Dépouillements

A model for natural soil with bonds / W. M. Yan in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 95–106 Titre : A model for natural soil with bonds Type de document : texte imprimé Auteurs : W. M. Yan, Auteur ; X.S. Li, Auteur Année de publication : 2011 Article en page(s) : pp. 95–106 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Constitutive  relations  Clays  Theoretical  analysis  Shear  strength  Plasticity  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents a thermodynamically consistent constitutive model for natural soils with bonds. In the model, the free energy (the internal energy available to do work) is contributed partly by the so-called frozen or locked energy, whose evolution is assumed to be homogeneously related to the irrecoverable deformation. During loading, the bonds existing in the natural soil not only boost the dissipation rate but also liberate certain historically accumulated locked energy. Such effects, however, are diminished as loading proceeds and the bonds are destroyed. The novel aspect of the present model is that it accommodates both the Mohr–Coulomb and critical-state failure modes, and the two modes are unified through the evolution law of a thermodynamic force associated with the locked bonding energy. As compared with the classical Cam-clay models, the model contains two additional material constants, where one is proposed by Collins & Kelly to improve the shape of the yield surface, and the other is dedicated to bonding evolution. The calibration procedure for the material parameters is provided. The capability of the model is demonstrated by a series of model simulations on a hypothetical bonded soil under various triaxial loading paths, and the model response is also compared with representative testing results in the literature. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.061 [article] A model for natural soil with bonds [texte imprimé] / W. M. Yan, Auteur ; X.S. Li, Auteur . - 2011 . - pp. 95–106. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 95–106 Mots-clés : Constitutive  relations  Clays  Theoretical  analysis  Shear  strength  Plasticity  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper presents a thermodynamically consistent constitutive model for natural soils with bonds. In the model, the free energy (the internal energy available to do work) is contributed partly by the so-called frozen or locked energy, whose evolution is assumed to be homogeneously related to the irrecoverable deformation. During loading, the bonds existing in the natural soil not only boost the dissipation rate but also liberate certain historically accumulated locked energy. Such effects, however, are diminished as loading proceeds and the bonds are destroyed. The novel aspect of the present model is that it accommodates both the Mohr–Coulomb and critical-state failure modes, and the two modes are unified through the evolution law of a thermodynamic force associated with the locked bonding energy. As compared with the classical Cam-clay models, the model contains two additional material constants, where one is proposed by Collins & Kelly to improve the shape of the yield surface, and the other is dedicated to bonding evolution. The calibration procedure for the material parameters is provided. The capability of the model is demonstrated by a series of model simulations on a hypothetical bonded soil under various triaxial loading paths, and the model response is also compared with representative testing results in the literature. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.061

Effect of relative density and stress level on the bearing capacity of footings on sand / D. Loukidis in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 107–119 Titre : Effect of relative density and stress level on the bearing capacity of footings on sand Type de document : texte imprimé Auteurs : D. Loukidis, Auteur ; R. Salgado, Auteur Année de publication : 2011 Article en page(s) : pp. 107–119 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Sands  Bearing  capacity  Anisotropy  Numerical  modelling  Plasticity  Footings/foundations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The design of shallow foundations relies on bearing capacity values calculated using empirical procedures that are based in part on solutions obtained using the method of characteristics, which assumes a soil that is perfectly plastic following an associated flow rule. In this paper the problem of strip and circular footings resting on the surface of a sand layer is analysed using the finite-element method. Analyses are performed using a two-surface plasticity constitutive model that realistically captures the aspects of the mechanical response of sands that are relevant to the bearing capacity problem. In particular, the model accounts for non-associated flow, strain-softening, and both stress-induced and inherent anisotropy. Based on the results of the analyses, the paper examines the validity of the bearing capacity factors N γ and shape factors s γ used in practice. A relationship for determining appropriate values of friction angle for use in bearing capacity calculations is also proposed. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.150.3771 [article] Effect of relative density and stress level on the bearing capacity of footings on sand [texte imprimé] / D. Loukidis, Auteur ; R. Salgado, Auteur . - 2011 . - pp. 107–119. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 107–119 Mots-clés : Sands  Bearing  capacity  Anisotropy  Numerical  modelling  Plasticity  Footings/foundations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The design of shallow foundations relies on bearing capacity values calculated using empirical procedures that are based in part on solutions obtained using the method of characteristics, which assumes a soil that is perfectly plastic following an associated flow rule. In this paper the problem of strip and circular footings resting on the surface of a sand layer is analysed using the finite-element method. Analyses are performed using a two-surface plasticity constitutive model that realistically captures the aspects of the mechanical response of sands that are relevant to the bearing capacity problem. In particular, the model accounts for non-associated flow, strain-softening, and both stress-induced and inherent anisotropy. Based on the results of the analyses, the paper examines the validity of the bearing capacity factors N γ and shape factors s γ used in practice. A relationship for determining appropriate values of friction angle for use in bearing capacity calculations is also proposed. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.150.3771

