The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Francois Renard - One of the best experts on this subject based on the ideXlab platform.
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failure patterns caused by localized rise in Pore Fluid overpressure and effective strength of rocks
Geophysical Research Letters, 2007Co-Authors: Alexander Y Rozhko, Yuri Y Podladchikov, Francois RenardAbstract:[1] In order to better understand the interaction between Pore-Fluid overpressure and failure patterns in rocks we consider a porous elasto-plastic medium in which a laterally localized overpressure line source is imposed at depth below the free surface. We solve numerically the Fluid filtration equation coupled to the gravitational force balance and poro-elasto-plastic rheology equations. Systematic numerical simulations, varying initial stress, intrinsic material properties and geometry, show the existence of five distinct failure patterns caused by either shear banding or tensile fracturing. The value of the critical Pore-Fluid overpressure pc at the onset of failure is derived from an analytical solution that is in excellent agreement with numerical simulations. Finally, we construct a phase-diagram that predicts the domains of the different failure patterns and pc at the onset of failure.
Sumi Siddiqua - One of the best experts on this subject based on the ideXlab platform.
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Developing a Relation Between Pore Fluid Salinity and Electrical Resistivity of Highly Compacted Bentonite
Geotechnical and Geological Engineering, 2019Co-Authors: Sumi Siddiqua, Sepehr RahimiAbstract:Highly compacted bentonite is an engineered barrier material that is being examined in the Canadian concept for storage of used fuel bundle in a deep geological repository. Having an estimation of the in situ ground water salinity will help to predict hydro-mechanical behavior of the engineered barriers as well as understanding of any potential corrosion of the cylinders of the used fuel bundles. The current research investigates the impact of Pore Fluid chemistry on the electrical resistivity of highly compacted bentonite. In these tests, Pore Fluid solutions were selected to represent groundwater salinity of host rocks locations of the Canadian DGR. Former studies found that electrical resistivity is a powerful tool to monitor the degree of saturation of barrier materials. Following the similar approach, this study suggests that the salinity of the highly compacted bentonite can be monitored by means of electrical resistivity to acquire a clearer picture of the deep geological repository’s performance.
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Impact of Pore Fluid chemistry on the thermal conductivity of bentonite–sand mixture
Environmental Earth Sciences, 2017Co-Authors: Sumi Siddiqua, Bardia Tabiatnejad, Greg SiemensAbstract:Thermal conductivity is an important parameter to consider when designing clay-based barriers for use in deep geological repositories (DGR). In the DGR environment, the infiltration of local saline groundwater can potentially change the Pore Fluid chemistry of a barrier over its lifetime. This change in chemistry is known to alter the thermal properties of the barrier materials. In order to examine the impact of Pore Fluid salinity on thermal conductivity, experiments were conducted under both distilled water and saline Pore Fluid conditions. The material mixtures were prepared at two different dry densities using two different salt types. Furthermore, five different thermal conductivity prediction models were selected and evaluated on their performance with respect to the experimental outcomes. In general, these results indicated that an increase in the constituent Pore Fluid’s salt concentration leads to a decrease in the thermal conductivity of the material. Additionally, the thermal conductivity values of the materials prepared at a high dry density were greater than of those compacted at a low dry density.
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Influence of Pore Fluid Chemistry on the Mechanical Properties of Clay-Based Materials
Geotechnical and Geological Engineering, 2014Co-Authors: Sumi Siddiqua, James Blatz, Alex Man, Greg Siemens, Bee Fong LimAbstract:The producers of nuclear waste, within all countries exploring options, including Canada, have determined the long-term solution to be a deep geological repository. In the Canadian concept, within the deep geologic repository a number of clay-based barriers will separate the containers from the surrounding geosphere. Following placement the surrounding groundwater will infiltrate into the repos-itory. In order to analyze the performance of the repository under very complex conditions, accurate material properties are required. The chemistry of the host rock is an important aspect as the behaviour of clay-based barrier materials could be affected by the saturating saline groundwater. This paper investigates the saturated mechanical behaviour of light backfill (composed of 50 % silica sand and 50 % Na-bentonite clay) and dense backfill (composed of 70 % crushed granite, 25 % glacial lake clay and 5 % Na-bentonite clay) and the quantifying the effect of Pore Fluid chemistry on the strength and compressibility behav-iour of the materials. The results indicate that light backfill behaviour is strongly influenced by its Pore Fluid chemistry while dense backfill shows limited effects. The material parameters of light backfill and dense backfill are interpreted for input into numerical simulations. These results and interpretation enrich the understanding of the mechanical response of light and dense backfill, two components of the sealing system of the Canadian deep geologic repository.
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evaluation of the impact of Pore Fluid chemistry on the hydromechanical behaviour of clay based sealing materials
Canadian Geotechnical Journal, 2011Co-Authors: Sumi Siddiqua, James Blatz, Greg Siemensg SiemensAbstract:The results of an experimental program undertaken to evaluate the impact of Pore Fluid salinity on the hydromechanical performance of light and dense backfill materials are presented. Light and dense backfills are engineered barrier materials that are being examined in the Canadian concept for storage of spent fuel in a deep geological repository. The current research investigates the impact of Pore Fluid chemistry on the swelling, compressibility, stiffness, and hydraulic conductivity parameters of light and dense backfills that are required as material parameters for analysis and design. In these tests, Pore Fluid chemistry was selected to represent groundwater within potential host units including granite and limestone rock. Results show that the performance of light backfill is significantly affected by changes in Pore Fluid chemistry. The swell potential of light backfill decreases with increasing salinity of the solution. The hydraulic conductivity decreases with increasing effective montmorillonite...
