Dépouillements

Benchmark of constitutive models for unsaturated soils / F. D'Onza in Géotechnique, Vol. 61 N° 4 (Avril 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 283–302 Titre : Benchmark of constitutive models for unsaturated soils Type de document : texte imprimé Auteurs : F. D'Onza, Auteur ; D. Gallipol, Auteur ; S. Wheeler, Auteur Année de publication : 2011 Article en page(s) : pp. 283–302 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Constitutive  relations  Laboratory  tests  Suction  Partial  saturation  Plasticity Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The paper presents a collaborative piece of research undertaken by seven research teams from different universities within the ‘Mechanics of Unsaturated Soils for Engineering' (MUSE) network. The objective is to benchmark different approaches to constitutive modelling of mechanical and water retention behaviour of unsaturated soils by comparing simulations of suction-controlled and constant water content laboratory tests. A set of 13 triaxial and oedometer laboratory tests, covering the mechanical and water retention behaviour of an unsaturated compacted silty soil under a variety of stress paths, has been provided by one of the seven participating teams. This data set has been used by the other six teams for calibrating a constitutive model of their choice, which has been subsequently employed for predicting strains and degree of saturation in three of the 13 tests used for calibration, as well as in one ‘blind' test for which experimental results had not been previously disclosed. By comparing predictions from all teams among themselves and against experimental data, the work highlights the capability of some of the current modelling approaches to reproduce specific features of the mechanical and water retention behaviour of unsaturated soils helping to identify potential areas of weakness where future research should focus. It also demonstrates the dispersion of results to be expected when different constitutive models, independently calibrated by different teams of researchers, are used to predict soil behaviour along the same stress path. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.283 [article] Benchmark of constitutive models for unsaturated soils [texte imprimé] / F. D'Onza, Auteur ; D. Gallipol, Auteur ; S. Wheeler, Auteur . - 2011 . - pp. 283–302. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 283–302 Mots-clés : Constitutive  relations  Laboratory  tests  Suction  Partial  saturation  Plasticity Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The paper presents a collaborative piece of research undertaken by seven research teams from different universities within the ‘Mechanics of Unsaturated Soils for Engineering' (MUSE) network. The objective is to benchmark different approaches to constitutive modelling of mechanical and water retention behaviour of unsaturated soils by comparing simulations of suction-controlled and constant water content laboratory tests. A set of 13 triaxial and oedometer laboratory tests, covering the mechanical and water retention behaviour of an unsaturated compacted silty soil under a variety of stress paths, has been provided by one of the seven participating teams. This data set has been used by the other six teams for calibrating a constitutive model of their choice, which has been subsequently employed for predicting strains and degree of saturation in three of the 13 tests used for calibration, as well as in one ‘blind' test for which experimental results had not been previously disclosed. By comparing predictions from all teams among themselves and against experimental data, the work highlights the capability of some of the current modelling approaches to reproduce specific features of the mechanical and water retention behaviour of unsaturated soils helping to identify potential areas of weakness where future research should focus. It also demonstrates the dispersion of results to be expected when different constitutive models, independently calibrated by different teams of researchers, are used to predict soil behaviour along the same stress path. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.283

Benchmark of experimental techniques for measuring and controlling suction / A. Tarantino in Géotechnique, Vol. 61 N° 4 (Avril 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 303–312 Titre : Benchmark of experimental techniques for measuring and controlling suction Type de document : texte imprimé Auteurs : A. Tarantino, Auteur ; D. Gallipoli, Auteur ; C. E. Augarde, Auteur Année de publication : 2011 Article en page(s) : pp. 303–312 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Laboratory  tests  Suction  Partial  saturation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The paper presents a benchmarking study carried out within the ‘Mechanics of Unsaturated Soils for Engineering' (MUSE) network aimed at comparing different techniques for measurement and control of suction. Techniques tested by the eight ‘Mechanics of Unsaturated Soils for Engineering' research teams include axis-translation (pressure plate and suction-controlled oedometer), high-capacity tensiometer and osmotic technique. The soil used in the exercise was a mixture of uniform sand, sodium bentonite (active clay) and kaolinite (non-active clay), which were all commercially available. Samples were prepared by one team and distributed to all other teams. They were normally consolidated from slurry under one-dimensional conditions (consolidometer) to a given vertical stress. The water retention characteristics of the initially saturated specimens were investigated along the main drying path. Specimens were de-saturated by applying suction through the liquid phase when using an axis-translation technique or osmotic method and de-saturated by air-drying, when suction was measured using high-capacity tensiometers. In general, the same technique was tested by at least two teams. The water retention curves obtained using the different techniques are compared and discrepancies are discussed in the paper. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.303 [article] Benchmark of experimental techniques for measuring and controlling suction [texte imprimé] / A. Tarantino, Auteur ; D. Gallipoli, Auteur ; C. E. Augarde, Auteur . - 2011 . - pp. 303–312. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 303–312 Mots-clés : Laboratory  tests  Suction  Partial  saturation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The paper presents a benchmarking study carried out within the ‘Mechanics of Unsaturated Soils for Engineering' (MUSE) network aimed at comparing different techniques for measurement and control of suction. Techniques tested by the eight ‘Mechanics of Unsaturated Soils for Engineering' research teams include axis-translation (pressure plate and suction-controlled oedometer), high-capacity tensiometer and osmotic technique. The soil used in the exercise was a mixture of uniform sand, sodium bentonite (active clay) and kaolinite (non-active clay), which were all commercially available. Samples were prepared by one team and distributed to all other teams. They were normally consolidated from slurry under one-dimensional conditions (consolidometer) to a given vertical stress. The water retention characteristics of the initially saturated specimens were investigated along the main drying path. Specimens were de-saturated by applying suction through the liquid phase when using an axis-translation technique or osmotic method and de-saturated by air-drying, when suction was measured using high-capacity tensiometers. In general, the same technique was tested by at least two teams. The water retention curves obtained using the different techniques are compared and discrepancies are discussed in the paper. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.303

