Documents disponibles écrits par cet auteur

Experimental investigation of the reinstallation of spudcan footings close to existing footprints / Mark J. Cassidy in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 4 (Avril 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 474–486 Titre : Experimental investigation of the reinstallation of spudcan footings close to existing footprints Type de document : texte imprimé Auteurs : Mark J. Cassidy, Auteur ; Chin Kau Quah, Auteur ; Kok Seng Foo, Auteur Année de publication : 2009 Article en page(s) : pp. 474–486 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Offshore  drilling  Shallow  foundations  Clays  Offshore  structures  Centrifuge  models  Installation  Footings Résumé : The large footprints that remain on the seabed after offshore mobile jack-up platforms have completed operations provide hazardous conditions for any future jack-up installation at that site. The slope of the footprint and varying soil strengths below the surface cause detrimental horizontal and moment loads to be induced on the spudcan during the preloading process where only vertical loads are expected. Experimental data from 12 tests investigating the reinstallation of a spudcan footing close to an existing footprint is presented in this paper. The experiments were carried out using a geotechnical drum centrifuge at a radial acceleration level equivalent to 250 times that of Earth’s gravity. The stiffness of the loading leg and model spudcan shape were scaled to ensure conditions of stress similitude between the model and prototype. In all of the experiments, an initial footprint was created. The spudcan was then offset and reinstalled with the combined vertical, horizontal, and moment loads on the spudcan recorded. The effects of reinstallation location, preloading levels, and change in leg stiffness were investigated. The worst location for reinstallation was found to be at an offset half a spudcan diameter from the initial spudcan installation. The horizontal and moment loads were also greater when a more extensive footprint was created by the initial spudcan being embedded deeper and with a higher preload. For the range of conditions tested, changing the leg stiffness did not affect the results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2847 [...] [article] Experimental investigation of the reinstallation of spudcan footings close to existing footprints [texte imprimé] / Mark J. Cassidy, Auteur ; Chin Kau Quah, Auteur ; Kok Seng Foo, Auteur . - 2009 . - pp. 474–486. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 474–486 Mots-clés : Offshore  drilling  Shallow  foundations  Clays  Offshore  structures  Centrifuge  models  Installation  Footings Résumé : The large footprints that remain on the seabed after offshore mobile jack-up platforms have completed operations provide hazardous conditions for any future jack-up installation at that site. The slope of the footprint and varying soil strengths below the surface cause detrimental horizontal and moment loads to be induced on the spudcan during the preloading process where only vertical loads are expected. Experimental data from 12 tests investigating the reinstallation of a spudcan footing close to an existing footprint is presented in this paper. The experiments were carried out using a geotechnical drum centrifuge at a radial acceleration level equivalent to 250 times that of Earth’s gravity. The stiffness of the loading leg and model spudcan shape were scaled to ensure conditions of stress similitude between the model and prototype. In all of the experiments, an initial footprint was created. The spudcan was then offset and reinstalled with the combined vertical, horizontal, and moment loads on the spudcan recorded. The effects of reinstallation location, preloading levels, and change in leg stiffness were investigated. The worst location for reinstallation was found to be at an offset half a spudcan diameter from the initial spudcan installation. The horizontal and moment loads were also greater when a more extensive footprint was created by the initial spudcan being embedded deeper and with a higher preload. For the range of conditions tested, changing the leg stiffness did not affect the results. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2847 [...]

