Documents disponibles écrits par cet auteur

An experimental and theoretical comparison between static and dynamic torsional soil tests / M. D. Bolton in Géotechnique, Vol. 39 N°4 (Decembre 1989) 

Public ISBD [article]  in Géotechnique > Vol. 39 N°4 (Decembre 1989) . - pp. 585 –599 Titre : An experimental and theoretical comparison between static and dynamic torsional soil tests Type de document : texte imprimé Auteurs : M. D. Bolton, Auteur ; J. M. R. Wilson, Auteur Année de publication : 2007 Article en page(s) : pp. 585 –599 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Damping  Torsion  Stiffness  Resonant  column  tests  Soil  properties Résumé : The dynamic properties of dry Leighton Buzzard sand have been investigated using a resonant column test apparatus. These data are compared with very low frequency cyclic tests on identical specimens of sand. The comparison indicates that the properties of dry sand are independent of frequency. A simple one-dimensional model of kinematic hardening plasticity is used to predict the dynamic behaviour of the sand. The input parameters for this model are based on the results of static tests. These may be conducted on standard laboratory equipment with only minor modifications. The predictions are in good agreement with the measured data. In particular, the frequency response close to resonance was correctly shown to be asymmetric and the reduction in the resonant frequency with increasing strain amplitude was also correctly represented. The practical consequences of these findings are assessed with regard to soil testing procedures and dynamic analyses of foundations. Particular emphasis is placed on the dynamic analyses of the foundations for vibrating machinery and offshore gravity structures. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.4.585 [article] An experimental and theoretical comparison between static and dynamic torsional soil tests [texte imprimé] / M. D. Bolton, Auteur ; J. M. R. Wilson, Auteur . - 2007 . - pp. 585 –599. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 39 N°4 (Decembre 1989) . - pp. 585 –599 Mots-clés : Damping  Torsion  Stiffness  Resonant  column  tests  Soil  properties Résumé : The dynamic properties of dry Leighton Buzzard sand have been investigated using a resonant column test apparatus. These data are compared with very low frequency cyclic tests on identical specimens of sand. The comparison indicates that the properties of dry sand are independent of frequency. A simple one-dimensional model of kinematic hardening plasticity is used to predict the dynamic behaviour of the sand. The input parameters for this model are based on the results of static tests. These may be conducted on standard laboratory equipment with only minor modifications. The predictions are in good agreement with the measured data. In particular, the frequency response close to resonance was correctly shown to be asymmetric and the reduction in the resonant frequency with increasing strain amplitude was also correctly represented. The practical consequences of these findings are assessed with regard to soil testing procedures and dynamic analyses of foundations. Particular emphasis is placed on the dynamic analyses of the foundations for vibrating machinery and offshore gravity structures. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.4.585

Energy conservation as a principle underlying mobilizable strength design for deep excavations / S. Y. Lam 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. 1062-1074 Titre : Energy conservation as a principle underlying mobilizable strength design for deep excavations Type de document : texte imprimé Auteurs : S. Y. Lam, Auteur ; M. D. Bolton, Auteur Année de publication : 2012 Article en page(s) : pp. 1062-1074 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Mobilizable  strength  design  Case  histories  Deep  excavation  Soil  stiffness Résumé : Finite-element analyses (FEA) and case histories of deep excavations in soft clay are used to validate a decision-making tool based on an extended mobilizable strength design (MSD) method that permits the designer an extremely simple method of predicting ground displacements during an undrained excavation. This newly extended MSD approach accommodates a number of issues that are important in underground construction between in situ walls, including alternative base heave mechanisms suitable either for wide excavations in relatively shallow soft clay strata or narrow excavations in relatively deep soft strata, the influence of support system stiffness in relation to the sequence of propping of the wall, and the capability of dealing with stratified ground. In addition, a simplified MSD framework is proposed for analyzing a database of 110 deep excavation case histories worldwide. The approach examines the governing factors controlling deformation in deep excavations and offers simple guidelines for designing support structures for deep excavations. These developments should make it possible for a design engineer to make informed decisions on the relationship between prop spacing and ground movements or the influence of wall stiffness and on the need for and influence of a jet-grouted base slab, for example, prior to conducting project-specific FEA. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i11/p1062_s1?isAuthorized=no [article] Energy conservation as a principle underlying mobilizable strength design for deep excavations [texte imprimé] / S. Y. Lam, Auteur ; M. D. Bolton, Auteur . - 2012 . - pp. 1062-1074. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 11 (Novembre 2011) . - pp. 1062-1074 Mots-clés : Mobilizable  strength  design  Case  histories  Deep  excavation  Soil  stiffness Résumé : Finite-element analyses (FEA) and case histories of deep excavations in soft clay are used to validate a decision-making tool based on an extended mobilizable strength design (MSD) method that permits the designer an extremely simple method of predicting ground displacements during an undrained excavation. This newly extended MSD approach accommodates a number of issues that are important in underground construction between in situ walls, including alternative base heave mechanisms suitable either for wide excavations in relatively shallow soft clay strata or narrow excavations in relatively deep soft strata, the influence of support system stiffness in relation to the sequence of propping of the wall, and the capability of dealing with stratified ground. In addition, a simplified MSD framework is proposed for analyzing a database of 110 deep excavation case histories worldwide. The approach examines the governing factors controlling deformation in deep excavations and offers simple guidelines for designing support structures for deep excavations. These developments should make it possible for a design engineer to make informed decisions on the relationship between prop spacing and ground movements or the influence of wall stiffness and on the need for and influence of a jet-grouted base slab, for example, prior to conducting project-specific FEA. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i11/p1062_s1?isAuthorized=no

