Documents disponibles écrits par cet auteur

Bearing capacity of spatially random cohesive soil using numerical limit analyses / Kiyonobu Kasama in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 11 (Novembre 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 11 (Novembre 2011) . - pp. 989-996 Titre : Bearing capacity of spatially random cohesive soil using numerical limit analyses Type de document : texte imprimé Auteurs : Kiyonobu Kasama, Auteur ; Andrew J. Whittle, Auteur Année de publication : 2012 Article en page(s) : pp. 989-996 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Bearing  capacity  Cohesive  soil  Limit  analysis  Monte  Carlo  method  Random  field  Probabilistic  analysis Résumé : This paper describes a probabilistic study of the two-dimensional bearing capacity of a vertically loaded strip footing on spatially random, cohesive soil using numerical limit analyses (NLA-CD). The analyses use a Cholesky decomposition (CD) technique with midpoint discretization to represent the spatial variation in undrained shear strength within finite-element meshes for both upper- and lower-bound analyses and assumes an isotropic correlation length. Monte Carlo simulations are then used to interpret the bearing capacity for selected ranges of the coefficient of variation in undrained shear strength and the ratio of correlation length to footing width. The results are compared directly with data from a very similar study in which bearing capacity realizations were computed using a method of local average subdivision (LAS) in a conventional displacement-based finite-element method (FEM-LAS). These comparisons show the same qualitative features but suggest that the published FEM calculations tend to overestimate the probability of failure at large correlation lengths. The NLA method offers a more convenient and computationally efficient approach for evaluating effects of variability in soil strength properties in geotechnical stability calculations. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i11/p989_s1?isAuthorized=no [article] Bearing capacity of spatially random cohesive soil using numerical limit analyses [texte imprimé] / Kiyonobu Kasama, Auteur ; Andrew J. Whittle, Auteur . - 2012 . - pp. 989-996. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 11 (Novembre 2011) . - pp. 989-996 Mots-clés : Bearing  capacity  Cohesive  soil  Limit  analysis  Monte  Carlo  method  Random  field  Probabilistic  analysis Résumé : This paper describes a probabilistic study of the two-dimensional bearing capacity of a vertically loaded strip footing on spatially random, cohesive soil using numerical limit analyses (NLA-CD). The analyses use a Cholesky decomposition (CD) technique with midpoint discretization to represent the spatial variation in undrained shear strength within finite-element meshes for both upper- and lower-bound analyses and assumes an isotropic correlation length. Monte Carlo simulations are then used to interpret the bearing capacity for selected ranges of the coefficient of variation in undrained shear strength and the ratio of correlation length to footing width. The results are compared directly with data from a very similar study in which bearing capacity realizations were computed using a method of local average subdivision (LAS) in a conventional displacement-based finite-element method (FEM-LAS). These comparisons show the same qualitative features but suggest that the published FEM calculations tend to overestimate the probability of failure at large correlation lengths. The NLA method offers a more convenient and computationally efficient approach for evaluating effects of variability in soil strength properties in geotechnical stability calculations. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i11/p989_s1?isAuthorized=no

Compression and creep of venice lagoon sands / Alex Sanzeni in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 10 (Octobre 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 10 (Octobre 2012) . - pp.1266–1276. Titre : Compression and creep of venice lagoon sands Type de document : texte imprimé Auteurs : Alex Sanzeni, Auteur ; Andrew J. Whittle, Auteur ; John T. Germaine, Auteur Année de publication : 2013 Article en page(s) : pp.1266–1276. Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Sand  compression  Creep  Soil  behavior  Model  calibration  Venice  Lagoon Résumé : A laboratory test program was conducted to evaluate the one-dimensional (1D) compression and creep properties of intact sand (and silty-sand) samples from a deep borehole at the Malamocco Inlet to the Venice Lagoon. The tests were performed with a constant rate of strain consolidometer and included special procedures for trimming the frozen samples and measuring strains during thawing and backpressure saturation. The specimens had variable fine fractions ranging from 6 to 21% and mica contents ranging from 1 to 10%. The results confirmed that there is a strong correlation between the creep rate coefficient and the compressibility index and between the swelling index and mica content. The compression behavior in all tests is well described by a nonlinear compression model with a unique limiting compression curve and a variable transition parameter that reflects the fines and mica content. Creep tests performed at different confining pressures are also well represented by a simple two-parameter model. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000696 [article] Compression and creep of venice lagoon sands [texte imprimé] / Alex Sanzeni, Auteur ; Andrew J. Whittle, Auteur ; John T. Germaine, Auteur . - 2013 . - pp.1266–1276. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 10 (Octobre 2012) . - pp.1266–1276. Mots-clés : Sand  compression  Creep  Soil  behavior  Model  calibration  Venice  Lagoon Résumé : A laboratory test program was conducted to evaluate the one-dimensional (1D) compression and creep properties of intact sand (and silty-sand) samples from a deep borehole at the Malamocco Inlet to the Venice Lagoon. The tests were performed with a constant rate of strain consolidometer and included special procedures for trimming the frozen samples and measuring strains during thawing and backpressure saturation. The specimens had variable fine fractions ranging from 6 to 21% and mica contents ranging from 1 to 10%. The results confirmed that there is a strong correlation between the creep rate coefficient and the compressibility index and between the swelling index and mica content. The compression behavior in all tests is well described by a nonlinear compression model with a unique limiting compression curve and a variable transition parameter that reflects the fines and mica content. Creep tests performed at different confining pressures are also well represented by a simple two-parameter model. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000696

