Dépouillements

Drained cyclic behaviour of loose Dogs Bay sand / S. Lopez-Querol in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 281–289 Titre : Drained cyclic behaviour of loose Dogs Bay sand Type de document : texte imprimé Auteurs : S. Lopez-Querol, Auteur ; M. R. Coop, Auteur Année de publication : 2012 Article en page(s) : pp. 281–289 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Calcareous  soils  Compaction  Dynamics  Sands Résumé : The results of drained cyclic triaxial tests performed on Dogs Bay sand (a carbonate sand) are discussed in this paper. For this sand it has been previously demonstrated that the critical state exists and is unique. The relationship between volumetric strains due to cyclic loading and the critical state of this material under monotonic conditions is explored here. Drained cyclic tests on loose samples have been carried out, applying different amplitudes of cyclic loading for samples that generally have initial states on the wet side of critical. The trends of behaviour are summarised, pointing out the relationship between initial state parameter, amplitude of cyclic loading and final change in the state parameter at equilibrium. Experimental evidence is also given to demonstrate that the sand has a memory of the volumetric strain that has previously occurred when different patterns of cyclic loading are consecutively applied and equilibrium has not been reached. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Drained cyclic behaviour of loose Dogs Bay sand [texte imprimé] / S. Lopez-Querol, Auteur ; M. R. Coop, Auteur . - 2012 . - pp. 281–289. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 281–289 Mots-clés : Calcareous  soils  Compaction  Dynamics  Sands Résumé : The results of drained cyclic triaxial tests performed on Dogs Bay sand (a carbonate sand) are discussed in this paper. For this sand it has been previously demonstrated that the critical state exists and is unique. The relationship between volumetric strains due to cyclic loading and the critical state of this material under monotonic conditions is explored here. Drained cyclic tests on loose samples have been carried out, applying different amplitudes of cyclic loading for samples that generally have initial states on the wet side of critical. The trends of behaviour are summarised, pointing out the relationship between initial state parameter, amplitude of cyclic loading and final change in the state parameter at equilibrium. Experimental evidence is also given to demonstrate that the sand has a memory of the volumetric strain that has previously occurred when different patterns of cyclic loading are consecutively applied and equilibrium has not been reached. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

Compression behaviour of natural and reconstituted clays / Z.-S. Hong in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 291–301 Titre : Compression behaviour of natural and reconstituted clays Type de document : texte imprimé Auteurs : Z.-S. Hong, Auteur ; L.-L. Zeng, Auteur ; Y.-J. Cui, Auteur Année de publication : 2012 Article en page(s) : pp. 291–301 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Clays  Compressibility  Laboratory  tests Résumé : The intercept of the l o g ( 1 + e ) – l o g σ ′ v straight line is introduced to describe the effect of the starting point on the compressibility of natural and reconstituted clays. It is found that when the effective stress exceeds the remoulded yield stress, the compression behaviour of reconstituted clays is controlled solely by the water content at the remoulded yield stress and the liquid limit. Comparison of the compression behaviour of natural and reconstituted clays indicates that their difference in compressibility is caused by soil structure and the difference in water content at the compression starting point. The compression behaviour of natural clays can be classified into three regimes: (a) the pre-yield regime, characterised by small compressibility, with soil structure restraining the deformation up to the consolidation yield stress; (b) the transitional regime, characterised by a gradual loss of soil structure when the effective stress is between the consolidation yield stress and the transitional stress; and (c) the post-transitional regime, characterised by the same change law in compression behaviour as reconstituted clays when the effective stress is higher than the transitional stress. For the investigated clays, the transitional stress is 1·0–3·5 times the consolidation yield stress. The compression index varies solely with the void ratio at an effective stress of 1·0 kPa for both natural clays in the post-transitional regime and reconstituted clays when the effective stress exceeds the remoulded yield stress, and when compressed in such cases the compression curves of both natural clays and reconstituted clays can be well normalised to a unique line using the void index. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Compression behaviour of natural and reconstituted clays [texte imprimé] / Z.-S. Hong, Auteur ; L.-L. Zeng, Auteur ; Y.-J. Cui, Auteur . - 2012 . - pp. 291–301. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 291–301 Mots-clés : Clays  Compressibility  Laboratory  tests Résumé : The intercept of the l o g ( 1 + e ) – l o g σ ′ v straight line is introduced to describe the effect of the starting point on the compressibility of natural and reconstituted clays. It is found that when the effective stress exceeds the remoulded yield stress, the compression behaviour of reconstituted clays is controlled solely by the water content at the remoulded yield stress and the liquid limit. Comparison of the compression behaviour of natural and reconstituted clays indicates that their difference in compressibility is caused by soil structure and the difference in water content at the compression starting point. The compression behaviour of natural clays can be classified into three regimes: (a) the pre-yield regime, characterised by small compressibility, with soil structure restraining the deformation up to the consolidation yield stress; (b) the transitional regime, characterised by a gradual loss of soil structure when the effective stress is between the consolidation yield stress and the transitional stress; and (c) the post-transitional regime, characterised by the same change law in compression behaviour as reconstituted clays when the effective stress is higher than the transitional stress. For the investigated clays, the transitional stress is 1·0–3·5 times the consolidation yield stress. The compression index varies solely with the void ratio at an effective stress of 1·0 kPa for both natural clays in the post-transitional regime and reconstituted clays when the effective stress exceeds the remoulded yield stress, and when compressed in such cases the compression curves of both natural clays and reconstituted clays can be well normalised to a unique line using the void index. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

