Documents disponibles écrits par cet auteur

Effect of loading mode on strain softening and instability behavior of sand in plane-strain tests / J. Chu in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N°1 (Janvier 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°1 (Janvier 2009) . - pp. 108–120 Titre : Effect of loading mode on strain softening and instability behavior of sand in plane-strain tests Type de document : texte imprimé Auteurs : J. Chu, Auteur ; D. Wanatowski, Auteur Année de publication : 2009 Article en page(s) : pp. 108–120 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Sand  Laboratory  tests  Plane  strain  Strain  softening Résumé : Experimental data to study the effect of loading mode on the strain softening and instability behavior of sand under plane-strain conditions are presented in this paper. A new plane-strain apparatus was adopted to conduct K0 consolidated drained and undrained tests under both deformation-controlled and load-controlled loading modes. The drained behavior of very loose and medium dense sand and the undrained behavior of very loose sand under plane-strain conditions were characterized. The test results show that the loading mode affects the postpeak behavior and controls whether strain softening or instability will occur in the postpeak region. Shear bands occurred in tests conducted on medium dense sand, but not in tests for very loose sand. The failure line and critical state line are not affected by the loading mode. The study also shows that the concept of a unique “ultimate state” for both dense and loose sand as previously established based on conventional drained triaxial tests is not supported by the plane-strain data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A1%2810 [...] [article] Effect of loading mode on strain softening and instability behavior of sand in plane-strain tests [texte imprimé] / J. Chu, Auteur ; D. Wanatowski, Auteur . - 2009 . - pp. 108–120. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°1 (Janvier 2009) . - pp. 108–120 Mots-clés : Sand  Laboratory  tests  Plane  strain  Strain  softening Résumé : Experimental data to study the effect of loading mode on the strain softening and instability behavior of sand under plane-strain conditions are presented in this paper. A new plane-strain apparatus was adopted to conduct K0 consolidated drained and undrained tests under both deformation-controlled and load-controlled loading modes. The drained behavior of very loose and medium dense sand and the undrained behavior of very loose sand under plane-strain conditions were characterized. The test results show that the loading mode affects the postpeak behavior and controls whether strain softening or instability will occur in the postpeak region. Shear bands occurred in tests conducted on medium dense sand, but not in tests for very loose sand. The failure line and critical state line are not affected by the loading mode. The study also shows that the concept of a unique “ultimate state” for both dense and loose sand as previously established based on conventional drained triaxial tests is not supported by the plane-strain data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A1%2810 [...]

Factors affecting pre-failure instability of sand under plane-strain conditions / D. Wanatowski in Géotechnique, Vol. 62 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 2 (Fevrier 2012) . - pp. 121 –135 Titre : Factors affecting pre-failure instability of sand under plane-strain conditions Type de document : texte imprimé Auteurs : D. Wanatowski, Auteur ; J. Chu, Auteur Année de publication : 2012 Article en page(s) : pp. 121 –135 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Liquefaction  Sands  Laboratory  tests  Slopes  Pore  pressures  Failure Résumé : Experimental data obtained from a plane-strain apparatus are presented in this paper to show that a pre-failure instability in the form of a rapid and sustained increase in strain rate can occur for both contractive and dilative sand under fully drained conditions. However, this type of instability is different from the runaway type of instability observed under undrained conditions, and has therefore been called conditional instability. Despite the differences, the conditions for both types of instability are the same for contractive sand. There are also other factors that affect the pre-failure instability of sand observed in the laboratory. These include the stress ratio, void ratio, sand state, load control mode and reduction rate of the effective confining stress. In this paper, these factors are discussed and analysed using experimental data obtained from undrained instability (or creep) tests and constant shear drained (CSD) tests carried out under plane-strain conditions. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.111 [article] Factors affecting pre-failure instability of sand under plane-strain conditions [texte imprimé] / D. Wanatowski, Auteur ; J. Chu, Auteur . - 2012 . - pp. 121 –135. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 2 (Fevrier 2012) . - pp. 121 –135 Mots-clés : Liquefaction  Sands  Laboratory  tests  Slopes  Pore  pressures  Failure Résumé : Experimental data obtained from a plane-strain apparatus are presented in this paper to show that a pre-failure instability in the form of a rapid and sustained increase in strain rate can occur for both contractive and dilative sand under fully drained conditions. However, this type of instability is different from the runaway type of instability observed under undrained conditions, and has therefore been called conditional instability. Despite the differences, the conditions for both types of instability are the same for contractive sand. There are also other factors that affect the pre-failure instability of sand observed in the laboratory. These include the stress ratio, void ratio, sand state, load control mode and reduction rate of the effective confining stress. In this paper, these factors are discussed and analysed using experimental data obtained from undrained instability (or creep) tests and constant shear drained (CSD) tests carried out under plane-strain conditions. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.111

