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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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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Modelling time-dependent behaviour of Murro test embankment / M. Karstunen in Géotechnique, Vol. 60 N° 10 (Octobre 2010)  

Public ISBD [article]  inGéotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 735-749 Titre : Modelling time-dependent behaviour of Murro test embankment Type de document : texte imprimé Auteurs : M. Karstunen, Auteur ; Z.-Y. Yin, Auteur Année de publication : 2011 Article en page(s) : pp. 735-749 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Anisotropy Clays Numerical modelling Time dependence Embankments Constitutive relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper investigates the time-dependent behaviour of Murro test embankment in Finland. The embankment was built in 1993 on a soft natural clay deposit, which exhibits large strain anisotropy, destructuration and viscosity. The study is based on extensive experimental data from triaxial and oedometer tests on intact and reconstituted soil samples which shed light on the influence of time on mechanical properties, including testing designed for studying soil anisotropy and destructuration. The interpretation of the results is done in the framework of a recently developed elasto-viscoplastic model EVP-SCLAY1S, which is used to simulate the soft soil deposit coupled with Biot's consolidation theory. The determination of model parameters from the test results demonstrates that the model can be relatively easily used for practical applications. Using these parameters, two-dimensional finite-element analyses have been made as large deformation analysis. The comparisons between calculations and measurements demonstrate that the proposed model can be satisfactorily used to describe the time-dependent behaviour of the embankment on structured clay. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.027 [article] Modelling time-dependent behaviour of Murro test embankment [texte imprimé] / M. Karstunen, Auteur ; Z.-Y. Yin, Auteur . - 2011 . - pp. 735-749. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 735-749 Mots-clés : Anisotropy Clays Numerical modelling Time dependence Embankments Constitutive relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper investigates the time-dependent behaviour of Murro test embankment in Finland. The embankment was built in 1993 on a soft natural clay deposit, which exhibits large strain anisotropy, destructuration and viscosity. The study is based on extensive experimental data from triaxial and oedometer tests on intact and reconstituted soil samples which shed light on the influence of time on mechanical properties, including testing designed for studying soil anisotropy and destructuration. The interpretation of the results is done in the framework of a recently developed elasto-viscoplastic model EVP-SCLAY1S, which is used to simulate the soft soil deposit coupled with Biot's consolidation theory. The determination of model parameters from the test results demonstrates that the model can be relatively easily used for practical applications. Using these parameters, two-dimensional finite-element analyses have been made as large deformation analysis. The comparisons between calculations and measurements demonstrate that the proposed model can be satisfactorily used to describe the time-dependent behaviour of the embankment on structured clay. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.027

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