosity associated with multiple pore-sizes; the model was successfully able to reproduce the observed porosity patterns, indicating that such an approach could be integrated into efforts to model the evolution of porosity in geological formations, including during CO2 sequestration.

  6. Upscaling of Transport Parameters in Reacting Porous Media; Pore-Scale Modelling

    NASA Astrophysics Data System (ADS)

    Raoof, Amir; Nick, Hamidreza M.; Hassanizadeh, Majid

    2014-05-01

    Pore scale modelling provides a tool for upscaling of flow and transport parameters in porous media. We use PoreFlow, a pore-network modelling tool capable of simulating fluid flow and multi-component reactive and adsorptive transport under saturated and variably saturated conditions. Simulations include: pore network generator, drainage simulator, calculation of pressure and velocity distributions, and modelling of reactive solute transport accounting for advection and diffusion. The pore space is represented using a multi-directional pore-network capable of capturing the random structure of a given porous media with user-defined directional connectivities for anisotropic pore structures. The chemical reactions can occur within the liquid phase, as well as between the liquid and solid phases which may result in an evolution of porosity and permeability. Potential applications are geological sequestration of CO2, affecting the reservoir rock transport properties as well as influencing the wellbore integrity, and acid-gas injection during enhanced oil recovery. Other examples will be provided, showing use of pore-scale information to determine macro-scale properties such as permeability-porosity changes, solute dispersivity, adsorption reaction coefficients, effective diffusion and tortuosity. Such information can be used as constitutive relations within continuum scale governing equations to model physical and chemical processes more accurately at the larger scales.

  7. Two interacting particles in a spherical pore

    NASA Astrophysics Data System (ADS)

    Urrutia, Ignacio; Castelletti, Gabriela

    2011-02-01

    In this work we analytically evaluate, for the first time, the exact canonical partition function for two interacting spherical particles into a spherical pore. The interaction with the spherical substrate and between particles is described by an attractive square-well and a square-shoulder potential. In addition, we obtain exact expressions for both the one particle and an averaged two particle density distribution. We develop a thermodynamic approach to few-body systems by introducing a method based on thermodynamic measures [I. Urrutia, J. Chem. Phys. 134, 104503 (2010)] for nonhard interaction potentials. This analysis enables us to obtain expressions for the pressure, the surface tension, and the equivalent magnitudes for the total and Gaussian curvatures. As a by-product, we solve systems composed of two particles outside a fixed spherical obstacle. We study the low density limit for a many-body system confined to a spherical cavity and a many-body system surrounding a spherical obstacle. From this analysis we derive the exact first order dependence of the surface tension and Tolman length. Our findings show that the Tolman length goes to zero in the case of a purely hard wall spherical substrate, but contains a zero order term in density for square-well and square-shoulder wall-fluid potentials. This suggests that any nonhard wall-fluid potential should produce a non-null zero order term in the Tolman length.

  8. Fabrication, properties, and applications of porous metals with directional pores

    PubMed Central

    NAKAJIMA, Hideo

    2010-01-01

    Lotus-type porous metals with aligned long cylindrical pores are fabricated by unidirectional solidification from the melt with a dissolved gas such as hydrogen, nitrogen, or oxygen. The gas atoms can be dissolved into the melt via a pressurized gas atmosphere or thermal decomposition of gaseous compounds. Three types of solidification techniques have been developed: mold casting, continuous zone melting, and continuous casting techniques. The last method is superior from the viewpoint of mass production of lotus metals. The observed anisotropic behaviors of the mechanical properties, sound absorption, and thermal conductivity are inherent to the anisotropic porous structure. In particular, the remarkable anisotropy in the mechanical strength is attributed to the stress concentration around the pores aligned perpendicular to the loading direction. Heat sinks are a promising application of lotus metals due to the high cooling performance with a large heat transfer. PMID:21084772

  9. Open pore structure analysis of lithium bearing ceramics

    NASA Astrophysics Data System (ADS)

    Elbel, H.

    1988-07-01

    The analysis of the open pore structure includes mercury porosimetry, helium stereopycnometry, gas permeability and specific surface area measurements. These methods were used in the analysis of different types of Li 2SiO 3 and Li 4SiO 4 specimens whose behaviour is tested under operation conditions in various irradiation experiments. Mercury porosimetry yielded density of the specimens, size distribution of the channels and amount of the open porosity. The correlation between mercury pressure and channel diameter was approximated by the Washburn equation. Density determinations by means of helium stereopycnometry demonstrated the existence of open pore volume below the mercury porosimetry detection. Additional information about the structure of open porosity was obtained by gas permeability measurements evaluated using the Carman relation, which is a generalization of the Hagen-Poiseuille law. This approach correlates structure parameters of the open porosity with permeability coefficients. The specific surface area was determined by applying the BET theory to volumetric nitrogen gas adsorption.

  10. Translocation of flexible polymersomes across pores at the nanoscale.

    PubMed

    Pegoraro, Carla; Cecchin, Denis; Madsen, Jeppe; Warren, Nicholas; Armes, Steven P; MacNeil, Sheila; Lewis, Andrew; Battaglia, Giuseppe

    2014-04-01

    Hierarchical biological systems such as tissues and organs are often characterised by highly crowded and packed environments with nanoscopic interconnections between them. Engineering nanovectors that can penetrate and diffuse across these is critical to ensure enhanced delivery and targeting. Here we demonstrate that flexible polymeric vesicles, known as polymersomes, enable the translocation of large macromolecules across both synthetic and biological porous systems. We compare the translocation across narrow pores of different polymersome formulations. We demonstrate that effective translocation depends on the right combination of mechanical properties and surface lubrication. We prove that with the effect of external gradients (e.g. osmotic pressure, capillarity, hydration, etc.) polymersomes can translocate across pores with diameters one order of magnitude smaller without breaking. We demonstrate that these properties are essential to develop effective tissue penetration and show polymersome mediated transdermal delivery of large macromolecules such as dextran and antibodies using human ex vivo skin. PMID:26828800

  11. Fabrication, properties, and applications of porous metals with directional pores.

    PubMed

    Nakajima, Hideo

    2010-01-01

    Lotus-type porous metals with aligned long cylindrical pores are fabricated by unidirectional solidification from the melt with a dissolved gas such as hydrogen, nitrogen, or oxygen. The gas atoms can be dissolved into the melt via a pressurized gas atmosphere or thermal decomposition of gaseous compounds. Three types of solidification techniques have been developed: mold casting, continuous zone melting, and continuous casting techniques. The last method is superior from the viewpoint of mass production of lotus metals. The observed anisotropic behaviors of the mechanical properties, sound absorption, and thermal conductivity are inherent to the anisotropic porous structure. In particular, the remarkable anisotropy in the mechanical strength is attributed to the stress concentration around the pores aligned perpendicular to the loading direction. Heat sinks are a promising application of lotus metals due to the high cooling performance with a large heat transfer. PMID:21084772

  12. Nanofiltration membranes with narrowed pore size distribution via pore wall modification.

    PubMed

    Du, Yong; Lv, Yan; Qiu, Wen-Ze; Wu, Jian; Xu, Zhi-Kang

    2016-06-30

    We propose a novel strategy for narrowing down the pore size distribution of ready-made nanofiltration membranes (NFMs) via pore wall modification. NFMs were subjected to the filtration of a highly reactive molecule solution, during which large pores were selectively reduced in size. The as-treated NFMs have high monovalent ion/divalent ion selectivity. PMID:27321407

  13. Petrophysical and magnetic pore network anisotropy of some cretaceous sandstone from Tushka Basin, Egypt

    NASA Astrophysics Data System (ADS)

    Nabawy, Bassem S.; Rochette, Pierre; Géraud, Yves

    2009-04-01

    Pore magnetic fabric is a well-established technique for the determination of pore elongation and preferred directions for migration of the interstitial fluids. This study further exemplify this technique on a set of the Nubia sandstones through a comparison with the pore anisotropy obtained from measuring permeability in three orthogonal directions in a gaz permeameter. The Nubia sandstones are represented in Tushka area (South Egypt) by quartz arenite of large porosity (29-40 per cent) which was measured on thin sections parallel and perpendicular to the bedding plane and petrophysically by helium pycnometry and ferrofluid injection at 1 bar pressure. Petrographically, there is a detectable difference between the porosity values in the bedding plane and in the perpendicular direction indicating inhomogeneity in the pore space network distribution. The petrophysical studies indicate large porosity and permeability values with some differences between the helium and ferrofluid porosity due to presence of micro pore spaces not accessible for the ferrofluid molecules having relatively high diameters and injected at low pressure. An overall agreement is observed between the permeability anisotropy and the magnetic grain and pore fabrics (magnetic anisotropy measured before and after ferrofluid injection). The three fabrics are mainly dominated by a bedding parallel foliation. In a few cases maximum permeability appears to be perpendicular to bedding. Within the bedding plane, maximum pore elongation direction from ferrofluid injection is NNW for Adindan and Kesieba formations and NW for Abu Simbil Formation. The maximum pore elongation direction for Abu Ballas samples showed a direction fluctuating around the E-W direction, the main fault trends in Tushka area. The pore fabric of Abu Ballas formation seems therefore to be structurally controlled, while it would be originated from palaeocurrent directions in the other formations.

  14. Fabrication of Porous Copper with Directional Pores through Thermal Decomposition of Compounds

    NASA Astrophysics Data System (ADS)

    Nakajima, Hideo; Ide, Takuya

    2008-02-01

    Lotus-type porous copper with aligned long cylindrical pores was fabricated by unidirectional solidification in an argon atmosphere. The hydrogen dissolved in molten copper through thermal decomposition of titanium hydride contained in the mold, which then formed hydrogen gas that evolved into the gas pores in the solidified copper. On the other hand, titanium may form oxides in the melt that serve as nucleation sites for insoluble hydrogen. The porosity and pore size decreased with increasing atmospheric argon pressure during the solidification, which can be explained by the Boyle-Charles law and the possible suppression of the decomposition due to external pressure. The addition of titanium hydride was more effective when it was added just before the melt solidified than when it was added to the melt. Moreover, the thermal decomposition method (TDM) is superior to the conventional fabrication method, which requires high pressure hydrogen gas. Thus, TDM is a promising fabrication technique for various lotus metals.

  15. Pore-fluid migration and the timing of the 2005 M8.7 Nias earthquake

    USGS Publications Warehouse

    Hughes, K.L.H.; Masterlark, Timothy; Mooney, W.D.

    2011-01-01

    Two great earthquakes have occurred recently along the Sunda Trench, the 2004 M9.2 Sumatra-Andaman earthquake and the 2005 M8.7 Nias earthquake. These earthquakes ruptured over 1600 km of adjacent crust within 3 mo of each other. We quantitatively present poroelastic deformation analyses suggesting that postseismic fluid flow and recovery induced by the Sumatra-Andaman earthquake advanced the timing of the Nias earthquake. Simple back-slip simulations indicate that the megapascal (MPa)-scale pore-pressure recovery is equivalent to 7 yr of interseismic Coulomb stress accumulation near the Nias earthquake hypocenter, implying that pore-pressure recovery of the Sumatra-Andaman earthquake advanced the timing of the Nias earthquake by ~7 yr. That is, in the absence of postseismic pore-pressure recovery, we predict that the Nias earthquake would have occurred in 2011 instead of 2005. ?? 2011 Geological Society of America.

  16. Merits of excess bagasse as fuel for generating electricity. [Florida

    SciTech Connect

    Perea, P.

    1981-05-01

    The rising cost of fuel oil improves the economics for sugar factories of using excess bagasse to produce more electricity than they require for sale to the public utility companies. Recently, the United States Sugar Corporation, in Florida, initiated the operation of a 20 MW plant fueled with excess bagasse only, and the electricity it generates is sold to a local utility. This constitutes a saving of 10 million liters of oil per year. The operating cycle is described of a system of high-pressure boilers and automatically controlled turbogenerator for the production of energy from bagasse. This system is a pre-engineered design which is very simple to install and operate and can be fitted in with the electric-generating installations which are normally found in practically any sugar factory without making significant modifications to the factory. An economic analysis is presented of power generation using excess bagasse for a 3MW unit and a 4MW unit.