On the role of bond breakage due to unloading in the behaviour of weak sandstones / G. Alvarado in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 303–316 Titre : On the role of bond breakage due to unloading in the behaviour of weak sandstones Type de document : texte imprimé Auteurs : G. Alvarado, Auteur ; M. R. Coop, Auteur ; S. Willson, Auteur Année de publication : 2012 Article en page(s) : pp. 303–316 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Fabric/structure  of  soils  Laboratory  tests  Rocks/rock  mechanics  Sands  Soft  rocks  Stiffness Résumé : A laboratory investigation was made of the effects of isotropic unloading on the mechanical behaviour of cemented sandstones, modelling in a simple way the influence of sampling on hydrocarbon reservoir sandstones that have been cemented at depth. Artificial samples of sandstone were created by allowing a cement to hydrate while a sand sample was under a high confining stress in a triaxial apparatus. Comparisons were then made between the behaviour of samples that had been unloaded to zero confining stress with that of samples tested at stress levels around that during cementing. It was found that the isotropic unloading damaged the cement, which had a significant effect on the small-strain and yielding behaviour but not on the strength and large-strain behaviour. Comparisons were also made with tests on natural samples of reservoir and analogue sandstones, and it was found that the artificial sandstone had reproduced the key elements of their behaviour. The intrinsic properties of all of the sandstones tested were found to be similar, although there were significant differences in the peak strengths and gross yielding envelopes. Cement content was found not to be the sole factor that influenced the peak and gross yield envelopes, and significant anisotropy was also revealed in one sandstone. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] On the role of bond breakage due to unloading in the behaviour of weak sandstones [texte imprimé] / G. Alvarado, Auteur ; M. R. Coop, Auteur ; S. Willson, Auteur . - 2012 . - pp. 303–316. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 303–316 Mots-clés : Fabric/structure  of  soils  Laboratory  tests  Rocks/rock  mechanics  Sands  Soft  rocks  Stiffness Résumé : A laboratory investigation was made of the effects of isotropic unloading on the mechanical behaviour of cemented sandstones, modelling in a simple way the influence of sampling on hydrocarbon reservoir sandstones that have been cemented at depth. Artificial samples of sandstone were created by allowing a cement to hydrate while a sand sample was under a high confining stress in a triaxial apparatus. Comparisons were then made between the behaviour of samples that had been unloaded to zero confining stress with that of samples tested at stress levels around that during cementing. It was found that the isotropic unloading damaged the cement, which had a significant effect on the small-strain and yielding behaviour but not on the strength and large-strain behaviour. Comparisons were also made with tests on natural samples of reservoir and analogue sandstones, and it was found that the artificial sandstone had reproduced the key elements of their behaviour. The intrinsic properties of all of the sandstones tested were found to be similar, although there were significant differences in the peak strengths and gross yielding envelopes. Cement content was found not to be the sole factor that influenced the peak and gross yield envelopes, and significant anisotropy was also revealed in one sandstone. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

Centrifuge study of capacity of a skirted foundation under eccentric transient and sustained uplift / H. E. Acosta-Martinez in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 317–328 Titre : Centrifuge study of capacity of a skirted foundation under eccentric transient and sustained uplift Type de document : texte imprimé Auteurs : H. E. Acosta-Martinez, Auteur ; S. Gourvenec, Auteur ; M. F. Randolph, Auteur Année de publication : 2012 Article en page(s) : pp. 317–328 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Bearing  capacity  Clays  Foundations  Model  tests  Offshore  engineering  Pore  pressures  Time  dependence Résumé : Environmental and buoyancy forces impart overturning moments and potentially direct uplift to offshore foundation systems. Shallow skirted foundations are an attractive design solution, as negative excess pore pressures developed within the soil plug provide temporary uplift resistance. This paper presents the results of beam centrifuge tests on a shallow skirted foundation in a lightly overconsolidated clay under eccentric transient and sustained uplift. When compared with the response under concentric uplift, the experimental results show a reduction in capacity and an increase in the rate of degradation of capacity under sustained loading. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Centrifuge study of capacity of a skirted foundation under eccentric transient and sustained uplift [texte imprimé] / H. E. Acosta-Martinez, Auteur ; S. Gourvenec, Auteur ; M. F. Randolph, Auteur . - 2012 . - pp. 317–328. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 317–328 Mots-clés : Bearing  capacity  Clays  Foundations  Model  tests  Offshore  engineering  Pore  pressures  Time  dependence Résumé : Environmental and buoyancy forces impart overturning moments and potentially direct uplift to offshore foundation systems. Shallow skirted foundations are an attractive design solution, as negative excess pore pressures developed within the soil plug provide temporary uplift resistance. This paper presents the results of beam centrifuge tests on a shallow skirted foundation in a lightly overconsolidated clay under eccentric transient and sustained uplift. When compared with the response under concentric uplift, the experimental results show a reduction in capacity and an increase in the rate of degradation of capacity under sustained loading. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