Seasonal ratcheting and softening in clay slopes, leading to first-time failure / W. A. Take in Géotechnique, Vol. 61 N° 9 (Septembre 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 9 (Septembre 2011) . - pp. 757-769 Titre : Seasonal ratcheting and softening in clay slopes, leading to first-time failure Type de document : texte imprimé Auteurs : W. A. Take, Auteur ; M. D. Bolton, Auteur Année de publication : 2011 Article en page(s) : pp. 757-769 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Centrifuge  modelling  Slopes  Clays  Failure Index. décimale : 551.4 Résumé : Centrifuge tests have been carried out on kaolin clay slopes subject to variations in surface rainfall and humidity corresponding, at model scale, to successive wet and dry seasons in the field. These model slopes have been instrumented with miniature high-capacity tensiometers, and the deformations of their cross-sections have been observed by digital photography and analysed by particle image velocimetry. Sequences of swelling and shrinkage have been seen to be potentially irreversible, leading to creep in the form of down-slope ratcheting, accompanied by progressive regional softening within the zone affected by the seasonal moisture movements. Ultimately, this regional softening has been seen to lead to slope failures, in which segments of soil have separated from the mass through the opening of tension cracks and the formation of a localised shear rupture. An analysis of the phase of episodic regional softening is presented here, based on a Spencer limit-equilibrium approach. These back-analyses illustrate that clay slopes which temporarily mobilise an average stress ratio in excess of the critical state stress ratio during any portion of a typical year may eventually be brought to a long-term failure under the action of seasonal variations of pore pressure. Conversely, it is hypothesised that clay slopes which can maintain their overall equilibrium without exceeding the critical state stress ratio may not experience progressive seasonal softening. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.125 [article] Seasonal ratcheting and softening in clay slopes, leading to first-time failure [texte imprimé] / W. A. Take, Auteur ; M. D. Bolton, Auteur . - 2011 . - pp. 757-769. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 9 (Septembre 2011) . - pp. 757-769 Mots-clés : Centrifuge  modelling  Slopes  Clays  Failure Index. décimale : 551.4 Résumé : Centrifuge tests have been carried out on kaolin clay slopes subject to variations in surface rainfall and humidity corresponding, at model scale, to successive wet and dry seasons in the field. These model slopes have been instrumented with miniature high-capacity tensiometers, and the deformations of their cross-sections have been observed by digital photography and analysed by particle image velocimetry. Sequences of swelling and shrinkage have been seen to be potentially irreversible, leading to creep in the form of down-slope ratcheting, accompanied by progressive regional softening within the zone affected by the seasonal moisture movements. Ultimately, this regional softening has been seen to lead to slope failures, in which segments of soil have separated from the mass through the opening of tension cracks and the formation of a localised shear rupture. An analysis of the phase of episodic regional softening is presented here, based on a Spencer limit-equilibrium approach. These back-analyses illustrate that clay slopes which temporarily mobilise an average stress ratio in excess of the critical state stress ratio during any portion of a typical year may eventually be brought to a long-term failure under the action of seasonal variations of pore pressure. Conversely, it is hypothesised that clay slopes which can maintain their overall equilibrium without exceeding the critical state stress ratio may not experience progressive seasonal softening. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.125

