Documents disponibles écrits par cet auteur

Cyclic behaviour and resistance of saturated sand under non-symmetrical loading / J. Yang in Géotechnique, Vol. LXI N° 1 (Janvier 2011) 

Public ISBD [article]  in Géotechnique > Vol. LXI N° 1 (Janvier 2011) . - pp. 59–73 Titre : Cyclic behaviour and resistance of saturated sand under non-symmetrical loading Type de document : texte imprimé Auteurs : J. Yang, Auteur ; H. Y. Sze, Auteur Année de publication : 2011 Article en page(s) : pp. 59–73 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Shear  strength  Earthquakes  Liquefaction  Laboratory  tests  Failure  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper reports findings from an experimental study that aimed to investigate the undrained behaviour of sand in non-symmetrical cyclic loading, and to clarify the role of initial static shear in liquefaction resistance. The testing programme, conducted on a standard sand under triaxial conditions, covers a broad range of initial states in terms of relative density, confining stress and initial shear stress ratio (α). Three distinct failure modes have been identified from the tests: flow-type failure, cyclic mobility and plastic strain accumulation. Of these, flow-type failure, characterised by abrupt runaway deformations without any prior warning, is the most critical, and pertains to sand in the loose state. The tests also demonstrate that the presence of initial static shear stress is beneficial to the liquefaction resistance of loose sand at low α levels, but it becomes detrimental at high α levels. In this connection the concept of threshold α is proposed, together with the use of a no-stress-reversal line for better characterisation of the effect of initial static shear. Furthermore, in the conceptual framework of critical state soil mechanics, a fairly good linear relationship has been established between the threshold α and the state parameter ψ that collectively accounts for the initial relative density and mean stress level. This relationship suggests that the threshold α decreases with increasing values of ψ , or with sand becoming looser than the critical state. It is further proposed that the concept of threshold α also applies to sand at high relative density, as long as the confining stress becomes sufficiently high. This proposal leads to a unified and consistent interpretation of the complicated static shear effect. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.019 [article] Cyclic behaviour and resistance of saturated sand under non-symmetrical loading [texte imprimé] / J. Yang, Auteur ; H. Y. Sze, Auteur . - 2011 . - pp. 59–73. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. LXI N° 1 (Janvier 2011) . - pp. 59–73 Mots-clés : Shear  strength  Earthquakes  Liquefaction  Laboratory  tests  Failure  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper reports findings from an experimental study that aimed to investigate the undrained behaviour of sand in non-symmetrical cyclic loading, and to clarify the role of initial static shear in liquefaction resistance. The testing programme, conducted on a standard sand under triaxial conditions, covers a broad range of initial states in terms of relative density, confining stress and initial shear stress ratio (α). Three distinct failure modes have been identified from the tests: flow-type failure, cyclic mobility and plastic strain accumulation. Of these, flow-type failure, characterised by abrupt runaway deformations without any prior warning, is the most critical, and pertains to sand in the loose state. The tests also demonstrate that the presence of initial static shear stress is beneficial to the liquefaction resistance of loose sand at low α levels, but it becomes detrimental at high α levels. In this connection the concept of threshold α is proposed, together with the use of a no-stress-reversal line for better characterisation of the effect of initial static shear. Furthermore, in the conceptual framework of critical state soil mechanics, a fairly good linear relationship has been established between the threshold α and the state parameter ψ that collectively accounts for the initial relative density and mean stress level. This relationship suggests that the threshold α decreases with increasing values of ψ , or with sand becoming looser than the critical state. It is further proposed that the concept of threshold α also applies to sand at high relative density, as long as the confining stress becomes sufficiently high. This proposal leads to a unified and consistent interpretation of the complicated static shear effect. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.019

Cyclic strength of sand under sustained shear stress / J. Yang in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 12 (Décembre 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1275-1285 Titre : Cyclic strength of sand under sustained shear stress Type de document : texte imprimé Auteurs : J. Yang, Auteur ; H. Y. Sze, Auteur Année de publication : 2012 Article en page(s) : pp. 1275-1285 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Critical  state  Cyclic  strength  Failure  Laboratory  tests  Liquefaction  Sands Résumé : The existence of initial shear stress can have a significant effect on the cyclic strength or liquefaction potential of sand. This effect is not yet fully understood because of a lack of convergence and consistency in the existing data and interpretations, leading to great uncertainty in quantifying the effect for practical applications. This paper presents new experimental results on a silica sand to validate the concept known as threshold α, below which the cyclic strength of sand increases with α and above which the cyclic strength decreases with α (with α representing the sustained shear stress level). On the basis of a series of monotonic loading tests on the same sand, and in the framework of critical state soil mechanics, it is further confirmed that threshold α can be well related to a state parameter in the void ratio-mean effective stress plane and thereby a unified and consistent interpretation can be established. A new platform is proposed on which the relationship between cyclic strength and state parameter is represented by a linear line, and this line will rotate clockwise as α increases. This platform provides an effective analytical tool for the study of the effect of sustained shear stress on the cyclic strength of sand. Moreover, the study also shows that the cyclic loading path is well linked with the monotonic loading path under different sustained shear stress levels, and this correspondence sheds light on the mechanisms underlying a variety of experimental observations. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1275_s1?isAuthorized=no [article] Cyclic strength of sand under sustained shear stress [texte imprimé] / J. Yang, Auteur ; H. Y. Sze, Auteur . - 2012 . - pp. 1275-1285. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 12 (Décembre 2011) . - pp. 1275-1285 Mots-clés : Critical  state  Cyclic  strength  Failure  Laboratory  tests  Liquefaction  Sands Résumé : The existence of initial shear stress can have a significant effect on the cyclic strength or liquefaction potential of sand. This effect is not yet fully understood because of a lack of convergence and consistency in the existing data and interpretations, leading to great uncertainty in quantifying the effect for practical applications. This paper presents new experimental results on a silica sand to validate the concept known as threshold α, below which the cyclic strength of sand increases with α and above which the cyclic strength decreases with α (with α representing the sustained shear stress level). On the basis of a series of monotonic loading tests on the same sand, and in the framework of critical state soil mechanics, it is further confirmed that threshold α can be well related to a state parameter in the void ratio-mean effective stress plane and thereby a unified and consistent interpretation can be established. A new platform is proposed on which the relationship between cyclic strength and state parameter is represented by a linear line, and this line will rotate clockwise as α increases. This platform provides an effective analytical tool for the study of the effect of sustained shear stress on the cyclic strength of sand. Moreover, the study also shows that the cyclic loading path is well linked with the monotonic loading path under different sustained shear stress levels, and this correspondence sheds light on the mechanisms underlying a variety of experimental observations. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i12/p1275_s1?isAuthorized=no