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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