An insight into the water retention properties of compacted clayey soils / E. Romero in Géotechnique, Vol. 61 N° 4 (Avril 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 313–328 Titre : An insight into the water retention properties of compacted clayey soils Type de document : texte imprimé Auteurs : E. Romero, Auteur ; G. Della Vecchia, Auteur ; C. Jommi, Auteur Année de publication : 2011 Article en page(s) : pp. 313–328 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Laboratory  tests  Suction  Partial  saturation  Fabric/Structure  of  soils  Clays  Compaction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Experimental data from different testing methodologies on different compacted clayey soils, with dominant bimodal pore size distribution, are presented and analysed, to provide a comprehensive picture of the evolution of the aggregated fabric along hydraulic and mechanical paths. Fabric changes are analysed both from the porous network viewpoint, by means of careful mercury intrusion porosimetry investigation, and from the soil skeleton viewpoint, by quantifying swelling and shrinkage of the aggregates in an environmental scanning electron microscopy study. The consequences of the aggregated fabric evolution on the water retention properties of compacted soils are analysed and discussed. A new model for water retention domain is proposed, which introduces a dependence of the intra-aggregate pore volume on water content. The model succeeds in tracking correctly the evolution of the hydraulic state of the different soils investigated along generalised hydromechanical paths. The proposed approach brings to light coupling between intra-aggregate and inter-aggregate pores in the retention properties of compacted clayey soils. Dependence of the air entry and the air occlusion values on swelling and shrinking of aggregates, besides void ratio, is introduced and discussed. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.313 [article] An insight into the water retention properties of compacted clayey soils [texte imprimé] / E. Romero, Auteur ; G. Della Vecchia, Auteur ; C. Jommi, Auteur . - 2011 . - pp. 313–328. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 313–328 Mots-clés : Laboratory  tests  Suction  Partial  saturation  Fabric/Structure  of  soils  Clays  Compaction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Experimental data from different testing methodologies on different compacted clayey soils, with dominant bimodal pore size distribution, are presented and analysed, to provide a comprehensive picture of the evolution of the aggregated fabric along hydraulic and mechanical paths. Fabric changes are analysed both from the porous network viewpoint, by means of careful mercury intrusion porosimetry investigation, and from the soil skeleton viewpoint, by quantifying swelling and shrinkage of the aggregates in an environmental scanning electron microscopy study. The consequences of the aggregated fabric evolution on the water retention properties of compacted soils are analysed and discussed. A new model for water retention domain is proposed, which introduces a dependence of the intra-aggregate pore volume on water content. The model succeeds in tracking correctly the evolution of the hydraulic state of the different soils investigated along generalised hydromechanical paths. The proposed approach brings to light coupling between intra-aggregate and inter-aggregate pores in the retention properties of compacted clayey soils. Dependence of the air entry and the air occlusion values on swelling and shrinking of aggregates, besides void ratio, is introduced and discussed. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.313

