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Journal of geotechnical and geoenvironmental engineering (ASCE) |
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Ajouter le résultat dans votre panierIs matric suction a stress variable? / Ning Lu in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°7 (Juillet 2008)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 899–905
Titre : Is matric suction a stress variable? Type de document : texte imprimé Auteurs : Ning Lu, Auteur Année de publication : 2008 Article en page(s) : pp. 899–905 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Suction Shear strength Unsaturated soils Stress Soil mechanics Résumé : The writer attempts to clarify and address two fundamental questions regarding the appropriate use of matric suction in unsaturated soil mechanics: Is matric suction a stress variable? and Is matric suction a stress state variable? These questions are examined by employing the universally accepted mechanical equilibrium principle, the concept of representative elementary volume (REV) for air-water-solid multiphase porous media, and physical and logical reasoning. It is clarified that matric suction is not a stress variable at a typical air-water-solid REV level, and it can be considered as a stress state variable. However, when it is considered as a stress state variable, there is an interdependency or coupling between matric suction and the net normal stress if both of them are concurrently used to describe the state of stress in unsaturated soils. It is illustrated that the answers to these questions bear important implications for the conceptualization, theorization, and application of unsaturated soil mechanics. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2889 [...] [article] Is matric suction a stress variable? [texte imprimé] / Ning Lu, Auteur . - 2008 . - pp. 899–905.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 899–905
Mots-clés : Suction Shear strength Unsaturated soils Stress Soil mechanics Résumé : The writer attempts to clarify and address two fundamental questions regarding the appropriate use of matric suction in unsaturated soil mechanics: Is matric suction a stress variable? and Is matric suction a stress state variable? These questions are examined by employing the universally accepted mechanical equilibrium principle, the concept of representative elementary volume (REV) for air-water-solid multiphase porous media, and physical and logical reasoning. It is clarified that matric suction is not a stress variable at a typical air-water-solid REV level, and it can be considered as a stress state variable. However, when it is considered as a stress state variable, there is an interdependency or coupling between matric suction and the net normal stress if both of them are concurrently used to describe the state of stress in unsaturated soils. It is illustrated that the answers to these questions bear important implications for the conceptualization, theorization, and application of unsaturated soil mechanics. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2889 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 906–916
Titre : Aging of HDPE Geomembrane in Three Composite Landfill Liner Configurations Type de document : texte imprimé Auteurs : R. Kerry Rowe, Auteur ; S. Rimal, Auteur Année de publication : 2008 Article en page(s) : pp. 906–916 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Durability Geomembranes Landfills Liners Service life Temperature Résumé : Laboratory-accelerated aging experiments conducted to examine the depletion of antioxidant from a geomembrane (GM) underlain by a geosynthetic clay liner (GCL) are described. Three different “protection” layers between the GM and overlying gravel and leachate are examined: (1) A traditional nonwoven geotextile (GT); (2) a GT-GCL; and (3) a GT-sand-GT layer. The GT-GCL protection layer gives an antioxidant depletion rate 0.59 to 0.66 times slower than the GT layer alone. The GT-sand-GT layer gives depletion rates 0.72–0.75 times that of the conventional GT alone. Based on Arrhenius modeling, the time required for depletion of antioxidants at 35°C is estimated to be 65 years for a GM with a GT-GCL protection layer, 50 years for a GT-sand-GT layer, and 40 years for a conventional GT protection layer. These times are all significantly greater than the depletion time for GM immersed in leachate (10 years) for the geomembrane tested. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2890 [...] [article] Aging of HDPE Geomembrane in Three Composite Landfill Liner Configurations [texte imprimé] / R. Kerry Rowe, Auteur ; S. Rimal, Auteur . - 2008 . - pp. 906–916.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 906–916
Mots-clés : Durability Geomembranes Landfills Liners Service life Temperature Résumé : Laboratory-accelerated aging experiments conducted to examine the depletion of antioxidant from a geomembrane (GM) underlain by a geosynthetic clay liner (GCL) are described. Three different “protection” layers between the GM and overlying gravel and leachate are examined: (1) A traditional nonwoven geotextile (GT); (2) a GT-GCL; and (3) a GT-sand-GT layer. The GT-GCL protection layer gives an antioxidant depletion rate 0.59 to 0.66 times slower than the GT layer alone. The GT-sand-GT layer gives depletion rates 0.72–0.75 times that of the conventional GT alone. Based on Arrhenius modeling, the time required for depletion of antioxidants at 35°C is estimated to be 65 years for a GM with a GT-GCL protection layer, 50 years for a GT-sand-GT layer, and 40 years for a conventional GT protection layer. These times are all significantly greater than the depletion time for GM immersed in leachate (10 years) for the geomembrane tested. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2890 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 917–928
