Documents disponibles écrits par cet auteur

Efficient approach to characterize strength anisotropy in soils / Zhiwei Gao in Journal of engineering mechanics, Vol. 138 N° 12 (Décembre 2012) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 138 N° 12 (Décembre 2012) . - pp.1447–1456. Titre : Efficient approach to characterize strength anisotropy in soils Type de document : texte imprimé Auteurs : Zhiwei Gao, Auteur ; Jidong Zhao, Auteur Année de publication : 2013 Article en page(s) : pp.1447–1456. Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Strength  anisotropy  Fabric  tensor  Joint  invariant  Sand  Natural  clay  Completely  decomposed  granite Résumé : Strength anisotropy in soils needs to be characterized by proper anisotropic failure criterion. This paper presents a novel yet simple methodology to generalize an isotropic failure criterion to account for strength anisotropy in soils. A salient ingredient of the method involves the introduction of the degree of cross anisotropy and an anisotropic variable, defined by the joint invariant of the deviatoric stress tensor and the deviatoric fabric tensor, into the frictional characteristic of the isotropic criterion. The well-received Lade’s failure criterion is taken as an example to demonstrate the generalization. Predictions using the newly generalized Lade’s criterion for a number of soils, including completely decomposed granite, glass beads (virtual sand), natural clays, sand, as well as silty sand, show good agreement with test data. The proposed approach has proved to be simple and generic, and can be effortlessly applied to many existing isotropic failure criteria to adapt them to account for strength anisotropy. The treatment also requires very few parameters, which can be conveniently calibrated from conventional laboratory tests in most cases. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000451 [article] Efficient approach to characterize strength anisotropy in soils [texte imprimé] / Zhiwei Gao, Auteur ; Jidong Zhao, Auteur . - 2013 . - pp.1447–1456. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 138 N° 12 (Décembre 2012) . - pp.1447–1456. Mots-clés : Strength  anisotropy  Fabric  tensor  Joint  invariant  Sand  Natural  clay  Completely  decomposed  granite Résumé : Strength anisotropy in soils needs to be characterized by proper anisotropic failure criterion. This paper presents a novel yet simple methodology to generalize an isotropic failure criterion to account for strength anisotropy in soils. A salient ingredient of the method involves the introduction of the degree of cross anisotropy and an anisotropic variable, defined by the joint invariant of the deviatoric stress tensor and the deviatoric fabric tensor, into the frictional characteristic of the isotropic criterion. The well-received Lade’s failure criterion is taken as an example to demonstrate the generalization. Predictions using the newly generalized Lade’s criterion for a number of soils, including completely decomposed granite, glass beads (virtual sand), natural clays, sand, as well as silty sand, show good agreement with test data. The proposed approach has proved to be simple and generic, and can be effortlessly applied to many existing isotropic failure criteria to adapt them to account for strength anisotropy. The treatment also requires very few parameters, which can be conveniently calibrated from conventional laboratory tests in most cases. ISSN : 0733-9399 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0000451

Evaluation on failure of fiber-reinforced sand / Zhiwei Gao in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 1 (Janvier 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 95-106 Titre : Evaluation on failure of fiber-reinforced sand Type de document : texte imprimé Auteurs : Zhiwei Gao, Auteur ; Jidong Zhao, Auteur Année de publication : 2013 Article en page(s) : pp. 95-106 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : fiber  reinforced  materials;  failures;  anisotropy;  triaxial  tests;  slope  stability;  sand  (soil  type) Résumé : Fiber reinforcement can help to enhance soil strength, stabilize near-surface soil layers, and mitigate the risk of soil liquefaction. Evaluation of the strength of fiber-reinforced soils needs a proper failure criterion. This study presents a three-dimensional failure criterion for fiber-reinforced sand. By assuming that the total strength of the composite is a combination of the shear resistance of the host soil and the reinforcement of fibers, a general anisotropic failure criterion is proposed with special emphasis on the effect of isotropically/anisotropically distributed fibers. An anisotropic variable, defined by the joint invariant of the deviatoric stress tensor and a deviatoric fiber distribution tensor, is introduced in the criterion to quantify the fiber orientation with respect to the strain rate/stress direction at failure. With further consideration of the fiber concentration and other factors such as aspect ratio, the proposed criterion is applied to predicting the failure of fiber-reinforced sand in conventional triaxial compression/extension tests for both isotropically and anisotropically distributed fiber cases. The predictions are in good agreement with the test results available in the literature. The practical significance of using this criterion for such problems as inclined slope stabilization is briefly discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000737 [article] Evaluation on failure of fiber-reinforced sand [texte imprimé] / Zhiwei Gao, Auteur ; Jidong Zhao, Auteur . - 2013 . - pp. 95-106. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 1 (Janvier 2013) . - pp. 95-106 Mots-clés : fiber  reinforced  materials;  failures;  anisotropy;  triaxial  tests;  slope  stability;  sand  (soil  type) Résumé : Fiber reinforcement can help to enhance soil strength, stabilize near-surface soil layers, and mitigate the risk of soil liquefaction. Evaluation of the strength of fiber-reinforced soils needs a proper failure criterion. This study presents a three-dimensional failure criterion for fiber-reinforced sand. By assuming that the total strength of the composite is a combination of the shear resistance of the host soil and the reinforcement of fibers, a general anisotropic failure criterion is proposed with special emphasis on the effect of isotropically/anisotropically distributed fibers. An anisotropic variable, defined by the joint invariant of the deviatoric stress tensor and a deviatoric fiber distribution tensor, is introduced in the criterion to quantify the fiber orientation with respect to the strain rate/stress direction at failure. With further consideration of the fiber concentration and other factors such as aspect ratio, the proposed criterion is applied to predicting the failure of fiber-reinforced sand in conventional triaxial compression/extension tests for both isotropically and anisotropically distributed fiber cases. The predictions are in good agreement with the test results available in the literature. The practical significance of using this criterion for such problems as inclined slope stabilization is briefly discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000737