Experimental study of wellbore instability in clays / Naeem O. Abdulhadi in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 8 (Août 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 8 (Août 2011) . - pp. 766-776 Titre : Experimental study of wellbore instability in clays Type de document : texte imprimé Auteurs : Naeem O. Abdulhadi, Auteur ; John T. Germaine, Auteur ; Andrew J. Whittle, Auteur Année de publication : 2011 Article en page(s) : pp. 766-776 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Borehole  instability  Clays  Laboratory  tests  Model  borehole  tests  Saturated  soils  Shear  strength  Thick-walled  cylinder  tests Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper presents the results of an extensive program of laboratory model wellbore tests that have been performed to study wellbore instability in saturated clays. The tests were conducted on resedimented Boston blue clay (RBBC) anisotropically consolidated to vertical effective stresses up to 10 MPa by using two custom-built thick-walled cylinder (TWC) devices with outer diameters Do = 7.6 and 15.2 cm. The experimental program investigated the effects of specimen geometry, mode of loading, strain rate, consolidation stress level, and overconsolidation ratio (OCR) on deformations of the model wellbore measured during undrained shearing. Results indicate that for normally consolidated clays most of the change in cavity pressure occurs at volumetric strains less than 5% after which the borehole becomes unstable. Increases in outer diameter and strain rate led to a reduction in the minimum borehole pressure. Stress-strain properties were interpreted by using an analysis procedure originally developed for undrained plane strain expansion of hollow cylinders. The backfigured undrained strength ratios from these analyses for normally consolidated specimens range from su/σvc′ = 0.19–0.22. Overconsolidation greatly improves the stability of the borehole, and interpreted undrained strength ratios from the TWC tests are consistent with well-known power law functions previously developed for elemental shear tests. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i8/p766_s1?isAuthorized=no [article] Experimental study of wellbore instability in clays [texte imprimé] / Naeem O. Abdulhadi, Auteur ; John T. Germaine, Auteur ; Andrew J. Whittle, Auteur . - 2011 . - pp. 766-776. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 8 (Août 2011) . - pp. 766-776 Mots-clés : Borehole  instability  Clays  Laboratory  tests  Model  borehole  tests  Saturated  soils  Shear  strength  Thick-walled  cylinder  tests Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper presents the results of an extensive program of laboratory model wellbore tests that have been performed to study wellbore instability in saturated clays. The tests were conducted on resedimented Boston blue clay (RBBC) anisotropically consolidated to vertical effective stresses up to 10 MPa by using two custom-built thick-walled cylinder (TWC) devices with outer diameters Do = 7.6 and 15.2 cm. The experimental program investigated the effects of specimen geometry, mode of loading, strain rate, consolidation stress level, and overconsolidation ratio (OCR) on deformations of the model wellbore measured during undrained shearing. Results indicate that for normally consolidated clays most of the change in cavity pressure occurs at volumetric strains less than 5% after which the borehole becomes unstable. Increases in outer diameter and strain rate led to a reduction in the minimum borehole pressure. Stress-strain properties were interpreted by using an analysis procedure originally developed for undrained plane strain expansion of hollow cylinders. The backfigured undrained strength ratios from these analyses for normally consolidated specimens range from su/σvc′ = 0.19–0.22. Overconsolidation greatly improves the stability of the borehole, and interpreted undrained strength ratios from the TWC tests are consistent with well-known power law functions previously developed for elemental shear tests. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i8/p766_s1?isAuthorized=no