  17. 49 CFR 192.381 - Service lines: Excess flow valve performance standards.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Meters, Service Regulators, and Service Lines § 192.381 Service lines: Excess flow valve performance... hour (0.57 cubic meters per hour); or (B) For an excess flow valve designed to prevent equalization of pressure across the valve, to no more than 0.4 cubic feet per hour (.01 cubic meters per hour); and (4)...

  18. 49 CFR 192.381 - Service lines: Excess flow valve performance standards.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Meters, Service Regulators, and Service Lines § 192.381 Service lines: Excess flow valve performance... hour (0.57 cubic meters per hour); or (B) For an excess flow valve designed to prevent equalization of pressure across the valve, to no more than 0.4 cubic feet per hour (.01 cubic meters per hour); and (4)...

  19. 49 CFR 192.381 - Service lines: Excess flow valve performance standards.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Meters, Service Regulators, and Service Lines § 192.381 Service lines: Excess flow valve performance... hour (0.57 cubic meters per hour); or (B) For an excess flow valve designed to prevent equalization of pressure across the valve, to no more than 0.4 cubic feet per hour (.01 cubic meters per hour); and (4)...

  20. 49 CFR 192.381 - Service lines: Excess flow valve performance standards.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Meters, Service Regulators, and Service Lines § 192.381 Service lines: Excess flow valve performance... hour (0.57 cubic meters per hour); or (B) For an excess flow valve designed to prevent equalization of pressure across the valve, to no more than 0.4 cubic feet per hour (.01 cubic meters per hour); and (4)...

  1. [Iodine excess induced thyroid dysfunction].

    PubMed

    Egloff, Michael; Philippe, Jacques

    2016-04-20

    The principle sources of iodine overload, amiodarone and radiologic contrast media, are frequently used in modern medicine. The thyroid gland exerts a protective effect against iodine excess by suppressing iodine internalization into the thyrocyte and iodine organification, the Wolff-Chaikoff effect. Insufficiency of this effect or lack of escape from it leads to hypo- or hyperthyroidism respectively. Amiodarone induced thyrotoxicosis is a complex condition marked by two different pathophysiological mechanisms with different treatments. Thyroid metabolism changes after exposure to radiologic contrast media are frequent, but they rarely need to be treated. High risk individuals need to be identifed in order to delay the exam or to monitor thyroid function or apply prophylactic measures in selected cases. PMID:27276725

  2. Diphoton excess and running couplings

    NASA Astrophysics Data System (ADS)

    Bae, Kyu Jung; Endo, Motoi; Hamaguchi, Koichi; Moroi, Takeo

    2016-06-01

    The recently observed diphoton excess at the LHC may suggest the existence of a singlet (pseudo-)scalar particle with a mass of 750 GeV which couples to gluons and photons. Assuming that the couplings to gluons and photons originate from loops of fermions and/or scalars charged under the Standard Model gauge groups, we show that there is a model-independent upper bound on the cross section σ (pp → S → γγ) as a function of the cutoff scale Λ and masses of the fermions and scalars in the loop. Such a bound comes from the fact that the contribution of each particle to the diphoton event amplitude is proportional to its contribution to the one-loop β functions of the gauge couplings. We also investigate the perturbativity of running Yukawa couplings in models with fermion loops, and show the upper bounds on σ (pp → S → γγ) for explicit models.

  3. Evaporative modeling for idealized lithographic pores

    NASA Astrophysics Data System (ADS)

    Oinuma, Ryoji; Best, Frederick

    2002-01-01

    As a demand for the high performance and small size electronics devices increased, the heat removal from those electronic devices for space use is getting critical factor more than devices on the earth due to the limitation of the size. The purpose of this paper is to show a study of optimized size of coherent pores or slits in the evaporative wick of a heat pipe to cool down the high heat flux density heat source. Our system considered in this paper consists of a plate heat source, the evaporative wick with coherent pores and conducting walls connecting between the heat source and the evaporator. The evaporation rate of working fluid along the meniscus interface in a micro-order pore or slit was calculated based on the kinetic theory and the statistical rate theory to find a proper diameter of pores to cool down the heat source effectively. The results show the smaller diameter of pores is preferred to achieve the smallest total size of the evaporator although it will involve the cost issue. As a demand for the high performance and small size electronics devices increased, the heat removal from those electronic devices for space use is getting critical factor more than devices on the earth due to the limitation of the size. The purpose of this paper is to show a study of optimized size of coherent pores or slits in the evaporative wick of a heat pipe to cool down the high heat flux density heat source. Our system considered in this paper consists of a plate heat source, the evaporative wick with coherent pores and conducting walls connecting between the heat source and the evaporator. The evaporation rate of working fluid along the meniscus interface in a micro-order pore or slit was calculated based on the kinetic theory and the statistical rate theory to find a proper diameter of pores to cool down the heat source effectively. The results show that the smaller diameter of pores uses the pore for evaporation effectively and is preferred to achieve the smallest

  4. A USANS/SANS study of the accessibility of pores in the Barnett Shale to methane and water

    USGS Publications Warehouse

    Ruppert, Leslie F.; Sakurovs, Richard; Blach, Tomasz P.; He, Lilin; Melnichenko, Yuri B.; Mildner, David F.; Alcantar-Lopez, Leo

    2013-01-01

    Shale is an increasingly important source of natural gas in the United States. The gas is held in fine pores that need to be accessed by horizontal drilling and hydrofracturing techniques. Understanding the nature of the pores may provide clues to making gas extraction more efficient. We have investigated two Mississippian Barnett Shale samples, combining small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) to determine the pore size distribution of the shale over the size range 10 nm to 10 μm. By adding deuterated methane (CD4) and, separately, deuterated water (D2O) to the shale, we have identified the fraction of pores that are accessible to these compounds over this size range. The total pore size distribution is essentially identical for the two samples. At pore sizes >250 nm, >85% of the pores in both samples are accessible to both CD4 and D2O. However, differences in accessibility to CD4 are observed in the smaller pore sizes (~25 nm). In one sample, CD4 penetrated the smallest pores as effectively as it did the larger ones. In the other sample, less than 70% of the smallest pores (4, but they were still largely penetrable by water, suggesting that small-scale heterogeneities in methane accessibility occur in the shale samples even though the total porosity does not differ. An additional study investigating the dependence of scattered intensity with pressure of CD4 allows for an accurate estimation of the pressure at which the scattered intensity is at a minimum. This study provides information about the composition of the material immediately surrounding the pores. Most of the accessible (open) pores in the 25 nm size range can be associated with either mineral matter or high reflectance organic material. However, a complementary scanning electron microscopy investigation shows that most of the pores in these shale samples are contained in the organic components. The neutron scattering results indicate that the pores are

  5. Pore-forming toxins: ancient, but never really out of fashion.

    PubMed

    Dal Peraro, Matteo; van der Goot, F Gisou

    2016-02-01

    Pore-forming toxins (PFTs) are virulence factors produced by many pathogenic bacteria and have long fascinated structural biologists, microbiologists and immunologists. Interestingly, pore-forming proteins with remarkably similar structures to PFTs are found in vertebrates and constitute part of their immune system. Recently, structural studies of several PFTs have provided important mechanistic insights into the metamorphosis of PFTs from soluble inactive monomers to cytolytic transmembrane assemblies. In this Review, we discuss the diverse pore architectures and membrane insertion mechanisms that have been revealed by these studies, and we consider how these features contribute to binding specificity for different membrane targets. Finally, we explore the potential of these structural insights to enable the development of novel therapeutic strategies that would prevent both the establishment of bacterial resistance and an excessive immune response. PMID:26639780

  6. Molecular mechanism of pore formation by actinoporins.

    PubMed

    Kristan, Katarina Crnigoj; Viero, Gabriella; Dalla Serra, Mauro; Macek, Peter; Anderluh, Gregor

    2009-12-15

    Actinoporins are effective pore-forming toxins produced by sea anemones. These extremely potent, basic 20 kDa proteins readily form pores in membranes that contain sphingomyelin. Much has been learned about the molecular basis of their pore-forming mechanism in recent years. Pore formation is a multi-step process that involves recognition of membrane sphingomyelin, firm binding to the membrane accompanied by the transfer of the N-terminal region to the lipid-water interface and finally pore formation after oligomerisation of three to four monomers. The final conductive pathway is formed by amphipathic alpha-helices, hence actinoporins are an important example of so-called alpha-helical pore-forming toxins. Actinoporins have become useful model proteins to study protein-membrane interactions, specific recognition of lipids in the membrane, and protein oligomerisation in the lipid milieu. Recent sequence and structural data of proteins similar to actinoporins indicate that they are not a unique family restricted to sea anemones as was long believed. An AF domain superfamily (abbreviated from actinoporin-like proteins and fungal fruit-body lectins) was defined and shown to contain members from three animal and two plant phyla. On the basis of functional properties of some members we hypothesise that AF domain proteins are peripheral membrane proteins. Finally, ability of actinoporins to form transmembrane pores has been exploited in some novel biomedical applications. PMID:19268680

  7. 12 CFR 1263.23 - Excess stock.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 7 2011-01-01 2011-01-01 false Excess stock. 1263.23 Section 1263.23 Banks and Banking FEDERAL HOUSING FINANCE AGENCY FEDERAL HOME LOAN BANKS MEMBERS OF THE BANKS Stock Requirements § 1263.23 Excess stock. (a) Sale of excess stock. Subject to the restriction in paragraph (b) of...

  8. 7 CFR 985.56 - Excess oil.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 8 2010-01-01 2010-01-01 false Excess oil. 985.56 Section 985.56 Agriculture... HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR WEST Order Regulating Handling Volume Limitations § 985.56 Excess oil. Oil of any class in excess of a producer's applicable annual allotment shall be identified...

  9. 7 CFR 985.56 - Excess oil.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 8 2011-01-01 2011-01-01 false Excess oil. 985.56 Section 985.56 Agriculture... HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR WEST Order Regulating Handling Volume Limitations § 985.56 Excess oil. Oil of any class in excess of a producer's applicable annual allotment shall be identified...

  10. 7 CFR 985.56 - Excess oil.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 8 2012-01-01 2012-01-01 false Excess oil. 985.56 Section 985.56 Agriculture... HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR WEST Order Regulating Handling Volume Limitations § 985.56 Excess oil. Oil of any class in excess of a producer's applicable annual allotment shall be identified...

  11. 7 CFR 985.56 - Excess oil.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 8 2013-01-01 2013-01-01 false Excess oil. 985.56 Section 985.56 Agriculture... HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR WEST Order Regulating Handling Volume Limitations § 985.56 Excess oil. Oil of any class in excess of a producer's applicable annual allotment shall be identified...

  12. 7 CFR 985.56 - Excess oil.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 8 2014-01-01 2014-01-01 false Excess oil. 985.56 Section 985.56 Agriculture... HANDLING OF SPEARMINT OIL PRODUCED IN THE FAR WEST Order Regulating Handling Volume Limitations § 985.56 Excess oil. Oil of any class in excess of a producer's applicable annual allotment shall be identified...

  13. 43 CFR 426.12 - Excess land.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 1 2011-10-01 2011-10-01 false Excess land. 426.12 Section 426.12 Public Lands: Interior Regulations Relating to Public Lands BUREAU OF RECLAMATION, DEPARTMENT OF THE INTERIOR ACREAGE LIMITATION RULES AND REGULATIONS § 426.12 Excess land. (a) The process of designating excess and nonexcess land. If a landowner owns...

  14. 10 CFR 904.10 - Excess energy.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 4 2011-01-01 2011-01-01 false Excess energy. 904.10 Section 904.10 Energy DEPARTMENT OF ENERGY GENERAL REGULATIONS FOR THE CHARGES FOR THE SALE OF POWER FROM THE BOULDER CANYON PROJECT Power Marketing § 904.10 Excess energy. (a) If excess Energy is determined by the United States to be...

  15. 10 CFR 904.10 - Excess energy.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 4 2013-01-01 2013-01-01 false Excess energy. 904.10 Section 904.10 Energy DEPARTMENT OF ENERGY GENERAL REGULATIONS FOR THE CHARGES FOR THE SALE OF POWER FROM THE BOULDER CANYON PROJECT Power Marketing § 904.10 Excess energy. (a) If excess Energy is determined by the United States to be...