Response evaluation of horizontally loaded pile groups in clayey soils / E.M. Comodromos in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 329–339 Titre : Response evaluation of horizontally loaded pile groups in clayey soils Type de document : texte imprimé Auteurs : E.M. Comodromos, Auteur ; M.C. Papadopoulou, Auteur Année de publication : 2012 Article en page(s) : pp. 329–339 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Numerical  modelling  Piles  Soil/structure  inter-action Résumé : The aim of this paper is to investigate the behaviour of laterally loaded pile groups with a rigid head, and correlate the response of a pile group to that of a single pile. For this purpose, a computationally intensive study using three-dimensional non-linear numerical analysis was carried out for different pile group arrangements in clayey soils. The responses of the pile groups were compared with that of the single pile, and the variation of the displacement amplification factor R a was then quantified. The influence of the number of piles, the spacing and the deflection level on the group response is discussed. A previously proposed relationship for predicting the response of a pile group, based on its configuration and the response of a single pile, has been modified to allow for soil shear strength that was found to affect the group response. The modified relationship provides a reasonable prediction for various group configurations in clayey soils. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Response evaluation of horizontally loaded pile groups in clayey soils [texte imprimé] / E.M. Comodromos, Auteur ; M.C. Papadopoulou, Auteur . - 2012 . - pp. 329–339. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 329–339 Mots-clés : Numerical  modelling  Piles  Soil/structure  inter-action Résumé : The aim of this paper is to investigate the behaviour of laterally loaded pile groups with a rigid head, and correlate the response of a pile group to that of a single pile. For this purpose, a computationally intensive study using three-dimensional non-linear numerical analysis was carried out for different pile group arrangements in clayey soils. The responses of the pile groups were compared with that of the single pile, and the variation of the displacement amplification factor R a was then quantified. The influence of the number of piles, the spacing and the deflection level on the group response is discussed. A previously proposed relationship for predicting the response of a pile group, based on its configuration and the response of a single pile, has been modified to allow for soil shear strength that was found to affect the group response. The modified relationship provides a reasonable prediction for various group configurations in clayey soils. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

Simple approach to predicting ground displacements caused by tunnelling in undrained anisotropic elastic soil / A. M. Puzrin in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 341–352 Titre : Simple approach to predicting ground displacements caused by tunnelling in undrained anisotropic elastic soil Type de document : texte imprimé Auteurs : A. M. Puzrin, Auteur ; J. B. Burland, Auteur ; J.R. Standing, Auteur Année de publication : 2012 Article en page(s) : pp. 341–352 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Anisotrop  Settlement  Tunnels Résumé : An attempt to develop a kinematically based approach to predicting ground settlements due to tunnelling is represented, by using the more reliable data of the commonly observed settlement troughs, rather than imposing the boundary conditions on the tunnel surface, which have a high level of uncertainty. The anisotropic elastic model used in this work is highly simplified, and the resulting analytical solution is of an approximate nature. Nevertheless, it seems to provide good agreement with both the shape and the magnitude of the observed settlement trough. Based on this solution, a modification is proposed for the widely used empirical Gaussian curve, by correlating the trough width parameter K with the ratio between the two anisotropic shear moduli, G hh/G vh. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Simple approach to predicting ground displacements caused by tunnelling in undrained anisotropic elastic soil [texte imprimé] / A. M. Puzrin, Auteur ; J. B. Burland, Auteur ; J.R. Standing, Auteur . - 2012 . - pp. 341–352. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 341–352 Mots-clés : Anisotrop  Settlement  Tunnels Résumé : An attempt to develop a kinematically based approach to predicting ground settlements due to tunnelling is represented, by using the more reliable data of the commonly observed settlement troughs, rather than imposing the boundary conditions on the tunnel surface, which have a high level of uncertainty. The anisotropic elastic model used in this work is highly simplified, and the resulting analytical solution is of an approximate nature. Nevertheless, it seems to provide good agreement with both the shape and the magnitude of the observed settlement trough. Based on this solution, a modification is proposed for the widely used empirical Gaussian curve, by correlating the trough width parameter K with the ratio between the two anisotropic shear moduli, G hh/G vh. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