Titre : Reliability-based analysis and design of strip footings against bearing capacity failure Type de document : texte imprimé Auteurs : Dalia S. Youssef Abdel Massih, Auteur ; Abdul-Hamid Soubra, Auteur ; Bak Kong Low, Auteur Année de publication : 2008 Article en page(s) : pp. 917–928 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Bearing capacity Earthquake loads Limit analysis Probability Reliability Shallow foundations Punching Failure loads Résumé : This paper presents a reliability-based approach for the analysis and design of a shallow strip footing subjected to a vertical load with or without pseudostatic seismic loading. Only the punching failure mode of the ultimate limit state is studied. The deterministic models are based on the upper-bound method of the limit analysis theory. The random variables used are the soil shear strength parameters and the horizontal seismic coefficient. The Hasofer-Lind reliability index and the failure probability are determined. A sensitivity analysis is also performed. The influence of the applied footing load on the reliability index and the corresponding design point is presented and discussed. It was shown that the negative correlation between the soil shear strength parameters highly increases the reliability of the foundation and that the failure probability is highly influenced by the coefficient of variation of the angle of internal friction of the soil and the horizontal seismic coefficient. For design, an iterative procedure is performed to determine the breadth of the footing for a target failure probability. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2891 [...] [article] Reliability-based analysis and design of strip footings against bearing capacity failure [texte imprimé] / Dalia S. Youssef Abdel Massih, Auteur ; Abdul-Hamid Soubra, Auteur ; Bak Kong Low, Auteur . - 2008 . - pp. 917–928.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 917–928
Mots-clés : Bearing capacity Earthquake loads Limit analysis Probability Reliability Shallow foundations Punching Failure loads Résumé : This paper presents a reliability-based approach for the analysis and design of a shallow strip footing subjected to a vertical load with or without pseudostatic seismic loading. Only the punching failure mode of the ultimate limit state is studied. The deterministic models are based on the upper-bound method of the limit analysis theory. The random variables used are the soil shear strength parameters and the horizontal seismic coefficient. The Hasofer-Lind reliability index and the failure probability are determined. A sensitivity analysis is also performed. The influence of the applied footing load on the reliability index and the corresponding design point is presented and discussed. It was shown that the negative correlation between the soil shear strength parameters highly increases the reliability of the foundation and that the failure probability is highly influenced by the coefficient of variation of the angle of internal friction of the soil and the horizontal seismic coefficient. For design, an iterative procedure is performed to determine the breadth of the footing for a target failure probability. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2891 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 929-937
Titre : Design of foundations on sensitive champlain clay subjected to cyclic loading Type de document : texte imprimé Auteurs : Adel M. Hanna, Auteur ; Khalid Javed, Auteur Année de publication : 2008 Article en page(s) : pp. 929-937 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Clays Stress Pore water pressure Drainage Foundation design Cyclic loads Résumé : Sensitive clay subjected to cyclic loading may experience gradual loss of its shear strength, which may lead to liquefaction. Foundations built on this clay would suffer extensive settlement and significant loss of bearing capacity or perhaps catastrophic failure. This paper presents an experimental investigation on sensitive (Champlain) clay obtained from the city of Rigaud, Quebec (Canada). Consolidation tests, static and cyclic undrained and drained triaxial tests were performed on representative samples of this clay. The objective of this investigation was to examine the influence of the physical and mechanical parameters, which govern the shear strength of sensitive clay subjected to cyclic loading. Based on the results of the present investigation and those available in the literature, it can be reported herein that the undrained response is the most critical for these foundations; furthermore, the preconsolidation pressure is considered as an important parameter in establishing the shear strength of sensitive clay. A design procedure is developed to determine the safe zone for the undrained and drained responses, within which a combination of the cyclic deviator stress and the number of cycles for a given soil/loading/site conditions can achieve a quasielastic resilient state without reaching failure. The proposed design procedure is applicable to all regions around the world, where sensitive clays can be found. Furthermore, this procedure can be adopted to examine the conditions of existing foundations built on sensitive clay at any time during its lifespan. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2892 [...] [article] Design of foundations on sensitive champlain clay subjected to cyclic loading [texte imprimé] / Adel M. Hanna, Auteur ; Khalid Javed, Auteur . - 2008 . - pp. 929-937.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 929-937
