Dépouillements

Modelling diffuse instabilities in sands under drained conditions / A.M. Ramos in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 471 –478 Titre : Modelling diffuse instabilities in sands under drained conditions Type de document : texte imprimé Auteurs : A.M. Ramos, Auteur ; J. E. Andrade, Auteur ; A. Lizcano, Auteur Année de publication : 2012 Article en page(s) : pp. 471 –478 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Sands  Failure  Numerical  modelling  Theoretical  analysis  Plasticity Résumé : This paper presents a criterion for detecting diffuse (homogeneous) instabilities in granular soils sheared under fully drained conditions. The criterion is based on bifurcation theory and applied to elasto-plasticity by allowing multiple incremental solutions in elasto-plastic soils, physically losing controllability of stress boundary conditions. Drained diffuse instabilities are poorly understood, and are induced by kinematic modes different from those observed in shear bands and liquefaction instabilities. Unlike shear bands, diffuse instabilities occur under fairly homogenous deformation modes and, unlike liquefaction, drained instabilities are not generated by the excess pore pressures. Recent experiments under drained constant shear report sudden homogeneous instabilities in samples of relatively dense and loose sands. The criterion presented in this paper is used in conjunction with an elasto-plasticity model for sands to predict and explain these reported drained instabilities. From a practical standpoint, these developments serve to expand the repertoire of potential instabilities that occur well before failure, and which have been reported in case studies of puzzling slope instability failures under fully drained conditions. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.109 [article] Modelling diffuse instabilities in sands under drained conditions [texte imprimé] / A.M. Ramos, Auteur ; J. E. Andrade, Auteur ; A. Lizcano, Auteur . - 2012 . - pp. 471 –478. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 471 –478 Mots-clés : Sands  Failure  Numerical  modelling  Theoretical  analysis  Plasticity Résumé : This paper presents a criterion for detecting diffuse (homogeneous) instabilities in granular soils sheared under fully drained conditions. The criterion is based on bifurcation theory and applied to elasto-plasticity by allowing multiple incremental solutions in elasto-plastic soils, physically losing controllability of stress boundary conditions. Drained diffuse instabilities are poorly understood, and are induced by kinematic modes different from those observed in shear bands and liquefaction instabilities. Unlike shear bands, diffuse instabilities occur under fairly homogenous deformation modes and, unlike liquefaction, drained instabilities are not generated by the excess pore pressures. Recent experiments under drained constant shear report sudden homogeneous instabilities in samples of relatively dense and loose sands. The criterion presented in this paper is used in conjunction with an elasto-plasticity model for sands to predict and explain these reported drained instabilities. From a practical standpoint, these developments serve to expand the repertoire of potential instabilities that occur well before failure, and which have been reported in case studies of puzzling slope instability failures under fully drained conditions. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.109

Failure of a trial embankment on peat in booneschans, the netherlands / C. Zwanenburg in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 479 –490 Titre : Failure of a trial embankment on peat in booneschans, the netherlands Type de document : texte imprimé Auteurs : C. Zwanenburg, Auteur ; E.J. Den Haan, Auteur ; G.A.M. Kruse, Auteur Année de publication : 2012 Article en page(s) : pp. 479 –490 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Organic  soils  Full-scale  tests  Failure  Embankments  Laboratory  tests Résumé : A trial embankment 6 m high was built on peat in the Netherlands, and brought to failure. The aim was to test whether innovative sensor technology could detect incipient failure in time. However, the data generated also made it possible to conduct a geotechnical assessment of stability. The paper discusses the relation between the parameters derived from laboratory tests, field measurements and behaviour observed in the field. Problems encountered in the standard triaxial testing of peat samples are discussed, as the samples tend to fail in tension. A trial pit through the failed embankment showed that there were wide tension cracks in the peat layer, indicating that the peat layer failed in tension, at least locally. However, horizontal movement dominates the overall failure mechanism. As an alternative to triaxial testing, direct simple shear (DSS) testing for the assessment of peat parameters is considered. The results of the DSS tests correspond well with field measurements and the back-analysis of the failure. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.094 [article] Failure of a trial embankment on peat in booneschans, the netherlands [texte imprimé] / C. Zwanenburg, Auteur ; E.J. Den Haan, Auteur ; G.A.M. Kruse, Auteur . - 2012 . - pp. 479 –490. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 479 –490 Mots-clés : Organic  soils  Full-scale  tests  Failure  Embankments  Laboratory  tests Résumé : A trial embankment 6 m high was built on peat in the Netherlands, and brought to failure. The aim was to test whether innovative sensor technology could detect incipient failure in time. However, the data generated also made it possible to conduct a geotechnical assessment of stability. The paper discusses the relation between the parameters derived from laboratory tests, field measurements and behaviour observed in the field. Problems encountered in the standard triaxial testing of peat samples are discussed, as the samples tend to fail in tension. A trial pit through the failed embankment showed that there were wide tension cracks in the peat layer, indicating that the peat layer failed in tension, at least locally. However, horizontal movement dominates the overall failure mechanism. As an alternative to triaxial testing, direct simple shear (DSS) testing for the assessment of peat parameters is considered. The results of the DSS tests correspond well with field measurements and the back-analysis of the failure. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.P.094

