Documents disponibles écrits par cet auteur

Coupled deformation–flow analysis for methane hydrate extraction / A. Klar in Géotechnique, Vol. 60 N° 10 (Octobre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 765-776 Titre : Coupled deformation–flow analysis for methane hydrate extraction Type de document : texte imprimé Auteurs : A. Klar, Auteur ; K. Soga, Auteur ; M. Y. A. Ng, Auteur Année de publication : 2011 Article en page(s) : pp. 765-776 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Water  flow  Groundwater  Shear  strength  Stress  analysis  Deformation  Permeability  Sands  Constitutive  relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Methane hydrate is estimated to be present in substantial amounts below deep sea floors. Particular scientific and engineering interests that encourage studies of mechanical behaviour of methane hydrate soils include submarine geohazards, such as the initiation of marine landslides through hydrate dissociation, wellbore stability and estimation of future gas production from wells. To study these problems, a formulation of a multi-physics model of methane hydrate flow coupled to soil deformation is developed. By assuming deformable porous media (soil matrix) that accommodate non-movable but dissociable hydrate, a two-phase flow formulation of water and methane gas is suggested according to Darcy's law and capillary pressure law. A single-phase elastic–perfectly plastic constitutive model for hydrate soil sediments, based on the concept of effective stress, is developed to account for the effect of hydrate saturation on mechanical strength and stiffness. The formulation is incorporated into the explicit scheme of finite-difference code FLAC by solving three boundary value problems in parallel. The code is used to simulate the behaviour of horizontal unsupported and supported wells in hydrate-bearing sediments under different in situ stress conditions during methane hydrate extraction. Axial force, bending moment and well displacements were compared for supported and unsupported wells. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.079-3799 [article] Coupled deformation–flow analysis for methane hydrate extraction [texte imprimé] / A. Klar, Auteur ; K. Soga, Auteur ; M. Y. A. Ng, Auteur . - 2011 . - pp. 765-776. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 10 (Octobre 2010) . - pp. 765-776 Mots-clés : Water  flow  Groundwater  Shear  strength  Stress  analysis  Deformation  Permeability  Sands  Constitutive  relations Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Methane hydrate is estimated to be present in substantial amounts below deep sea floors. Particular scientific and engineering interests that encourage studies of mechanical behaviour of methane hydrate soils include submarine geohazards, such as the initiation of marine landslides through hydrate dissociation, wellbore stability and estimation of future gas production from wells. To study these problems, a formulation of a multi-physics model of methane hydrate flow coupled to soil deformation is developed. By assuming deformable porous media (soil matrix) that accommodate non-movable but dissociable hydrate, a two-phase flow formulation of water and methane gas is suggested according to Darcy's law and capillary pressure law. A single-phase elastic–perfectly plastic constitutive model for hydrate soil sediments, based on the concept of effective stress, is developed to account for the effect of hydrate saturation on mechanical strength and stiffness. The formulation is incorporated into the explicit scheme of finite-difference code FLAC by solving three boundary value problems in parallel. The code is used to simulate the behaviour of horizontal unsupported and supported wells in hydrate-bearing sediments under different in situ stress conditions during methane hydrate extraction. Axial force, bending moment and well displacements were compared for supported and unsupported wells. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.9.p.079-3799

Theoretical study on pile length optimization of pile groups and piled rafts / Y. F. Leung in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 319-330 Titre : Theoretical study on pile length optimization of pile groups and piled rafts Type de document : texte imprimé Auteurs : Y. F. Leung, Auteur ; A. Klar, Auteur ; K. Soga, Auteur Article en page(s) : pp. 319-330 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Pile  groups  Optimization  Raft  foundations Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Pile groups are frequently designed with equal or similar pile lengths. However, the significant interaction effects among equal-length piles imply that this may not be the optimized configuration. This paper presents the optimization analyses of piled rafts and freestanding pile groups, where pile lengths are varied across the group to optimize the overall foundation performance. The results of the analyses are applicable in cases where the piles derive a majority of the capacity from the frictional resistance. It is demonstrated that, with the same amount of total pile material, an optimized pile length configuration can both increase the overall stiffness of the foundation and reduce the differential settlements that may cause distortion and cracking of the superstructure. The benefits of the optimization can be translated to economic and environmental savings as less material is required to attain the required level of foundation performances. The reliability of the optimization benefits in relation to construction-induced variability is also discussed. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...] [article] Theoretical study on pile length optimization of pile groups and piled rafts [texte imprimé] / Y. F. Leung, Auteur ; A. Klar, Auteur ; K. Soga, Auteur . - pp. 319-330. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 2 (Fevrier 2010) . - pp. 319-330 Mots-clés : Pile  groups  Optimization  Raft  foundations Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : Pile groups are frequently designed with equal or similar pile lengths. However, the significant interaction effects among equal-length piles imply that this may not be the optimized configuration. This paper presents the optimization analyses of piled rafts and freestanding pile groups, where pile lengths are varied across the group to optimize the overall foundation performance. The results of the analyses are applicable in cases where the piles derive a majority of the capacity from the frictional resistance. It is demonstrated that, with the same amount of total pile material, an optimized pile length configuration can both increase the overall stiffness of the foundation and reduce the differential settlements that may cause distortion and cracking of the superstructure. The benefits of the optimization can be translated to economic and environmental savings as less material is required to attain the required level of foundation performances. The reliability of the optimization benefits in relation to construction-induced variability is also discussed. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.aip.org/vsearch/servlet/VerityServlet?KEY=JGGEFK&smode=strres [...]