Mots-clés : Clays Stress Pore water pressure Drainage Foundation design Cyclic loads Résumé : Sensitive clay subjected to cyclic loading may experience gradual loss of its shear strength, which may lead to liquefaction. Foundations built on this clay would suffer extensive settlement and significant loss of bearing capacity or perhaps catastrophic failure. This paper presents an experimental investigation on sensitive (Champlain) clay obtained from the city of Rigaud, Quebec (Canada). Consolidation tests, static and cyclic undrained and drained triaxial tests were performed on representative samples of this clay. The objective of this investigation was to examine the influence of the physical and mechanical parameters, which govern the shear strength of sensitive clay subjected to cyclic loading. Based on the results of the present investigation and those available in the literature, it can be reported herein that the undrained response is the most critical for these foundations; furthermore, the preconsolidation pressure is considered as an important parameter in establishing the shear strength of sensitive clay. A design procedure is developed to determine the safe zone for the undrained and drained responses, within which a combination of the cyclic deviator stress and the number of cycles for a given soil/loading/site conditions can achieve a quasielastic resilient state without reaching failure. The proposed design procedure is applicable to all regions around the world, where sensitive clays can be found. Furthermore, this procedure can be adopted to examine the conditions of existing foundations built on sensitive clay at any time during its lifespan. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2892 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 938–948
Titre : Application of seismic refraction tomography in karst terrane Type de document : texte imprimé Auteurs : Dennis R. Hiltunen, Auteur ; Bruce J. Cramer, Auteur Année de publication : 2008 Article en page(s) : pp. 938–948 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Seismic effects Refraction Karst Boreholes Bridge foundations Résumé : Seismic refraction tomography field data were collected on several bridge foundation sites in Pennsylvania, in close proximity to geotechnical boring locations. Profiles determined from these field measurements were plotted against drilling data, and these comparisons revealed the ability of seismic wave velocities to differentiate overburden soil from rock. In addition, foundation construction data were collected at each of the sites and compared with refraction test results determined prior to construction. In particular, top of rock revealed by an excavation, and pile tip elevations at driving refusal, were compared with refraction test results. From these data it appears that seismic wave tomograms can characterize the soil/rock interface, and that it is possible to predict expected design pile lengths based upon a measured P -wave velocity tomogram. It can be concluded from these site comparisons that geophysical techniques such as seismic refraction tomography can provide important additional information to site characterization for bridge foundations in karst terrane. However, these techniques should not be viewed as a replacement, but should be conducted during design stage site investigation to aid selection of borehole locations and other testing needs. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2893 [...] [article] Application of seismic refraction tomography in karst terrane [texte imprimé] / Dennis R. Hiltunen, Auteur ; Bruce J. Cramer, Auteur . - 2008 . - pp. 938–948.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 938–948
Mots-clés : Seismic effects Refraction Karst Boreholes Bridge foundations Résumé : Seismic refraction tomography field data were collected on several bridge foundation sites in Pennsylvania, in close proximity to geotechnical boring locations. Profiles determined from these field measurements were plotted against drilling data, and these comparisons revealed the ability of seismic wave velocities to differentiate overburden soil from rock. In addition, foundation construction data were collected at each of the sites and compared with refraction test results determined prior to construction. In particular, top of rock revealed by an excavation, and pile tip elevations at driving refusal, were compared with refraction test results. From these data it appears that seismic wave tomograms can characterize the soil/rock interface, and that it is possible to predict expected design pile lengths based upon a measured P -wave velocity tomogram. It can be concluded from these site comparisons that geophysical techniques such as seismic refraction tomography can provide important additional information to site characterization for bridge foundations in karst terrane. However, these techniques should not be viewed as a replacement, but should be conducted during design stage site investigation to aid selection of borehole locations and other testing needs. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2893 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 949–959