R. Vassallo - One of the best experts on this subject based on the ideXlab platform.
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Residual strength and creep behaviour on the slip surface of specimens of a landslide in marine origin clay shales: influence of Pore Fluid composition
Landslides, 2015Co-Authors: C. Di Maio, G. Scaringi, R. VassalloAbstract:Active landslides in clay shales are widespread in Mediterranean countries. One of their characteristics is that the mobilized shear strength corresponds to the residual strength. The residual friction angle of clays depends on Pore Fluid composition which, in formations of marine origin, could have changed after emersion from the sea because of a number of processes, e.g., contact with rain or fresh water. This study aims at evaluating the influence of Pore Fluid composition and of its changes on the behaviour of Costa della Gaveta landslide, used as a case study. The natural Pore Fluid composition was analysed; then, the influence of such composition on the residual strength, and the effects of its variation on the shear creep behaviour were investigated. The paper shows that the natural Pore Fluid is a composite salt solution with variable concentration. It exhibits characteristics close to those of seawater at about 30 m depth, whereas it is very dilute close to the ground surface. Salt solutions at various concentrations and distilled water were thus used to simulate in the laboratory tests the effects of the different natural Pore solutions. The results show that the residual friction angle varies significantly within the field concentration range. Moreover, exposure to distilled water causes a noticeable decrease in the residual strength during tests under constant shear displacement rate. Consistently, under constant driving shear stresses, time dependent displacements are observed, evolving with primary, secondary and tertiary creep phases, characterized, respectively, by decreasing, constant and increasing displacement rates.
Stuart Crampin - One of the best experts on this subject based on the ideXlab platform.
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indication of high Pore Fluid pressures in a seismically active fault zone
Geophysical Journal International, 2002Co-Authors: Stuart Crampin, Theodora Volti, Sebastien F M Chastin, Agust Gudmundsson, Ragnar StefanssonAbstract:SUMMARY Polarisations of seismic shear-wave splitting observed above small earthquakes in Iceland are typically approximately NE to SW, parallel to the direction of maximum horizontal stress. In contrast, the polarisations of shear-waves at three new stations sited over the Husav´ ik-Flatey Fault, a major seismically-active transform fault in northern Iceland, are approximately NW to SE, orthogonal to the stress-aligned polarisations elsewhere. Modelling suggests that these 90 ◦ -flips in polarisations are caused by propagation through cracks containing Fluids at high Pore-Fluid pressures within one or two MPa of the critical stress. These observations suggest that high Pore-Fluid pressures, which play a key role in earthquake source mechanisms, can be monitored by analysing shear-wave splitting above seismically-active fault planes.
C. Di Maio - One of the best experts on this subject based on the ideXlab platform.
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Residual strength and creep behaviour on the slip surface of specimens of a landslide in marine origin clay shales: influence of Pore Fluid composition
Landslides, 2015Co-Authors: C. Di Maio, G. Scaringi, R. VassalloAbstract:Active landslides in clay shales are widespread in Mediterranean countries. One of their characteristics is that the mobilized shear strength corresponds to the residual strength. The residual friction angle of clays depends on Pore Fluid composition which, in formations of marine origin, could have changed after emersion from the sea because of a number of processes, e.g., contact with rain or fresh water. This study aims at evaluating the influence of Pore Fluid composition and of its changes on the behaviour of Costa della Gaveta landslide, used as a case study. The natural Pore Fluid composition was analysed; then, the influence of such composition on the residual strength, and the effects of its variation on the shear creep behaviour were investigated. The paper shows that the natural Pore Fluid is a composite salt solution with variable concentration. It exhibits characteristics close to those of seawater at about 30 m depth, whereas it is very dilute close to the ground surface. Salt solutions at various concentrations and distilled water were thus used to simulate in the laboratory tests the effects of the different natural Pore solutions. The results show that the residual friction angle varies significantly within the field concentration range. Moreover, exposure to distilled water causes a noticeable decrease in the residual strength during tests under constant shear displacement rate. Consistently, under constant driving shear stresses, time dependent displacements are observed, evolving with primary, secondary and tertiary creep phases, characterized, respectively, by decreasing, constant and increasing displacement rates.
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Residual strength of kaolin and bentonite: the influence of their constituent Pore Fluid
Geotechnique, 1994Co-Authors: C. Di Maio, G. B. FenellifAbstract:The residual strength of clays is affected by their mineral composition and by the nature of their constituent Pore Fluid. In principle, both factors may influence either strength parameters or stresses, but it is not yet completely clear how this influence works. Previous publications have elucidated some aspects of clay residual strength behaviour. This Paper investigates further the roles of minerals and Pore Fluid composition on the residual strength of clayey soils. It describes and analyses tests on kaolin, bentonite and their mixtures exposed to distilled water and sodium choride solutions with given concentrations. The results show that the shear strength of kaolin is not affected by the solutions used, whereas the residual strength of bentonite varies greatly because of the inward salt diffusion towards the clay. Further, for the clay mixtures with any of the Pore Fluids considered, the weaker component has the greater influence on the behaviour of the mixture. La resistance residuelle des argile...
