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Jean Sulem - One of the best experts on this subject based on the ideXlab platform.
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Numerical Analysis of Strain Localization in Rocks with Thermo-hydro-mechanical Couplings Using Cosserat Continuum
Rock Mechanics and Rock Engineering, 2018Co-Authors: Hadrien Rattez, Jean Sulem, Ioannis Stefanou, Manolis Veveakis, Thomas PouletAbstract:A numerical model for thermo-hydro-mechanical strong couplings in an elasto-plastic Cosserat continuum is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. This model allows specifically to study the complete stress–strain response of a rock specimen, as well as the size of the strain Localization Zone for a rock taking into account its microstructure. The numerical implementation in a finite element code is presented, matching adequately analytical solutions or results from other simulations found in the literature. Two different applications of the numerical model are also presented to highlight its capabilities. The first one is a biaxial test on a saturated weak sandstone, for which the influence on the stress–strain response of the characteristic size of the microstructure and of thermal pressurization is investigated. The second one is the rapid shearing of a mature fault Zone in the brittle part of the lithosphere. In this example, the evolution of the thickness of the localized Zone and the influence of the permeability change on the stress–strain response are studied.
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the importance of thermo hydro mechanical couplings and microstructure to strain Localization in 3d continua with application to seismic faults part i theory and linear stability analysis
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: Hadrien Rattez, Ioannis Stefanou, Jean SulemAbstract:Abstract A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. The presence of internal lengths in Cosserat continua enables to estimate the thickness of the Localization Zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault Zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized Zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.
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The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain Localization in 3D continua with application to seismic faults. Part I: Theory and Linear Stability Analysis
Journal of the Mechanics and Physics of Solids, 2018Co-Authors: Ioannis Stefanou, Hadrien Rattez, Jean SulemAbstract:A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. Furthermore, the presence of an internal length in Cosserat continua enables to estimate the thickness of the Localization Zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault Zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized Zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.
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Strain Localization and Slip Instability in a Strain-Rate Hardening, Chemically Weakening Material
Journal of Applied Mechanics, 2012Co-Authors: Nicolas Brantut, Jean SulemAbstract:The stability of steady slip and homogeneous shear is studied for rate-hardening materials undergoing chemical reactions that produce weaker materials (reaction-weakening process), in drained conditions. In a spring- slider configuration, a linear perturbation analysis provides analytical expressions of the critical stiffness below which unstable slip occurs. In the framework of a frictional constitutive law, numerical tests are performed to study the effects of a nonlinear reaction kinetics on the evolution of the instability. Slip instabilities can be stopped at relatively small slip rates (only a few orders of magnitude higher than the forcing velocity) when the reactant is fully depleted. The stability analysis of homogeneous shear provides an independent estimate of the thickness of the shear Localization Zone due to the reaction weakening, which can be as low as 0.1 m in the case of lizardite dehydration. The potential effect of thermo-chemical pore fluid pressurization during dehydration is discussed, and shown to be negligible compared to the reaction-weakening effect. We finally argue that the slip instabilities originating from the reaction-weakening process could be a plausible candidate for intermediate depth earthquakes in subduction Zones.
Noël Challamel - One of the best experts on this subject based on the ideXlab platform.
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A variationally based nonlocal damage model to predict diffuse microcracking evolution
International Journal of Mechanical Sciences, 2010Co-Authors: Noël ChallamelAbstract:Abstract We explore a variationally based nonlocal damage model, based on a combination of a nonlocal variable and a local damage variable. The model is physically motivated by the concept of “nonlocal” effective stress. The energy functional which depends on the displacement and the damage fields is given for a one-dimensional bar problem. The higher-order boundary conditions at the boundary of the elasto-damaged Zone are rigorously derived. We show that the gradient damage models can be obtained as particular cases of such a formulation (as an asymptotic case). Some new analytical solutions will be presented for a simplified formulation where the stress–strain damage law is only expressed in a local way. These Continuum Damage Mechanics models are well suited for the tension behaviour of quasi-brittle materials, such as rock or concrete materials. It is theoretically shown that the damage Zone evolves with the load level. This dependence of the Localization Zone to the loading parameter is a basic feature, which is generally well accepted, from an experimental point of view. The computation of the nonlocal inelastic problem is based on a numerical solution obtained from a nonlinear boundary value problem. The numerical treatment of the nonlinear nonlocal damage problem is investigated, with some specific attention devoted to the damageable interface tracking. A bending cantilever beam is also studied from the new variationally based nonlocal damage model. Wood’s paradox is solved with such a nonlocal damage formulation. Finally, an anisotropic nonlocal tensorial damage model with unilateral effect is also introduced from variational arguments, and numerically characterized in simple loading situations.
