Documents disponibles écrits par cet auteur

Investigation of the potential of bottom water jetting to ease spudcan extraction in soft clay / C. Gaudin in Géotechnique, Vol. 61 N° 12 (Décembre 2011) 

Public ISBD [article]  in Géotechnique > Vol. 61 N° 12 (Décembre 2011) . - pp. 1043–1054 Titre : Investigation of the potential of bottom water jetting to ease spudcan extraction in soft clay Type de document : texte imprimé Auteurs : C. Gaudin, Auteur ; B. Bienen, Auteur ; M. J. Cassidy, Auteur Année de publication : 2012 Article en page(s) : pp. 1043–1054 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Centrifuge  modelling  Suction  Clays  Water  flow  Offshore  engineering  Consolidation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Retrieval of jack-up rigs at the end of their operations is common practice in the offshore industry, notably to move the rigs to another drilling location. In some cases the process is difficult, time consuming and costly, because the high extraction resistance on the jack-up's spudcan footings can exceed the capacity of the rig to pull. This is particularly the case in soft clay, where significant suction is developed at the spudcan invert. The main option available to operators to ease the spudcan extraction resistance is to use a jetting system at the spudcan invert to attempt to break the suction generated. However, there is a general consensus within the offshore industry that jetting systems, under their current configurations, have a limited efficiency. Centrifuge experiments have been performed at the University of Western Australia in order to understand the mechanisms taking place during jetting extraction, and to provide recommendations to optimise the jetting performance. A reduced-scale spudcan model simulating a 17·11 m diameter prototype spudcan with jets has been tested at 200 times the acceleration of Earth's gravity (known as 200g). It was extracted from penetrations of up to 1·5 diameters in normally consolidated clay at variable extraction rates and variable jetting flow rates. Measurements of the generated suction and the total extraction resistance after a preloading period have provided insight into the extraction mechanisms with jetting. The study has demonstrated that jetting can lead to significant reduction in extraction resistance, provided that the extraction rate is fast enough to ensure undrained extraction, and that a sufficiently high flow rate is applied with respect to the extraction rate. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.152 [article] Investigation of the potential of bottom water jetting to ease spudcan extraction in soft clay [texte imprimé] / C. Gaudin, Auteur ; B. Bienen, Auteur ; M. J. Cassidy, Auteur . - 2012 . - pp. 1043–1054. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 61 N° 12 (Décembre 2011) . - pp. 1043–1054 Mots-clés : Centrifuge  modelling  Suction  Clays  Water  flow  Offshore  engineering  Consolidation Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : Retrieval of jack-up rigs at the end of their operations is common practice in the offshore industry, notably to move the rigs to another drilling location. In some cases the process is difficult, time consuming and costly, because the high extraction resistance on the jack-up's spudcan footings can exceed the capacity of the rig to pull. This is particularly the case in soft clay, where significant suction is developed at the spudcan invert. The main option available to operators to ease the spudcan extraction resistance is to use a jetting system at the spudcan invert to attempt to break the suction generated. However, there is a general consensus within the offshore industry that jetting systems, under their current configurations, have a limited efficiency. Centrifuge experiments have been performed at the University of Western Australia in order to understand the mechanisms taking place during jetting extraction, and to provide recommendations to optimise the jetting performance. A reduced-scale spudcan model simulating a 17·11 m diameter prototype spudcan with jets has been tested at 200 times the acceleration of Earth's gravity (known as 200g). It was extracted from penetrations of up to 1·5 diameters in normally consolidated clay at variable extraction rates and variable jetting flow rates. Measurements of the generated suction and the total extraction resistance after a preloading period have provided insight into the extraction mechanisms with jetting. The study has demonstrated that jetting can lead to significant reduction in extraction resistance, provided that the extraction rate is fast enough to ensure undrained extraction, and that a sufficiently high flow rate is applied with respect to the extraction rate. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.8.p.152

Physical modelling of the push-over capacity of a jack-up structure on sand in a geotechnical centrifuge / B. Bienen in Canadian geotechnical journal, Vol. 46 N° 2 (Fevrier 2009) 