Modified UH model / Yangping Yao in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 7 (Juillet 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 860–868 Titre : Modified UH model : Constitutive modeling of overconsolidated clays based on a parabolic hvorslev envelope Type de document : texte imprimé Auteurs : Yangping Yao, Auteur ; Zhiwei Gao, Auteur ; Jidong Zhao, Auteur Année de publication : 2012 Article en page(s) : pp. 860–868 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Clay  Overconsolidation  Critical  state  Unified  hardening  Hvorslev  envelope Résumé : Most clays, either naturally deposited or man-made, possess a certain degree of overconsolidation owing to tamping, cyclic loading, erosion, excavation, and/or changes in groundwater tables. An easy-to-use constitutive model for overconsolidated clays is useful for relevant engineering applications. In this paper, a simple model is proposed for overconsolidated clays based on the unified-hardening (UH) model. To evaluate the potential peak stress ratio of overconsolidated clays, a parabolic Hvorslev envelope rather than a straight envelope (used in the original UH model) is adopted. The proposed parabolic Hvorslev envelope passes through the origin of the mean stress-deviatoric stress plane. It has a slope of 3 as the overconsolidation ratio (OCR) approaches infinity and intersects with the critical state line as the OCR reaches unity. This modification leads to more realistic predictions for highly overconsolidated clays than does the original UH model with a straight Hvorslev envelope and is consistent with the critical state soil mechanics in which the higher peak stress ratio in overconsolidated clays is a result of interlocking (or dilatancy) rather than cohesion. The modified UH model retains the same parameters as those in the modified Cam-clay model. Reasonable agreement between the model predictions and experimental data demonstrates that the modified model is capable of addressing the fundamental behavior of overconsolidated clays. The present model is developed for reconstituted clays with an isotropic fabric. The potential improvement of the model, taking into account anisotropy and structural effects, is discussed. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000649 [article] Modified UH model : Constitutive modeling of overconsolidated clays based on a parabolic hvorslev envelope [texte imprimé] / Yangping Yao, Auteur ; Zhiwei Gao, Auteur ; Jidong Zhao, Auteur . - 2012 . - pp. 860–868. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 7 (Juillet 2012) . - pp. 860–868 Mots-clés : Clay  Overconsolidation  Critical  state  Unified  hardening  Hvorslev  envelope Résumé : Most clays, either naturally deposited or man-made, possess a certain degree of overconsolidation owing to tamping, cyclic loading, erosion, excavation, and/or changes in groundwater tables. An easy-to-use constitutive model for overconsolidated clays is useful for relevant engineering applications. In this paper, a simple model is proposed for overconsolidated clays based on the unified-hardening (UH) model. To evaluate the potential peak stress ratio of overconsolidated clays, a parabolic Hvorslev envelope rather than a straight envelope (used in the original UH model) is adopted. The proposed parabolic Hvorslev envelope passes through the origin of the mean stress-deviatoric stress plane. It has a slope of 3 as the overconsolidation ratio (OCR) approaches infinity and intersects with the critical state line as the OCR reaches unity. This modification leads to more realistic predictions for highly overconsolidated clays than does the original UH model with a straight Hvorslev envelope and is consistent with the critical state soil mechanics in which the higher peak stress ratio in overconsolidated clays is a result of interlocking (or dilatancy) rather than cohesion. The modified UH model retains the same parameters as those in the modified Cam-clay model. Reasonable agreement between the model predictions and experimental data demonstrates that the modified model is capable of addressing the fundamental behavior of overconsolidated clays. The present model is developed for reconstituted clays with an isotropic fabric. The potential improvement of the model, taking into account anisotropy and structural effects, is discussed. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000649