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A variationally based nonlocal damage model to predict diffuse microcracking evolution
International Journal of Mechanical Sciences, 2010Co-Authors: Noël ChallamelAbstract:We explore a variationally based nonlocal damage model, based on a combination of a nonlocal variable and a local damage variable. The model is physically motivated by the concept of ''nonlocal'' effective stress. The energy functional which depends on the displacement and the damage fields is given for a one-dimensional bar problem. The higher-order boundary conditions at the boundary of the elasto-damaged Zone are rigorously derived. We show that the gradient damage models can be obtained as particular cases of such a formulation (as an asymptotic case). Some new analytical solutions will be presented for a simplified formulation where the stress-strain damage law is only expressed in a local way. These Continuum Damage Mechanics models are well suited for the tension behaviour of quasi-brittle materials, such as rock or concrete materials. It is theoretically shown that the damage Zone evolves with the load level. This dependence of the Localization Zone to the loading parameter is a basic feature, which is generally well accepted, from an experimental point of view. The computation of the nonlocal inelastic problem is based on a numerical solution obtained from a nonlinear boundary value problem. The numerical treatment of the nonlinear nonlocal damage problem is investigated, with some specific attention devoted to the damageable interface tracking. A bending cantilever beam is also studied from the new variationally based nonlocal damage model. Wood's paradox is solved with such a nonlocal damage formulation. Finally, an anisotropic nonlocal tensorial damage model with unilateral effect is also introduced from variational arguments, and numerically characterized in simple loading situations. (C) 2010 Elsevier Ltd. All rights reserved.
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some closed form solutions to simple beam problems using nonlocal gradient damage theory
International Journal of Damage Mechanics, 2009Co-Authors: Noël Challamel, Charles Casandjian, Christophe LanosAbstract:In this article, a family of damage models which leads to the analytical solvability of the nonlocal evolution problem of a homogeneous bar in tension is defined. Explicit gradient damage models and implicit gradient damage models are investigated in a simple structural framework. The natural boundary conditions are derived from a variational principle, and are obtained at the boundary of the damage Zone. It is shown that these damage models are the only ones leading to a linear differential equation of the strain variable. Some closed-form solutions are then available, providing a useful framework for the verification of computational models. Furthermore, these continuum damage mechanics models are well suited for the tension behavior of quasi-brittle materials, such as rock or concrete materials. It is theoretically shown that the damage Zone evolves with the load level. This dependence of the Localization Zone to the loading parameter, is a basic feature, which is generally well accepted, from an experimental point of view. The strain profiles are also theoretically obtained, and corroborate well with what is usually numerically found for such nonlocal models. An imperfection analysis shows that the softening evolution problem is well posed in presence of strength imperfections. However, explicit gradient damage models lead to physically questionable results, in presence of imperfections. It is then recommended to use implicit gradient damage
Hadrien Rattez - One of the best experts on this subject based on the ideXlab platform.
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Numerical Analysis of Strain Localization in Rocks with Thermo-hydro-mechanical Couplings Using Cosserat Continuum
Rock Mechanics and Rock Engineering, 2018Co-Authors: Hadrien Rattez, Jean Sulem, Ioannis Stefanou, Manolis Veveakis, Thomas PouletAbstract:A numerical model for thermo-hydro-mechanical strong couplings in an elasto-plastic Cosserat continuum is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. This model allows specifically to study the complete stress–strain response of a rock specimen, as well as the size of the strain Localization Zone for a rock taking into account its microstructure. The numerical implementation in a finite element code is presented, matching adequately analytical solutions or results from other simulations found in the literature. Two different applications of the numerical model are also presented to highlight its capabilities. The first one is a biaxial test on a saturated weak sandstone, for which the influence on the stress–strain response of the characteristic size of the microstructure and of thermal pressurization is investigated. The second one is the rapid shearing of a mature fault Zone in the brittle part of the lithosphere. In this example, the evolution of the thickness of the localized Zone and the influence of the permeability change on the stress–strain response are studied.
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the importance of thermo hydro mechanical couplings and microstructure to strain Localization in 3d continua with application to seismic faults part i theory and linear stability analysis
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: Hadrien Rattez, Ioannis Stefanou, Jean SulemAbstract:Abstract A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. The presence of internal lengths in Cosserat continua enables to estimate the thickness of the Localization Zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault Zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized Zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.