Pipe-soil interaction model incorporating large lateral displacements in calcareous sand / Yinghui Tian in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 3 (Mars 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 279-287 Titre : Pipe-soil interaction model incorporating large lateral displacements in calcareous sand Type de document : texte imprimé Auteurs : Yinghui Tian, Auteur ; Mark J. Cassidy, Auteur Année de publication : 2011 Article en page(s) : pp. 279-287 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Pipe-soil  interaction  On-bottom  stability  Strain-hardening  plasticity  Centrifuge  test  Calcareous  sand,  Berm  effect Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The use of the plasticity theory offers an attractive framework to encapsulate the behavior of a pipe and the underlying soil in terminology consistent with pipeline structural analysis. Models that express the pipe-soil behavior purely in terms of the loads on a segment of pipe and the corresponding displacements have been suggested, although verification with geotechnical centrifuge experiments has been limited to relatively small lateral displacements (i.e., less than two pipe diameters). Over larger movements, the berms that build up alongside the pipe affect the load-displacement behavior, with existing strain-hardening plasticity models incapable of simulating this transition. This technical note provides experimental evidence of pipe-soil behavior for lateral displacements for up to five diameters. It further presents observations from 20 centrifuge experiments of a prototype 1-m-diameter pipe in calcareous sand. The results are used to validate the modification of a pipe-soil model to include the horizontal displacement hardening of the yield surface. Retrospective numerical simulations of the centrifuge experiments verify the modified model’s performances for lateral displacements of up to five diameters which was also the extent of the centrifuge experiments. This incorporation of large lateral displacements has significant application in on-bottom stability analysis as displacement-based design becomes more prevalent. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i3/p279_s1?isAuthorized=no [article] Pipe-soil interaction model incorporating large lateral displacements in calcareous sand [texte imprimé] / Yinghui Tian, Auteur ; Mark J. Cassidy, Auteur . - 2011 . - pp. 279-287. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 3 (Mars 2011) . - pp. 279-287 Mots-clés : Pipe-soil  interaction  On-bottom  stability  Strain-hardening  plasticity  Centrifuge  test  Calcareous  sand,  Berm  effect Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The use of the plasticity theory offers an attractive framework to encapsulate the behavior of a pipe and the underlying soil in terminology consistent with pipeline structural analysis. Models that express the pipe-soil behavior purely in terms of the loads on a segment of pipe and the corresponding displacements have been suggested, although verification with geotechnical centrifuge experiments has been limited to relatively small lateral displacements (i.e., less than two pipe diameters). Over larger movements, the berms that build up alongside the pipe affect the load-displacement behavior, with existing strain-hardening plasticity models incapable of simulating this transition. This technical note provides experimental evidence of pipe-soil behavior for lateral displacements for up to five diameters. It further presents observations from 20 centrifuge experiments of a prototype 1-m-diameter pipe in calcareous sand. The results are used to validate the modification of a pipe-soil model to include the horizontal displacement hardening of the yield surface. Retrospective numerical simulations of the centrifuge experiments verify the modified model’s performances for lateral displacements of up to five diameters which was also the extent of the centrifuge experiments. This incorporation of large lateral displacements has significant application in on-bottom stability analysis as displacement-based design becomes more prevalent. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i3/p279_s1?isAuthorized=no

Undrained bearing capacity of deeply buried flat circular footings under general loading / Youhu Zhang in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 3 (Mars 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 385-397 Titre : Undrained bearing capacity of deeply buried flat circular footings under general loading Type de document : texte imprimé Auteurs : Youhu Zhang, Auteur ; Britta Bienen, Auteur ; Mark J. Cassidy, Auteur Année de publication : 2012 Article en page(s) : pp. 385-397 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Footings  Numerical  modeling  Offshore  engineering  Bearing  capacity  Combined  loading  Clays Résumé : Estimation of a footing’s bearing capacity under general loading is a topic of wide interest, especially for the offshore energy industry. Although there have been several studies in the past few decades on shallow footings under general loading, limited work has been done for deeply buried footings. This paper presents results of a numerical investigation into the undrained bearing capacity of deeply buried flat circular footings in clay of both uniform and linearly increasing shear strength profiles. The footings’ uniaxial bearing capacities and failure surfaces under combined vertical, horizontal, and moment loading are reported. The results are analyzed in the context of application by the mobile jack-up industry, for which understanding of the circular spudcan footing’s bearing capacity under general loading is required for site-specific assessments. The paper also presents a parametric study on the effect of a footing’s aspect ratio (thickness/diameter) on its bearing capacity. To conclude, a closed-form expression is proposed to formulate the failure surfaces of the footings under general loading. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i3/p385_s1?isAuthorized=no [article] Undrained bearing capacity of deeply buried flat circular footings under general loading [texte imprimé] / Youhu Zhang, Auteur ; Britta Bienen, Auteur ; Mark J. Cassidy, Auteur . - 2012 . - pp. 385-397. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 3 (Mars 2012) . - pp. 385-397 Mots-clés : Footings  Numerical  modeling  Offshore  engineering  Bearing  capacity  Combined  loading  Clays Résumé : Estimation of a footing’s bearing capacity under general loading is a topic of wide interest, especially for the offshore energy industry. Although there have been several studies in the past few decades on shallow footings under general loading, limited work has been done for deeply buried footings. This paper presents results of a numerical investigation into the undrained bearing capacity of deeply buried flat circular footings in clay of both uniform and linearly increasing shear strength profiles. The footings’ uniaxial bearing capacities and failure surfaces under combined vertical, horizontal, and moment loading are reported. The results are analyzed in the context of application by the mobile jack-up industry, for which understanding of the circular spudcan footing’s bearing capacity under general loading is required for site-specific assessments. The paper also presents a parametric study on the effect of a footing’s aspect ratio (thickness/diameter) on its bearing capacity. To conclude, a closed-form expression is proposed to formulate the failure surfaces of the footings under general loading. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i3/p385_s1?isAuthorized=no