Numerical simulation of pressure-controlled cavity expansion process in clay at constant volumetric expansion rate / A.T. Yeung in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 353–357 Titre : Numerical simulation of pressure-controlled cavity expansion process in clay at constant volumetric expansion rate Type de document : texte imprimé Auteurs : A.T. Yeung, Auteur ; S. K. A. Au, Auteur ; T.H. Lam, Auteur Année de publication : 2012 Article en page(s) : pp. 353–357 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Clays  Compaction  Grouting  Laboratory  tests  Numerical  modelling  Pore  pressures Résumé : The cavity expansion theory is being applied to describe many geotechnical engineering processes. Many of these processes are controlled by the cavity volumetric expansion rate in practice. As soil is not an elastic material, the injection pressure is a non-linear function of the cavity volume, rendering it very difficult to produce the appropriate time history of injection pressure so that the controlled cavity volumetric expansion rate can be simulated. In this technical note, an algorithm to develop the time history of injection pressure using appropriate soil properties to generate the required cavity volumetric expansion rate in clay is presented. The simulation and experimental results of a series of laboratory-scale compaction grouting experiments are presented as an example to demonstrate the validity of the approach. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Numerical simulation of pressure-controlled cavity expansion process in clay at constant volumetric expansion rate [texte imprimé] / A.T. Yeung, Auteur ; S. K. A. Au, Auteur ; T.H. Lam, Auteur . - 2012 . - pp. 353–357. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 353–357 Mots-clés : Clays  Compaction  Grouting  Laboratory  tests  Numerical  modelling  Pore  pressures Résumé : The cavity expansion theory is being applied to describe many geotechnical engineering processes. Many of these processes are controlled by the cavity volumetric expansion rate in practice. As soil is not an elastic material, the injection pressure is a non-linear function of the cavity volume, rendering it very difficult to produce the appropriate time history of injection pressure so that the controlled cavity volumetric expansion rate can be simulated. In this technical note, an algorithm to develop the time history of injection pressure using appropriate soil properties to generate the required cavity volumetric expansion rate in clay is presented. The simulation and experimental results of a series of laboratory-scale compaction grouting experiments are presented as an example to demonstrate the validity of the approach. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

Stable inversion of measured V P and V S to estimate porosity in fluid-saturated soils / C.G. Lai in Géotechnique, Vol. 62 N° 4 (Avril 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 359–364 Titre : Stable inversion of measured V P and V S to estimate porosity in fluid-saturated soils Type de document : texte imprimé Auteurs : C.G. Lai, Auteur ; J.G.F. Crempien de la Carrera, Auteur Année de publication : 2012 Article en page(s) : pp. 359–364 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Dynamics  In  situ  testing  Theoretical  analysis Résumé : Porosity is an important state parameter which controls the response of porous materials under both static and dynamic loading. The possibility of determining porosity from direct inversion of V P and V S, which are routinely measured in geophysical prospecting, is appealing. A methodology has been recently proposed and successfully applied to a number of sites and it is based on the apparent insensitivity of porosity on Poisson ratio of the soil skeleton ν SK, which is a priori an unknown quantity. So far, however, the functional dependence of porosity on ν SK has only marginally been investigated and doubts arise regarding whether the method is always applicable. This study attempts to investigate thoroughly the stability of the inversion of measured V S and V P to estimate porosity and to assess the degree of well-posedness of the procedure for all the combinations of V P and V S relevant in real soils. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4# [article] Stable inversion of measured V P and V S to estimate porosity in fluid-saturated soils [texte imprimé] / C.G. Lai, Auteur ; J.G.F. Crempien de la Carrera, Auteur . - 2012 . - pp. 359–364. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 4 (Avril 2012) . - pp. 359–364 Mots-clés : Dynamics  In  situ  testing  Theoretical  analysis Résumé : Porosity is an important state parameter which controls the response of porous materials under both static and dynamic loading. The possibility of determining porosity from direct inversion of V P and V S, which are routinely measured in geophysical prospecting, is appealing. A methodology has been recently proposed and successfully applied to a number of sites and it is based on the apparent insensitivity of porosity on Poisson ratio of the soil skeleton ν SK, which is a priori an unknown quantity. So far, however, the functional dependence of porosity on ν SK has only marginally been investigated and doubts arise regarding whether the method is always applicable. This study attempts to investigate thoroughly the stability of the inversion of measured V S and V P to estimate porosity and to assess the degree of well-posedness of the procedure for all the combinations of V P and V S relevant in real soils. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/issue/geot/62/4#

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