  16. 10 CFR 904.10 - Excess energy.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 4 2010-01-01 2010-01-01 false Excess energy. 904.10 Section 904.10 Energy DEPARTMENT OF ENERGY GENERAL REGULATIONS FOR THE CHARGES FOR THE SALE OF POWER FROM THE BOULDER CANYON PROJECT Power Marketing § 904.10 Excess energy. (a) If excess Energy is determined by the United States to be...

  17. 10 CFR 904.10 - Excess energy.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 4 2012-01-01 2012-01-01 false Excess energy. 904.10 Section 904.10 Energy DEPARTMENT OF ENERGY GENERAL REGULATIONS FOR THE CHARGES FOR THE SALE OF POWER FROM THE BOULDER CANYON PROJECT Power Marketing § 904.10 Excess energy. (a) If excess Energy is determined by the United States to be...

  18. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials.

    PubMed

    Félix, V; Jannot, Y; Degiovanni, A

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10(-1) to 10(5) Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent. PMID:22667640

  19. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    NASA Astrophysics Data System (ADS)

    Félix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-01

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10-1 to 105 Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  20. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    SciTech Connect

    Felix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-15

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10{sup -1} to 10{sup 5} Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  1. Pore-scale investigation on stress-dependent characteristics of granular packs and the impact of pore deformation on fluid distribution

    SciTech Connect

    Yoon, Hongkyu; Klise, Katherine A.; Torrealba, Victor A.; Karpyn, Zuleima T.; Crandall, D.

    2015-05-25

    Understanding the effect of changing stress conditions on multiphase flow in porous media is of fundamental importance for many subsurface activities including enhanced oil recovery, water drawdown from aquifers, soil confinement, and geologic carbon storage. Geomechanical properties of complex porous systems are dynamically linked to flow conditions, but their feedback relationship is often oversimplified due to the difficulty of representing pore-scale stress deformation and multiphase flow characteristics in high fidelity. In this work, we performed pore-scale experiments of single- and multiphase flow through bead packs at different confining pressure conditions to elucidate compaction-dependent characteristics of granular packs and their impact on fluid flow. A series of drainage and imbibition cycles were conducted on a water-wet, soda-lime glass bead pack under varying confining stress conditions. Simultaneously, X-ray micro-CT was used to visualize and quantify the degree of deformation and fluid distribution corresponding with each stress condition and injection cycle. Micro-CT images were segmented using a gradient-based method to identify fluids (e.g., oil and water), and solid phase redistribution throughout the different experimental stages. Changes in porosity, tortuosity, and specific surface area were quantified as a function of applied confining pressure. Results demonstrate varying degrees of sensitivity of these properties to confining pressure, which suggests that caution must be taken when considering scalability of these properties for practical modeling purposes. Changes in capillary number with confining pressure are attributed to the increase in pore velocity as a result of pore contraction. Furthermore, this increase in pore velocity was found to have a marginal impact on average phase trapping at different confining pressures.

  2. Pore-scale investigation on stress-dependent characteristics of granular packs and the impact of pore deformation on fluid distribution

    DOE PAGESBeta

    Yoon, Hongkyu; Klise, Katherine A.; Torrealba, Victor A.; Karpyn, Zuleima T.; Crandall, D.

    2015-05-25

    Understanding the effect of changing stress conditions on multiphase flow in porous media is of fundamental importance for many subsurface activities including enhanced oil recovery, water drawdown from aquifers, soil confinement, and geologic carbon storage. Geomechanical properties of complex porous systems are dynamically linked to flow conditions, but their feedback relationship is often oversimplified due to the difficulty of representing pore-scale stress deformation and multiphase flow characteristics in high fidelity. In this work, we performed pore-scale experiments of single- and multiphase flow through bead packs at different confining pressure conditions to elucidate compaction-dependent characteristics of granular packs and their impactmore » on fluid flow. A series of drainage and imbibition cycles were conducted on a water-wet, soda-lime glass bead pack under varying confining stress conditions. Simultaneously, X-ray micro-CT was used to visualize and quantify the degree of deformation and fluid distribution corresponding with each stress condition and injection cycle. Micro-CT images were segmented using a gradient-based method to identify fluids (e.g., oil and water), and solid phase redistribution throughout the different experimental stages. Changes in porosity, tortuosity, and specific surface area were quantified as a function of applied confining pressure. Results demonstrate varying degrees of sensitivity of these properties to confining pressure, which suggests that caution must be taken when considering scalability of these properties for practical modeling purposes. Changes in capillary number with confining pressure are attributed to the increase in pore velocity as a result of pore contraction. Furthermore, this increase in pore velocity was found to have a marginal impact on average phase trapping at different confining pressures.« less

  3. Generalized formula for the surface stiffness of fluid-saturated porous media containing parallel pore channels

    SciTech Connect

    Nagy, P.B.; Nayfeh, A.H.

    1995-09-25

    The surface stiffness of a fluid-saturated porous solid is defined as the ratio between a small change in capillary pressure and the average displacement of the boundary due to the resulting rise or fall of the fluid level in the pore channels. When the surface pores are structurally open, the surface stiffness is entirely due to the stiffness of the microscopic fluid membranes extended by capillary forces over the surface pores. Due to interfacial tension between the immiscible wetting fluid in the pores and nonwetting fluid (air) above the surface, essentially closed-pore boundary conditions can prevail at the interface. It has recently been shown that the surface stiffness of a porous material containing cylindrical pores can be calculated simply as the surface tension of the saturating fluid divided by the static permeability of the porous solid [P. B. Nagy, Appl. Phys. Lett. {bold 60}, 2735 (1992)]. In this letter, we show that the same simple relationship can be generalized for the surface stiffness of fluid-saturated porous media containing parallel prismatic pore channels of any number, size, or shape. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  4. Mars: Crustal pore volume, cryospheric depth, and the global occurrence of groundwater

    NASA Technical Reports Server (NTRS)

    Clifford, Stephen M.

    1987-01-01

    It is argued that most of the Martian hydrosphere resides in a porous outer layer of crust that, based on a lunar analogy, appears to extend to a depth of about 10 km. The total pore volume of this layer is sufficient to store the equivalent of a global ocean of water some 500 to 1500 m deep. Thermal modeling suggests that about 300 to 500 m of water could be stored as ice within the crust. Any excess must exist as groundwater.

  5. Analytical applications for pore-forming proteins.

    PubMed

    Kasianowicz, John J; Balijepalli, Arvind K; Ettedgui, Jessica; Forstater, Jacob H; Wang, Haiyan; Zhang, Huisheng; Robertson, Joseph W F

    2016-03-01

    Proteinaceous nanometer-scale pores are ubiquitous in biology. The canonical ionic channels (e.g., those that transport Na(+), K(+), Ca(2+), and Cl(-) across cell membranes) play key roles in many cellular processes, including nerve and muscle activity. Another class of channels includes bacterial pore-forming toxins, which disrupt cell function, and can lead to cell death. We describe here the recent development of these toxins for a wide range of biological sensing applications. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale. PMID:26431785

  6. High temperature ion channels and pores

    NASA Technical Reports Server (NTRS)

    Kang, Xiaofeng (Inventor); Gu, Li Qun (Inventor); Cheley, Stephen (Inventor); Bayley, Hagan (Inventor)

    2011-01-01

    The present invention includes an apparatus, system and method for stochastic sensing of an analyte to a protein pore. The protein pore may be an engineer protein pore, such as an ion channel at temperatures above 55.degree. C. and even as high as near 100.degree. C. The analyte may be any reactive analyte, including chemical weapons, environmental toxins and pharmaceuticals. The analyte covalently bonds to the sensor element to produce a detectable electrical current signal. Possible signals include change in electrical current. Detection of the signal allows identification of the analyte and determination of its concentration in a sample solution. Multiple analytes present in the same solution may also be detected.

  7. Control of pore size in epoxy systems.

    SciTech Connect

    Sawyer, Patricia Sue; Lenhart, Joseph Ludlow; Lee, Elizabeth; Kallam, Alekhya; Majumdar, Partha; Dirk, Shawn M.; Gubbins, Nathan; Chisholm, Bret J.; Celina, Mathias Christopher; Bahr, James; Klein, Robert J.

    2009-01-01

    Both conventional and combinatorial approaches were used to study the pore formation process in epoxy based polymer systems. Sandia National Laboratories conducted the initial work and collaborated with North Dakota State University (NDSU) using a combinatorial research approach to produce a library of novel monomers and crosslinkers capable of forming porous polymers. The library was screened to determine the physical factors that control porosity, such as porogen loading, polymer-porogen interactions, and polymer crosslink density. We have identified the physical and chemical factors that control the average porosity, pore size, and pore size distribution within epoxy based systems.

  8. Enlarged facial pores: an update on treatments.

    PubMed

    Dong, Joanna; Lanoue, Julien; Goldenberg, Gary

    2016-07-01

    Enlarged facial pores remain a common dermatologic and cosmetic concern from acne and rosacea, among other conditions, that is difficult to treat due to the multifactorial nature of their pathogenesis and negative impact on patients' quality of life. Enlarged facial pores are primarily treated through addressing associative factors, such as increased sebum production and cutaneous aging. We review the current treatment modalities for enlarged or dense facial pores, including topical retinoids, chemical peels, oral antiandrogens, and lasers and devices, with a focus on newer therapies. PMID:27529707

  9. On the application of focused ion beam nanotomography in characterizing the 3D pore space geometry of Opalinus clay

    NASA Astrophysics Data System (ADS)

    Keller, Lukas M.; Holzer, Lorenz; Wepf, Roger; Gasser, Philippe; Münch, Beat; Marschall, Paul

    The evaluation and optimization of radioactive disposal systems requires a comprehensive understanding of mass transport processes. Among others, mass transport in porous geomaterials depends crucially on the topology and geometry of the pore space. Thus, understanding the mechanism of mass transport processes ultimately requires a 3D characterization of the pore structure. Here, we demonstrate the potential of focused ion beam nanotomography (FIB-nT) in characterizing the 3D geometry of pore space in clay rocks, i.e. Opalinus clay. In order to preserve the microstructure and to reduce sample preparation artefacts we used high pressure freezing and subsequent freeze drying to prepare the samples. Resolution limitations placed the lower limit in pore radii that can be analyzed by FIB-nT to about 10-15 nm. Image analysis and the calculation of pore size distribution revealed that pores with radii larger than 15 nm are related to a porosity of about 3 vol.%. To validate the method, we compared the pores size distribution obtained by FIB-nT with the one obtained by N 2 adsorption analysis. The latter yielded a porosity of about 13 vol.%. This means that FIB-nT can describe around 20-30% of the total pore space. For pore radii larger than 15 nm the pore size distribution obtained by FIB-nT and N 2 adsorption analysis were in good agreement. This suggests that FIB-nT can provide representative data on the spatial distribution of pores for pore sizes in the range of about 10-100 nm. Based on the spatial analysis of 3D data we extracted information on the spatial distribution of pore space geometrical properties.

  10. A new method of evaluating tight gas sands pore structure from nuclear magnetic resonance (NMR) logs

    NASA Astrophysics Data System (ADS)

    Xiao, Liang; Mao, Zhi-qiang; Xie, Xiu-hong

    2016-04-01

    Tight gas sands always display such characteristics of ultra-low porosity, permeability, high irreducible water, low resistivity contrast, complicated pore structure and strong heterogeneity, these make that the conventional methods are invalid. Many effective gas bearing formations are considered as dry zones or water saturated layers, and cannot be identified and exploited. To improve tight gas sands evaluation, the best method is quantitative characterizing rock pore structure. The mercury injection capillary pressure (MICP) curves are advantageous in predicting formation pore structure. However, the MICP experimental measurements are limited due to the environment and economy factors, this leads formation pore structure cannot be consecutively evaluated. Nuclear magnetic resonance (NMR) logs are considered to be promising in evaluating rock pore structure. Generally, to consecutively quantitatively evaluate tight gas sands pore structure, the best method is constructing pseudo Pc curves from NMR logs. In this paper, based on the analysis of lab experimental results for 20 core samples, which were drilled from tight gas sandstone reservoirs of Sichuan basin, and simultaneously applied for lab MICP and NMR measurements, the relationships of piecewise power function between nuclear magnetic resonance (NMR) transverse relaxation T2 time and pore-throat radius Rc are established. A novel method, which is used to transform NMR reverse cumulative curve as pseudo capillary pressure (Pc) curve is proposed, and the corresponding model is established based on formation classification. By using this model, formation pseudo Pc curves can be consecutively synthesized. The pore throat radius distribution, and pore structure evaluation parameters, such as the average pore throat radius (Rm), the threshold pressure (Pd), the maximum pore throat radius (Rmax) and so on, can also be precisely extracted. After this method is extended into field applications, several tight gas

  11. Pore fluids and the LGM ocean salinity-Reconsidered

    NASA Astrophysics Data System (ADS)

    Wunsch, Carl

    2016-03-01

    Pore fluid chlorinity/salinity data from deep-sea cores related to the salinity maximum of the last glacial maximum (LGM) are analyzed using estimation methods deriving from linear control theory. With conventional diffusion coefficient values and no vertical advection, results show a very strong dependence upon initial conditions at -100 ky. Earlier inferences that the abyssal Southern Ocean was strongly salt-stratified in the LGM with a relatively fresh North Atlantic Ocean are found to be consistent within uncertainties of the salinity determination, which remain of order ±1 g/kg. However, an LGM Southern Ocean abyss with an important relative excess of salt is an assumption, one not required by existing core data. None of the present results show statistically significant abyssal salinity values above the global average, and results remain consistent, apart from a general increase owing to diminished sea level, with a more conventional salinity distribution having deep values lower than the global mean. The Southern Ocean core does show a higher salinity than the North Atlantic one on the Bermuda Rise at different water depths. Although much more sophisticated models of the pore-fluid salinity can be used, they will only increase the resulting uncertainties, unless considerably more data can be obtained. Results are consistent with complex regional variations in abyssal salinity during deglaciation, but none are statistically significant.