Titre : Modeling liquefaction by a multimechanism model Type de document : texte imprimé Auteurs : A. Anandarajah, Auteur Année de publication : 2008 Article en page(s) : pp. 949–959 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Liquefaction Elastoplasticity Granular materials Anisotropy Stress strain relations Résumé : An anisotropic constitutive model was recently presented for describing the stress–strain behavior of granular materials with considerations for the initial and induced anisotropy. The model was developed within the framework of a microstructural theory known as the sliding–rolling theory. The resulting model falls within the definition of multimechanism models. The model was shown to satisfactorily represent the drained and undrained behaviors under monotonic loading. The framework used in the model allows extension to describe the behavior under cyclic loading, which is the subject of the present paper. Specifically, the model is further developed for representing the undrained behavior of granular materials under one- and two-way cyclic loading, some of which cause liquefaction resulting in large strain accumulations and the others lead to limited pore pressure and strain accumulations. The validity of the model is verified using triaxial data on Nevada sand. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2894 [...] [article] Modeling liquefaction by a multimechanism model [texte imprimé] / A. Anandarajah, Auteur . - 2008 . - pp. 949–959.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 949–959
Mots-clés : Liquefaction Elastoplasticity Granular materials Anisotropy Stress strain relations Résumé : An anisotropic constitutive model was recently presented for describing the stress–strain behavior of granular materials with considerations for the initial and induced anisotropy. The model was developed within the framework of a microstructural theory known as the sliding–rolling theory. The resulting model falls within the definition of multimechanism models. The model was shown to satisfactorily represent the drained and undrained behaviors under monotonic loading. The framework used in the model allows extension to describe the behavior under cyclic loading, which is the subject of the present paper. Specifically, the model is further developed for representing the undrained behavior of granular materials under one- and two-way cyclic loading, some of which cause liquefaction resulting in large strain accumulations and the others lead to limited pore pressure and strain accumulations. The validity of the model is verified using triaxial data on Nevada sand. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2894 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 960–971
Titre : Initial shear modulus of remolded sand-clay mixtures Type de document : texte imprimé Auteurs : Suguru Yamada, Auteur ; Masayuki Hyodo, Auteur ; Rolando P. Orense, Auteur Année de publication : 2008 Article en page(s) : pp. 960–971 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Shear modulus Dynamic properties Material properties Clays Mixtures Cyclic tests Soil dynamics Résumé : This paper presents the dynamic properties of undisturbed and remolded clays and sand-clay mixtures based on the results of undrained hollow cylindrical torsional cyclic simple shear tests. The clays were obtained from different sites having a wide range of plasticity, covering fluvial and marine sediments. The main focus of this investigation is the dynamic properties of sand-clay mixtures whose properties are intermediate between those of clays and sands. The initial shear moduli are examined in terms of fines content, and conventional plasticity index. An equivalent plasticity index has been defined in the present investigation and a better correlation is obtained between the initial shear modulus of sand-clay mixtures and this parameter than with the conventional plasticity index. Further, a simple method has been suggested to determine the equivalent plasticity index based on the conventional consistency limit tests and grain size analysis. An empirical correlation for predicting the initial shear modulus is also proposed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2896 [...] [article] Initial shear modulus of remolded sand-clay mixtures [texte imprimé] / Suguru Yamada, Auteur ; Masayuki Hyodo, Auteur ; Rolando P. Orense, Auteur . - 2008 . - pp. 960–971.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 960–971
Mots-clés : Shear modulus Dynamic properties Material properties Clays Mixtures Cyclic tests Soil dynamics Résumé : This paper presents the dynamic properties of undisturbed and remolded clays and sand-clay mixtures based on the results of undrained hollow cylindrical torsional cyclic simple shear tests. The clays were obtained from different sites having a wide range of plasticity, covering fluvial and marine sediments. The main focus of this investigation is the dynamic properties of sand-clay mixtures whose properties are intermediate between those of clays and sands. The initial shear moduli are examined in terms of fines content, and conventional plasticity index. An equivalent plasticity index has been defined in the present investigation and a better correlation is obtained between the initial shear modulus of sand-clay mixtures and this parameter than with the conventional plasticity index. Further, a simple method has been suggested to determine the equivalent plasticity index based on the conventional consistency limit tests and grain size analysis. An empirical correlation for predicting the initial shear modulus is also proposed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2896 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 972–981