Load transfer from a raft to a pile with an interposed layer / V. Fioravante in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 121–132 Titre : Load transfer from a raft to a pile with an interposed layer Type de document : texte imprimé Auteurs : V. Fioravante, Auteur Année de publication : 2011 Article en page(s) : pp. 121–132 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Piles  Centrifuge  modelling  Rafts  Soil/Structure  interaction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The load transfer mechanisms between a pile and a raft with an interposed granular layer have been studied by means of centrifuge physical model tests. The tests were carried out with an instrumented single model pile in two configurations: in direct contact with the raft and separated from the raft by a coarse granular layer. As the model tests show, a granular layer beneath a raft changes the pile shaft behaviour significantly compared with that exhibited by a pile in contact; it allows downward relative raft–pile and soil–pile displacement and the consequent development of negative skin friction around the upper pile shaft perimeter. Hence, the raft load is partially transferred to the pile through the pile head and partially through the negative skin friction of the upper shaft. The contact pile reduces the raft stress on the soil, and then a piled raft stiffness results that is close to that of a free-standing pile up to yield load and close to that of an unpiled raft after the yield load has been reached; the non-contact pile increases the piled raft stiffness over the whole investigated settlement range with respect to the unpiled raft. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00187 [article] Load transfer from a raft to a pile with an interposed layer [texte imprimé] / V. Fioravante, Auteur . - 2011 . - pp. 121–132. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 121–132 Mots-clés : Piles  Centrifuge  modelling  Rafts  Soil/Structure  interaction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The load transfer mechanisms between a pile and a raft with an interposed granular layer have been studied by means of centrifuge physical model tests. The tests were carried out with an instrumented single model pile in two configurations: in direct contact with the raft and separated from the raft by a coarse granular layer. As the model tests show, a granular layer beneath a raft changes the pile shaft behaviour significantly compared with that exhibited by a pile in contact; it allows downward relative raft–pile and soil–pile displacement and the consequent development of negative skin friction around the upper pile shaft perimeter. Hence, the raft load is partially transferred to the pile through the pile head and partially through the negative skin friction of the upper shaft. The contact pile reduces the raft stress on the soil, and then a piled raft stiffness results that is close to that of a free-standing pile up to yield load and close to that of an unpiled raft after the yield load has been reached; the non-contact pile increases the piled raft stiffness over the whole investigated settlement range with respect to the unpiled raft. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00187