Model prediction of static liquefaction / Giuseppe Buscarnera in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 3 (Mars 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 3 (Mars 2013) . - pp. 420-432 Titre : Model prediction of static liquefaction : influence of the initial state on potential instabilities Type de document : texte imprimé Auteurs : Giuseppe Buscarnera, Auteur ; Andrew J. Whittle, Auteur Année de publication : 2013 Article en page(s) : pp. 420-432 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : soil  liquefaction;  mechanical  properties;  constitutive  models;  sand  (soil  type);  predictions Résumé : This paper examines the influence of the initial state of sands on the potential for undrained instability. The main goal is to illustrate how advanced constitutive modeling of sand behavior can be used to evaluate the susceptibility for static liquefaction. The methodology is based on the concept of latent instability, in which the potential for collapse is contingent on particular boundary conditions. A generalized effective stress soil model, MIT-S1, is used to support the analysis and is combined with a theoretical approach for identifying loss of control owing to undrained shear perturbations. The theory is evaluated using experimental evidence available for Toyoura sand to point out the key role of void ratio and consolidation history and to provide experimental validation for the theory. Model predictions are then used to disclose the subtle role of drained preloading paths in promoting liquefaction instabilities. The ability of the constitutive model to reproduce the interplay between undrained kinematic constraints and material failure is fundamental in predicting potential instabilities arising from changes in drainage conditions. The examples shed light on the mechanics of static liquefaction and set a framework for applying the principles of material stability to the triggering analysis of flow slides induced by undrained shear perturbations. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000779 [article] Model prediction of static liquefaction : influence of the initial state on potential instabilities [texte imprimé] / Giuseppe Buscarnera, Auteur ; Andrew J. Whittle, Auteur . - 2013 . - pp. 420-432. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 3 (Mars 2013) . - pp. 420-432 Mots-clés : soil  liquefaction;  mechanical  properties;  constitutive  models;  sand  (soil  type);  predictions Résumé : This paper examines the influence of the initial state of sands on the potential for undrained instability. The main goal is to illustrate how advanced constitutive modeling of sand behavior can be used to evaluate the susceptibility for static liquefaction. The methodology is based on the concept of latent instability, in which the potential for collapse is contingent on particular boundary conditions. A generalized effective stress soil model, MIT-S1, is used to support the analysis and is combined with a theoretical approach for identifying loss of control owing to undrained shear perturbations. The theory is evaluated using experimental evidence available for Toyoura sand to point out the key role of void ratio and consolidation history and to provide experimental validation for the theory. Model predictions are then used to disclose the subtle role of drained preloading paths in promoting liquefaction instabilities. The ability of the constitutive model to reproduce the interplay between undrained kinematic constraints and material failure is fundamental in predicting potential instabilities arising from changes in drainage conditions. The examples shed light on the mechanics of static liquefaction and set a framework for applying the principles of material stability to the triggering analysis of flow slides induced by undrained shear perturbations. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000779

Particle network model for simulating the filtration of a microfine cement grout in sand / Yun Sung Kim in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N°2 (Février 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 224–236 Titre : Particle network model for simulating the filtration of a microfine cement grout in sand Type de document : texte imprimé Auteurs : Yun Sung Kim, Auteur ; Andrew J. Whittle, Auteur Année de publication : 2009 Article en page(s) : pp. 224–236 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Cements  Filtration  Grouting  Networks  Sand  Simulation Résumé : This paper describes the application of a quasi-one-demensional (1D) network, bubble model to simulate the filtration of a microfine cement suspension injected through a column of sand. The bubble model represents the soil column as a series of homogeneous sites linked through bundles of cylindrical bonds that characterize the distribution of pores. The model captures mechanisms of particle sieving at the inlet sites and infiltration within each of the bonds under the action of hydrodynamic and gravitational forces. The behavior of each bond is based on numerical simulations of particle transport, collection, mounding, and clogging within a cylindrical model pore. Two empirical parameters are introduced to account for uncertainties in particle attachment at the pore wall and observed mechanisms of resuspension of hindered particles. In principal, these parameters can be calibrated from measurements of effluent concentrations. The bubble model provides useful physical insights to explain the transient dynamics of filtration processes. The model is able to provide consistent predictions of pore pressures measured in 1D column injection tests reported in the literature. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2822 [...] [article] Particle network model for simulating the filtration of a microfine cement grout in sand [texte imprimé] / Yun Sung Kim, Auteur ; Andrew J. Whittle, Auteur . - 2009 . - pp. 224–236. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N°2 (Février 2009) . - pp. 224–236 Mots-clés : Cements  Filtration  Grouting  Networks  Sand  Simulation Résumé : This paper describes the application of a quasi-one-demensional (1D) network, bubble model to simulate the filtration of a microfine cement suspension injected through a column of sand. The bubble model represents the soil column as a series of homogeneous sites linked through bundles of cylindrical bonds that characterize the distribution of pores. The model captures mechanisms of particle sieving at the inlet sites and infiltration within each of the bonds under the action of hydrodynamic and gravitational forces. The behavior of each bond is based on numerical simulations of particle transport, collection, mounding, and clogging within a cylindrical model pore. Two empirical parameters are introduced to account for uncertainties in particle attachment at the pore wall and observed mechanisms of resuspension of hindered particles. In principal, these parameters can be calibrated from measurements of effluent concentrations. The bubble model provides useful physical insights to explain the transient dynamics of filtration processes. The model is able to provide consistent predictions of pore pressures measured in 1D column injection tests reported in the literature. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A2%2822 [...]

Prediction and interpretation of the performance of a deep excavation in Berlin sand / Maria A. Nikolinakou in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 11 (Novembre 2011) 

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