Titre : Strain-dependent dynamic properties of remolded sand-clay mixtures Type de document : texte imprimé Auteurs : Suguru Yamada, Auteur ; Masayuki Hyodo, Auteur ; Rolando P. Orense, Auteur Année de publication : 2008 Article en page(s) : pp. 972–981 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Shear modulus Damping Dynamic properties Material properties Clays Mixtures Cyclic tests Soil dynamics Résumé : A series of undrained cyclic torsional simple shear tests using hollow cylindrical torsional shear apparatus was carried out to investigate the dynamic shear moduli and damping properties of clayey specimens with various sand contents and plasticity indices. The clayey soils used were collected from various sites along the coast of west Japan. Among these clayey soils, a clay sample with intermediate plasticity and another with high plasticity were mixed with silica sand at different proportions in order to examine the dynamic properties of sand-clay mixtures. In addition, experiments were carried out on undisturbed and remolded natural clay specimens with various plasticities. The effects of plasticity, loading frequency and confining pressure on the strain dependent normalized shear modulus and damping ratio were examined. Based on the results, empirical correlations for predicting the normalized shear modulus and damping ratio of remolded sand-clay mixtures at various shear strain levels were proposed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2897 [...] [article] Strain-dependent dynamic properties of remolded sand-clay mixtures [texte imprimé] / Suguru Yamada, Auteur ; Masayuki Hyodo, Auteur ; Rolando P. Orense, Auteur . - 2008 . - pp. 972–981.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 972–981
Mots-clés : Shear modulus Damping Dynamic properties Material properties Clays Mixtures Cyclic tests Soil dynamics Résumé : A series of undrained cyclic torsional simple shear tests using hollow cylindrical torsional shear apparatus was carried out to investigate the dynamic shear moduli and damping properties of clayey specimens with various sand contents and plasticity indices. The clayey soils used were collected from various sites along the coast of west Japan. Among these clayey soils, a clay sample with intermediate plasticity and another with high plasticity were mixed with silica sand at different proportions in order to examine the dynamic properties of sand-clay mixtures. In addition, experiments were carried out on undisturbed and remolded natural clay specimens with various plasticities. The effects of plasticity, loading frequency and confining pressure on the strain dependent normalized shear modulus and damping ratio were examined. Based on the results, empirical correlations for predicting the normalized shear modulus and damping ratio of remolded sand-clay mixtures at various shear strain levels were proposed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2897 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 982–991
Titre : Singularities of geotechnical properties of complex soils in seismic regions Type de document : texte imprimé Auteurs : Ramón Verdugo, Auteur Année de publication : 2008 Article en page(s) : pp. 982–991 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Soil dynamics Microstructure Volcanic ash Seismic effects Clays Résumé : Volcanic activity results in a wide range of soil types with very unusual characteristics, the most remarkable of which are volcanic ash clays containing the clay minerals allophane and imogolite. In addition to these soils, volcanic activity often produces the special environmental conditions that result in the formation of diatomaceous soils, namely, water rich in dissolved silica. These soils consist of individual particles containing intraparticle voids filled with water, resulting in a very unique porous particle morphology that is quite different than stereotypical sedimentary soils. This paper presents a series of careful laboratory tests on samples of both materials found in Chile. These tests demonstrate that soils weathered from volcanic ash develop yield pressures that are similar to the preconsolidation pressure of sedimentary soils. This type of soil also shows a dramatic change in properties due to drying. In addition, diatomaceous soils and those containing allophane have very low densities, in spite of which they develop remarkably high shear strength. The need for their properties to be properly understood and taken into account in geotechnical design, especially seismic design, is emphasized, since the location of these soils generally coincides with earthquake activity, which, like volcanic activity, arises from tectonic plate interaction. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2898 [...] [article] Singularities of geotechnical properties of complex soils in seismic regions [texte imprimé] / Ramón Verdugo, Auteur . - 2008 . - pp. 982–991.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 982–991
Mots-clés : Soil dynamics Microstructure Volcanic ash Seismic effects Clays Résumé : Volcanic activity results in a wide range of soil types with very unusual characteristics, the most remarkable of which are volcanic ash clays containing the clay minerals allophane and imogolite. In addition to these soils, volcanic activity often produces the special environmental conditions that result in the formation of diatomaceous soils, namely, water rich in dissolved silica. These soils consist of individual particles containing intraparticle voids filled with water, resulting in a very unique porous particle morphology that is quite different than stereotypical sedimentary soils. This paper presents a series of careful laboratory tests on samples of both materials found in Chile. These tests demonstrate that soils weathered from volcanic ash develop yield pressures that are similar to the preconsolidation pressure of sedimentary soils. This type of soil also shows a dramatic change in properties due to drying. In addition, diatomaceous soils and those containing allophane have very low densities, in spite of which they develop remarkably high shear strength. The need for their properties to be properly understood and taken into account in geotechnical design, especially seismic design, is emphasized, since the location of these soils generally coincides with earthquake activity, which, like volcanic activity, arises from tectonic plate interaction. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2898 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 992–1004