Mechanical properties of cemented scrap rubber tyre chips / W. Y. Tsoi in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 133–141 Titre : Mechanical properties of cemented scrap rubber tyre chips Type de document : texte imprimé Auteurs : W. Y. Tsoi, Auteur ; K. M. Lee, Auteur Année de publication : 2011 Article en page(s) : pp. 133–141 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Compressibility  Stress  analysis  Geosynthetics  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Lightly cemented scrap rubber tyre chips have been proposed as a ductile, porous and lightweight geomaterial for various engineering applications. Both drained and undrained triaxial compression tests on the material were conducted. Despite the high flexibility of the rubber chips and hence their higher ductility, the material behaviour was found to be generally similar to that of typical cemented soils. Data points with the same deviatoric strain in p′–q space were linked up to form a series of equi-deviatoric strain lines, and a degradable cohesion intercept is observed in the plot. There was also a tentative critical state line in p′–q–e space (e being the void ratio) that was consistent with the corresponding ‘parent soil' (unbonded, cement-coated chips). In an unloading–reloading stress–strain curve the unloading path was practically identical to the reloading path in a constant-p′ test, but more curved in a consolidated drained test. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.033 [article] Mechanical properties of cemented scrap rubber tyre chips [texte imprimé] / W. Y. Tsoi, Auteur ; K. M. Lee, Auteur . - 2011 . - pp. 133–141. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 133–141 Mots-clés : Compressibility  Stress  analysis  Geosynthetics  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Lightly cemented scrap rubber tyre chips have been proposed as a ductile, porous and lightweight geomaterial for various engineering applications. Both drained and undrained triaxial compression tests on the material were conducted. Despite the high flexibility of the rubber chips and hence their higher ductility, the material behaviour was found to be generally similar to that of typical cemented soils. Data points with the same deviatoric strain in p′–q space were linked up to form a series of equi-deviatoric strain lines, and a degradable cohesion intercept is observed in the plot. There was also a tentative critical state line in p′–q–e space (e being the void ratio) that was consistent with the corresponding ‘parent soil' (unbonded, cement-coated chips). In an unloading–reloading stress–strain curve the unloading path was practically identical to the reloading path in a constant-p′ test, but more curved in a consolidated drained test. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.033

A subgrade reaction solution for piles to stabilise landslides / F. Cai in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 143–151 Titre : A subgrade reaction solution for piles to stabilise landslides Type de document : texte imprimé Auteurs : F. Cai, Auteur ; K. Ugai, Auteur Année de publication : 2011 Article en page(s) : pp. 143–151 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Slopes  Soil/Structure  interaction  Soil  stabilisation  Landslides  Piles Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper reports a subgrade reaction solution for piles used to stabilise landslides where the sliding layer laterally moves with a displacement decreasing linearly with depth. The developed subgrade reaction solution can deal with the case in which pile segments in both sliding and stable layers are not flexible, and can also calculate the pile response under the additional resistance required to stabilise the landslide. Transforming coordinate systems, the conventional solution can be obtained from the developed subgrade reaction solution for the case in which the movement of the sliding layer is uniform with depth. Two case studies indicate that the pile response, especially the maximum bending moment, calculated by using the developed subgrade reaction solution, was consistent with the measurements. The movement gradient of the sliding layer had a significant influence on the response of stabilising piles, and it usually increased the maximum bending moment of the pile segment in the stable layer. Stabilising piles would be potentially unsafe if such influence were not considered in design. Using the developed subgrade reaction solution, dimensionless design charts were created for the case in which the pile segment in the sliding layer is not flexible. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.026 [article] A subgrade reaction solution for piles to stabilise landslides [texte imprimé] / F. Cai, Auteur ; K. Ugai, Auteur . - 2011 . - pp. 143–151. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 143–151 Mots-clés : Slopes  Soil/Structure  interaction  Soil  stabilisation  Landslides  Piles Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper reports a subgrade reaction solution for piles used to stabilise landslides where the sliding layer laterally moves with a displacement decreasing linearly with depth. The developed subgrade reaction solution can deal with the case in which pile segments in both sliding and stable layers are not flexible, and can also calculate the pile response under the additional resistance required to stabilise the landslide. Transforming coordinate systems, the conventional solution can be obtained from the developed subgrade reaction solution for the case in which the movement of the sliding layer is uniform with depth. Two case studies indicate that the pile response, especially the maximum bending moment, calculated by using the developed subgrade reaction solution, was consistent with the measurements. The movement gradient of the sliding layer had a significant influence on the response of stabilising piles, and it usually increased the maximum bending moment of the pile segment in the stable layer. Stabilising piles would be potentially unsafe if such influence were not considered in design. Using the developed subgrade reaction solution, dimensionless design charts were created for the case in which the pile segment in the sliding layer is not flexible. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.026

