Documents disponibles écrits par cet auteur

Experimental behaviour of compacted marls / R. Cardoso in Géotechnique, Vol. 62 N° 11 (Novembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 999 –1012 Titre : Experimental behaviour of compacted marls Type de document : texte imprimé Auteurs : R. Cardoso, Auteur ; E. Maranha Des Neves, Auteur ; E. E. Alonso, Auteur Année de publication : 2012 Article en page(s) : pp. 999 –1012 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Suction  Soft  rocks  Embankments  Partial  saturation  Compaction  Fabric/structure  of  soils Résumé : Jurassic marls from Abadia, Portugal, were used in the construction of some motorway embankments. Large fragments of this evolving material remained after the construction process, and their degradation was of concern because of the expected change of the engineering properties of the compacted material. The material exhibits a very complex behaviour, which is difficult to reproduce with existing constitutive models for unsaturated structured materials. This paper focuses on understanding and providing data on the interaction between the pure marls (rock) and the aggregate behaviour. It presents the main results of tests performed to characterise the hydro-mechanical behaviour of compacted marls in specimens prepared with different grading size distributions and subjected to oedometer tests where both stress and suction changes were applied. The experimental data obtained were analysed, considering the presence of fragments and their degradation. The marl matrix was characterised to complete the existing data previously published for this material, but now with the purpose of providing a better explanation for the volumetric behaviour of the aggregate. The discussion is assisted by the explanation provided by a simple elasto-plastic model for unsaturated soils. Discrepancies with model predictions help to highlight the singularity of the marl aggregate. Compacted marls behave as materials in the transition between rockfill (when the fragments remain brittle) and a clayey soil (when the degradation accumulates). Therefore the compacted marl exhibits a dual behaviour. If it is dry, deformations are explained by the breakage of particles and rearrangement of the structure. If it is wet, the compacted marl is dominated by bond degradation of the material, the release of swelling potential and simultaneous changes in the stiffness and strength of the fragments. It appears that the transition from dry to wet can be identified by the current suction; moreover, it is rather abrupt. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.093 [article] Experimental behaviour of compacted marls [texte imprimé] / R. Cardoso, Auteur ; E. Maranha Des Neves, Auteur ; E. E. Alonso, Auteur . - 2012 . - pp. 999 –1012. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 11 (Novembre 2012) . - pp. 999 –1012 Mots-clés : Suction  Soft  rocks  Embankments  Partial  saturation  Compaction  Fabric/structure  of  soils Résumé : Jurassic marls from Abadia, Portugal, were used in the construction of some motorway embankments. Large fragments of this evolving material remained after the construction process, and their degradation was of concern because of the expected change of the engineering properties of the compacted material. The material exhibits a very complex behaviour, which is difficult to reproduce with existing constitutive models for unsaturated structured materials. This paper focuses on understanding and providing data on the interaction between the pure marls (rock) and the aggregate behaviour. It presents the main results of tests performed to characterise the hydro-mechanical behaviour of compacted marls in specimens prepared with different grading size distributions and subjected to oedometer tests where both stress and suction changes were applied. The experimental data obtained were analysed, considering the presence of fragments and their degradation. The marl matrix was characterised to complete the existing data previously published for this material, but now with the purpose of providing a better explanation for the volumetric behaviour of the aggregate. The discussion is assisted by the explanation provided by a simple elasto-plastic model for unsaturated soils. Discrepancies with model predictions help to highlight the singularity of the marl aggregate. Compacted marls behave as materials in the transition between rockfill (when the fragments remain brittle) and a clayey soil (when the degradation accumulates). Therefore the compacted marl exhibits a dual behaviour. If it is dry, deformations are explained by the breakage of particles and rearrangement of the structure. If it is wet, the compacted marl is dominated by bond degradation of the material, the release of swelling potential and simultaneous changes in the stiffness and strength of the fragments. It appears that the transition from dry to wet can be identified by the current suction; moreover, it is rather abrupt. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.093