Titre : Characterization of cemented sand by experimental and numerical investigations Type de document : texte imprimé Auteurs : Y. H. Wang, Auteur ; S. C. Leung, Auteur Année de publication : 2008 Article en page(s) : pp. 992–1004 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Discrete elements Stress Bonding Banding Triaxial tests Dilatancy Résumé : In this study, the effects of cementation on the stress–dilatancy and strength of cemented sand are investigated through experimental characterizations using triaxial tests and numerical simulations using the discrete element method. At small strains, dilatancy is hindered by the intact bonding network that produces a web-patterned force chain. After yielding, the increase in the dilatancy accelerates. Two competing but intimately related processes determine the peak strength: Bond breakages cause a strength reduction but the associated dilatancy leads to a strength increase. This finding and the experimental observation that the dilatancy at the peak state increases with increasing cement content explain why the measured peak-state strength parameters, c′ and ϕ′p , are relevant to the cement content. With increasing strain, the force-chain distribution gradually changes to a thick columnar shape, which mostly appears inside the shear band. At the ultimate state, the cementing bonds remain to form clusters, even within the shear band. The existence of clusters not only helps maintain the overall volumetric dilation but also prevents force-chain buckling, which in turn increases the associated strength. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2899 [...] [article] Characterization of cemented sand by experimental and numerical investigations [texte imprimé] / Y. H. Wang, Auteur ; S. C. Leung, Auteur . - 2008 . - pp. 992–1004.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 992–1004
Mots-clés : Discrete elements Stress Bonding Banding Triaxial tests Dilatancy Résumé : In this study, the effects of cementation on the stress–dilatancy and strength of cemented sand are investigated through experimental characterizations using triaxial tests and numerical simulations using the discrete element method. At small strains, dilatancy is hindered by the intact bonding network that produces a web-patterned force chain. After yielding, the increase in the dilatancy accelerates. Two competing but intimately related processes determine the peak strength: Bond breakages cause a strength reduction but the associated dilatancy leads to a strength increase. This finding and the experimental observation that the dilatancy at the peak state increases with increasing cement content explain why the measured peak-state strength parameters, c′ and ϕ′p , are relevant to the cement content. With increasing strain, the force-chain distribution gradually changes to a thick columnar shape, which mostly appears inside the shear band. At the ultimate state, the cementing bonds remain to form clusters, even within the shear band. The existence of clusters not only helps maintain the overall volumetric dilation but also prevents force-chain buckling, which in turn increases the associated strength. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2899 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1005–1009
Titre : Vapor adsorption index for expansive soil classification Type de document : texte imprimé Auteurs : Likos, William J., Auteur Année de publication : 2008 Article en page(s) : pp. 1005–1009 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Swelling Expansive soils Clays Suction Hydration Missouri Colorado Résumé : A laboratory index defined as gravimetric water content at ambient relative humidity of 75% (w75) is proposed for qualitatively classifying the swelling potential of clays and clayey soils (e.g., low, moderate, high). The methodology is calibrated by comparison with existing plasticity-based and suction-based classification methodologies for a series of natural clays from Missouri and Colorado and clay mixtures prepared to represent a wide range of swelling potential. Procedures are described for obtaining w75 by placing samples in the headspace of an environmental chamber maintained under controlled humidity using a saturated NaCl solution. The proposed methodology has potential advantages over existing expansive soil classification methods because a large number of samples may be tested concurrently, no specialized testing equipment is required, and testing procedures may be readily automated. Measurements may be obtained in as little as 3–5days with coefficients of variation ranging from 5 to 25%. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...] [article] Vapor adsorption index for expansive soil classification [texte imprimé] / Likos, William J., Auteur . - 2008 . - pp. 1005–1009.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1005–1009
