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Influence of strain rate and acceleration on the behaviour of reconstituted clays at small strains / K. K. Sorensen in Géotechnique, Vol. 60 N° 10 (Octobre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 751-763 Titre : Influence of strain rate and acceleration on the behaviour of reconstituted clays at small strains Type de document : texte imprimé Auteurs : K. K. Sorensen, Auteur ; B. A. Baudet, Auteur ; B. Simpson, Auteur Année de publication : 2011 Article en page(s) : pp. 751-763 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Clays  Stiffness  Time  dependence  Laboratory  tests  Dynamics  Creep Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper attempts to bridge the gap between the well-known characteristics of strain rate-independent elastic stiffness and of the time-dependent behaviour of clays at large strains. Effects of acceleration, strain rate and ageing are examined in the very small to small strain region, using results from tests on reconstituted London Clay and kaolin. Static measurements of the shear modulus at small strains, using local instrumentation, indicate that the shear modulus is rate-independent when the soil is subjected to elastic deformations only. Most often, in practice, soil specimens are left to rest between the compression and shearing stages, until deformations associated with creep become negligible. The testing strain rate imposed upon shearing induces a temporary acceleration of strains, which results in very high measured stiffnesses. Test data show, however, that when the shearing axial strain rate is of the same order of magnitude as that measured at the end of the compression/creep stage, the remaining plastic creep strains influence the measured stiffness, which is then measured to be comparatively low. Test data also seem to show that temporary strain acceleration may hide effects of recent stress path rotation. Additionally, bender element tests were performed during isotropic compression tests with changes in stress rate and creep stages. The data indicate that the strain rate affects the value of the dynamic shear modulus of the soil. It is suggested that the increase in dynamic shear modulus during short-term creep is caused by mechanisms linked to the gradual decrease in strain rate during creep, but further investigation would be needed to clarify which physical mechanisms. A new method to account for strain rate in evaluating the dynamic shear modulus of normally consolidated reconstituted clays is finally proposed. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.07.d.147 [article] Influence of strain rate and acceleration on the behaviour of reconstituted clays at small strains [texte imprimé] / K. K. Sorensen, Auteur ; B. A. Baudet, Auteur ; B. Simpson, Auteur . - 2011 . - pp. 751-763. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 751-763 Mots-clés : Clays  Stiffness  Time  dependence  Laboratory  tests  Dynamics  Creep Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper attempts to bridge the gap between the well-known characteristics of strain rate-independent elastic stiffness and of the time-dependent behaviour of clays at large strains. Effects of acceleration, strain rate and ageing are examined in the very small to small strain region, using results from tests on reconstituted London Clay and kaolin. Static measurements of the shear modulus at small strains, using local instrumentation, indicate that the shear modulus is rate-independent when the soil is subjected to elastic deformations only. Most often, in practice, soil specimens are left to rest between the compression and shearing stages, until deformations associated with creep become negligible. The testing strain rate imposed upon shearing induces a temporary acceleration of strains, which results in very high measured stiffnesses. Test data show, however, that when the shearing axial strain rate is of the same order of magnitude as that measured at the end of the compression/creep stage, the remaining plastic creep strains influence the measured stiffness, which is then measured to be comparatively low. Test data also seem to show that temporary strain acceleration may hide effects of recent stress path rotation. Additionally, bender element tests were performed during isotropic compression tests with changes in stress rate and creep stages. The data indicate that the strain rate affects the value of the dynamic shear modulus of the soil. It is suggested that the increase in dynamic shear modulus during short-term creep is caused by mechanisms linked to the gradual decrease in strain rate during creep, but further investigation would be needed to clarify which physical mechanisms. A new method to account for strain rate in evaluating the dynamic shear modulus of normally consolidated reconstituted clays is finally proposed. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.07.d.147

The mechanics of fibre-reinforced sand / A. P. S. Santos in Géotechnique, Vol. 60 N° 10 (Octobre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 791-799 Titre : The mechanics of fibre-reinforced sand Type de document : texte imprimé Auteurs : A. P. S. Santos, Auteur ; N. C. Consoli, Auteur ; B. A. Baudet, Auteur Année de publication : 2011 Article en page(s) : pp. 791-799 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Reinforced  soils  Sands  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Fibres can be an effective means of reinforcing soils. This paper presents data from laboratory triaxial tests on quartzitic sand reinforced with polypropylene fibres. By keeping the studied composite consistent throughout the study (host sand and fibre characteristics kept constant), it has been possible to develop a framework of behaviour for the sand–fibre material, which provides a solid base for future research on fibre-reinforced soils. Data from previous work and from new tests have been analysed within the Critical State framework, that is in terms of normal compression line, critical state line and state boundary surface. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.159 [article] The mechanics of fibre-reinforced sand [texte imprimé] / A. P. S. Santos, Auteur ; N. C. Consoli, Auteur ; B. A. Baudet, Auteur . - 2011 . - pp. 791-799. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 791-799 Mots-clés : Reinforced  soils  Sands  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Fibres can be an effective means of reinforcing soils. This paper presents data from laboratory triaxial tests on quartzitic sand reinforced with polypropylene fibres. By keeping the studied composite consistent throughout the study (host sand and fibre characteristics kept constant), it has been possible to develop a framework of behaviour for the sand–fibre material, which provides a solid base for future research on fibre-reinforced soils. Data from previous work and from new tests have been analysed within the Critical State framework, that is in terms of normal compression line, critical state line and state boundary surface. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.159