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

A microstructurally based effective stress for unsaturated soils / E. E. Alonso in Géotechnique, Vol. 60 N° 12 (Décembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 12 (Décembre 2010) . - pp. 913–925 Titre : A microstructurally based effective stress for unsaturated soils Type de document : texte imprimé Auteurs : E. E. Alonso, Auteur ; J. M. Pereira, Auteur ; J. Vaunat, Auteur Année de publication : 2011 Article en page(s) : pp. 913–925 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Pore  pressures  Constitutive  relations  Suction  Stiffness  Shear  strength  Partial  saturation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Current alternative choices of stress state variables in unsaturated soils are described and compared, with a special focus on the use of an effective stress. Experimental data on stiffness and shear strength evolution with suction suggest that the proportion of suction contributing to the effective stress is often much smaller than predicted by the term ‘suction times degree of saturation' generally used in effective stress expressions of the Bishop type. It is suggested that effective stress in unsaturated soils should be related to soil microstructure. An effective degree of saturation is defined as describing the volume of water partially filling the soil macroporosity. This effective degree of saturation defines the proportion of the prevailing suction that actually contributes to the effective stress. Two alternative expressions (piecewise linear and non-linear) are proposed for the effective degree of saturation. They offer a similar performance. Available data on stiffness and shear strength variation with suction of a few different soils, ranging from a markedly granular material to high-plasticity clay, have been analysed. The analysis supports the proposed microstructural interpretation of the effective stress. Indeed, for granular soils the effective degree of saturation is almost equal to the total degree of saturation, and therefore the Bishop-type expression generally used as an effective stress is recovered. As the soil becomes more plastic, the proportion of free water reduces, and the contribution of suction to the effective stress reduces. At the limit, when the proportion of free water is negligible (this is the case of high-plasticity clays at high values of suction) the proposed effective stress reduces to the net stress (excess of total stress over the air pressure). The proposed effective stress equation may be identified if information on the amount of immobile water is available for a given soil. Water retention or porosimetry data provide this information. This has been shown by comparing the present proposal with independently obtained information about immobile water in high-plasticity clays. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.002 [article] A microstructurally based effective stress for unsaturated soils [texte imprimé] / E. E. Alonso, Auteur ; J. M. Pereira, Auteur ; J. Vaunat, Auteur . - 2011 . - pp. 913–925. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 12 (Décembre 2010) . - pp. 913–925 Mots-clés : Pore  pressures  Constitutive  relations  Suction  Stiffness  Shear  strength  Partial  saturation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Current alternative choices of stress state variables in unsaturated soils are described and compared, with a special focus on the use of an effective stress. Experimental data on stiffness and shear strength evolution with suction suggest that the proportion of suction contributing to the effective stress is often much smaller than predicted by the term ‘suction times degree of saturation' generally used in effective stress expressions of the Bishop type. It is suggested that effective stress in unsaturated soils should be related to soil microstructure. An effective degree of saturation is defined as describing the volume of water partially filling the soil macroporosity. This effective degree of saturation defines the proportion of the prevailing suction that actually contributes to the effective stress. Two alternative expressions (piecewise linear and non-linear) are proposed for the effective degree of saturation. They offer a similar performance. Available data on stiffness and shear strength variation with suction of a few different soils, ranging from a markedly granular material to high-plasticity clay, have been analysed. The analysis supports the proposed microstructural interpretation of the effective stress. Indeed, for granular soils the effective degree of saturation is almost equal to the total degree of saturation, and therefore the Bishop-type expression generally used as an effective stress is recovered. As the soil becomes more plastic, the proportion of free water reduces, and the contribution of suction to the effective stress reduces. At the limit, when the proportion of free water is negligible (this is the case of high-plasticity clays at high values of suction) the proposed effective stress reduces to the net stress (excess of total stress over the air pressure). The proposed effective stress equation may be identified if information on the amount of immobile water is available for a given soil. Water retention or porosimetry data provide this information. This has been shown by comparing the present proposal with independently obtained information about immobile water in high-plasticity clays. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.002