Public ISBD [article]  in Canadian geotechnical journal > Vol. 46 N° 2 (Fevrier 2009) . - pp. 190–207 Titre : Physical modelling of the push-over capacity of a jack-up structure on sand in a geotechnical centrifuge Type de document : texte imprimé Auteurs : B. Bienen, Auteur ; M. J. Cassidy, Auteur ; C. Gaudin, Auteur Article en page(s) : pp. 190–207 Note générale : Sciences de la Terre Langues : Anglais (eng) Mots-clés : Jack-up  Physical  modelling  Centrifuge  Structure–soil  interaction  Three-dimensional  Plate-forme  auto-élévatrice  Modélisation  physique  Centrifuge  Interaction  structure–sol  Trois  dimensions Index. décimale : 550 Sciences auxiliaires de la géologie. Résumé : Offshore jack-up drilling rigs are subjected to loading from wind, waves, and current in addition to their self-weight. This applies combined loading in all six degrees-of-freedom in space on the footings. Although the foundation–soil interaction is crucial to the overall response of a jack-up structure, current state-of-the-art models to predict jack-up footing behaviour, developed using data from single footing experiments, have not been validated for such multi-footing systems under general combined loading. This paper introduces the experimental development of a three-legged model jack-up and loading apparatus designed to investigate the rig’s response — in particular the footing load paths — under combined loading in three dimensions. Push-over experiments were performed in a geotechnical beam centrifuge on silica sand. Experimental results of two tests on dense sand are discussed, highlighting differences in response and mode of failure depending on the loading direction of the jack-up. The importance of three-dimensional modelling is also stressed by experimentally demonstrating that the symmetric load case is not necessarily conservative. Les plates-formes de forages en mer subissent des charges provenant du vent, des vagues et des courants en plus de leur masse. Ceci implique des charges combinées dans les six degrés de liberté dans l’espace sur les semelles. Malgré que les interactions fondations–sol soient cruciales dans l’établissement de la réponse de la plate-forme, les modèles intégrant les connaissances actuelles pour la prédiction du comportement des semelles des plates-formes, qui ont été développés à partir de données provenant d’essais à une semelle, n’ont pas été validés pour des systèmes avec semelles multiples soumis à des charges combinées. Ce papier présente le développement expérimental d’un modèle de plate-forme à trois pattes et d’un appareil de chargement conçu pour investiguer la réponse de la plate-forme - plus particulièrement le cheminement de charge de la semelle – soumis à un chargement combiné en trois dimensions. Des expériences en déplacement latéraux ont été effectuées dans une centrifuge géotechnique sur du sable de silice. Les résultats expérimentaux des deux essais sur du sable dense sont discutés, démontrant les différences de réponses et de mode de rupture dépendamment de la direction de la charge sur la plate-forme. L’importance de la modélisation en trois dimensions est valorisée en démontrant expérimentalement que le scénario de charge symétrique n’est pas nécessairement conservateur. DEWEY : 550 ISSN : 0008-3674 En ligne : http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=f [...] [article] Physical modelling of the push-over capacity of a jack-up structure on sand in a geotechnical centrifuge [texte imprimé] / B. Bienen, Auteur ; M. J. Cassidy, Auteur ; C. Gaudin, Auteur . - pp. 190–207. Sciences de la Terre Langues : Anglais (eng) in Canadian geotechnical journal > Vol. 46 N° 2 (Fevrier 2009) . - pp. 190–207 Mots-clés : Jack-up  Physical  modelling  Centrifuge  Structure–soil  interaction  Three-dimensional  Plate-forme  auto-élévatrice  Modélisation  physique  Centrifuge  Interaction  structure–sol  Trois  dimensions Index. décimale : 550 Sciences auxiliaires de la géologie. Résumé : Offshore jack-up drilling rigs are subjected to loading from wind, waves, and current in addition to their self-weight. This applies combined loading in all six degrees-of-freedom in space on the footings. Although the foundation–soil interaction is crucial to the overall response of a jack-up structure, current state-of-the-art models to predict jack-up footing behaviour, developed using data from single footing experiments, have not been validated for such multi-footing systems under general combined loading. This paper introduces the experimental development of a three-legged model jack-up and loading apparatus designed to investigate the rig’s response — in particular the footing load paths — under combined loading in three dimensions. Push-over experiments were performed in a geotechnical beam centrifuge on silica sand. Experimental results of two tests on dense sand are discussed, highlighting differences in response and mode of failure depending on the loading direction of the jack-up. The importance of three-dimensional modelling is also stressed by experimentally demonstrating that the symmetric load case is not necessarily conservative. Les plates-formes de forages en mer subissent des charges provenant du vent, des vagues et des courants en plus de leur masse. Ceci implique des charges combinées dans les six degrés de liberté dans l’espace sur les semelles. Malgré que les interactions fondations–sol soient cruciales dans l’établissement de la réponse de la plate-forme, les modèles intégrant les connaissances actuelles pour la prédiction du comportement des semelles des plates-formes, qui ont été développés à partir de données provenant d’essais à une semelle, n’ont pas été validés pour des systèmes avec semelles multiples soumis à des charges combinées. Ce papier présente le développement expérimental d’un modèle de plate-forme à trois pattes et d’un appareil de chargement conçu pour investiguer la réponse de la plate-forme - plus particulièrement le cheminement de charge de la semelle – soumis à un chargement combiné en trois dimensions. Des expériences en déplacement latéraux ont été effectuées dans une centrifuge géotechnique sur du sable de silice. Les résultats expérimentaux des deux essais sur du sable dense sont discutés, démontrant les différences de réponses et de mode de rupture dépendamment de la direction de la charge sur la plate-forme. L’importance de la modélisation en trois dimensions est valorisée en démontrant expérimentalement que le scénario de charge symétrique n’est pas nécessairement conservateur. DEWEY : 550 ISSN : 0008-3674 En ligne : http://rparticle.web-p.cisti.nrc.ca/rparticle/AbstractTemplateServlet?calyLang=f [...]

