Elastic model for partially saturated granular materials / P.-Y. Hicher in Journal of engineering mechanics, Vol. 134 n°6 (Juin 2008)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.505–513. Titre : Elastic model for partially saturated granular materials Type de document : texte imprimé Auteurs : P.-Y. Hicher, Auteur ; C. S. Chang, Auteur Année de publication : 2008 Article en page(s) : pp.505–513. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Granular materials Stress strain relations Elastic deformation Unsaturated soils Soil suction Micromechanics Résumé : This paper presents the development of an elastic model for partially saturated granular materials based on micromechanical factor consideration. A granular material is considered as an assembly of particles. The stress-strain relationship for an assembly can be determined by integrating the behavior at all interparticle contacts and by using a static hypothesis, which relates the average stress of the granular assembly to a mean field of particle contact forces. As for the nonsaturated state, capillary forces at grain contacts are added to the contact forces created by an external load. These are then calculated as a function of the degree of saturation, depending on the grain size distribution and on the void ratio of the granular assembly. Hypothesizing a Hertz-Mindlin law for the grain contacts leads to an elastic nonlinear behavior of the particulate material. The prediction of the stress-strain model is compared to experimental results obtained from several different granular materials in dry, partially saturated and fully saturated states. The numerical predictions demonstrate that the model is capable of taking into account the influence of key parameters, such as degree of saturation, void ratio, and mean stress. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2850 [...] [article] Elastic model for partially saturated granular materials [texte imprimé] / P.-Y. Hicher, Auteur ; C. S. Chang, Auteur . - 2008 . - pp.505–513. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 134 n°6 (Juin 2008) . - pp.505–513. Mots-clés : Granular materials Stress strain relations Elastic deformation Unsaturated soils Soil suction Micromechanics Résumé : This paper presents the development of an elastic model for partially saturated granular materials based on micromechanical factor consideration. A granular material is considered as an assembly of particles. The stress-strain relationship for an assembly can be determined by integrating the behavior at all interparticle contacts and by using a static hypothesis, which relates the average stress of the granular assembly to a mean field of particle contact forces. As for the nonsaturated state, capillary forces at grain contacts are added to the contact forces created by an external load. These are then calculated as a function of the degree of saturation, depending on the grain size distribution and on the void ratio of the granular assembly. Hypothesizing a Hertz-Mindlin law for the grain contacts leads to an elastic nonlinear behavior of the particulate material. The prediction of the stress-strain model is compared to experimental results obtained from several different granular materials in dry, partially saturated and fully saturated states. The numerical predictions demonstrate that the model is capable of taking into account the influence of key parameters, such as degree of saturation, void ratio, and mean stress. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%290733-9399%282008%29134%3A6%2850 [...]

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Elastoplastic model for clay with microstructural consideration / C. S. Chang in Journal of engineering mechanics, Vol. 135 N° 9 (Septembre 2009)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 135 N° 9 (Septembre 2009) . - pp. 917-931 Titre : Elastoplastic model for clay with microstructural consideration Type de document : texte imprimé Auteurs : C. S. Chang, Auteur ; P.-Y. Hicher, Auteur ; Z.-Y. Yin, Auteur Article en page(s) : pp. 917-931 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Clays Microstructures Stress strain relations Anisotropy Elastoplasticity. Résumé : Clay material can be considered as a collection of clusters, which interact with each other mainly through mechanical forces. From this point of view, clay is modeled by analogy to granular material in this paper. An elastoplastic stress-strain relationship for clay is derived by using the granular mechanics approach developed in previous studies for sand. However, unlike sand, clay deformation is generated not only by the mobilizing but also by compressing clusters. Thus, in addition to the Mohr-Coulomb's plastic shear sliding and a dilatancy type flow rule, a plastic normal deformation has been modeled for two clusters in compression. The overall stress-strain relationship can then be obtained from the mobilization and compressing of clusters through a static hypothesis of the macro-micro relations. The predictions are compared with the experimental results for clay under both drained and undrained triaxial loading conditions. Three different types of clay, including remolded and natural clay, have been selected to evaluate the model's performance. The comparisons verify that this model is capable of accurately reproducing the overall behavior of clay, which accounts for the influence of key parameters such as void ratio and mean stress. A section of this paper is devoted to show the model's capability of considering the influence of inherent anisotropy on the stress-strain response under undrained triaxial loading conditions. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...] [article] Elastoplastic model for clay with microstructural consideration [texte imprimé] / C. S. Chang, Auteur ; P.-Y. Hicher, Auteur ; Z.-Y. Yin, Auteur . - pp. 917-931. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 9 (Septembre 2009) . - pp. 917-931 Mots-clés : Clays Microstructures Stress strain relations Anisotropy Elastoplasticity. Résumé : Clay material can be considered as a collection of clusters, which interact with each other mainly through mechanical forces. From this point of view, clay is modeled by analogy to granular material in this paper. An elastoplastic stress-strain relationship for clay is derived by using the granular mechanics approach developed in previous studies for sand. However, unlike sand, clay deformation is generated not only by the mobilizing but also by compressing clusters. Thus, in addition to the Mohr-Coulomb's plastic shear sliding and a dilatancy type flow rule, a plastic normal deformation has been modeled for two clusters in compression. The overall stress-strain relationship can then be obtained from the mobilization and compressing of clusters through a static hypothesis of the macro-micro relations. The predictions are compared with the experimental results for clay under both drained and undrained triaxial loading conditions. Three different types of clay, including remolded and natural clay, have been selected to evaluate the model's performance. The comparisons verify that this model is capable of accurately reproducing the overall behavior of clay, which accounts for the influence of key parameters such as void ratio and mean stress. A section of this paper is devoted to show the model's capability of considering the influence of inherent anisotropy on the stress-strain response under undrained triaxial loading conditions. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JENMDT&smode=strres [...]