The bearing capacity of footings on granular soils. I, Numerical analysis / C. K. Lau in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 627–638 Titre : The bearing capacity of footings on granular soils. I, Numerical analysis Type de document : texte imprimé Auteurs : C. K. Lau, Auteur ; M. D. Bolton, Auteur Année de publication : 2011 Article en page(s) : pp. 627–638 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Stress  analysis  Bearing  capacity  Shear  strength  Footings/foundations  Plasticity  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The method of characteristics has been used to determine the bearing capacity of shallow foundations, in either plane-strain or axisymmetric condition. Most previous solutions for granular soils were based either on a straight (c, φ ) envelope or simply on a constant angle of shearing, φ . For granular soils, sec φ usually varies linearly with the logarithm of mean effective stress. A new method of calculation permits φ to vary throughout the stress field as an arbitrary (or empirical) function of stress. This method is verified for both plane-strain and axisymmetric conditions by forcing a variation in sec φ equivalent to generating a constant-cohesion envelope, for which solutions already exist. The variable- φ analysis is used to demonstrate the highly significant effect of stress variation around and beneath a footing. Finally, it is shown that an equivalent constant value φ m can be derived empirically, using the new solutions to identify an equivalent mean effective stress p m. However, only the variable- φ solution can simultaneously capture the bearing capacity and the geometry of the bearing mechanism. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00206 [article] The bearing capacity of footings on granular soils. I, Numerical analysis [texte imprimé] / C. K. Lau, Auteur ; M. D. Bolton, Auteur . - 2011 . - pp. 627–638. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 627–638 Mots-clés : Stress  analysis  Bearing  capacity  Shear  strength  Footings/foundations  Plasticity  Numerical  modelling Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The method of characteristics has been used to determine the bearing capacity of shallow foundations, in either plane-strain or axisymmetric condition. Most previous solutions for granular soils were based either on a straight (c, φ ) envelope or simply on a constant angle of shearing, φ . For granular soils, sec φ usually varies linearly with the logarithm of mean effective stress. A new method of calculation permits φ to vary throughout the stress field as an arbitrary (or empirical) function of stress. This method is verified for both plane-strain and axisymmetric conditions by forcing a variation in sec φ equivalent to generating a constant-cohesion envelope, for which solutions already exist. The variable- φ analysis is used to demonstrate the highly significant effect of stress variation around and beneath a footing. Finally, it is shown that an equivalent constant value φ m can be derived empirically, using the new solutions to identify an equivalent mean effective stress p m. However, only the variable- φ solution can simultaneously capture the bearing capacity and the geometry of the bearing mechanism. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00206

The bearing capacity of footings on granular soils. II, Experimental evidence / C. K. Lau in Géotechnique, Vol. 61 N° 8 (Août 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 639–650 Titre : The bearing capacity of footings on granular soils. II, Experimental evidence Type de document : texte imprimé Auteurs : C. K. Lau, Auteur ; M. D. Bolton, Auteur Année de publication : 2011 Article en page(s) : pp. 639–650 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Footings/foundations  Centrifuge  modelling  Sands  Model  tests  Bearing  capacity  Silts Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Scale effects, especially stress-level effects, cause considerable confusion in the calculation of bearing capacity on granular soils. A companion paper describes a new method of calculation that explicitly allows for the variation of sec φ with mean effective stress p. This approach is validated here for the case of model circular footings on dense beds of silica sand and silica silt. The models were tested at 1g with surcharge to explore the N q behaviour, and in a centrifuge to determine self-weight effects for N γ . It is shown that triaxial φ values expressed as a function of the logarithm of p can be used to predict model bearing capacities within a deviation in φ of 2°. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00207 [article] The bearing capacity of footings on granular soils. II, Experimental evidence [texte imprimé] / C. K. Lau, Auteur ; M. D. Bolton, Auteur . - 2011 . - pp. 639–650. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 8 (Août 2011) . - pp. 639–650 Mots-clés : Footings/foundations  Centrifuge  modelling  Sands  Model  tests  Bearing  capacity  Silts Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Scale effects, especially stress-level effects, cause considerable confusion in the calculation of bearing capacity on granular soils. A companion paper describes a new method of calculation that explicitly allows for the variation of sec φ with mean effective stress p. This approach is validated here for the case of model circular footings on dense beds of silica sand and silica silt. The models were tested at 1g with surcharge to explore the N q behaviour, and in a centrifuge to determine self-weight effects for N γ . It is shown that triaxial φ values expressed as a function of the logarithm of p can be used to predict model bearing capacities within a deviation in φ of 2°. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00207

Uplift mechanisms of pipes buried in sand / C. Y. Cheuk in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°2 (Fevrier 2008) 

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