  12. Monitoring CO2 invasion processes at the pore scale using geological labs on chip.

    PubMed

    Morais, S; Liu, N; Diouf, A; Bernard, D; Lecoutre, C; Garrabos, Y; Marre, S

    2016-09-21

    In order to investigate at the pore scale the mechanisms involved during CO2 injection in a water saturated pore network, a series of displacement experiments is reported using high pressure micromodels (geological labs on chip - GLoCs) working under real geological conditions (25 < T (°C) < 75 and 4.5 < p (MPa) < 8). The experiments were focused on the influence of three experimental parameters: (i) the p, T conditions, (ii) the injection flow rates and (iii) the pore network characteristics. By using on-chip optical characterization and imaging approaches, the CO2 saturation curves as a function of either time or the number of pore volume injected were determined. Three main mechanisms were observed during CO2 injection, namely, invasion, percolation and drying, which are discussed in this paper. Interestingly, besides conventional mechanisms, two counterintuitive situations were observed during the invasion and drying processes. PMID:27494277

  13. Pore-network study of bubble growth in porous media driven by heat transfer

    SciTech Connect

    Satik, C.; Yortsos, Y.C.

    1996-05-01

    We present experimental and theoretical investigations of vapor phase growth in pore-network models of porous media. Visualization experiments of boiling of ethyl alcohol in horizontal etched-glass micromodels were conducted. The vapor phase was observed to grow into a disordered pattern following a sequence of pressurization and pore-filling steps. At sufficiently small cluster sizes, growth occurred `one pore at a time,` leading to invasion percolation patterns. Single-bubble (cluster) growth was next simulated with a pore-network simulator that includes heat transfer (convection and conduction), and capillary and viscous forces, although not gravity. A boundary in the parameter space was delineated that separates patterns of growth dictated solely by capillarity (invasion percolation) from other patterns. The region of validity of invasion percolation was found to decrease as the supersaturation (heat flux), the capillary number, the thermal diffusivity, and the vapor cluster size increase. Implications to continuum models are discussed. 33 refs., 9 figs.

  14. Advanced NMR-based techniques for pore structure analysis of coal. Final project report

    SciTech Connect

    Smith, D.M.; Hua, D.W.

    1996-02-01

    During the 3 year term of the project, new methods have been developed for characterizing the pore structure of porous materials such as coals, carbons, and amorphous silica gels. In general, these techniques revolve around; (1) combining multiple techniques such as small-angle x-ray scattering (SAXS) and adsorption of contrast-matched adsorbates or {sup 129}Xe NMR and thermoporometry (the change in freezing point with pore size), (2) combining adsorption isotherms over several pressure ranges to obtain a more complete description of pore filling, or (3) applying NMR ({sup 129}Xe, {sup 14}N{sub 2}, {sup 15}N{sub 2}) techniques with well-defined porous solids with pores in the large micropore size range (>1 nm).

  15. Deformation by pore collapse in the Shu'aiba limestone: An experimental study

    NASA Astrophysics Data System (ADS)

    Al-Ghamdi, Mohammed A.

    The mechanical properties of the Shu'aiba limestone, the main reservoir in Shaybah field, Saudi Arabia, are investigated in this study. Stresses at failure are measured in the laboratory for cylindrical rock samples taken from the Shu'aiba reservoir. A failure envelope is constructed, from the critical stress states at failure, which shows that this reservoir material is mechanically weak. Experiments are carried out in the conventional uniaxial, triaxial, and hydrostatic compression modes to examine the different failure characteristics of this limestone. Two main hypotheses concerning the deformation behavior of the Shu'aiba limestone are tested in this study. The first hypothesis deals with failure by a mechanism known as "pore collapse" in which the rock deforms by reduction of pore space. Pore collapse is found to be the dominant mechanism of deformation in this limestone under triaxial and hydrostatic compression loading. The effect of initial porosity on the critical effective pressure at the onset of pore collapse is examined. A linear relationship exists by which the critical effective pressure at the onset of pore collapse can be predicted from initial porosities in the range 20% to 30%. The second hypothesis states that an increase in temperature should lower the critical effective pressure values that we measure in room temperature experiments for the same material. Conducting experiments at 90°C and 150°C on essentially the same samples used in room temperature experiments shows a considerable drop in critical effective pressures at the onset of pore collapse. Initial porosities are found to be linearly related to the critical effective pressures for the porosity range of 20% to 31%.

  16. Rock Pore Structure as Main Reason of Rock Deterioration

    NASA Astrophysics Data System (ADS)

    Ondrášik, Martin; Kopecký, Miloslav

    2014-03-01

    even when the temperature decreases to -20 ºC, and the second group F in which the pore water freezes. It has been found that the rocks from group N contain critical portion of adsorbed water in pores which prevents freezing of the pore water. The presence of adsorbed water enables thermodynamic processes related to osmosis which are dominantly responsible for deterioration of rocks from group N. A high correlation (R = 0.81) between content of adsorbed water and freeze-thaw loss was proved and can be used as durability estimator of rocks from group N. The rock deterioration of group F is caused not only by osmosis, but also by some other processes and influences, such as hydraulic pressure, permeability, grain size, rock and mineral tensile strength, degree of saturation, etc., and the deterioration cannot be predicted yet without the freeze-thaw test. Since the contents of absorbed water and ratio between adsorbed and bulk water (of which the absorbed water consists) is controlled by the porosity and pore structure, it can be concluded that the deterioration of some rocks is strongly related to rock pore structure.

  17. Idealized Shale Sorption Isotherm Measurements to Determine Pore Volume, Pore Size Distribution, and Surface Area

    NASA Astrophysics Data System (ADS)

    Holmes, R.; Wang, B.; Aljama, H.; Rupp, E.; Wilcox, J.

    2014-12-01

    One method for mitigating the impacts of anthropogenic CO2-related climate change is the sequestration of CO2 in depleted gas and oil reservoirs, including shale. The accurate characterization of the heterogeneous material properties of shale, including pore volume, surface area, pore size distributions (PSDs) and composition is needed to understand the interaction of CO2 with shale. Idealized powdered shale sorption isotherms were created by varying incremental amounts of four essential components by weight. The first two components, organic carbon and clay, have been shown to be the most important components for CO2 uptake in shales. Organic carbon was represented by kerogen isolated from a Silurian shale, and clay groups were represented by illite from the Green River shale formation. The rest of the idealized shale was composed of equal parts by weight of SiO2 to represent quartz and CaCO3 to represent carbonate components. Baltic, Eagle Ford, and Barnett shale sorption measurements were used to validate the idealized samples. The idealized and validation shale sorption isotherms were measured volumetrically using low pressure N2 (77K) and CO2 (273K) adsorbates on a Quantachrome Autosorb IQ2. Gravimetric isotherms were also produced for a subset of these samples using CO2 and CH4adsorbates under subsurface temperature and pressure conditions using a Rubotherm magnetic suspension balance. Preliminary analyses were inconclusive in validating the idealized samples. This could be a result of conflicting reports of total organic carbon (TOC) content in each sample, a problem stemming from the heterogeneity of the samples and different techniques used for measuring TOC content. The TOC content of the validation samples (Eagle Ford and Barnett) was measured by Rock-Eval pyrolysis at Weatherford Laboratories, while the TOC content in the Baltic validation samples was determined by LECO TOC. Development of a uniform process for measuring TOC in the validation samples is

  18. Homogeneous alignment of liquid crystalline dendrimers confined in a slit-pore. A simulation study

    NASA Astrophysics Data System (ADS)

    Workineh, Zerihun G.; Vanakaras, Alexandros G.

    2016-03-01

    In this work we present results from isobaric-isothermal (NPT) Monte Carlo simulation studies of model liquid crystalline dendrimer (LCDr) systems confined in a slit-pore made of two parallel flat walls. The dendrimers are modelled as a collection of spherical and ellipsoidal particles corresponding to the junction points of the dendritic core and to the mesogenic units respectively. Assuming planar uniform (unidirectional) soft anchoring of the mesogenic units on the substrates we investigate the conformational and alignment properties of the LCDr system at different thermodynamic state points. Tractable coarse grained force fields have been used from our previous work. At low pressures the interior of the pore is almost empty, since almost all LCDrs are anchored to the substrates forming two-dimensional smectic-like structures with the mesogens aligned along the aligning direction of the substrates. As the pressure grows the LCDrs occupy the whole pore. However, even at low temperatures, the smectic organization does not transmit in the interior of the pore and is preserved for distances of 2-3 mesogenic diameters from the walls. For this reason, the global orientational order decreases with increasing pressure (density). In the vicinity (2-3 mesogenic diameters) of the pore walls, mesogenic units preserve the smectic structure whose layers are separated by layers of spherical beads. In this region individual LCDrs possess a rod like shape.

  19. Homogeneous alignment of liquid crystalline dendrimers confined in a slit-pore. A simulation study.

    PubMed

    Workineh, Zerihun G; Vanakaras, Alexandros G

    2016-03-23

    In this work we present results from isobaric-isothermal (NPT) Monte Carlo simulation studies of model liquid crystalline dendrimer (LCDr) systems confined in a slit-pore made of two parallel flat walls. The dendrimers are modelled as a collection of spherical and ellipsoidal particles corresponding to the junction points of the dendritic core and to the mesogenic units respectively. Assuming planar uniform (unidirectional) soft anchoring of the mesogenic units on the substrates we investigate the conformational and alignment properties of the LCDr system at different thermodynamic state points. Tractable coarse grained force fields have been used from our previous work. At low pressures the interior of the pore is almost empty, since almost all LCDrs are anchored to the substrates forming two-dimensional smectic-like structures with the mesogens aligned along the aligning direction of the substrates. As the pressure grows the LCDrs occupy the whole pore. However, even at low temperatures, the smectic organization does not transmit in the interior of the pore and is preserved for distances of 2-3 mesogenic diameters from the walls. For this reason, the global orientational order decreases with increasing pressure (density). In the vicinity (2-3 mesogenic diameters) of the pore walls, mesogenic units preserve the smectic structure whose layers are separated by layers of spherical beads. In this region individual LCDrs possess a rod like shape. PMID:26903080

  20. Frenkel-Halsey-Hill equation, dimensionality of adsorption, and pore anisotropy.

    PubMed

    Pomonis, Philippos J; Tsaousi, Eleni T

    2009-09-01

    The Frenkel-Halsey-Hill (FHH) equation V/V(m) approximately [log(P(0)/P)](-1/s) is revisited in relation to the meaning of its exponent in a specific intermediate range of pressure where capillary condensation occurs. It has been suggested in the past that plots of the form log V = constant - (D - 3)[loglog(P(0)/P)], or its equivalent log S = const - (D - 2) log r, can be used for the estimation of the dimensionality D of the adsorbing surface from those parts of the slopes at low pressure corresponding to straight lines. In the present study it is shown that, for pores of cylindrical geometry and at a specific range of pressure where those pores are filled-up during the process of capillary condensation, the local slopes d log V/d loglog[(P(0)/P)] or d log S/d log r, of plots similar to the above, may be used to estimate the pore anisotropy b of the adsorbing space from the relationships log b = [[d log V/d loglog[(P(0)/P)] - 3] log(0.5r) or log b = [[d log S/d log r] - 2] log(0.5r). These observations lead to the physicogeometrical conjunction that, during capillary condensation in cylindrical pores, usually assumed in nitrogen porosimetry, the scaling dimension of pore anisotropy b, scaled in units of radius r, is related to the dimensionality D of the process. PMID:19705894

  1. Block copolymer structures in nano-pores

    NASA Astrophysics Data System (ADS)

    Pinna, Marco; Guo, Xiaohu; Zvelindovsky, Andrei

    2010-03-01

    We present results of coarse-grained computer modelling of block copolymer systems in cylindrical and spherical nanopores on Cell Dynamics Simulation. We study both cylindrical and spherical pores and systematically investigate structures formed by lamellar, cylinders and spherical block copolymer systems for various pore radii and affinity of block copolymer blocks to the pore walls. The obtained structures include: standing lamellae and cylinders, ``onions,'' cylinder ``knitting balls,'' ``golf-ball,'' layered spherical, ``virus''-like and mixed morphologies with T-junctions and U-type defects [1]. Kinetics of the structure formation and the differences with planar films are discussed. Our simulations suggest that novel porous nano-containers can be formed by confining block copolymers in pores of different geometries [1,2]. [4pt] [1] M. Pinna, X. Guo, A.V. Zvelindovsky, Polymer 49, 2797 (2008).[0pt] [2] M. Pinna, X. Guo, A.V. Zvelindovsky, J. Chem. Phys. 131, 214902 (2009).