Predicting rainfall-induced landslide potential along a mountain road in Taiwan / Ching, J. in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 153–166 Titre : Predicting rainfall-induced landslide potential along a mountain road in Taiwan Type de document : texte imprimé Auteurs : Ching, J., Auteur ; H. J. Liao, Auteur ; J.-Y. Lee, Auteur Année de publication : 2011 Article en page(s) : pp. 153–166 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Landslides  Slopes  Failure  Statistical  analysis Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper gives a brief introduction on the background and current status of rainfall-induced landslides along a mountain road (Route T-18) in Taiwan and presents a detailed analysis based on the Gaussian process model for predicting locations and occurrence times of future landslides using post Chi-Chi earthquake historical data. Based on inherent and man-made features of failed and not-failed slopes, locations of possible future landslides owing to rainfall along Route T-18 are predicted. Together with historical rainfall data, a rainfall fragility graph is established. The analysis results show that the Gaussian process model is effective in predicting landslide potentials and probabilities. Comparisons of the Gaussian process analysis and the discriminant function analysis are made, which show that the former outperforms the latter in many respects. The results are valuable for predicting where and when landslides would occur along Route T-18 in future heavy rainfalls. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.119.3740 [article] Predicting rainfall-induced landslide potential along a mountain road in Taiwan [texte imprimé] / Ching, J., Auteur ; H. J. Liao, Auteur ; J.-Y. Lee, Auteur . - 2011 . - pp. 153–166. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 153–166 Mots-clés : Landslides  Slopes  Failure  Statistical  analysis Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper gives a brief introduction on the background and current status of rainfall-induced landslides along a mountain road (Route T-18) in Taiwan and presents a detailed analysis based on the Gaussian process model for predicting locations and occurrence times of future landslides using post Chi-Chi earthquake historical data. Based on inherent and man-made features of failed and not-failed slopes, locations of possible future landslides owing to rainfall along Route T-18 are predicted. Together with historical rainfall data, a rainfall fragility graph is established. The analysis results show that the Gaussian process model is effective in predicting landslide potentials and probabilities. Comparisons of the Gaussian process analysis and the discriminant function analysis are made, which show that the former outperforms the latter in many respects. The results are valuable for predicting where and when landslides would occur along Route T-18 in future heavy rainfalls. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.119.3740

Consolidation around partially embedded seabed pipelines / K. Krost in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 167–173 Titre : Consolidation around partially embedded seabed pipelines Type de document : texte imprimé Auteurs : K. Krost, Auteur ; S. M. Gourvenec, Auteur ; D. J. White, Auteur Année de publication : 2011 Article en page(s) : pp. 167–173 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Offshore  engineering  Soil/Structure  interaction  Consolidation  numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : When a pipeline is laid on a soft clay seabed, excess pore pressure is generated. During the subsequent dissipation process, the effective stress at the pipe–soil interface and the available axial pipe–soil resistance rise. This ‘set-up' of axial resistance is an important consideration in various aspects of pipeline design, including the mitigation of thermal and pressure-induced expansion, the stability of the pipeline on sloping ground and the assessment of pipe–soil forces during installation. A set of finite-element analyses has been conducted to assess the pore pressure dissipation and consolidation beneath partially embedded seabed pipelines, extending existing solutions for strip footings. It is shown that the curved shape of a pipeline increases the normalised rate of consolidation compared with a strip footing. Dissipation curves for various levels of embedment are presented and the calculated response is shown to compare well with data from a field test conducted on a soft clay. The dissipation curves have been used to derive the development of effective contact force between the pipe and the seabed as consolidation progresses. These results highlight the significant enhancement of this force – and therefore the available axial resistance – that arises from a ‘wedging effect' related to the curvature of the pipe–soil contact surface. This wedging effect leads to a beneficial enhancement of the axial resistance. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.t.015 [article] Consolidation around partially embedded seabed pipelines [texte imprimé] / K. Krost, Auteur ; S. M. Gourvenec, Auteur ; D. J. White, Auteur . - 2011 . - pp. 167–173. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 167–173 Mots-clés : Offshore  engineering  Soil/Structure  interaction  Consolidation  numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : When a pipeline is laid on a soft clay seabed, excess pore pressure is generated. During the subsequent dissipation process, the effective stress at the pipe–soil interface and the available axial pipe–soil resistance rise. This ‘set-up' of axial resistance is an important consideration in various aspects of pipeline design, including the mitigation of thermal and pressure-induced expansion, the stability of the pipeline on sloping ground and the assessment of pipe–soil forces during installation. A set of finite-element analyses has been conducted to assess the pore pressure dissipation and consolidation beneath partially embedded seabed pipelines, extending existing solutions for strip footings. It is shown that the curved shape of a pipeline increases the normalised rate of consolidation compared with a strip footing. Dissipation curves for various levels of embedment are presented and the calculated response is shown to compare well with data from a field test conducted on a soft clay. The dissipation curves have been used to derive the development of effective contact force between the pipe and the seabed as consolidation progresses. These results highlight the significant enhancement of this force – and therefore the available axial resistance – that arises from a ‘wedging effect' related to the curvature of the pipe–soil contact surface. This wedging effect leads to a beneficial enhancement of the axial resistance. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.t.015