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Evaluation of Two Homogenization Techniques for Modeling the Elastic Behavior of Materials / P.-Y. Hicher in Journal of engineering mechanics, Vol.131, N°11 (Novembre 2005)  

Public ISBD [article]  inJournal of engineering mechanics > Vol.131, N°11 (Novembre 2005) . - 1184-1194 p. Titre : Evaluation of Two Homogenization Techniques for Modeling the Elastic Behavior of Materials Titre original : Evaluation de Deux Techniques d'Homogénéisation pour Modeler le Comportement Elastique des Matériaux Type de document : texte imprimé Auteurs : P.-Y. Hicher, Auteur ; C. S. Chang, Auteur ; Ooi, J. Y., Éditeur scientifique Année de publication : 2005 Article en page(s) : 1184-1194 p. Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Granular materials Stress strain relations Anisotropy Constitutive models Elasticity Micro mechanics Homogeneity Matériaux granulaires Relations de contrainte-tension Anisotropie Modèles constitutifs Micro-mécanique d'élasticité Homogénéité Index. décimale : 621.34 Résumé : This Paper discusses the capabilities of two homogenization techniques to accurately represent the elastic behavior of granular materials considered as assemblies of randomly distributed particles. The Stress strain relationship for the assembly is determined by integrating the behavior of the interparticle contacts in all orientations, using two different homogenization methods, namely the kinematic method and the static method. The Numerical predictions obtained by these two homogenization techniques are compared to results obtained during experimental studies on different granular materials. Relations between elastic constants of the assembly, interparticle properties, and fabric parameters are discussed, as well as the capabilities of the models to take into account inherent and stress induced anisotropy for differents stress conditions. Cet article discute les possibilités de deux techniques d'homogénéisation pour représenter exactement le comportement élastique des matériaux granulaires considérés comme ensembles des particules aléatoirement distribuées. Le rapport de contrainte-tension pour l'assemblée est déterminé en intégrant le comportement des contacts d'interparticle dans toutes les orientations, en utilisant deux méthodes différentes d'homogénéisation, à savoir la méthode cinématique et la méthode statique. Les prévisions numériques obtenues par ces deux techniques d'homogénéisation sont comparées aux résultats obtenus pendant des études expérimentales sur différents matériaux granulaires. Des relations entre les constantes élastiques de l'assemblée, les propriétés d'interparticle, et les paramètres de tissu sont discutées, comme les possibilités des modèles pour tenir compte d'inhérent et pour soumettre à une contrainte l'anisotropie induite pour l'effort de differents conditions. En ligne : chang@ecs.umass.edu [article] Evaluation of Two Homogenization Techniques for Modeling the Elastic Behavior of Materials = Evaluation de Deux Techniques d'Homogénéisation pour Modeler le Comportement Elastique des Matériaux [texte imprimé] / P.-Y. Hicher, Auteur ; C. S. Chang, Auteur ; Ooi, J. Y., Éditeur scientifique . - 2005 . - 1184-1194 p. Génie Mécanique Langues : Anglais (eng) in Journal of engineering mechanics > Vol.131, N°11 (Novembre 2005) . - 1184-1194 p. Mots-clés : Granular materials Stress strain relations Anisotropy Constitutive models Elasticity Micro mechanics Homogeneity Matériaux granulaires Relations de contrainte-tension Anisotropie Modèles constitutifs Micro-mécanique d'élasticité Homogénéité Index. décimale : 621.34 Résumé : This Paper discusses the capabilities of two homogenization techniques to accurately represent the elastic behavior of granular materials considered as assemblies of randomly distributed particles. The Stress strain relationship for the assembly is determined by integrating the behavior of the interparticle contacts in all orientations, using two different homogenization methods, namely the kinematic method and the static method. The Numerical predictions obtained by these two homogenization techniques are compared to results obtained during experimental studies on different granular materials. Relations between elastic constants of the assembly, interparticle properties, and fabric parameters are discussed, as well as the capabilities of the models to take into account inherent and stress induced anisotropy for differents stress conditions. Cet article discute les possibilités de deux techniques d'homogénéisation pour représenter exactement le comportement élastique des matériaux granulaires considérés comme ensembles des particules aléatoirement distribuées. Le rapport de contrainte-tension pour l'assemblée est déterminé en intégrant le comportement des contacts d'interparticle dans toutes les orientations, en utilisant deux méthodes différentes d'homogénéisation, à savoir la méthode cinématique et la méthode statique. Les prévisions numériques obtenues par ces deux techniques d'homogénéisation sont comparées aux résultats obtenus pendant des études expérimentales sur différents matériaux granulaires. Des relations entre les constantes élastiques de l'assemblée, les propriétés d'interparticle, et les paramètres de tissu sont discutées, comme les possibilités des modèles pour tenir compte d'inhérent et pour soumettre à une contrainte l'anisotropie induite pour l'effort de differents conditions. En ligne : chang@ecs.umass.edu