  2. The open pore conformation of potassium channels

    NASA Astrophysics Data System (ADS)

    Jiang, Youxing; Lee, Alice; Chen, Jiayun; Cadene, Martine; Chait, Brian T.; MacKinnon, Roderick

    2002-05-01

    Living cells regulate the activity of their ion channels through a process known as gating. To open the pore, protein conformational changes must occur within a channel's membrane-spanning ion pathway. KcsA and MthK, closed and opened K+ channels, respectively, reveal how such gating transitions occur. Pore-lining `inner' helices contain a `gating hinge' that bends by approximately 30°. In a straight conformation four inner helices form a bundle, closing the pore near its intracellular surface. In a bent configuration the inner helices splay open creating a wide (12Å) entryway. Amino-acid sequence conservation suggests a common structural basis for gating in a wide range of K+ channels, both ligand- and voltage-gated. The open conformation favours high conduction by compressing the membrane field to the selectivity filter, and also permits large organic cations and inactivation peptides to enter the pore from the intracellular solution.

  3. DESIGN MANUAL: FINE PORE AERATION SYSTEMS

    EPA Science Inventory

    This manual presents the best current practices for selecting, designing, operating, maintaining, and controlling fine pore aeration systems used in the treatment of municipal wastewater. It was prepared by the American Society of Civil Engineers Committee on Oxygen Transfer unde...

  4. Adsorption and excess fission xenon

    NASA Technical Reports Server (NTRS)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    1982-01-01

    The adsorption of Xe and Kr on lunar soil 10084 was measured by a method that employs only very low fractions of monolayer coverage. Results are presented as parameters for calculation of the Henry constant for adsorption as a function of temperature. The adsorption potentials are about 3 kcal/mole for Kr and 5 kcal/mole for Xe; heating the sample in vacuum increased the Xe potential to nearly 7 kcal/mole. Henry constants at the characteristic lunar temperature are about 0.3 cu cm STP/g-atm. These data were applied to consider whether adsorption is important in producing the excess fission Xe effect characteristic of highland breccias. Sorption equilibrium with a transient lunar atmosphere vented fission Xe produces concentrations seven orders of magnitude lower than observed concentrations. Higher concentrations result because of the resistance of the regolith to upward diffusion of Xe. A diffusion coefficient of 0.26 sq cm/sec is estimated for this process.

  5. Visualization of enzyme activities inside earthworm pores

    NASA Astrophysics Data System (ADS)

    Hoang, Duyen; Razavi, Bahar S.

    2015-04-01

    In extremely dynamic microhabitats as bio-pores made by earthworm, the in situ enzyme activities are assumed as a footprint of complex biotic interactions. Our study focused on the effect of earthworm on the enzyme activities inside bio-pores and visualizing the differences between bio-pores and earthworm-free soil by zymography technique (Spohn and Kuzyakov, 2013). For the first time, we aimed at quantitative imaging of enzyme activities in bio-pores. Lumbricus terrestris L. was placed into transparent box (15×20×15cm). After two weeks when bio-pore systems were formed by earthworms, we visualized in situ enzyme activities of five hydrolytic enzymes (β-glucosidase, cellobiohydrolase, chitinase, xylanase, leucine-aminopeptidase, and phosphatase. Zymography showed higher activity of β-glucosidase, chitinase, xylanase and phosphatase in biopores comparing to bulk soil. However, the differences in activity of cellobiohydrolase and leucine aminopeptidase between bio-pore and bulk soil were less pronounced. This demonstrated an applicability of zymography approach to monitor and to distinguish the in situ activity of hydrolytic enzymes in soil biopores.

  6. Pore-Scale Modeling of Reactive-Multiphase-Buoyant Flow for Carbon Capture and Storage

    NASA Astrophysics Data System (ADS)

    Anwar, S.; Cunningham, J. A.; Trotz, M.; Thomas, M. W.; Stewart, M.

    2010-12-01

    Physical and geochemical processes at multiple scales are yet to be understood for the storage of carbon dioxide (CO2) in aquifers and the concomitant mitigation of CO2 concentration in the atmosphere. In deep saline aquifers, the pores in the potential aquifers for CO2 storage are initially filled with saline water (brine). The entrapment of brine in pores after injection of CO2 is controlled by capillary forces and by the inertial force driving CO2 inside the carbonate aquifer. The entrapped/residual brine will be a site for geochemical reactions which could alter the pore network and/or the permeability of the formation. Therefore, the pore-scale understanding of displacement of resident brine by CO2 is critical to evaluate the storage efficiency of carbonate aquifers and to quantify any dissolution or precipitation of minerals (e.g., gypsum, calcite, dolomite). In this project, we have developed a multiphase flow model, based on the lattice Boltzmann equation, that can describe pore-scale displacement of brine by invading CO2. The multiphase flow model is applied to three different pore networks saturated with brine. The amount of brine trapped after invasion of the domain by CO2 is strongly dependent on the pore network. We also examine the effects of CO2 density and viscosity (which depend on formation temperature and pressure) on the amount of entrapped brine. Only by resolving the flow at the pore scale can we predict the residual brine saturation and other parameters which control CO2 sequestration in deep saline aquifers. Future work will focus on coupling the pore-scale multiphase flow model to a chemistry model to predict mineral dissolution and precipitation.

  7. Gel injection successfully shuts off excess water

    SciTech Connect

    1995-11-01

    Unocal applied a high-temperature organic polymer gel in Feather field Well H-43 in the UK North Sea to reduce water production in them more-permeable upper perforated section of the Brent Sand. The operation and technical details of the polymer system developed by Unocal, and how it was applied, are described in paper SPE 30426, ``Water shut off in the North Sea; Testing a new polymer system in the Heather field, UKCS Block 2/5.`` The authors concluded that the new gel system successfully isolated the Upper Brent water production, increasing oil production and decreasing water production. Lower perforations were successfully isolated using sized calcium carbonate suspended in an HEC polymer--a technique difficult to monitor in the deviated well. Batch mixing provided ``excellent`` quality gel, closely matching lab measured performance. And the gel required no pre-cooling in the near-wellbore area. Some 1,100 bbl were injected without excessive wellhead pressure, at 1 bpm. A summary of the paper`s highlights is presented here.

  8. Etiologies and sequelae of excessive daytime sleepiness.

    PubMed

    Roth, T; Roehrs, T A

    1996-01-01

    Excessive daytime sleepiness (EDS), the primary complaint of patients seen in sleep clinics, affects up to 12% of the general population. The effects of EDS can be debilitating and even life threatening. Patients with EDS may exhibit psychosocial distress, decreased work or school performance, and increased risk for accidents. The differential diagnosis of EDS requires objective assessments, such as polysomnography and the Multiple Sleep Latency Test. There are four major causes of EDS: (1) central nervous system (CNS) pathologic abnormalities, such as narcolepsy and idiopathic CNS hypersomnia; (2) qualitative or quantitative sleep deficiencies, such as sleep apnea and insufficient nocturnal sleep; (3) misalignments of the body's circadian pacemaker with the environment (eg. jet lag or shift work); and (4) drugs, which can increase sleepiness either therapeutically or as a side effect. Depending on etiology, management strategies for EDS include extension of time in bed, naps, surgery, various medical devices (eg, oral appliances, continuous positive airway pressure), and pharmacotherapy. Pharmacotherapy is generally achieved with stimulants, such as amphetamine sulfate, methylphenidate, and pemoline or newer, safer compounds like modafinil. PMID:8879887

  9. Pore Formation Upon Nitriding Iron and Iron-Based Alloys: The Role of Alloying Elements and Grain Boundaries

    NASA Astrophysics Data System (ADS)

    Schwarz, B.; Göhring, H.; Meka, S. R.; Schacherl, R. E.; Mittemeijer, E. J.

    2014-12-01

    Pure iron and a series of iron-based Fe-Me alloys (with Me = Al, Si, Cr, Co, Ni, and Ge) were nitrided in a NH3/H2 gas mixture at 923 K (650 °C). Different nitriding potentials were applied to investigate the development of pores under ferrite and austenite stabilizing conditions. In all cases, pores developed in the nitrided microstructure, i.e., also and strikingly pure ferritic iron exhibited pore development. The pore development is shown to be caused by the decomposition of (homogeneous) nitrogen-rich Fe(-Me)-N phase into nitrogen-depleted Fe(-Me)-N phase and molecular N2 gas. The latter, gas phase can be associated with such high pressure that the surrounding iron-based matrix can yield. Thermodynamic assessments indicate that continued decomposition, i.e., beyond the state where yielding is initiated, is possible. Precipitating alloying-element nitrides, i.e., AlN, CrN, or Si3N4, in the diffusion zone below the surface, hinder the formation of pores due to the competition of alloying-element nitride (Me x N y ) precipitation and pore (N2) development; alloying elements reducing the solubility of nitrogen enhance pore formation. No pore formation was observed upon nitriding a single crystalline pure iron specimen, nitrided under ferrite stabilizing conditions, thereby exhibiting the essential function of grain boundaries for nucleation of pores.

  10. Mechanical properties, pore size distribution, and pore solution of fly ash-belite cement mortars

    SciTech Connect

    Guerrero, A.; Goni, S.; Macias, A.; Luxan, M.P.

    1999-11-01

    The mechanical properties, pore size distribution, and extracted pore solution of fly ash-belite cement (FABC) mortars were studied for a period of 200 days. The influence of the calcination temperature, which ranged from 700 to 900 C, of the fly ash-belite cement was discussed. The evolution with hydration time of the pore size distribution was followed by mercury intrusion porosimetry, and the results correlated with those of flexural and compressive strength. The pore solution was expressed and analyzed at different times of hydration.

  11. Active pore space utilization in nanoporous carbon-based supercapacitors: Effects of conductivity and pore accessibility

    NASA Astrophysics Data System (ADS)

    Seredych, Mykola; Koscinski, Mikolaj; Sliwinska-Bartkowiak, Malgorzata; Bandosz, Teresa J.

    2012-12-01

    Composites of commercial graphene and nanoporous sodium-salt-polymer-derived carbons were prepared with 5 or 20 weight% graphene. The materials were characterized using the adsorption of nitrogen, SEM/EDX, thermal analysis, Raman spectroscopy and potentiometric titration. The samples' conductivity was also measured. The performance of the carbon composites in energy storage was linked to their porosity and electronic conductivity. The small pores (<0.7) were found as very active for double layer capacitance. It was demonstrated that when double layer capacitance is a predominant mechanism of charge storage, the degree of the pore space utilization for that storage can be increased by increasing the conductivity of the carbons. That active pore space utilization is defined as gravimetric capacitance per unit pore volume in pores smaller than 0.7 nm. Its magnitude is affected by conductivity of the carbon materials. The functional groups, besides pseudocapacitive contribution, increased the wettability and thus the degree of the pore space utilization. Graphene phase, owing to its conductivity, also took part in an insitu increase of the small pore accessibility and thus the capacitance of the composites via enhancing an electron transfer to small pores and thus imposing the reduction of groups blocking the pores for electrolyte ions.

