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Nasser Khalili - One of the best experts on this subject based on the ideXlab platform.
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Effective Stress in Unsaturated Soils: Review with New Evidence
International Journal of Geomechanics, 2004Co-Authors: Nasser Khalili, F. Geiser, G. E. BlightAbstract:The application of the Effective Stress principle to unsaturated soils is critically reviewed, and the reasons underlying the difficulties in previous investigations of the Effective Stress in unsaturated soils are highlighted. The validity of the relationship proposed by Khalili and Khabbaz in 1998 for the determination of the Effective Stress parameter, χ, is examined using an extensive array of experimental data. It is shown that quantitative predictions of shear strength and volume change in unsaturated soils can be made using the Effective Stress Concept. The uniqueness of the critical state line in the deviatoric Stress–Effective mean Stress plane for saturated as well as unsaturated soils is investigated, and the incremental form of the Effective Stress parameter is derived.
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On the Constitutive Modelling of Thermo-Hydro-Mechanical Coupling in Elastic Media with Double Porosity
Coupled Thermo-Hydro-Mechanical-Chemical Processes in Geo-Systems - Fundamentals Modelling Experiments and Applications, 2004Co-Authors: Nasser Khalili, A.p.s. SelvaduraiAbstract:Abstract The partial differential equations governing non-isothermal flow and deformation in an elastic medium with double porosity are presented. The governing equations satisfy an Effective Stress Concept, Darcy's law, Fourier' law and the equations of Hookean thermoelasticity. The equations are derived using a systematic macroscopic approach that satisfies conservation laws applicable to balance of linear momentum, mass and energy. The Thermo-Hydro-Mechanical coupling take into account processes associated with: thermal expansion, thermal convection by moving fluid, fluid flux due to temperature gradients, heat flux due to pressure gradients, fluid and heat exchange between the two pore system, and the heat of phase compression.
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A fully coupled constitutive model for thermo-hydro-mechanical analysis in elastic media with double porosity
Geophysical Research Letters, 2003Co-Authors: Nasser Khalili, A.p.s. SelvaduraiAbstract:[1] The partial differential equations governing non-isothermal flow and deformation in an elastic medium with double porosity are presented. The governing equations satisfy an Effective Stress Concept, Darcy's law, Fourier' law and the equations of Hookean thermoelasticity. The equations are derived using a systematic macroscopic approach that satisfies conservation laws applicable to balance of linear momentum, mass and energy. The Thermo-Hydro-Mechanical coupling take into account processes associated with: thermal expansion, thermal convection by moving fluid, fluid flux due to temperature gradients, heat flux due to pressure gradients, fluid and heat exchange between the two pore system, and the heat of phase compression.
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An Effective Stress based numerical model for hydro-mechanical analysis in unsaturated porous media
Computational Mechanics, 2000Co-Authors: Nasser Khalili, M H Khabbaz, S. ValliappanAbstract:A fully coupled flow-deformation model is presented for the behaviour of unsaturated porous media. The governing equations are derived based on the equations of equilibrium, Effective Stress Concept, Darcy's law, Henry's law, and the conservation of fluid mass. Macroscopic coupling between the flow and deformation fields is established through the Effective Stress parameters. The microscopic link between the volumetric deformations of the two pore system (i.e. the pore-air and the pore-water) is established using Betti's reciprocal theorem. Both links are essential for a proper modelling of flow and deformation in unsaturated porous media. The discretised form of the governing equations is obtained using the finite element technique. As application of the model, experimental results from several laboratory tests reported in the literature are modelled numerically. Good agreement is obtained between the numerical and the experimental results in all cases.
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Application of Effective Stress Concept to Unsaturated Soils
1999Co-Authors: Nasser Khalili, M H KhabbazAbstract:The application of the Effective Stress Concept to unsaturated soils is critically reviewed. The validity and the appropriateness of the relationship proposed by Khalili and Khabbaz (1996, 1998) for the determination of the Effective Stress parameter χ are examined using both shear strength and volumetric change data. Extremely good agreement is obtained between the measured and predicted values in all cases. It is shown that quantitative predictions of shear strength and deformation in unsaturated soils can be made using the Effective Stress Concept. The model parameters will be exactly the same as those used in saturated soils, except for a single parameter which can be determined in any soil physics laboratory. This is in contrast to the current models of unsaturated soils which require extensive laboratory testing.
Francesco Pesavento - One of the best experts on this subject based on the ideXlab platform.
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the solid phase Stress tensor in porous media mechanics and the hill mandel condition
Journal of The Mechanics and Physics of Solids, 2009Co-Authors: William G Gray, Bernhard A. Schrefler, Francesco PesaventoAbstract:Abstract An assessment of the Stress tensors used currently for the modeling of partially saturated porous media is made which includes Concepts like total Stress, solid phase Stress, and solid pressure. Thermodynamically constrained averaging theory is used to derive the solid phase Stress tensor. It is shown that in the upscaling procedure the Hill conditions are satisfied, which is not trivial. The Stress tensor is then compared to traditional Stress measures. The physical meaning of two forms of solid pressure and of the Biot coefficient is clarified. Finally, a Bishop–Skempton like form of the Stress tensor is obtained and a form of the total Stress tensor that does not make use of the Effective Stress Concept.