Hydromechanical behaviour of compacted granular expansive mixtures: experimental and constitutive study / E. E. Alonso in Géotechnique, Vol. 61 N° 4 (Avril 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 329–344 Titre : Hydromechanical behaviour of compacted granular expansive mixtures: experimental and constitutive study Type de document : texte imprimé Auteurs : E. E. Alonso, Auteur ; E. Romero, Auteur ; C. Hoffmann, Auteur Année de publication : 2011 Article en page(s) : pp. 329–344 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Clays  Laboratory  tests  Fabric/Structure  of  soils  Suction  Partial  saturation  Compaction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Compacted granular mixtures of high-density bentonite pellets have been evaluated as an alternative buffer material to fill the empty space around nuclear waste disposal canisters in horizontal drifts. Despite the obvious benefits of these compacted mixtures (the backfilling operation becomes easier and the gaps between the host rock and the buffer are minimised), there are several aspects of concern such as the effective blockage of the large inter-pellet pores due to granule swelling – this blockage improves the water permeability properties – and the tendency to develop initial collapses before reaching an adequate swelling pressure. Selected test results of a comprehensive laboratory experimental programme are presented to gain insight into the hydromechanical response of this multi-porosity compacted material. To improve the information on local transient behaviour, simulation-assisted techniques using a double-structure constitutive model are used. The paper presents a physically based one-dimensional model to simulate experimental results of different transient processes, such as the progressive loss of permeability during wetting and the occurrence of concurrent phenomena during fast flooding at constant stress (initial collapse of the granular arrangement and parallel expansion of granules). DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.329 [article] Hydromechanical behaviour of compacted granular expansive mixtures: experimental and constitutive study [texte imprimé] / E. E. Alonso, Auteur ; E. Romero, Auteur ; C. Hoffmann, Auteur . - 2011 . - pp. 329–344. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 329–344 Mots-clés : Clays  Laboratory  tests  Fabric/Structure  of  soils  Suction  Partial  saturation  Compaction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Compacted granular mixtures of high-density bentonite pellets have been evaluated as an alternative buffer material to fill the empty space around nuclear waste disposal canisters in horizontal drifts. Despite the obvious benefits of these compacted mixtures (the backfilling operation becomes easier and the gaps between the host rock and the buffer are minimised), there are several aspects of concern such as the effective blockage of the large inter-pellet pores due to granule swelling – this blockage improves the water permeability properties – and the tendency to develop initial collapses before reaching an adequate swelling pressure. Selected test results of a comprehensive laboratory experimental programme are presented to gain insight into the hydromechanical response of this multi-porosity compacted material. To improve the information on local transient behaviour, simulation-assisted techniques using a double-structure constitutive model are used. The paper presents a physically based one-dimensional model to simulate experimental results of different transient processes, such as the progressive loss of permeability during wetting and the occurrence of concurrent phenomena during fast flooding at constant stress (initial collapse of the granular arrangement and parallel expansion of granules). DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.329

Experimental observations of the stress regime in unsaturated compacted clay when laterally confined / J. L. Boyd in Géotechnique, Vol. 61 N° 4 (Avril 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 345–363 Titre : Experimental observations of the stress regime in unsaturated compacted clay when laterally confined Type de document : texte imprimé Auteurs : J. L. Boyd, Auteur ; V. Sivakumar, Auteur Année de publication : 2011 Article en page(s) : pp. 345–363 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Retaining  walls  Stress  path  Suction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Construction processes often involve reformation of the landscape, which will inevitably encompass compaction of artificially placed soils. A common application of fill materials is their use as backfill in many engineering applications, for example behind a retaining wall. The post-construction behaviour of clay fills is complex with respect to stresses and deformation when the fills become saturated over time. Heavily compacted fills swells significantly more than the lightly compacted fills. This will produce enhanced lateral stresses if the fill is laterally restrained. The work presented in this paper examines how the stress regime in unsaturated clay fills changes with wetting under laterally restrained conditions. Specimens of compacted kaolin, with different initial conditions, were wetted to various values of suction under zero lateral strain at constant net overburden pressure which allowed the concept of K 0 (the ratio between the net horizontal stress and the net vertical stress) to be examined. Tests were also carried out to examine the traditional concept of the earth pressure coefficient ‘at rest' under loading and unloading and its likely effects on the stress–strain properties. The results have shown that the stress regime (i.e. the lateral stress) changes significantly during wetting under laterally restrained conditions. The magnitude of the change is affected by the initial condition of the soil. The results have also indicated that the earth pressure coefficient ‘at rest' during loading (under the normally consolidated condition) is unaffected by suction and such loading conditions inevitably lead to the development of anisotropic stress–strain properties DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.345 [article] Experimental observations of the stress regime in unsaturated compacted clay when laterally confined [texte imprimé] / J. L. Boyd, Auteur ; V. Sivakumar, Auteur . - 2011 . - pp. 345–363. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 4 (Avril 2011) . - pp. 345–363 Mots-clés : Retaining  walls  Stress  path  Suction Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Construction processes often involve reformation of the landscape, which will inevitably encompass compaction of artificially placed soils. A common application of fill materials is their use as backfill in many engineering applications, for example behind a retaining wall. The post-construction behaviour of clay fills is complex with respect to stresses and deformation when the fills become saturated over time. Heavily compacted fills swells significantly more than the lightly compacted fills. This will produce enhanced lateral stresses if the fill is laterally restrained. The work presented in this paper examines how the stress regime in unsaturated clay fills changes with wetting under laterally restrained conditions. Specimens of compacted kaolin, with different initial conditions, were wetted to various values of suction under zero lateral strain at constant net overburden pressure which allowed the concept of K 0 (the ratio between the net horizontal stress and the net vertical stress) to be examined. Tests were also carried out to examine the traditional concept of the earth pressure coefficient ‘at rest' under loading and unloading and its likely effects on the stress–strain properties. The results have shown that the stress regime (i.e. the lateral stress) changes significantly during wetting under laterally restrained conditions. The magnitude of the change is affected by the initial condition of the soil. The results have also indicated that the earth pressure coefficient ‘at rest' during loading (under the normally consolidated condition) is unaffected by suction and such loading conditions inevitably lead to the development of anisotropic stress–strain properties DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.2011.61.4.345

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