Mots-clés : Swelling Expansive soils Clays Suction Hydration Missouri Colorado Résumé : A laboratory index defined as gravimetric water content at ambient relative humidity of 75% (w75) is proposed for qualitatively classifying the swelling potential of clays and clayey soils (e.g., low, moderate, high). The methodology is calibrated by comparison with existing plasticity-based and suction-based classification methodologies for a series of natural clays from Missouri and Colorado and clay mixtures prepared to represent a wide range of swelling potential. Procedures are described for obtaining w75 by placing samples in the headspace of an environmental chamber maintained under controlled humidity using a saturated NaCl solution. The proposed methodology has potential advantages over existing expansive soil classification methods because a large number of samples may be tested concurrently, no specialized testing equipment is required, and testing procedures may be readily automated. Measurements may be obtained in as little as 3–5days with coefficients of variation ranging from 5 to 25%. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1010–1014
Titre : Use of state-dependent strength in estimating end bearing capacity of piles in sand Type de document : texte imprimé Auteurs : J. Yang, Auteur ; F. Mu, Auteur Année de publication : 2008 Article en page(s) : pp. 1010–1014 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Bearing capacity Piles Pile foundations Sand Shear strength Résumé : The pressure and density dependence of the shear strength of sand poses a tricky problem in pile foundation design. In this study, a correlation is suggested to link the effective friction angle of sand with its initial confining pressure and relative density, and a simple approach incorporating this correlation is presented for predicting pile end bearing capacity. Assessment of the approach against pile load tests shows reasonably good agreement between predictions and measurements. It is also shown that the effect of the state-dependent strength is particularly important in cases where long piles are installed in dense sand deposits and the use of critical state friction angle will produce a conservative prediction in such cases. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...] [article] Use of state-dependent strength in estimating end bearing capacity of piles in sand [texte imprimé] / J. Yang, Auteur ; F. Mu, Auteur . - 2008 . - pp. 1010–1014.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1010–1014
Mots-clés : Bearing capacity Piles Pile foundations Sand Shear strength Résumé : The pressure and density dependence of the shear strength of sand poses a tricky problem in pile foundation design. In this study, a correlation is suggested to link the effective friction angle of sand with its initial confining pressure and relative density, and a simple approach incorporating this correlation is presented for predicting pile end bearing capacity. Assessment of the approach against pile load tests shows reasonably good agreement between predictions and measurements. It is also shown that the effect of the state-dependent strength is particularly important in cases where long piles are installed in dense sand deposits and the use of critical state friction angle will produce a conservative prediction in such cases. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1015–1020
Titre : Lateral behavior of vertical pile group embedded in stabilized earth slope Type de document : texte imprimé Auteurs : Mostafa El Sawwaf, Auteur Année de publication : 2008 Article en page(s) : pp. 1015–1020 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Model tests Pile groups Sand Slopes Lateral loads Geogrids Résumé : An experimental study of the lateral behavior of vertical pile groups embedded in reinforced and nonreinforced sandy earth slopes was carried out. The model tests include studies of group configurations, pile spacing, embedment length of pile, relative densities of sand, and location of pile groups relative to the slope crest. Several configurations of geogrid reinforcement with different lengths, widths, and number of layers were used to reinforce a sandy slope of 1 (V) : 1.5 (H) . Pile groups of 2×2 and 3×3 along with center-to-center pile spacing of 2D , 3D , and 4.5D and piles with embedment length to diameter ratios of L∕D=12 and 22 were considered. Based on test results, geogrid parameters that give the maximum lateral capacity improvement are presented and discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...] [article] Lateral behavior of vertical pile group embedded in stabilized earth slope [texte imprimé] / Mostafa El Sawwaf, Auteur . - 2008 . - pp. 1015–1020.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1015–1020
Mots-clés : Model tests Pile groups Sand Slopes Lateral loads Geogrids Résumé : An experimental study of the lateral behavior of vertical pile groups embedded in reinforced and nonreinforced sandy earth slopes was carried out. The model tests include studies of group configurations, pile spacing, embedment length of pile, relative densities of sand, and location of pile groups relative to the slope crest. Several configurations of geogrid reinforcement with different lengths, widths, and number of layers were used to reinforce a sandy slope of 1 (V) : 1.5 (H) . Pile groups of 2×2 and 3×3 along with center-to-center pile spacing of 2D , 3D , and 4.5D and piles with embedment length to diameter ratios of L∕D=12 and 22 were considered. Based on test results, geogrid parameters that give the maximum lateral capacity improvement are presented and discussed. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1021–1024