Evolution of stabilised creeping landslides / A. M. Puzrin in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 491–501 Titre : Evolution of stabilised creeping landslides Type de document : texte imprimé Auteurs : A. M. Puzrin, Auteur ; A. Schmid, Auteur Année de publication : 2012 Article en page(s) : pp. 491–501 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Creep  Soil  stabilisation  Landslides  Case  history Résumé : A simple analytical model is proposed to quantify evolution of a creeping landslide stabilised by a retaining wall, or by a natural barrier at the bottom of the sliding mass. Development in time of both the landslide displacements and the earth pressure acting on the retaining structure is obtained in the closed form, with the latter given by the classical Terzaghi expression for the average degree of consolidation. Depending on the value of the long-term safety factor, the landslide either eventually slows down, asymptotically approaching final displacements, or the soil behind the retaining wall comes to a passive failure, followed by a post-failure evolution of the landslide. The model is capable of quantifying both scenarios, with some of its features successfully validated against the monitoring and geotechnical data from the two case studies: the Combe Chopin and Ganter landslides in Switzerland. For the Combe Chopin landslide, which came to a standstill, the model has demonstrated its ability to predict final downhill displacements and their development in time. For the Ganter landslide, which failed and achieved steady-state velocity, the model correctly predicted the long-term landslide evolution and the effects of drainage and erosion on the displacement rates. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.041 [article] Evolution of stabilised creeping landslides [texte imprimé] / A. M. Puzrin, Auteur ; A. Schmid, Auteur . - 2012 . - pp. 491–501. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 491–501 Mots-clés : Creep  Soil  stabilisation  Landslides  Case  history Résumé : A simple analytical model is proposed to quantify evolution of a creeping landslide stabilised by a retaining wall, or by a natural barrier at the bottom of the sliding mass. Development in time of both the landslide displacements and the earth pressure acting on the retaining structure is obtained in the closed form, with the latter given by the classical Terzaghi expression for the average degree of consolidation. Depending on the value of the long-term safety factor, the landslide either eventually slows down, asymptotically approaching final displacements, or the soil behind the retaining wall comes to a passive failure, followed by a post-failure evolution of the landslide. The model is capable of quantifying both scenarios, with some of its features successfully validated against the monitoring and geotechnical data from the two case studies: the Combe Chopin and Ganter landslides in Switzerland. For the Combe Chopin landslide, which came to a standstill, the model has demonstrated its ability to predict final downhill displacements and their development in time. For the Ganter landslide, which failed and achieved steady-state velocity, the model correctly predicted the long-term landslide evolution and the effects of drainage and erosion on the displacement rates. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.041

Thermo-mechanical behaviour of energy piles / B. L. Amatya in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 503 –519 Titre : Thermo-mechanical behaviour of energy piles Type de document : texte imprimé Auteurs : B. L. Amatya, Auteur ; K. Soga, Auteur ; P. J. Bourne-Webb, Auteur Année de publication : 2012 Article en page(s) : pp. 503 –519 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Field  instrumentation  Full-scale  tests  Piles  Design  Temperature  effects  Stress  analysis Résumé : Energy piles are an effective and economic means of using geothermal energy resources for heating and cooling buildings, contributing to legislative requirements for renewable energy in new construction. While such piles have been used for around 25 years with no apparent detrimental effect, there is limited understanding of their thermo-mechanical behaviour. This paper synthesises the results from three published field studies and illustrates some of the engineering behaviour of such piles during heating and cooling. Simplified load transfer mechanisms for a single pile subjected to pure thermal loadings (i.e. without mechanical load) and combined thermo-mechanical loadings have been developed and are used to interpret the field data with regard to change in axial stress and shaft friction during heating and cooling. The effect of end restraint and ground conditions on the thermo-mechanical response of energy piles is discussed. Values of change in axial stress and mobilised shaft friction due to thermal effects that may be useful in the design of energy piles are presented. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.116 [article] Thermo-mechanical behaviour of energy piles [texte imprimé] / B. L. Amatya, Auteur ; K. Soga, Auteur ; P. J. Bourne-Webb, Auteur . - 2012 . - pp. 503 –519. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 503 –519 Mots-clés : Field  instrumentation  Full-scale  tests  Piles  Design  Temperature  effects  Stress  analysis Résumé : Energy piles are an effective and economic means of using geothermal energy resources for heating and cooling buildings, contributing to legislative requirements for renewable energy in new construction. While such piles have been used for around 25 years with no apparent detrimental effect, there is limited understanding of their thermo-mechanical behaviour. This paper synthesises the results from three published field studies and illustrates some of the engineering behaviour of such piles during heating and cooling. Simplified load transfer mechanisms for a single pile subjected to pure thermal loadings (i.e. without mechanical load) and combined thermo-mechanical loadings have been developed and are used to interpret the field data with regard to change in axial stress and shaft friction during heating and cooling. The effect of end restraint and ground conditions on the thermo-mechanical response of energy piles is discussed. Values of change in axial stress and mobilised shaft friction due to thermal effects that may be useful in the design of energy piles are presented. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.116