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The solid phase Stress tensor in porous media mechanics and the Hill–Mandel condition
Journal of The Mechanics and Physics of Solids, 2009Co-Authors: William G Gray, Bernhard A. Schrefler, Francesco PesaventoAbstract:Abstract An assessment of the Stress tensors used currently for the modeling of partially saturated porous media is made which includes Concepts like total Stress, solid phase Stress, and solid pressure. Thermodynamically constrained averaging theory is used to derive the solid phase Stress tensor. It is shown that in the upscaling procedure the Hill conditions are satisfied, which is not trivial. The Stress tensor is then compared to traditional Stress measures. The physical meaning of two forms of solid pressure and of the Biot coefficient is clarified. Finally, a Bishop–Skempton like form of the Stress tensor is obtained and a form of the total Stress tensor that does not make use of the Effective Stress Concept.
Bernhard A. Schrefler - One of the best experts on this subject based on the ideXlab platform.
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the solid phase Stress tensor in porous media mechanics and the hill mandel condition
Journal of The Mechanics and Physics of Solids, 2009Co-Authors: William G Gray, Bernhard A. Schrefler, Francesco PesaventoAbstract:Abstract An assessment of the Stress tensors used currently for the modeling of partially saturated porous media is made which includes Concepts like total Stress, solid phase Stress, and solid pressure. Thermodynamically constrained averaging theory is used to derive the solid phase Stress tensor. It is shown that in the upscaling procedure the Hill conditions are satisfied, which is not trivial. The Stress tensor is then compared to traditional Stress measures. The physical meaning of two forms of solid pressure and of the Biot coefficient is clarified. Finally, a Bishop–Skempton like form of the Stress tensor is obtained and a form of the total Stress tensor that does not make use of the Effective Stress Concept.
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The solid phase Stress tensor in porous media mechanics and the Hill–Mandel condition
Journal of The Mechanics and Physics of Solids, 2009Co-Authors: William G Gray, Bernhard A. Schrefler, Francesco PesaventoAbstract:Abstract An assessment of the Stress tensors used currently for the modeling of partially saturated porous media is made which includes Concepts like total Stress, solid phase Stress, and solid pressure. Thermodynamically constrained averaging theory is used to derive the solid phase Stress tensor. It is shown that in the upscaling procedure the Hill conditions are satisfied, which is not trivial. The Stress tensor is then compared to traditional Stress measures. The physical meaning of two forms of solid pressure and of the Biot coefficient is clarified. Finally, a Bishop–Skempton like form of the Stress tensor is obtained and a form of the total Stress tensor that does not make use of the Effective Stress Concept.
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A parallel algorithm for thermo-hydro-mechanical analysis of deforming porous media
Computational Mechanics, 1996Co-Authors: X. Wang, Dariusz Gawin, Bernhard A. SchreflerAbstract:In this paper, a parallel Newton-Raphson algorithm with domain decomposition is developed to solve fully coupled heat, water and gas flow in deformable porous media. The model makes use of the modified Effective Stress Concept together with the capillary pressure relationship. Phase change and latent heat transfer are also taken into account. The chosen macroscopic field variables are displacement, capillary pressure, gas pressure and temperature. The parallel program is developed on a cluster of workstations. The PVM (Parallel Virtual Machine) system is used to handle communications among networked workstations. An implementation of this parallel method on workstations is discussed, the speedup and efficiency of this method being demonstrated by numerical examples.
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Coupled heat, water and gas flow in deformable porous media
International Journal for Numerical Methods in Fluids, 1995Co-Authors: Dariusz Gawin, Paolo Baggio, Bernhard A. SchreflerAbstract:A fully coupled numerical model to simulate the slow transient phenomena involving heat and mass transfer in deforming porous media is developed. It makes use of the modified Effective Stress Concept together with the capillary pressure relationship. The heat transfer through conduction and convection as well as the latent heat transfer (evaporation and/or condensation) is taken into account. The governing equations in terms of displacements, temperature, capillary pressure and gas pressure are coupled non-linear differential equatiosn and are solved by the finite element method. The model is validated with respect to a documented experiment on semisaturated soil behaviour. Two other examples involving subsidence due to pumping from a phreatic aquifer and thermoelastic consolidation of saturated and semisaturated media are also presented.
Adrian R. Russell - One of the best experts on this subject based on the ideXlab platform.