  12. Eutrophication in the northern Adriatic Sea: Pore water and sediment studies

    SciTech Connect

    Hammond, D.E.; Berelson, W.M. ); Giordani, P.; Langone, L.; Frignani, M.; Ravaioli, M. )

    1990-01-09

    The northern Adriatic Sea has been plagued by problems of eutrophication. This area is relatively shallow (maximum depth = 60m), becoming stratified during the summer months which inhibits oxygen transport to bottom waters. Anthropogenic nutrient loading in rivers entering the northern Adriatic (Po River being the largest) has increased nutrient input to this system and stimulated algal growth. Cores were collected for studies of pore water and solid phase chemistry at 6 stations in this region. [sup 210]Pb was used to constrain sediment accumulation rates and a range of 0-0.5 cm/yr was determined at different stations. Excess [sup 234]Th was only found in the upper 1-2 cm, suggesting that bioturbation is largely restricted to shallow depths. Pore water profiles show evidence of irrigation, and mean diffusive fluxes for oxygen, silica phosphate and ammonia are generally 20-90% of the fluxes obtained from benthic chamber measurements. This is consistent with previous work in this area in which studies of radon fluxes indicated that irrigation plays an important role in sediment-water exchange. Pore water profiles in the northern portion of the study area (near the Po River Delta) were markedly different than profiles in the south; sediments in the north are substantially more acidic and have high concentrations of dissolved iron and phosphate. From the alkalinity vs. TCO[sub 2] relationship in sediment pore waters it appears that differences in reactions involving the reduction of iron oxides and the exchange of magnesium for iron in clays are responsible for this regional difference in pore water properties. Sediments close to the Po apparently undergo more iron-magnesium exchange, while more distal sediments are limited in their ability to do so. Other pore water observations are limited in their ability to do so. Other pore water observations and trends regarding the shape of the silica profiles (which show shallow maxima) will be discussed.

  13. Pore Size Effect on Methane Adsorption in Mesoporous Silica Materials Studied by Small-Angle Neutron Scattering.

    PubMed

    Chiang, Wei-Shan; Fratini, Emiliano; Baglioni, Piero; Chen, Jin-Hong; Liu, Yun

    2016-09-01

    Methane adsorption in model mesoporous silica materials with the size range characteristic of shale is studied by small-angle neutron scattering (SANS). Size effect on the temperature-dependent gas adsorption at methane pressure about 100 kPa is investigated by SANS using MCM-41 and SBA-15 as adsorbents. Above the gas-liquid condensation temperature, the thickness of the adsorption layer is found to be roughly constant as a function of the temperature. Moreover, the gas adsorption properties, such as the adsorbed layer thickness and the specific amount of adsorbed gas, have little dependence on the pore size being studied, i.e., pore radius of 16.5 and 34.1 Å, but are mainly affected by the roughness of the pore surfaces. Hence, the surface properties of the pore wall are more dominant than the pore size in determining the methane gas adsorption of pores at the nanometer size range. Not surprisingly, the gas-liquid condensation temperature is observed to be sensitive to pore size and shifts to higher temperature when the pore size is smaller. Below the gas-liquid condensation temperature, even though the majority of gas adsorption experiments/simulations have assumed the density of confined liquid to be the same as the bulk density, the measured methane mass density in our samples is found to be appreciably smaller than the bulk methane density regardless of the pore sizes studied here. The mass density of liquid/solid methane in pores with different sizes shows different temperature dependence below the condensation temperature. With decreasing temperature, the methane density in larger pores (SBA-15) abruptly increases at approximately 65 K and then plateaus. In contrast, the density in smaller pores (MCM-41) monotonically increases with decreasing temperature before reaching a plateau at approximately 30 K. PMID:27512895

  14. Integrating mercury injection and nitrogen adsorption data to characterize marine sediment pore systems: An example from the Nankai Trough

    NASA Astrophysics Data System (ADS)

    Daigle, H.; Thomas, B.

    2013-12-01

    Fine-grained, clay-rich marine sediments typically exhibit complex pore geometries due to the presence of high-aspect-ratio clay particles, nannofossils, and diagenetically altered grain fragments. The pore systems in these sediments have a wide range of shapes and may contain significant pore volume in mesopores (1-25 nm radius) and micropores (< 1 nm radius). This renders pore size measurements difficult, even in samples with high porosity. Porosity values from mercury injection capillary pressure (MICP) measurements performed on samples from Integrated Ocean Drilling Program (IODP) Sites C0011, C0012, and C0018 in the Nankai Trough offshore Japan were compared to porosity determined by proton nuclear magnetic resonance (NMR) in the laboratory. The MICP porosities were systematically lower than the NMR porosities by up to 26% of the NMR porosity value. This porosity mismatch is due to the presence of pores with radii smaller than the effective lower limit of MICP measurements, which is 10-40 nm for this data set. Nitrogen gas adsorption offers a means to characterize pores between ~0.87 nm and ~100 nm radius, thus measuring the portion of the pore size distribution not investigated by MICP measurements. Combining MICP and nitrogen gas adsorption data yields a more complete characterization of the pore system of marine sediments. Merged MICP and nitrogen gas adsorption data obtained for the Nankai Trough samples yield porosity values that more accurately match the NMR porosity values, indicating that the entire pore space of the samples can be measured by a combination of the two techniques. These samples possess significant quantities of porosity below the resolution of MICP (>10% of pore volume), even in samples with porosity exceeding 65%. This work illustrates the complexity of marine sediment pore systems even at shallow depths of burial, and provides a new method for assessing pore sizes in scientific ocean drilling studies.

  15. Facial skin pores: a multiethnic study.

    PubMed

    Flament, Frederic; Francois, Ghislain; Qiu, Huixia; Ye, Chengda; Hanaya, Tomoo; Batisse, Dominique; Cointereau-Chardon, Suzy; Seixas, Mirela Donato Gianeti; Dal Belo, Susi Elaine; Bazin, Roland

    2015-01-01

    Skin pores (SP), as they are called by laymen, are common and benign features mostly located on the face (nose, cheeks, etc) that generate many aesthetic concerns or complaints. Despite the prevalence of skin pores, related literature is scarce. With the aim of describing the prevalence of skin pores and anatomic features among ethnic groups, a dermatoscopic instrument, using polarized lighting, coupled to a digital camera recorded the major features of skin pores (size, density, coverage) on the cheeks of 2,585 women in different countries and continents. A detection threshold of 250 μm, correlated to clinical scorings by experts, was input into a specific software to further allow for automatic counting of the SP density (N/cm(2)) and determination of their respective sizes in mm(2). Integrating both criteria also led to establishing the relative part of the skin surface (as a percentage) that is actually covered by SP on cheeks. The results showed that the values of respective sizes, densities, and skin coverage: 1) were recorded in all studied subjects; 2) varied greatly with ethnicity; 3) plateaued with age in most cases; and 4) globally refected self-assessment by subjects, in particular those who self-declare having "enlarged pores" like Brazilian women. Inversely, Chinese women were clearly distinct from other ethnicities in having very low density and sizes. Analyzing the present results suggests that facial skin pore's morphology as perceived by human eye less result from functional criteria of associated appendages such as sebaceous glands. To what extent skin pores may be viewed as additional criteria of a photo-altered skin is an issue to be further addressed. PMID:25733918

  16. Low pore connectivity in natural rock

    NASA Astrophysics Data System (ADS)

    Hu, Qinhong; Ewing, Robert P.; Dultz, Stefan

    2012-05-01

    As repositories for CO2 and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air-water system) and diffusion rate than expected from classical behavior.

  17. The Arabidopsis Nuclear Pore and Nuclear Envelope

    PubMed Central

    Meier, Iris; Brkljacic, Jelena

    2010-01-01

    The nuclear envelope is a double membrane structure that separates the eukaryotic cytoplasm from the nucleoplasm. The nuclear pores embedded in the nuclear envelope are the sole gateways for macromolecular trafficking in and out of the nucleus. The nuclear pore complexes assembled at the nuclear pores are large protein conglomerates composed of multiple units of about 30 different nucleoporins. Proteins and RNAs traffic through the nuclear pore complexes, enabled by the interacting activities of nuclear transport receptors, nucleoporins, and elements of the Ran GTPase cycle. In addition to directional and possibly selective protein and RNA nuclear import and export, the nuclear pore gains increasing prominence as a spatial organizer of cellular processes, such as sumoylation and desumoylation. Individual nucleoporins and whole nuclear pore subcomplexes traffic to specific mitotic locations and have mitotic functions, for example at the kinetochores, in spindle assembly, and in conjunction with the checkpoints. Mutants of nucleoporin genes and genes of nuclear transport components lead to a wide array of defects from human diseases to compromised plant defense responses. The nuclear envelope acts as a repository of calcium, and its inner membrane is populated by functionally unique proteins connected to both chromatin and—through the nuclear envelope lumen—the cytoplasmic cytoskeleton. Plant nuclear pore and nuclear envelope research—predominantly focusing on Arabidopsis as a model—is discovering both similarities and surprisingly unique aspects compared to the more mature model systems. This chapter gives an overview of our current knowledge in the field and of exciting areas awaiting further exploration. PMID:22303264

  18. Soil pore structure and substrate C mineralization

    NASA Astrophysics Data System (ADS)

    Sleutel, Steven; Maenhout, Peter; Vanhoorebeke, Luc; Cnudde, Veerle; De Neve, Stefaan

    2014-05-01

    Our aim was to investigate the complex interactions between soil pore structure, soil biota and decomposition of added OM substrates. We report on a lab incubation experiment in which CO2 respiration from soil cores was monitored (headspace GC analysis) and an X-ray CT approach yielded soil pore size distributions. Such combined use of X-ray CT with soil incubation studies was obstructed, until now, by many practical constraints such as CT-volume quality, limited resolution, scanning time and complex soil pore network quantification, which have largely been overcome in this study. We incubated a sandy loam soil (with application of ground grass or sawdust) in 18 small aluminium rings (Ø 1 cm, h 1 cm). Bulk density was adjusted to 1.1 or 1.3 Mg m-3 (compaction) and 6 rings were filled at a coarser Coarse Sand:Fine Sand:Silt+Clay ratio. While compaction induced a strong reduction in the cumulative C mineralization for both grass and sawdust substrates, artificial change to a coarser soil texture only reduced net C mineralization from the added sawdust. There thus appears to be a strong interaction effect between soil pore structure and substrate type on substrate decomposition. Correlation coefficients between the C mineralization rates and volumes of 7 pore size classes (from the X-ray CT data) also showed an increasing positive correlation with increasing pore size. Since any particulate organic matter initially present in the soil was removed prior to the experiment (sieving, ashing the >53µm fraction and recombining with the <53µm fraction), the added OM can be localized by means of X-ray CT. Through on-going image analysis the surrounding porosity of the added grass or sawdust particles is being quantified to further study the interaction between the soil pore structure and substrate decomposition.

  19. Low pore connectivity in natural rock.

    PubMed

    Hu, Qinhong; Ewing, Robert P; Dultz, Stefan

    2012-05-15

    As repositories for CO(2) and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air-water system) and diffusion rate than expected from classical behavior. PMID:22507286

  20. Low Pore Connectivity in Natural Rock

    SciTech Connect

    Hu, Qinhong; Ewing, Robert P.; Dultz, Stefan

    2012-05-15

    As repositories for CO₂ and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air–water system) and diffusion rate than expected from classical behavior.

  1. Interactions between bedforms, turbulence and pore flow

    NASA Astrophysics Data System (ADS)

    Blois, G.; Best, J.; Sambrook Smith, G.; Hardy, R. J.; Lead, J.