Dynamic Winkler modulus for axially loaded piles / G. Anoyatis in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 521 –536 Titre : Dynamic Winkler modulus for axially loaded piles Type de document : texte imprimé Auteurs : G. Anoyatis, Auteur ; G. Mylonakis, Auteur Année de publication : 2012 Article en page(s) : pp. 521 –536 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Soil/structure  interaction  Dynamics  Theoretical  analysis  Piles  Elasticity  Vibration Résumé : The problem of axial dynamic pile–soil interaction and its analytical representation using the concept of a dynamic Winkler support are revisited. It is shown that depth- and frequency-dependent Winkler springs and dashpots, obtained by dividing the complex-valued side friction and the corresponding displacements along the pile, may faithfully describe the interaction effect, contrary to the common perception that the Winkler concept is always approximate. An axisymmetric wave solution, based on linear elastodynamic theory, is then derived for the harmonic steady-state response of finite and infinitely long piles in a homogeneous viscoelastic soil stratum, with the former type of pile resting on rigid rock. The pile is modelled as a continuum, without the restrictions associated with strength-of-materials approximations. Closed-form solutions are obtained for: (a) the displacement field in the soil and the pile; (b) the stiffness and damping (‘impedance') coefficients at the pile head; (c) the actual, depth-dependent, dynamic Winkler moduli; and (d) a set of fictitious, depth-independent Winkler moduli to match the dynamic response at the pile head. Results are presented in terms of dimensionless graphs, tables and simple equations that provide insight into the complex physics of the problem. The predictions of the model compare favourably with existing solutions, while new results and simple design-oriented formulae are presented. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.052 [article] Dynamic Winkler modulus for axially loaded piles [texte imprimé] / G. Anoyatis, Auteur ; G. Mylonakis, Auteur . - 2012 . - pp. 521 –536. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 521 –536 Mots-clés : Soil/structure  interaction  Dynamics  Theoretical  analysis  Piles  Elasticity  Vibration Résumé : The problem of axial dynamic pile–soil interaction and its analytical representation using the concept of a dynamic Winkler support are revisited. It is shown that depth- and frequency-dependent Winkler springs and dashpots, obtained by dividing the complex-valued side friction and the corresponding displacements along the pile, may faithfully describe the interaction effect, contrary to the common perception that the Winkler concept is always approximate. An axisymmetric wave solution, based on linear elastodynamic theory, is then derived for the harmonic steady-state response of finite and infinitely long piles in a homogeneous viscoelastic soil stratum, with the former type of pile resting on rigid rock. The pile is modelled as a continuum, without the restrictions associated with strength-of-materials approximations. Closed-form solutions are obtained for: (a) the displacement field in the soil and the pile; (b) the stiffness and damping (‘impedance') coefficients at the pile head; (c) the actual, depth-dependent, dynamic Winkler moduli; and (d) a set of fictitious, depth-independent Winkler moduli to match the dynamic response at the pile head. Results are presented in terms of dimensionless graphs, tables and simple equations that provide insight into the complex physics of the problem. The predictions of the model compare favourably with existing solutions, while new results and simple design-oriented formulae are presented. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.052