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Rigid Retaining Walls Interacting with Unsaturated Soils in Axial Symmetry
Lecture Notes in Civil Engineering, 2017Co-Authors: Adrian R. RussellAbstract:The slip line theory is applied to the problem of an axisymmetric retaining wall interacting with unsaturated soil. Active and passive failures of a rigid vertical wall are considered. The slip line governing equations assume the limiting equilibrium state of a Mohr-Coulomb soil. A linear variation of the contribution of suction to the Effective Stress with depth is assumed. A standard finite difference method is used to solve the governing equations. The finite difference procedures were validated with recently published literature on axisymmetric retaining walls retaining dry soils. It is shown that adopting the Effective Stress Concept enables the influence of suction in unsaturated soils to be considered in a simple way. An example of analysis is presented to illustrate this. Moreover, the paper shows significant influence of the length scale and the magnitude of the circumferential Stress on computed earth pressures.
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Stability charts for curvilinear slopes in unsaturated soils
Soils and Foundations, 2017Co-Authors: Adrian R. RussellAbstract:Abstract This paper presents charts derived from stability analyses of curvilinear slopes in non-homogeneous unsaturated soils. The charts enable quick and inexpensive stability analyses to be conducted in practice. The soils are assumed to obey the Mohr-Coulomb failure criterion. Suction effects are captured using the Effective Stress Concept. Cohesion and the contribution of suction to the Effective Stress are linear functions of depth. It is shown that a stable curvilinear slope profile is uniquely governed by dimensionless parameters. The charts are presented using these dimensionless parameters and may be used in the preliminary design of stable curvilinear slopes. In general, suction has a similar influence to cohesion, and as the contribution of suction to Effective Stress increases, steeper curvilinear slopes become stable. An example of application is included showing the design of a curvilinear slope.
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bearing capacity of strip footings on unsaturated soils by the slip line theory
E3S Web of Conferences, 2016Co-Authors: Adrian R. RussellAbstract:The bearing capacity of strip footings on unsaturated soils is studied using slip line theory. The suction profiles considered are non-uniform with depth and correspond to vertical flow of water by infiltration or evaporation. The slip line theory assumes a plastic equilibrium state of a Mohr-Coulomb soil in which suction influences are included using the Effective Stress Concept. This paper shows that the influence of a non-uniform suction profile on bearing capacity is significant. When the contribution of suction to the Effective Stress can be approximated as a function that varies linearly with depth, the effects of suction on bearing capacity can be represented in dimensionless form in separate charts for smooth and rough footings. Using the charts the bearing capacity can be determined for any combination of friction angle, footing width, surcharge, soil unit weight and linear profiles of cohesion and the contribution of suction to the Effective Stress.
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Slip line theory applied to a retaining wall–unsaturated soil interaction problem
Computers and Geotechnics, 2014Co-Authors: Adrian R. RussellAbstract:Abstract An extension of slip line theory to unsaturated soils is presented and applied to the problem of a rigid retaining wall rotating about its toe into unsaturated soils. Suction is introduced using the Effective Stress Concept. Soil–wall interface friction is defined carefully. The influence of suction on limiting passive earth pressures is analysed for two soils under steady state evaporation and infiltration. Suction increases the limiting passive Stress at the soil–wall interface, with a dependence on the steady state flow type. The displacement of the retained soil is studied assuming the wall undergoes a rotation increment. The results show a clear difference in the displacement for evaporation and infiltration.
William G Gray - One of the best experts on this subject based on the ideXlab platform.
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the solid phase Stress tensor in porous media mechanics and the hill mandel condition
Journal of The Mechanics and Physics of Solids, 2009Co-Authors: William G Gray, Bernhard A. Schrefler, Francesco PesaventoAbstract:Abstract An assessment of the Stress tensors used currently for the modeling of partially saturated porous media is made which includes Concepts like total Stress, solid phase Stress, and solid pressure. Thermodynamically constrained averaging theory is used to derive the solid phase Stress tensor. It is shown that in the upscaling procedure the Hill conditions are satisfied, which is not trivial. The Stress tensor is then compared to traditional Stress measures. The physical meaning of two forms of solid pressure and of the Biot coefficient is clarified. Finally, a Bishop–Skempton like form of the Stress tensor is obtained and a form of the total Stress tensor that does not make use of the Effective Stress Concept.
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The solid phase Stress tensor in porous media mechanics and the Hill–Mandel condition
Journal of The Mechanics and Physics of Solids, 2009Co-Authors: William G Gray, Bernhard A. Schrefler, Francesco PesaventoAbstract:Abstract An assessment of the Stress tensors used currently for the modeling of partially saturated porous media is made which includes Concepts like total Stress, solid phase Stress, and solid pressure. Thermodynamically constrained averaging theory is used to derive the solid phase Stress tensor. It is shown that in the upscaling procedure the Hill conditions are satisfied, which is not trivial. The Stress tensor is then compared to traditional Stress measures. The physical meaning of two forms of solid pressure and of the Biot coefficient is clarified. Finally, a Bishop–Skempton like form of the Stress tensor is obtained and a form of the total Stress tensor that does not make use of the Effective Stress Concept.