    2010-12-01

    A widespread occurrence of flow-form interaction in rivers is represented by subaqueous bedforms such as dunes. Many models have been proposed to explain how bedform generation and evolution are driven by turbulent flow structures that control the incipient motion of cohesionless sediments and later bedform development. However, most of these models have assumed such bedforms to be migrating over an impermeable bed, and that any surface-subsurface flow interaction is negligible. However, for some gravel-bed rivers the porosity can be high, up to 43%, which may result in significant flow both through the permeable bed (hyporheic flow) and across the surface-subsurface interface. The mass and momentum exchange occurring at the interface may have a strong impact on the structure of turbulent flow in the near-bed region. In the case of a dune, its topography induces a local pressure gradient that enhances flow across the interface. This results in a flow structure that may be radically different from that commonly proposed by past work. This paper presents results from a simplified laboratory model akin to a fine-grained bedform generated on top of a coarser sediment bed. Particle imaging velocimetry (PIV) measurements were conducted in order to characterise flow both over and underneath an idealised 2-dimensional dune (0.41 m long, 0.056 m high and having a leeside angle of 27°) overlaying a packed bed of uniform size spheres (D = 0.04 m diameter). Experiments were conducted in free surface flow conditions (Froude number = 0.1; Reynolds number = 25,000) for one bedform height: flow depth ratio (0.31). The flow above the dune was measured using a standard PIV technique while a novel endoscopic PIV (EPIV) system allowed collection of flow data within the pore spaces beneath the dune. The results show that topographically-induced subsurface flow significantly modifies the structure of flow in the leeside of the dune, resulting in a flow field that is radically different

  2. Effect of temperature and pore fluid on the strength of porous limestone

    NASA Astrophysics Data System (ADS)

    Lisabeth, Harrison P.; Zhu, Wenlu

    2015-09-01

    The presence of pore fluid in rocks generally reduces brittle strength. The role of water weakening in porous carbonate rocks and the effect of enhanced deformation on concomitant transport property evolution are poorly understood. The interaction between pore fluid and deformation mechanisms in carbonate rocks is complicated by crystal plasticity and solubility in calcite at low temperatures and pressures. To explore this system, we perform conventional triaxial deformation experiments on Indiana Limestone (~16% porosity) over a range of temperatures (23-75°C) and effective confining pressures (10-50 MPa). Samples are deformed with pore fluids of different saturation states with respect to calcite host rock. Samples tend to fail by distributed deformation. Sample permeability is reduced by up to an order of magnitude during deformation, even in samples exhibiting dilatancy. Compactive yield strength, associated with shear-enhanced compaction, is greatly reduced in saturated samples compared to dry samples. Dilatancy is suppressed and compaction enhanced at elevated pressures. Greater weakening effects are observed when pore fluid is far-from-equilibrium with carbonate rock. Observed weakening results from the interaction between microcracking, mechanical twinning, and pressure solution.

  3. Hydrochromic Approaches to Mapping Human Sweat Pores.

    PubMed

    Park, Dong-Hoon; Park, Bum Jun; Kim, Jong-Man

    2016-06-21

    Hydrochromic materials, which undergo changes in their light absorption and/or emission properties in response to water, have been extensively investigated as humidity sensors. Recent advances in the design of these materials have led to novel applications, including monitoring the water content of organic solvents, water-jet-based rewritable printing on paper, and hydrochromic mapping of human sweat pores. Our interest in this area has focused on the design of hydrochromic materials for human sweat pore mapping. We recognized that materials appropriate for this purpose must have balanced sensitivities to water. Specifically, while they should not undergo light absorption and/or emission transitions under ambient moisture conditions, the materials must have sufficiently high hydrochromic sensitivities that they display responses to water secreted from human sweat pores. In this Account, we describe investigations that we have carried out to develop hydrochromic substances that are suitable for human sweat pore mapping. Polydiacetylenes (PDAs) have been extensively investigated as sensor matrices because of their stimulus-responsive color change property. We found that incorporation of headgroups composed of hygroscopic ions such as cesium or rubidium and carboxylate counterions enables PDAs to undergo a blue-to-red colorimetric transition as well as a fluorescence turn-on response to water. Very intriguingly, the small quantities of water secreted from human sweat pores were found to be sufficient to trigger fluorescence turn-on responses of the hydrochromic PDAs, allowing precise mapping of human sweat pores. Since the hygroscopic ion-containing PDAs developed in the initial stage display a colorimetric transition under ambient conditions that exist during humid summer periods, a new system was designed. A PDA containing an imidazolium ion was found to be stable under all ambient conditions and showed temperature-dependent hydrochromism corresponding to a

  4. Analysis of a spatially deconvolved solar pore

    NASA Astrophysics Data System (ADS)

    Quintero Noda, C.; Shimizu, T.; Ruiz Cobo, B.; Suematsu, Y.; Katsukawa, Y.; Ichimoto, K.

    2016-08-01

    Solar pores are active regions with large magnetic field strengths and apparent simple magnetic configurations. Their properties resemble the ones found for the sunspot umbra although pores do not show penumbra. Therefore, solar pores present themselves as an intriguing phenomenon that is not completely understood. We examine in this work a solar pore observed with Hinode/SP using two state of the art techniques. The first one is the spatial deconvolution of the spectropolarimetric data that allows removing the stray light contamination induced by the spatial point spread function of the telescope. The second one is the inversion of the Stokes profiles assuming local thermodynamic equilibrium that let us to infer the atmospheric physical parameters. After applying these techniques, we found that the spatial deconvolution method does not introduce artefacts, even at the edges of the magnetic structure, where large horizontal gradients are detected on the atmospheric parameters. Moreover, we also describe the physical properties of the magnetic structure at different heights finding that, in the inner part of the solar pore, the temperature is lower than outside, the magnetic field strength is larger than 2 kG and unipolar, and the line-of-sight velocity is almost null. At neighbouring pixels, we found low magnetic field strengths of same polarity and strong downward motions that only occur at the low photosphere, below the continuum optical depth log τ = -1. Finally, we studied the spatial relation between different atmospheric parameters at different heights corroborating the physical properties described before.

  5. Analysis of a spatially deconvolved solar pore

    NASA Astrophysics Data System (ADS)

    Quintero Noda, C.; Shimizu, T.; Cobo, B. Ruiz; Suematsu, Y.; Katsukawa, Y.; Ichimoto, K.

    2016-05-01

    Solar pores are active regions with large magnetic field strengths and apparent simple magnetic configurations. Their properties resemble the ones found for the sunspot umbra although pores do not show penumbra. Therefore, solar pores present themselves as an intriguing phenomenon that is not completely understood. We examine in this work a solar pore observed with Hinode/SP using two state of the art techniques. The first one is the spatial deconvolution of the spectropolarimetric data that allows removing the stray light contamination induced by the spatial point spread function of the telescope. The second one is the inversion of the Stokes profiles assuming local thermodynamic equilibrium that let us to infer the atmospheric physical parameters. After applying these techniques, we found that the spatial deconvolution method does not introduce artefacts, even at the edges of the magnetic structure, where large horizontal gradients are detected on the atmospheric parameters. Moreover, we also describe the physical properties of the magnetic structure at different heights finding that, in the inner part of the solar pore, the temperature is lower than outside, the magnetic field strength is larger than 2 kG and unipolar, and the LOS velocity is almost null. At neighbouring pixels, we found low magnetic field strengths of same polarity and strong downward motions that only occur at the low photosphere, below the continuum optical depth log τ = -1. Finally, we studied the spatial relation between different atmospheric parameters at different heights corroborating the physical properties described before.

  6. Performance of Small Pore Microchannel Plates

    NASA Technical Reports Server (NTRS)

    Siegmund, O. H. W.; Gummin, M. A.; Ravinett, T.; Jelinsky, S. R.; Edgar, M.

    1995-01-01

    Small pore size microchannel plates (MCP's) are needed to satisfy the requirements for future high resolution small and large format detectors for astronomy. MCP's with pore sizes in the range 5 micron to 8 micron are now being manufactured, but they are of limited availability and are of small size. We have obtained sets of Galileo 8 micron and 6.5 micron MCP's, and Philips 6 micron and 7 micron pore MCP's, and compared them to our larger pore MCP Z stacks. We have tested back to back MCP stacks of four of these MCP's and achieved gains greater than 2 x 1O(exp 7) with pulse height distributions of less than 40% FWHM, and background rates of less than 0.3 events sec(exp -1) cm(exp -2). Local counting rates up to approx. 100 events/pore/sec have been attained with little drop of the MCP gain. The bare MCP quantum efficiencies are somewhat lower than those expected, however. Flat field images are characterized by an absence of MCP fixed pattern noise.

  7. Organization of the Mitochondrial Apoptotic BAK Pore

    PubMed Central

    Aluvila, Sreevidya; Mandal, Tirtha; Hustedt, Eric; Fajer, Peter; Choe, Jun Yong; Oh, Kyoung Joon

    2014-01-01

    The multidomain pro-apoptotic Bcl-2 family proteins BAK and BAX are believed to form large oligomeric pores in the mitochondrial outer membrane during apoptosis. Formation of these pores results in the release of apoptotic factors including cytochrome c from the intermembrane space into the cytoplasm, where they initiate the cascade of events that lead to cell death. Using the site-directed spin labeling method of electron paramagnetic resonance (EPR) spectroscopy, we have determined the conformational changes that occur in BAK when the protein targets to the membrane and forms pores. The data showed that helices α1 and α6 disengage from the rest of the domain, leaving helices α2-α5 as a folded unit. Helices α2-α5 were shown to form a dimeric structure, which is structurally homologous to the recently reported BAX “BH3-in-groove homodimer.” Furthermore, the EPR data and a chemical cross-linking study demonstrated the existence of a hitherto unknown interface between BAK BH3-in-groove homodimers in the oligomeric BAK. This novel interface involves the C termini of α3 and α5 helices. The results provide further insights into the organization of the BAK oligomeric pores by the BAK homodimers during mitochondrial apoptosis, enabling the proposal of a BAK-induced lipidic pore with the topography of a “worm hole.” PMID:24337568

  8. Modeling Tissue Growth Within Nonwoven Scaffolds Pores

    PubMed Central

    Church, Jeffrey S.; Alexander, David L.J.; Russell, Stephen J.; Ingham, Eileen; Ramshaw, John A.M.; Werkmeister, Jerome A.

    2011-01-01

    In this study we present a novel approach for predicting tissue growth within the pores of fibrous tissue engineering scaffolds. Thin nonwoven polyethylene terephthalate scaffolds were prepared to characterize tissue growth within scaffold pores, by mouse NR6 fibroblast cells. On the basis of measurements of tissue lengths at fiber crossovers and along fiber segments, mathematical models were determined during the proliferative phase of cell growth. Tissue growth at fiber crossovers decreased with increasing interfiber angle, with exponential relationships determined on day 6 and 10 of culture. Analysis of tissue growth along fiber segments determined two growth profiles, one with enhanced growth as a result of increased tissue lengths near the fiber crossover, achieved in the latter stage of culture. Derived mathematical models were used in the development of a software program to visualize predicted tissue growth within a pore. This study identifies key pore parameters that contribute toward tissue growth, and suggests models for predicting this growth, based on fibroblast cells. Such models may be used in aiding scaffold design, for optimum pore infiltration during the tissue engineering process. PMID:20687775

  9. Hydrated Excess Protons Can Create Their Own Water Wires

    PubMed Central

    2014-01-01

    Grotthuss shuttling of an excess proton charge defect through hydrogen bonded water networks has long been the focus of theoretical and experimental studies. In this work we show that there is a related process in which water molecules move (“shuttle”) through a hydrated excess proton charge defect in order to wet the path ahead for subsequent proton charge migration. This process is illustrated through reactive molecular dynamics simulations of proton transport through a hydrophobic nanotube, which penetrates through a hydrophobic region. Surprisingly, before the proton enters the nanotube, it starts “shooting” water molecules into the otherwise dry space via Grotthuss shuttling, effectively creating its own water wire where none existed before. As the proton enters the nanotube (by 2–3 Å), it completes the solvation process, transitioning the nanotube to the fully wet state. By contrast, other monatomic cations (e.g., K+) have just the opposite effect, by blocking the wetting process and making the nanotube even drier. As the dry nanotube gradually becomes wet when the proton charge defect enters it, the free energy barrier of proton permeation through the tube via Grotthuss shuttling drops significantly. This finding suggests that an important wetting mechanism may influence proton translocation in biological systems, i.e., one in which protons “create” their own water structures (water “wires”) in hydrophobic spaces (e.g., protein pores) before migrating through them. An existing water wire, e.g., one seen in an X-ray crystal structure or MD simulations without an explicit excess proton, is therefore not a requirement for protons to transport through hydrophobic spaces. PMID:25369445