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The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain Localization in 3D continua with application to seismic faults. Part I: Theory and Linear Stability Analysis
Journal of the Mechanics and Physics of Solids, 2018Co-Authors: Ioannis Stefanou, Hadrien Rattez, Jean SulemAbstract:A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. Furthermore, the presence of an internal length in Cosserat continua enables to estimate the thickness of the Localization Zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault Zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized Zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.
Ioannis Stefanou - One of the best experts on this subject based on the ideXlab platform.
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Numerical Analysis of Strain Localization in Rocks with Thermo-hydro-mechanical Couplings Using Cosserat Continuum
Rock Mechanics and Rock Engineering, 2018Co-Authors: Hadrien Rattez, Jean Sulem, Ioannis Stefanou, Manolis Veveakis, Thomas PouletAbstract:A numerical model for thermo-hydro-mechanical strong couplings in an elasto-plastic Cosserat continuum is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. This model allows specifically to study the complete stress–strain response of a rock specimen, as well as the size of the strain Localization Zone for a rock taking into account its microstructure. The numerical implementation in a finite element code is presented, matching adequately analytical solutions or results from other simulations found in the literature. Two different applications of the numerical model are also presented to highlight its capabilities. The first one is a biaxial test on a saturated weak sandstone, for which the influence on the stress–strain response of the characteristic size of the microstructure and of thermal pressurization is investigated. The second one is the rapid shearing of a mature fault Zone in the brittle part of the lithosphere. In this example, the evolution of the thickness of the localized Zone and the influence of the permeability change on the stress–strain response are studied.
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the importance of thermo hydro mechanical couplings and microstructure to strain Localization in 3d continua with application to seismic faults part i theory and linear stability analysis
Journal of The Mechanics and Physics of Solids, 2018Co-Authors: Hadrien Rattez, Ioannis Stefanou, Jean SulemAbstract:Abstract A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. The presence of internal lengths in Cosserat continua enables to estimate the thickness of the Localization Zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault Zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized Zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.
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The importance of Thermo-Hydro-Mechanical couplings and microstructure to strain Localization in 3D continua with application to seismic faults. Part I: Theory and Linear Stability Analysis
Journal of the Mechanics and Physics of Solids, 2018Co-Authors: Ioannis Stefanou, Hadrien Rattez, Jean SulemAbstract:A Thermo-Hydro-Mechanical (THM) model for Cosserat continua is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. A general framework is presented to conduct a bifurcation analysis for elasto-plastic Cosserat continua with THM couplings and predict the onset of instability. Furthermore, the presence of an internal length in Cosserat continua enables to estimate the thickness of the Localization Zone. This is done by performing a linear stability analysis of the system and looking for the selected wavelength corresponding to the instability mode with fastest finite growth coefficient. These concepts are applied to the study of fault Zones under fast shearing. For doing so, we consider a model of a sheared saturated infinite granular layer. The influence of THM couplings on the bifurcation state and the shear band width is investigated. Taking representative parameters for a centroidal fault gouge, the evolution of the thickness of the localized Zone under continuous shear is studied. Furthermore, the effect of grain crushing inside the shear band is explored by varying the internal length of the constitutive law.
Thomas Poulet - One of the best experts on this subject based on the ideXlab platform.
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Numerical Analysis of Strain Localization in Rocks with Thermo-hydro-mechanical Couplings Using Cosserat Continuum
Rock Mechanics and Rock Engineering, 2018Co-Authors: Hadrien Rattez, Jean Sulem, Ioannis Stefanou, Manolis Veveakis, Thomas PouletAbstract:A numerical model for thermo-hydro-mechanical strong couplings in an elasto-plastic Cosserat continuum is developed to explore the influence of frictional heating and thermal pore fluid pressurization on the strain Localization phenomenon. This model allows specifically to study the complete stress–strain response of a rock specimen, as well as the size of the strain Localization Zone for a rock taking into account its microstructure. The numerical implementation in a finite element code is presented, matching adequately analytical solutions or results from other simulations found in the literature. Two different applications of the numerical model are also presented to highlight its capabilities. The first one is a biaxial test on a saturated weak sandstone, for which the influence on the stress–strain response of the characteristic size of the microstructure and of thermal pressurization is investigated. The second one is the rapid shearing of a mature fault Zone in the brittle part of the lithosphere. In this example, the evolution of the thickness of the localized Zone and the influence of the permeability change on the stress–strain response are studied.