Titre : Modeling pile capacity using support vector machines and generalized regression neural network Type de document : texte imprimé Auteurs : Mahesh Pal, Auteur ; Surinder Deswal, Auteur Année de publication : 2008 Article en page(s) : pp. 1021–1024 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Piles Neural networks Vector analysis Stress wave Résumé : This note investigates the potential of support vector machines based regression approach to model the static pile capacity from dynamic stress-wave data. A data set of 105 prestressed precast high strength concrete spun pipe piles is used. Radial basis function and polynomial kernel based support vector machines were used to model the total pile capacity and results were compared with a generalized regression neural network approach. A total of 81 data set were used to train, whereas the remaining 24 data sets were used to test the created model. A correlation coefficient value of 0.977 was achieved by generalized regression neural network in comparison to values of 0.967 and 0.964 achieved by radial basis function and polynomial kernel based support vector machines, respectively. Results suggest an improved performance by generalized regression neural network based approach in comparison to support vector machines but polynomial kernel based support vector machines provide a linear relationship to predict total pile capacity using stress-wave data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...] [article] Modeling pile capacity using support vector machines and generalized regression neural network [texte imprimé] / Mahesh Pal, Auteur ; Surinder Deswal, Auteur . - 2008 . - pp. 1021–1024.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1021–1024
Mots-clés : Piles Neural networks Vector analysis Stress wave Résumé : This note investigates the potential of support vector machines based regression approach to model the static pile capacity from dynamic stress-wave data. A data set of 105 prestressed precast high strength concrete spun pipe piles is used. Radial basis function and polynomial kernel based support vector machines were used to model the total pile capacity and results were compared with a generalized regression neural network approach. A total of 81 data set were used to train, whereas the remaining 24 data sets were used to test the created model. A correlation coefficient value of 0.977 was achieved by generalized regression neural network in comparison to values of 0.967 and 0.964 achieved by radial basis function and polynomial kernel based support vector machines, respectively. Results suggest an improved performance by generalized regression neural network based approach in comparison to support vector machines but polynomial kernel based support vector machines provide a linear relationship to predict total pile capacity using stress-wave data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...]
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1021–1024
Titre : Modeling pile capacity using support vector machines and generalized regression neural network Type de document : texte imprimé Auteurs : Mahesh Pal, Auteur ; Surinder Deswal, Auteur Année de publication : 2008 Article en page(s) : pp. 1021–1024 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Piles Neural networks Vector analysis Stress wave Résumé : This note investigates the potential of support vector machines based regression approach to model the static pile capacity from dynamic stress-wave data. A data set of 105 prestressed precast high strength concrete spun pipe piles is used. Radial basis function and polynomial kernel based support vector machines were used to model the total pile capacity and results were compared with a generalized regression neural network approach. A total of 81 data set were used to train, whereas the remaining 24 data sets were used to test the created model. A correlation coefficient value of 0.977 was achieved by generalized regression neural network in comparison to values of 0.967 and 0.964 achieved by radial basis function and polynomial kernel based support vector machines, respectively. Results suggest an improved performance by generalized regression neural network based approach in comparison to support vector machines but polynomial kernel based support vector machines provide a linear relationship to predict total pile capacity using stress-wave data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...] [article] Modeling pile capacity using support vector machines and generalized regression neural network [texte imprimé] / Mahesh Pal, Auteur ; Surinder Deswal, Auteur . - 2008 . - pp. 1021–1024.
Geotechnical and geoenvironmental engineering
Langues : Anglais (eng)
in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°7 (Juillet 2008) . - pp. 1021–1024
Mots-clés : Piles Neural networks Vector analysis Stress wave Résumé : This note investigates the potential of support vector machines based regression approach to model the static pile capacity from dynamic stress-wave data. A data set of 105 prestressed precast high strength concrete spun pipe piles is used. Radial basis function and polynomial kernel based support vector machines were used to model the total pile capacity and results were compared with a generalized regression neural network approach. A total of 81 data set were used to train, whereas the remaining 24 data sets were used to test the created model. A correlation coefficient value of 0.977 was achieved by generalized regression neural network in comparison to values of 0.967 and 0.964 achieved by radial basis function and polynomial kernel based support vector machines, respectively. Results suggest an improved performance by generalized regression neural network based approach in comparison to support vector machines but polynomial kernel based support vector machines provide a linear relationship to predict total pile capacity using stress-wave data. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A7%2810 [...]
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