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Mechanical behaviour of gas-charged marine plastic sediments / N. Sultan in Géotechnique, Vol. 62 N° 9 (Septembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 751 –766 Titre : Mechanical behaviour of gas-charged marine plastic sediments Type de document : texte imprimé Auteurs : N. Sultan, Auteur ; V. De Gennaro, Auteur ; A. Puech, Auteur Année de publication : 2012 Article en page(s) : pp. 751 –766 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Constitutive  relations  Offshore  engineering  Plasticity  Compressibility  Shear  strength Résumé : Understanding how free gas modifies the mechanical behaviour of marine plastic sediments remains a challenging issue. Special triaxial tests were carried out on natural sediments recovered from the Gulf of Guinea. Special attention was devoted to the laboratory preparation procedure, involving saturation of natural marine sediment samples with carbonated water and generation of free gas following undrained unloading. Experimental data show that soil destructuration and damage generated by gas expansion and exsolution are at the origin of (a) the increase in the isotropic compressibility and decrease in the preconsolidation pressure, and (b) the decrease in the peak undrained strength and abrupt increase of the pore pressure during undrained shearing. The experimental data also show that flooding of gas bubbles and dissolution of free gas do not imply a complete strength recovery of natural sediments. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.002 [article] Mechanical behaviour of gas-charged marine plastic sediments [texte imprimé] / N. Sultan, Auteur ; V. De Gennaro, Auteur ; A. Puech, Auteur . - 2012 . - pp. 751 –766. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 751 –766 Mots-clés : Constitutive  relations  Offshore  engineering  Plasticity  Compressibility  Shear  strength Résumé : Understanding how free gas modifies the mechanical behaviour of marine plastic sediments remains a challenging issue. Special triaxial tests were carried out on natural sediments recovered from the Gulf of Guinea. Special attention was devoted to the laboratory preparation procedure, involving saturation of natural marine sediment samples with carbonated water and generation of free gas following undrained unloading. Experimental data show that soil destructuration and damage generated by gas expansion and exsolution are at the origin of (a) the increase in the isotropic compressibility and decrease in the preconsolidation pressure, and (b) the decrease in the peak undrained strength and abrupt increase of the pore pressure during undrained shearing. The experimental data also show that flooding of gas bubbles and dissolution of free gas do not imply a complete strength recovery of natural sediments. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.002

Strain-rate effects in deep marine clays from the Gulf of Guinea / S. S. Torisu in Géotechnique, Vol. 62 N° 9 (Septembre 2012) 

Public ISBD [article]  in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 767 –775 Titre : Strain-rate effects in deep marine clays from the Gulf of Guinea Type de document : texte imprimé Auteurs : S. S. Torisu, Auteur ; J. M. Pereira, Auteur ; V. De Gennaro, Auteur Année de publication : 2012 Article en page(s) : pp. 767 –775 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Creep  Laboratory  tests  Stress  path  Fabric/structure  of  soils  Time  dependence  Shear  strength  Clays Résumé : Current developments in deepwater offshore oil production in the Gulf of Guinea (GoG) make it necessary to characterise the mechanical behaviour of the GoG deepwater sediments better. This paper examines some aspects of the strain-rate-dependent behaviour of intact and reconstituted GoG clay specimens. Results from isotropic compression and undrained shearing laboratory tests with changing rates of stress and strain are presented. They show that the soil generally follows an isotach behaviour, with clear strain-rate dependence of the stress–strain behaviour and pore pressure response in the undrained shear tests. The effects of structure and its degradation on the time-dependent response of the sediments seem to confirm general trends observed in other structured clays. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.015 [article] Strain-rate effects in deep marine clays from the Gulf of Guinea [texte imprimé] / S. S. Torisu, Auteur ; J. M. Pereira, Auteur ; V. De Gennaro, Auteur . - 2012 . - pp. 767 –775. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 62 N° 9 (Septembre 2012) . - pp. 767 –775 Mots-clés : Creep  Laboratory  tests  Stress  path  Fabric/structure  of  soils  Time  dependence  Shear  strength  Clays Résumé : Current developments in deepwater offshore oil production in the Gulf of Guinea (GoG) make it necessary to characterise the mechanical behaviour of the GoG deepwater sediments better. This paper examines some aspects of the strain-rate-dependent behaviour of intact and reconstituted GoG clay specimens. Results from isotropic compression and undrained shearing laboratory tests with changing rates of stress and strain are presented. They show that the soil generally follows an isotach behaviour, with clear strain-rate dependence of the stress–strain behaviour and pore pressure response in the undrained shear tests. The effects of structure and its degradation on the time-dependent response of the sediments seem to confirm general trends observed in other structured clays. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.12.OG.015