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Micromechanical analysis for interparticle and assembly instability of sand / C. S. Chang in Journal of engineering mechanics, Vol. 137 N° 3 (Mars 2011)  

Public ISBD [article]  inJournal of engineering mechanics > Vol. 137 N° 3 (Mars 2011) . - pp.155-168 Titre : Micromechanical analysis for interparticle and assembly instability of sand Type de document : texte imprimé Auteurs : C. S. Chang, Auteur ; Z.-Y. Yin, Auteur ; P.-Y. Hicher, Auteur Année de publication : 2011 Article en page(s) : pp.155-168 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Granular material Instability Strain softening Micromechanics Stress-strain relationship Sand. Résumé : Instability of granular material may lead to catastrophic events such as the gross collapse of earth structures, and thus it is an important topic in geotechnical engineering. In this paper, we adopt the micromechanics approach for constitutive modeling, in which the soil is considered an assembly of particles, and the stress-strain relationship for the assembly is determined by integrating the behavior of the interparticle contacts in all orientations. Although analyses regarding material instability have been extensively studied for a soil element at the constitutive level, it has not been considered at the interparticle contact level. Through an eigenvalue analysis, two modes of instability are identified at the local contact level: the singularity of tangential stiffness matrix and the loss of positiveness of second-order work. The constitutive model is applied to simulate drained and undrained triaxial tests on Toyoura sand of various densities under various confining pressures. The predictions are compared with experimentally measured instability at the assembly level. The modes of stability at the interparticle contact level and their relations to the overall instability of the assembly are also analyzed DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i3/p155_s1?isAuthorized=no [article] Micromechanical analysis for interparticle and assembly instability of sand [texte imprimé] / C. S. Chang, Auteur ; Z.-Y. Yin, Auteur ; P.-Y. Hicher, Auteur . - 2011 . - pp.155-168. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 137 N° 3 (Mars 2011) . - pp.155-168 Mots-clés : Granular material Instability Strain softening Micromechanics Stress-strain relationship Sand. Résumé : Instability of granular material may lead to catastrophic events such as the gross collapse of earth structures, and thus it is an important topic in geotechnical engineering. In this paper, we adopt the micromechanics approach for constitutive modeling, in which the soil is considered an assembly of particles, and the stress-strain relationship for the assembly is determined by integrating the behavior of the interparticle contacts in all orientations. Although analyses regarding material instability have been extensively studied for a soil element at the constitutive level, it has not been considered at the interparticle contact level. Through an eigenvalue analysis, two modes of instability are identified at the local contact level: the singularity of tangential stiffness matrix and the loss of positiveness of second-order work. The constitutive model is applied to simulate drained and undrained triaxial tests on Toyoura sand of various densities under various confining pressures. The predictions are compared with experimentally measured instability at the assembly level. The modes of stability at the interparticle contact level and their relations to the overall instability of the assembly are also analyzed DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.org/emo/resource/1/jenmdt/v137/i3/p155_s1?isAuthorized=no

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