Documents disponibles écrits par cet auteur

Limit analysis of the undrained bearing capacity of offshore pipelines / C. M. Martin in Géotechnique, Vol. 62 N° 9 (Septembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 847 –863 Titre : Limit analysis of the undrained bearing capacity of offshore pipelines Type de document : texte imprimé Auteurs : C. M. Martin, Auteur ; D. J. White, Auteur Année de publication : 2012 Article en page(s) : pp. 847 –863 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Clays  Pipelines  Numerical  modelling  Bearing  capacity  Offshore  engineering Résumé : The ultimate bearing capacity of a rigid, plane-strain pipe segment embedded in undrained clay is studied using numerical limit analysis. The pipe is considered to be ‘wished in place' at invert penetrations ranging from zero to five pipe diameters, thus providing coverage of both on-bottom (partially embedded) and trenched (fully embedded) offshore pipelines. The soil is modelled as a rigid-plastic Tresca material with either uniform strength or strength proportional to depth. The effects of soil weight, interface roughness and interface tensile capacity are investigated in a systematic manner. All calculations are performed using the finite-element limit analysis code OxLim, which uses adaptive mesh refinement to compute tightly bracketed lower- and upper-bound plasticity solutions. The velocity fields from the upper-bound analyses provide the corresponding failure mechanisms. The paper initially focuses on purely vertical loading (penetration and uplift), and then addresses combined vertical and horizontal loading. A comprehensive set of design curves and failure envelopes is presented, with the results explained in terms of the changing failure mechanisms. These results are immediately applicable in practice. In particular, current industry-standard procedures for design against pipeline upheaval are critically reviewed, and are shown to have potentially unconservative shortcomings. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.016 [article] Limit analysis of the undrained bearing capacity of offshore pipelines [texte imprimé] / C. M. Martin, Auteur ; D. J. White, Auteur . - 2012 . - pp. 847 –863. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 847 –863 Mots-clés : Clays  Pipelines  Numerical  modelling  Bearing  capacity  Offshore  engineering Résumé : The ultimate bearing capacity of a rigid, plane-strain pipe segment embedded in undrained clay is studied using numerical limit analysis. The pipe is considered to be ‘wished in place' at invert penetrations ranging from zero to five pipe diameters, thus providing coverage of both on-bottom (partially embedded) and trenched (fully embedded) offshore pipelines. The soil is modelled as a rigid-plastic Tresca material with either uniform strength or strength proportional to depth. The effects of soil weight, interface roughness and interface tensile capacity are investigated in a systematic manner. All calculations are performed using the finite-element limit analysis code OxLim, which uses adaptive mesh refinement to compute tightly bracketed lower- and upper-bound plasticity solutions. The velocity fields from the upper-bound analyses provide the corresponding failure mechanisms. The paper initially focuses on purely vertical loading (penetration and uplift), and then addresses combined vertical and horizontal loading. A comprehensive set of design curves and failure envelopes is presented, with the results explained in terms of the changing failure mechanisms. These results are immediately applicable in practice. In particular, current industry-standard procedures for design against pipeline upheaval are critically reviewed, and are shown to have potentially unconservative shortcomings. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.016

Numerical simulation of pushover tests on a model jack-up platform on clay / G. Vlahos in Géotechnique, Vol. 61 N° 11 (Novembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 11 (Novembre 2010) . - pp. 947-960 Titre : Numerical simulation of pushover tests on a model jack-up platform on clay Type de document : texte imprimé Auteurs : G. Vlahos, Auteur ; M. J. Cassidy, Auteur ; C. M. Martin, Auteur Année de publication : 2011 Article en page(s) : pp. 947-960 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Offshore  engineering  Plasticity  Soil–structure  interaction  Numerical  modelling  Model  tests  Footings/foundations  Clays Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper assesses a method for predicting the ultimate capacity and failure mode of a model jack-up platform subjected to monotonic pushover tests on soft clay. Separate structural and geotechnical analyses are incapable of making such predictions, so in this work integrated structural/geotechnical simulations are evaluated against detailed experimental pushover data. The commercial finite-element program Abaqus is used, with standard beam elements representing the jack-up structure and a user-defined element describing the behaviour of each spudcan footing by means of a force-resultant plasticity model. This model takes a macro-element approach by expressing the foundation behaviour purely in terms of the loads on the spudcan and the corresponding displacements. Although the model has proven ability to simulate the single-footing experiments from which it was derived, the load paths experienced by the spudcans of a three-legged jack-up are significantly different. To investigate this, numerical simulations of three experimental pushover tests on a 1:250 scale model jack-up have been performed. The tests represent jack-ups with different leg lengths and load orientations. The integrated numerical modelling approach successfully predicts three different failure modes, although the predictions of ultimate pushover capacity are consistently conservative. Because previously published parameters were used for the foundation model, these predictions demonstrate the versatility of the spudcan model in the context of a multi-footing structure, and confirm the effectiveness of the integrated analysis technique. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.114 [article] Numerical simulation of pushover tests on a model jack-up platform on clay [texte imprimé] / G. Vlahos, Auteur ; M. J. Cassidy, Auteur ; C. M. Martin, Auteur . - 2011 . - pp. 947-960. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 11 (Novembre 2010) . - pp. 947-960 Mots-clés : Offshore  engineering  Plasticity  Soil–structure  interaction  Numerical  modelling  Model  tests  Footings/foundations  Clays Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : This paper assesses a method for predicting the ultimate capacity and failure mode of a model jack-up platform subjected to monotonic pushover tests on soft clay. Separate structural and geotechnical analyses are incapable of making such predictions, so in this work integrated structural/geotechnical simulations are evaluated against detailed experimental pushover data. The commercial finite-element program Abaqus is used, with standard beam elements representing the jack-up structure and a user-defined element describing the behaviour of each spudcan footing by means of a force-resultant plasticity model. This model takes a macro-element approach by expressing the foundation behaviour purely in terms of the loads on the spudcan and the corresponding displacements. Although the model has proven ability to simulate the single-footing experiments from which it was derived, the load paths experienced by the spudcans of a three-legged jack-up are significantly different. To investigate this, numerical simulations of three experimental pushover tests on a 1:250 scale model jack-up have been performed. The tests represent jack-ups with different leg lengths and load orientations. The integrated numerical modelling approach successfully predicts three different failure modes, although the predictions of ultimate pushover capacity are consistently conservative. Because previously published parameters were used for the foundation model, these predictions demonstrate the versatility of the spudcan model in the context of a multi-footing structure, and confirm the effectiveness of the integrated analysis technique. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.114