Modelling the response of Lechago earth and rockfill dam / E. E. Alonso in Géotechnique, Vol. 61 N° 5 (Mai 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 5 (Mai 2011) . - pp. 387–407 Titre : Modelling the response of Lechago earth and rockfill dam Type de document : texte imprimé Auteurs : E. E. Alonso, Auteur ; S. Olivella, Auteur ; A. Soriano, Auteur Année de publication : 2011 Article en page(s) : pp. 387–407 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Field  instrumentation  Compaction  Numerical  modelling  Dams  Case  history Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Lechago dam (Teruel, Spain) is a 40 m high zoned earth and rockfill dam sitting on soft continental deltaic deposits. A relatively narrow central clay core is stabilised by wide rockfill shoulders. The dam was well instrumented and continuous records of stress development, pore-water pressures and vertical displacements are available for the construction period. Compaction conditions were followed by means of laboratory and in situ control tests. Core clay material was investigated by means of tests performed on compacted specimens of tertiary clays. Rockfill samples were excavated in outcrops of highly fractured Cambrian quartzitic shale. A testing programme on compacted rockfill gravels was conducted under relative humidity control in a large-diameter oedometer and triaxial cells. A coupled finite-element model has been developed to analyse the tests performed and dam behaviour during construction. Model predictions, essentially based on laboratory tests, are compared with measurements during construction. The predicted response of the dam under an assumed programme of impounding is also given. In the future, once impounding occurs, it will be possible to compare these predictions with actual dam performance. The paper provides an integrated description of the dam design, construction and early behaviour. It presents a procedure to interpret available data (laboratory as well as in situ data) on compacted materials from the perspective of modern constitutive models. It also provides an evaluation of the capabilities of advanced numerical tools to reproduce the measured dam behaviour. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.sip11.p.013 [article] Modelling the response of Lechago earth and rockfill dam [texte imprimé] / E. E. Alonso, Auteur ; S. Olivella, Auteur ; A. Soriano, Auteur . - 2011 . - pp. 387–407. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 5 (Mai 2011) . - pp. 387–407 Mots-clés : Field  instrumentation  Compaction  Numerical  modelling  Dams  Case  history Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Lechago dam (Teruel, Spain) is a 40 m high zoned earth and rockfill dam sitting on soft continental deltaic deposits. A relatively narrow central clay core is stabilised by wide rockfill shoulders. The dam was well instrumented and continuous records of stress development, pore-water pressures and vertical displacements are available for the construction period. Compaction conditions were followed by means of laboratory and in situ control tests. Core clay material was investigated by means of tests performed on compacted specimens of tertiary clays. Rockfill samples were excavated in outcrops of highly fractured Cambrian quartzitic shale. A testing programme on compacted rockfill gravels was conducted under relative humidity control in a large-diameter oedometer and triaxial cells. A coupled finite-element model has been developed to analyse the tests performed and dam behaviour during construction. Model predictions, essentially based on laboratory tests, are compared with measurements during construction. The predicted response of the dam under an assumed programme of impounding is also given. In the future, once impounding occurs, it will be possible to compare these predictions with actual dam performance. The paper provides an integrated description of the dam design, construction and early behaviour. It presents a procedure to interpret available data (laboratory as well as in situ data) on compacted materials from the perspective of modern constitutive models. It also provides an evaluation of the capabilities of advanced numerical tools to reproduce the measured dam behaviour. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.sip11.p.013

Predicting the behavior of an earth and rockfill dam under construction / L. M. Costa in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 7 (Juillet 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 851–862 Titre : Predicting the behavior of an earth and rockfill dam under construction Type de document : texte imprimé Auteurs : L. M. Costa, Auteur ; E. E. Alonso, Auteur Année de publication : 2009 Article en page(s) : pp. 851–862 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Dams  Rockfill  Dam  construction  Soil  compaction  Unsaturated  soils  Finite  element  method  Predictions Résumé : This paper presents an application of a coupled hydromechanical formulation for compacted and rockfill materials to simulate the construction and impoundment of a zoned earth dam. The constitutive relation used to model the mechanical behavior of the shoulder, filter and core materials is the Barcelona Basic Model for unsaturated materials. The hydraulic behavior of dam materials requires the specification of their water retention characteristics and their permeabilities, which will be expressed as a function of porosity and degree of saturation. The model was used in the design stage of Lechago’s dam (Teruel, Spain), currently under construction. Soil parameters were obtained by laboratory tests performed on materials to be used in the dam. The step-by-step construction (following the sequence construction of nine horizontal layers, besides the downstream preloading layers) and subsequent impounding of the reservoir was simulated in a prediction exercise, which will be hopefully confronted with actual construction measurements in the near future. A parametric study was also performed to evaluate the effects of the compaction water content of the core material on the behavior of the dam. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000058 [article] Predicting the behavior of an earth and rockfill dam under construction [texte imprimé] / L. M. Costa, Auteur ; E. E. Alonso, Auteur . - 2009 . - pp. 851–862. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 851–862 Mots-clés : Dams  Rockfill  Dam  construction  Soil  compaction  Unsaturated  soils  Finite  element  method  Predictions Résumé : This paper presents an application of a coupled hydromechanical formulation for compacted and rockfill materials to simulate the construction and impoundment of a zoned earth dam. The constitutive relation used to model the mechanical behavior of the shoulder, filter and core materials is the Barcelona Basic Model for unsaturated materials. The hydraulic behavior of dam materials requires the specification of their water retention characteristics and their permeabilities, which will be expressed as a function of porosity and degree of saturation. The model was used in the design stage of Lechago’s dam (Teruel, Spain), currently under construction. Soil parameters were obtained by laboratory tests performed on materials to be used in the dam. The step-by-step construction (following the sequence construction of nine horizontal layers, besides the downstream preloading layers) and subsequent impounding of the reservoir was simulated in a prediction exercise, which will be hopefully confronted with actual construction measurements in the near future. A parametric study was also performed to evaluate the effects of the compaction water content of the core material on the behavior of the dam. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000058

Progressive failure of Aznalcóllar dam using the material point method / F. Zabala in Géotechnique, Vol. 61 N° 9 (Septembre 2011) 

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