  10. Hydrated Excess Protons Can Create Their Own Water Wires.

    PubMed

    Peng, Yuxing; Swanson, Jessica M J; Kang, Seung-gu; Zhou, Ruhong; Voth, Gregory A

    2015-07-23

    Grotthuss shuttling of an excess proton charge defect through hydrogen bonded water networks has long been the focus of theoretical and experimental studies. In this work we show that there is a related process in which water molecules move ("shuttle") through a hydrated excess proton charge defect in order to wet the path ahead for subsequent proton charge migration. This process is illustrated through reactive molecular dynamics simulations of proton transport through a hydrophobic nanotube, which penetrates through a hydrophobic region. Surprisingly, before the proton enters the nanotube, it starts "shooting" water molecules into the otherwise dry space via Grotthuss shuttling, effectively creating its own water wire where none existed before. As the proton enters the nanotube (by 2-3 Å), it completes the solvation process, transitioning the nanotube to the fully wet state. By contrast, other monatomic cations (e.g., K(+)) have just the opposite effect, by blocking the wetting process and making the nanotube even drier. As the dry nanotube gradually becomes wet when the proton charge defect enters it, the free energy barrier of proton permeation through the tube via Grotthuss shuttling drops significantly. This finding suggests that an important wetting mechanism may influence proton translocation in biological systems, i.e., one in which protons "create" their own water structures (water "wires") in hydrophobic spaces (e.g., protein pores) before migrating through them. An existing water wire, e.g., one seen in an X-ray crystal structure or MD simulations without an explicit excess proton, is therefore not a requirement for protons to transport through hydrophobic spaces. PMID:25369445

  11. Pore space analysis of NAPL distribution in sand-clay media

    USGS Publications Warehouse

    Matmon, D.; Hayden, N.J.

    2003-01-01

    This paper introduces a conceptual model of clays and non-aqueous phase liquids (NAPLs) at the pore scale that has been developed from a mathematical unit cell model, and direct micromodel observation and measurement of clay-containing porous media. The mathematical model uses a unit cell concept with uniform spherical grains for simulating the sand in the sand-clay matrix (???10% clay). Micromodels made with glass slides and including different clay-containing porous media were used to investigate the two clays (kaolinite and montmorillonite) and NAPL distribution within the pore space. The results were used to understand the distribution of NAPL advancing into initially saturated sand and sand-clay media, and provided a detailed analysis of the pore-scale geometry, pore size distribution, NAPL entry pressures, and the effect of clay on this geometry. Interesting NAPL saturation profiles were observed as a result of the complexity of the pore space geometry with the different packing angles and the presence of clays. The unit cell approach has applications for enhancing the mechanistic understanding and conceptualization, both visually and mathematically, of pore-scale processes such as NAPL and clay distribution. ?? 2003 Elsevier Science Ltd. All rights reserved.

  12. Pressurized liquid filled tendons

    SciTech Connect

    Burns, G.E.

    1987-05-12

    This patent describes an apparatus for detecting a leak in a tension leg platform tendon, comprising: a fluid-tight tensioned tubular tendon, the tendon connected on its upper end to a buoyant offshore structure and on its lower end to an anchor means. The anchor means is connected to the sea floor; means for supplying liquid to the tendon; means for pressurizing the liquid in excess of the maximum hydrostatic pressure exerted by the sea water on the tendon; and means for monitoring pressure, the means monitoring variations in liquid pressure to the tendon.

  13. Limestone characterization to model damage from acidic precipitation: Effect of pore structure on mass transfer

    USGS Publications Warehouse

    Leith, S.D.; Reddy, M.M.; Irez, W.F.; Heymans, M.J.

    1996-01-01

    The pore structure of Salem limestone is investigated, and conclusions regarding the effect of the pore geometry on modeling moisture and contaminant transport are discussed based on thin section petrography, scanning electron microscopy, mercury intrusion porosimetry, and nitrogen adsorption analyses. These investigations are compared to and shown to compliment permeability and capillary pressure measurements for this common building stone. Salem limestone exhibits a bimodal pore size distribution in which the larger pores provide routes for convective mass transfer of contaminants into the material and the smaller pores lead to high surface area adsorption and reaction sites. Relative permeability and capillary pressure measurements of the air/water system indicate that Salem limestone exhibits high capillarity end low effective permeability to water. Based on stone characterization, aqueous diffusion and convection are believed to be the primary transport mechanisms for pollutants in this stone. The extent of contaminant accumulation in the stone depends on the mechanism of partitioning between the aqueous and solid phases. The described characterization techniques and modeling approach can be applied to many systems of interest such as acidic damage to limestone, mass transfer of contaminants in concrete and other porous building materials, and modeling pollutant transport in subsurface moisture zones.

  14. Using Microfluidics for Visualisation of Displacement Mechanisms on Pore Network Models

    NASA Astrophysics Data System (ADS)

    Gerami Kaviri Nejad, A.; Mostaghimi, P.; Armstrong, R. T.; Rafeie, M.; Ebrahimi Warkiani, M.

    2015-12-01

    We use microfluidic methods for studying displacement mechanisms of immiscible fluids including drainage and imbibition in porous media at the pore scale. We use soft lithography method to make 4' diameter silicon wafer to be used as a mould of our designs. We have fabricated a range of microfluidic chips based on a range of patterns including pore junction with unequal throats, junction of throats with different coordination numbers, and junction of tortuous throats. We also fabricate more complex networks as a combination of the mentioned simple patterns. Decane and water are used as the wetting and non-wetting phases, respectively. Using high-resolution microscopy, we visualise the displacement processes and the movement of the interface between two fluids at different saturations. We initially test to micromodel chip for modelling drainage into a pore junction and compare our results with the prediction by the Young-Laplace equations. Then we focus on the sequence of pore filling and effects of pore space geometry, tortuosity and the injection rate. We use plasma treating to vary the contact angle and then study the effects of wettability on interface movement. Using accurate pump and pressure controller, we measure pressure drop across the micromodels at different time. By image processing of fluids distribution in the microfluidic chip, saturation of both phases can be estimated. Then, we plot relative permeability versus saturation curves for different pore space geometries. Our results can be used for validation of numerical two phase flow simulation and also we provide novel suggestions for modifying the equations of motion in pore network models.

  15. Pore-Water Extraction Intermediate-Scale Laboratory Experiments and Numerical Simulations

    SciTech Connect

    Oostrom, Martinus; Freedman, Vicky L.; Wietsma, Thomas W.; Truex, Michael J.

    2011-06-30

    A series of flow cell experiments was conducted to demonstrate the process of water removal through pore-water extraction in unsaturated systems. In this process, a vacuum (negative pressure) is applied at the extraction well establishing gas and water pressure gradients towards the well. The gradient may force water and dissolved contaminants, such as 99Tc, to move towards the well. The tested flow cell configurations consist of packings, with or without fine-grained well pack material, representing, in terms of particle size distribution, subsurface sediments at the SX tank farm. A pore water extraction process should not be considered to be equal to soil vapor extraction because during soil vapor extraction, the main goal may be to maximize gas removal. For pore water extraction systems, pressure gradients in both the gas and water phases need to be considered while for soil vapor extraction purposes, gas phase flow is the only concern. In general, based on the limited set (six) of flow experiments that were conducted, it can be concluded that pore water extraction rates and cumulative outflow are related to water content, the applied vacuum, and the dimensions of the sediment layer providing the extracted water. In particular, it was observed that application of a 100-cm vacuum (negative pressure) in a controlled manner leads to pore-water extraction until the water pressure gradients towards the well approach zero. Increased cumulative outflow was obtained with an increase in initial water content from 0.11 to 0.18, an increase in the applied vacuum to 200 cm, and when the water-supplying sediment was not limited. The experimental matrix was not sufficiently large to come to conclusions regarding maximizing cumulative outflow.

  16. PORE STRUCTURE MODEL OF CEMENT HYDRATES CONSIDERING PORE WATER CONTENT AND REACTION PROCESS UNDER ARBITRARY HUMIDITY

    NASA Astrophysics Data System (ADS)

    Fujikura, Yusuke; Oshita, Hideki

    A simulation model to estimate the pore structure of cement hydrates by curing in arbitrary relative humidity is presented. This paper describes procedures for predicting phase compositions based on the classical hydration model of Portland cement, calculating the particle size distribution of constituent phases and evaluating the pore size distribution by stereological and statistical considerations. And to estimate the water content in pore structure under any relative humidity, we proposed the simulation model of adsorption isotherm model based on the pore structure. To evaluate the effectiveness of this model, simulation results were compared with experimental results of the pore size distribution measured by mercury porosimetry. As a result, it was found that the experimental and simulated results were in close agreement, and the simulated results indicated characterization of the po re structure of cement hydrates.

  17. Emulsion formation at the Pore-Scale

    NASA Astrophysics Data System (ADS)

    Armstrong, R. T.; Van Den Bos, P.; Berg, S.

    2012-12-01

    The use of surfactant cocktails to produce ultra-low interfacial tension between water and oil is an enhanced oil recovery method. In phase behavior tests three distinct emulsion phases are observed: (1) oil-in-water emulsion; (2) microemulsion; and (3) water-in-oil emulsion. However, it is unknown how phase behavior manifests at the pore-scale in a porous media system. What is the time scale needed for microemulsion formation? Where in the pore-space do the microemulsions form? And in what order do the different emulsion phases arrange during oil bank formation? To answer these questions micromodel experiments were conducted. These experiments are used to build a conceptual model for phase behavior at the pore-scale.

  18. Modeling Soil Pore Oxygen in Restored Wetlands

    NASA Astrophysics Data System (ADS)

    Rubol, S.; Loecke, T.; Burgin, A. J.; Franz, T.

    2015-12-01

    Soil pore oxygen (O2) is usually modeled indirectly as a function of soil moisture. However, using soil moisture to describe the oxic /anoxic status of a soil may not be sufficient accurate, especially when soil pore O2 rapidly changes, as following hydrological forcing. As first step, we use the dataset collected in the constructed wetland near Dayton, OH, by Loecke and Burgin, to reconstruct the environmental functions and re-aeration status of the soil. The dataset consist of 24 Apogee sensors and 24 soil moisture and temperature sensors located at 10 cm depth in upland, transitional and submerged zone (see Figure 1). Data were recorded over two years at temporal interval of 30 minutes. Then, we explore the capability of existing biogeochemical models to predict metabolic activity and the soil pore O2. Figure1: Restored wetland field site with soil O2 sensors (yellow stars) in upland (red), transitional (green) and submerged (blue) zones.

  19. Optical detection of pores in adipocyte membrane

    NASA Astrophysics Data System (ADS)

    Yanina, I. Yu.; Doubrovski, V. A.; Tuchin, V. V.

    2013-08-01

    Structures that can be interpreted as cytoplasm droplets leaking through the membrane are experimentally detected on the membranes of adipocytes using optical digital microscopy. The effect of an aqueous alcohol solution of brilliant green on the amount and sizes of structures is studied. It is demonstrated that the optical irradiation of the adipocytes that are sensitized with the aid of the brilliant green leads to an increase in the amount of structures (pores) after the irradiation. The experimental results confirm the existence of an earlier-proposed effect of photochemical action on the sensitized cells of adipose tissue that involves additional formation of pores in the membrane of the sensitized cell under selective optical irradiation. The proposed method for the detection of micropores in the membrane of adipose tissue based on the detection of the cytoplasm droplets leaking from the cell can be considered as a method for the optical detection of nanosized pores.

  20. 43 CFR 426.12 - Excess land.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... as excess is binding on the land. However, the landowner may change the designation under the...) If the status of land is changed by law or regulations. (1) If the district had a contract with... 25, 1926 (43 U.S.C. 423e); (ii) If the status of this land changes from nonexcess into excess after...

  1. 43 CFR 426.12 - Excess land.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... as excess is binding on the land. However, the landowner may change the designation under the...) If the status of land is changed by law or regulations. (1) If the district had a contract with... 25, 1926 (43 U.S.C. 423e); (ii) If the status of this land changes from nonexcess into excess after...

  2. 43 CFR 426.12 - Excess land.