Is the quasi-steady state a real behaviour? / J. Yang in Géotechnique, Vol. 61 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 175–183 Titre : Is the quasi-steady state a real behaviour? : a micromechanical perspective Type de document : texte imprimé Auteurs : J. Yang, Auteur ; B. B. Dai, Auteur Année de publication : 2011 Article en page(s) : pp. 175–183 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fabric/Structure  of  soils  Sands  Constitutive  relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Whether the so-called quasi-steady state is a real material response is a fundamental yet controversial question in the study of undrained shear behaviour of sand. An attempt is made here to clarify the question from a micromechanical viewpoint by means of a grain-scale modelling technique combined with statistical analyses. The study shows that the quasi-steady state is a real behaviour rather than a test-induced phenomenon; it is a transition state, and can be regarded as the result of spatial rearrangement of discrete particles sheared under the constant-volume condition. The quasi-steady state has distinct features that make it different from the steady state at both the macro scale and micro scale. During the loading process, the average number of contacts per particle decreases with strain until the quasi-steady state emerges, and after that it increases gradually to an approximately constant value at large deformations associated with the steady state. This result suggests that the loss of contacts is most pronounced at the quasi-steady state. The study also shows that the contact normal forces and particle rotations play a major role in the deformation process, whereas the contributions of contact tangential forces and particle sliding appear to be minor. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.129 [article] Is the quasi-steady state a real behaviour? : a micromechanical perspective [texte imprimé] / J. Yang, Auteur ; B. B. Dai, Auteur . - 2011 . - pp. 175–183. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 2 (Fevrier 2011) . - pp. 175–183 Mots-clés : Fabric/Structure  of  soils  Sands  Constitutive  relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Whether the so-called quasi-steady state is a real material response is a fundamental yet controversial question in the study of undrained shear behaviour of sand. An attempt is made here to clarify the question from a micromechanical viewpoint by means of a grain-scale modelling technique combined with statistical analyses. The study shows that the quasi-steady state is a real behaviour rather than a test-induced phenomenon; it is a transition state, and can be regarded as the result of spatial rearrangement of discrete particles sheared under the constant-volume condition. The quasi-steady state has distinct features that make it different from the steady state at both the macro scale and micro scale. During the loading process, the average number of contacts per particle decreases with strain until the quasi-steady state emerges, and after that it increases gradually to an approximately constant value at large deformations associated with the steady state. This result suggests that the loss of contacts is most pronounced at the quasi-steady state. The study also shows that the contact normal forces and particle rotations play a major role in the deformation process, whereas the contributions of contact tangential forces and particle sliding appear to be minor. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.129

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