Numerical model of electro-osmotic consolidation in clay / L. Hu in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 537 –541 Titre : Numerical model of electro-osmotic consolidation in clay Type de document : texte imprimé Auteurs : L. Hu, Auteur ; W. Wu, Auteur ; H. Wu, Auteur Année de publication : 2012 Article en page(s) : pp. 537 –541 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Numerical  modelling  Electrokinetics  Consolidation  Pore  pressures Résumé : Electro-osmotic consolidation is a unique soil improvement technique. A physics-based model for electro-osmotic consolidation is proposed, in which Biot's consolidation equation is coupled with the electro-osmotic flow and control equation for an electrical field, and the displacement of soil mass and pore-water pressure can be obtained. Furthermore, the non-linear variation of the mechanical and electrical properties of the soil mass during consolidation is incorporated into the model. The numerical solution agrees well with the analytical solution. The developed model can predict the ground displacement and provide useful data for the design of an electro-osmosis treatment system. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.008 [article] Numerical model of electro-osmotic consolidation in clay [texte imprimé] / L. Hu, Auteur ; W. Wu, Auteur ; H. Wu, Auteur . - 2012 . - pp. 537 –541. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 537 –541 Mots-clés : Numerical  modelling  Electrokinetics  Consolidation  Pore  pressures Résumé : Electro-osmotic consolidation is a unique soil improvement technique. A physics-based model for electro-osmotic consolidation is proposed, in which Biot's consolidation equation is coupled with the electro-osmotic flow and control equation for an electrical field, and the displacement of soil mass and pore-water pressure can be obtained. Furthermore, the non-linear variation of the mechanical and electrical properties of the soil mass during consolidation is incorporated into the model. The numerical solution agrees well with the analytical solution. The developed model can predict the ground displacement and provide useful data for the design of an electro-osmosis treatment system. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.008

Failure envelope of artificially cemented sand / N. C. Consoli in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 543 –547 Titre : Failure envelope of artificially cemented sand Type de document : texte imprimé Auteurs : N. C. Consoli, Auteur ; R. Caberlon Cruz, Auteur ; B. S. Consoli, Auteur Année de publication : 2012 Article en page(s) : pp. 543 –547 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Sands  Ground  improvement  Laboratory  tests  Failure  Reinforced  soils  Shear  strength  Soil  stabilisation Résumé : The present research aims to quantify the influence of the amount of cement, the porosity and the porosity/cement ratio in the assessment of tensile strength and triaxial strength of an artificially cemented sand, as well as in the development of a failure criterion to represent the non-linear failure envelopes of the studied sand–cement mixtures. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.037 [article] Failure envelope of artificially cemented sand [texte imprimé] / N. C. Consoli, Auteur ; R. Caberlon Cruz, Auteur ; B. S. Consoli, Auteur . - 2012 . - pp. 543 –547. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 543 –547 Mots-clés : Sands  Ground  improvement  Laboratory  tests  Failure  Reinforced  soils  Shear  strength  Soil  stabilisation Résumé : The present research aims to quantify the influence of the amount of cement, the porosity and the porosity/cement ratio in the assessment of tensile strength and triaxial strength of an artificially cemented sand, as well as in the development of a failure criterion to represent the non-linear failure envelopes of the studied sand–cement mixtures. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.P.037

Hypoplastic cam-clay model / D. MAšíN in Géotechnique, Vol. 62 N° 6 (Juin 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 549 –553 Titre : Hypoplastic cam-clay model Type de document : texte imprimé Auteurs : D. MAšíN, Auteur Année de publication : 2012 Article en page(s) : pp. 549 –553 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Stiffness  Stress  path  Plasticity  Constitutive  relations  Clays Résumé : A rearrangement of the hypoplastic constitutive equation is proposed that enables the incorporation of an asymptotic state boundary surface of an arbitrary predefined shape into the model, with any corresponding asymptotic strain-rate direction. This opens the way for further development of hypoplastic models. To demonstrate the flexibility of the proposed approach, a hypoplastic equivalent of the modified Cam-clay model is developed. A comparison of the predictions of the elasto-plastic and hypoplastic models reveals the merits of the hypoplastic formulation. Although both models predict the same asymptotic states, hypoplasticity predicts a smooth transition between overconsolidated and normally consolidated states, and thus accounts for the non-linearity of the soil behaviour inside the state boundary surface in a natural manner. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.019 [article] Hypoplastic cam-clay model [texte imprimé] / D. MAšíN, Auteur . - 2012 . - pp. 549 –553. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 6 (Juin 2012) . - pp. 549 –553 Mots-clés : Stiffness  Stress  path  Plasticity  Constitutive  relations  Clays Résumé : A rearrangement of the hypoplastic constitutive equation is proposed that enables the incorporation of an asymptotic state boundary surface of an arbitrary predefined shape into the model, with any corresponding asymptotic strain-rate direction. This opens the way for further development of hypoplastic models. To demonstrate the flexibility of the proposed approach, a hypoplastic equivalent of the modified Cam-clay model is developed. A comparison of the predictions of the elasto-plastic and hypoplastic models reveals the merits of the hypoplastic formulation. Although both models predict the same asymptotic states, hypoplasticity predicts a smooth transition between overconsolidated and normally consolidated states, and thus accounts for the non-linearity of the soil behaviour inside the state boundary surface in a natural manner. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.11.T.019

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