A plasticity model to assess the keying of plate anchors / M. J. Cassidy in Géotechnique, Vol. 62 N° 9 (Septembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 825 –836 Titre : A plasticity model to assess the keying of plate anchors Type de document : texte imprimé Auteurs : M. J. Cassidy, Auteur ; C. Gaudin, Auteur ; M. F. Randolph, Auteur Année de publication : 2012 Article en page(s) : pp. 825 –836 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Anchors  Plasticity  Numerical  modelling  Clays  Centrifuge  modelling  Offshore  engineering Résumé : Suction-embedded plate anchors (SEPLAs) have been developed to answer the growing need for anchors to withstand significant vertical loading. The concept combines the advantage of suction caissons (known penetration depth and location) and ‘drag-embedded' plate anchors (efficiency and low cost). The main issue associated with SEPLAs relates to the keying process, as the anchor is first loaded, and the associated loss of embedment and reduction in capacity. The paper presents a plasticity model developed to predict the trajectory and load development during anchor keying, and up to peak load. Rigid plasticity is assumed, allowing the kinematics of the anchor to be determined from a yield surface and associated plastic potential. The trajectory and performance of a typical SEPLA are predicted using the model, and are compared with results from centrifuge tests and large-deformation finite-element analysis. The anchor loss of embedment ranged from ∼0·2 to 1·5 times the anchor height for loading inclinations between 40° and 90° from the horizontal. The model was used further to calculate the anchor loss of embedment and capacity for varying padeye offsets. Results indicated that the loss of embedment could be reduced significantly by increasing the offset, but at the detriment of the ultimate anchor capacity. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.009 [article] A plasticity model to assess the keying of plate anchors [texte imprimé] / M. J. Cassidy, Auteur ; C. Gaudin, Auteur ; M. F. Randolph, Auteur . - 2012 . - pp. 825 –836. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 825 –836 Mots-clés : Anchors  Plasticity  Numerical  modelling  Clays  Centrifuge  modelling  Offshore  engineering Résumé : Suction-embedded plate anchors (SEPLAs) have been developed to answer the growing need for anchors to withstand significant vertical loading. The concept combines the advantage of suction caissons (known penetration depth and location) and ‘drag-embedded' plate anchors (efficiency and low cost). The main issue associated with SEPLAs relates to the keying process, as the anchor is first loaded, and the associated loss of embedment and reduction in capacity. The paper presents a plasticity model developed to predict the trajectory and load development during anchor keying, and up to peak load. Rigid plasticity is assumed, allowing the kinematics of the anchor to be determined from a yield surface and associated plastic potential. The trajectory and performance of a typical SEPLA are predicted using the model, and are compared with results from centrifuge tests and large-deformation finite-element analysis. The anchor loss of embedment ranged from ∼0·2 to 1·5 times the anchor height for loading inclinations between 40° and 90° from the horizontal. The model was used further to calculate the anchor loss of embedment and capacity for varying padeye offsets. Results indicated that the loss of embedment could be reduced significantly by increasing the offset, but at the detriment of the ultimate anchor capacity. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.009