Tunneling beneath buried pipes / A. M. Marshall in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 12 (Décembre 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1664-1672 Titre : Tunneling beneath buried pipes : view of soil strain and its effect on pipeline behavior Type de document : texte imprimé Auteurs : A. M. Marshall, Auteur ; A. Klar, Auteur ; R. J. Mair, Auteur Année de publication : 2011 Article en page(s) : pp. 1664-1672 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Tunneling  Pipeline  Soil-structure  interaction  Centrifuge  Elastic  continuum Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The paper examines the problem of tunneling beneath buried pipelines and the relationship between soil strains and pipeline bending behavior. Data are presented from centrifuge tests in which tunnel volume loss was induced in sand beneath pipelines of varying stiffness properties. The model tunnel and pipelines were all placed at a Perspex wall of the centrifuge strong box such that image-based deformation analyses could be performed. The method provided detailed data of subsurface soil and pipe displacements and illustrated the soil-pipe interaction mechanisms that occurred during tunnel volume loss, including the formation of a gap beneath the pipes. The relationship between tunnel volume loss, soil strain, and pipe bending behavior is illustrated. Experimental results of pipe bending moments are compared against predictions: (1) assuming the pipe simply follows greenfield displacements; (2) using an elastic continuum solution; and (3) using a new method in which an “out-of-plane” shear argument, due to soil-pipe interaction, is introduced into the elastic continuum solution. It is shown that the new method gives the best prediction of experimental pipe bending moments. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i12/p1664_s1?isAuthorized=no [article] Tunneling beneath buried pipes : view of soil strain and its effect on pipeline behavior [texte imprimé] / A. M. Marshall, Auteur ; A. Klar, Auteur ; R. J. Mair, Auteur . - 2011 . - pp. 1664-1672. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1664-1672 Mots-clés : Tunneling  Pipeline  Soil-structure  interaction  Centrifuge  Elastic  continuum Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The paper examines the problem of tunneling beneath buried pipelines and the relationship between soil strains and pipeline bending behavior. Data are presented from centrifuge tests in which tunnel volume loss was induced in sand beneath pipelines of varying stiffness properties. The model tunnel and pipelines were all placed at a Perspex wall of the centrifuge strong box such that image-based deformation analyses could be performed. The method provided detailed data of subsurface soil and pipe displacements and illustrated the soil-pipe interaction mechanisms that occurred during tunnel volume loss, including the formation of a gap beneath the pipes. The relationship between tunnel volume loss, soil strain, and pipe bending behavior is illustrated. Experimental results of pipe bending moments are compared against predictions: (1) assuming the pipe simply follows greenfield displacements; (2) using an elastic continuum solution; and (3) using a new method in which an “out-of-plane” shear argument, due to soil-pipe interaction, is introduced into the elastic continuum solution. It is shown that the new method gives the best prediction of experimental pipe bending moments. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i12/p1664_s1?isAuthorized=no

Tunnels in sands / A. M. Marshall in Géotechnique, Vol. 62 N° 5 (Mai 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 385 –399 Titre : Tunnels in sands : The effect of size, depth and volume loss on greenfield displacements Type de document : texte imprimé Auteurs : A. M. Marshall, Auteur ; R. Farrell, Auteur ; A. Klar, Auteur Année de publication : 2012 Article en page(s) : pp. 385 –399 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Tunnels  Settlement  Centrifuge  modelling  Sands Résumé : This paper examines the effect that tunnel size, depth and volume loss have on greenfield soil displacements above tunnels in sandy ground. The results of a series of plane-strain centrifuge tests performed on tunnels in a dry silica sand are examined. The cover-to-diameter ratio, C/D, of the tunnels ranged from 1·3 to 4·4. Features of greenfield settlement trough shape, both surface and subsurface, are illustrated by examining soil displacement data obtained using an image-based deformation measurement technique. The effects of tunnel size, depth and volume loss are demonstrated, and the suitability of typical fitting curves is discussed. The complex volumetric behaviour of drained soil is illustrated by comparing tunnel volume loss with the volume loss experienced by the soil. A set of equations is developed that provide a method of evaluating the change of settlement trough shape with tunnel size, depth and volume loss. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.047 [article] Tunnels in sands : The effect of size, depth and volume loss on greenfield displacements [texte imprimé] / A. M. Marshall, Auteur ; R. Farrell, Auteur ; A. Klar, Auteur . - 2012 . - pp. 385 –399. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 5 (Mai 2012) . - pp. 385 –399 Mots-clés : Tunnels  Settlement  Centrifuge  modelling  Sands Résumé : This paper examines the effect that tunnel size, depth and volume loss have on greenfield soil displacements above tunnels in sandy ground. The results of a series of plane-strain centrifuge tests performed on tunnels in a dry silica sand are examined. The cover-to-diameter ratio, C/D, of the tunnels ranged from 1·3 to 4·4. Features of greenfield settlement trough shape, both surface and subsurface, are illustrated by examining soil displacement data obtained using an image-based deformation measurement technique. The effects of tunnel size, depth and volume loss are demonstrated, and the suitability of typical fitting curves is discussed. The complex volumetric behaviour of drained soil is illustrated by comparing tunnel volume loss with the volume loss experienced by the soil. A set of equations is developed that provide a method of evaluating the change of settlement trough shape with tunnel size, depth and volume loss. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.10.P.047