Instability conditions of loose sand in plane strain / J. Chu in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°1 (Janvier 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 136–142 Titre : Instability conditions of loose sand in plane strain Type de document : texte imprimé Auteurs : J. Chu, Auteur ; D. Wanatowski, Auteur Année de publication : 2008 Article en page(s) : pp. 136–142 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Laboratory  tests  Liquefaction  Sand  Stress  strain  relations Résumé : When a loose sand specimen is loaded under an undrained condition, it may become unstable. The instability conditions may be specified by an instability line determined using undrained tests. However, the instability behavior of sand has seldom been studied under plane-strain conditions. Experimental data obtained under both triaxial and plane-strain conditions are presented in this paper to define the instability conditions of loose sand under plane-strain conditions. Using the state parameter, a unified relationship can be established between the normalized slope of instability line and the state parameters for both axisymmetric and plane-strain conditions. Using this relationship, the instability conditions established under axisymmetric conditions can also be used for plane-strain conditions. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2813 [...] [article] Instability conditions of loose sand in plane strain [texte imprimé] / J. Chu, Auteur ; D. Wanatowski, Auteur . - 2008 . - pp. 136–142. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 136–142 Mots-clés : Laboratory  tests  Liquefaction  Sand  Stress  strain  relations Résumé : When a loose sand specimen is loaded under an undrained condition, it may become unstable. The instability conditions may be specified by an instability line determined using undrained tests. However, the instability behavior of sand has seldom been studied under plane-strain conditions. Experimental data obtained under both triaxial and plane-strain conditions are presented in this paper to define the instability conditions of loose sand under plane-strain conditions. Using the state parameter, a unified relationship can be established between the normalized slope of instability line and the state parameters for both axisymmetric and plane-strain conditions. Using this relationship, the instability conditions established under axisymmetric conditions can also be used for plane-strain conditions. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2813 [...]

Instability of loose sand under drained conditions / J. Chu in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 207-216 Titre : Instability of loose sand under drained conditions Type de document : texte imprimé Auteurs : J. Chu, Auteur ; W. K. Leong, Auteur ; W. L. Loke, Auteur Année de publication : 2012 Article en page(s) : pp. 207-216 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Constitutive  relations  Failures  Laboratory  tests  Sand  Shear  strength Résumé : A type of prefailure instability which occurs under fully drained conditions is studied in this paper. It is observed experimentally that when a specimen is sheared along a drained stress path involving a decrease in effective mean stress, it becomes unstable after the stress path crosses an instability line. The instability occurring under drained conditions is different from the type observed under undrained conditions. The differences and similarities between the two types of instability are elaborated. The practical implication of the study in analyzing the failure mechanisms of granular soil slope is also discussed. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p207_s1?isAuthorized=no [article] Instability of loose sand under drained conditions [texte imprimé] / J. Chu, Auteur ; W. K. Leong, Auteur ; W. L. Loke, Auteur . - 2012 . - pp. 207-216. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 207-216 Mots-clés : Constitutive  relations  Failures  Laboratory  tests  Sand  Shear  strength Résumé : A type of prefailure instability which occurs under fully drained conditions is studied in this paper. It is observed experimentally that when a specimen is sheared along a drained stress path involving a decrease in effective mean stress, it becomes unstable after the stress path crosses an instability line. The instability occurring under drained conditions is different from the type observed under undrained conditions. The differences and similarities between the two types of instability are elaborated. The practical implication of the study in analyzing the failure mechanisms of granular soil slope is also discussed. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p207_s1?isAuthorized=no