Documents disponibles écrits par cet auteur

Effect of surface heave on response of partially embedded pipelines on clay / R. S. Merifield in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 6 (Juin 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 6 (Juin 2009) . - pp. 819–829 Titre : Effect of surface heave on response of partially embedded pipelines on clay Type de document : texte imprimé Auteurs : R. S. Merifield, Auteur ; D. J. White, Auteur ; M. F. Randolph, Auteur Année de publication : 2009 Article en page(s) : pp. 819–829 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Pipelines  Clays  Plasticity  Offshore  structures  Finite  element  method  Soil  mechanics  Collapse  loads  Cohesive  soils  Embedment Résumé : The as-laid embedment of an on-bottom pipeline strongly influences the resulting thermal insulation, and the resistance to subsequent axial and lateral movement of the pipeline. Reliable assessment of these parameters is essential for the design of offshore pipelines. Static vertical penetration of a pipe into a soft clay seabed—which can be modeled as an undrained process—causes heave of soil on each side of the pipeline. The heaved soil contributes to the vertical penetration resistance and the horizontal capacity. This paper describes a series of large deformation finite-element analyses of pipe penetration, supported by a simple analytical assessment of the heave process. The conventional bearing capacity approach to the analysis of pipe penetration is reviewed, and modifications for the effects of soil weight and heave are presented. It is shown that in soft soil conditions—which are typical for deep water—the soil self-weight contributes a significant portion of the vertical penetration resistance and horizontal capacity. If heave is neglected, the soil weight leads to a vertical force due to buoyancy, based on Archimedes’ principle. When heave is considered, the soil weight contributes an additional component of vertical load, exceeding simple buoyancy, due to the distorted geometry of the soil surface. Archimedes’ principle does not apply. The finite-element analyses, benchmarked against rigorous plasticity solutions, are used to calibrate simple expressions for predicting static vertical pipe penetration, and the resulting horizontal capacity. These simple solutions allow the conventional bearing capacity approach to be used in a manner which correctly accounts for the effects of soil self-weight and heave. An approximate solution for predicting the “local” pipe embedment—relative to the raised soil level immediately adjacent to the pipe—is derived. The local embedment significantly exceeds the nominal embedment relative to the original soil surface. This effect counteracts the tendency for heave to reduce the embedment by raising the penetration resistance. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000070 [article] Effect of surface heave on response of partially embedded pipelines on clay [texte imprimé] / R. S. Merifield, Auteur ; D. J. White, Auteur ; M. F. Randolph, Auteur . - 2009 . - pp. 819–829. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 6 (Juin 2009) . - pp. 819–829 Mots-clés : Pipelines  Clays  Plasticity  Offshore  structures  Finite  element  method  Soil  mechanics  Collapse  loads  Cohesive  soils  Embedment Résumé : The as-laid embedment of an on-bottom pipeline strongly influences the resulting thermal insulation, and the resistance to subsequent axial and lateral movement of the pipeline. Reliable assessment of these parameters is essential for the design of offshore pipelines. Static vertical penetration of a pipe into a soft clay seabed—which can be modeled as an undrained process—causes heave of soil on each side of the pipeline. The heaved soil contributes to the vertical penetration resistance and the horizontal capacity. This paper describes a series of large deformation finite-element analyses of pipe penetration, supported by a simple analytical assessment of the heave process. The conventional bearing capacity approach to the analysis of pipe penetration is reviewed, and modifications for the effects of soil weight and heave are presented. It is shown that in soft soil conditions—which are typical for deep water—the soil self-weight contributes a significant portion of the vertical penetration resistance and horizontal capacity. If heave is neglected, the soil weight leads to a vertical force due to buoyancy, based on Archimedes’ principle. When heave is considered, the soil weight contributes an additional component of vertical load, exceeding simple buoyancy, due to the distorted geometry of the soil surface. Archimedes’ principle does not apply. The finite-element analyses, benchmarked against rigorous plasticity solutions, are used to calibrate simple expressions for predicting static vertical pipe penetration, and the resulting horizontal capacity. These simple solutions allow the conventional bearing capacity approach to be used in a manner which correctly accounts for the effects of soil self-weight and heave. An approximate solution for predicting the “local” pipe embedment—relative to the raised soil level immediately adjacent to the pipe—is derived. The local embedment significantly exceeds the nominal embedment relative to the original soil surface. This effect counteracts the tendency for heave to reduce the embedment by raising the penetration resistance. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000070

Ultimate uplift capacity of multiplate helical type anchors in clay / R. S. Merifield in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 7 (Juillet 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 7 (Juillet 2011) . - pp. 704-716 Titre : Ultimate uplift capacity of multiplate helical type anchors in clay Type de document : texte imprimé Auteurs : R. S. Merifield, Auteur Année de publication : 2011 Article en page(s) : pp. 704-716 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Anchors  Numerical  modeling  and  analysis  Theoretical  analysis  Clays  Plasticity Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : In recent years, the use of helical anchors has expanded beyond their traditional use in the electrical power industry. The advantages of rapid installation and immediate loading capability have resulted in their being used in more traditional civil engineering infrastructure applications. Unfortunately, our current understanding of these anchors is unsatisfactory, and the underlying theoretical framework adopted by engineers has proven to be largely inappropriate and inadequate. A better understanding of helical anchor behavior will lead to increased confidence in design, a wider acceptance as a foundation alternative, and more economic and safer designs. The primary aim of this research is to use numerical modeling techniques to better understand multiplate circular anchor foundation behavior in clay soils. A practical design framework for multiplate anchor foundations will be established to replace existing semiempirical design methods that are inadequate and have been found to be excessively under- or overconservative. This framework can then be used by design engineers to confidently estimate the pullout capacity of multiplate anchors under tension loading. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i7/p704_s1?isAuthorized=no [article] Ultimate uplift capacity of multiplate helical type anchors in clay [texte imprimé] / R. S. Merifield, Auteur . - 2011 . - pp. 704-716. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 7 (Juillet 2011) . - pp. 704-716 Mots-clés : Anchors  Numerical  modeling  and  analysis  Theoretical  analysis  Clays  Plasticity Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : In recent years, the use of helical anchors has expanded beyond their traditional use in the electrical power industry. The advantages of rapid installation and immediate loading capability have resulted in their being used in more traditional civil engineering infrastructure applications. Unfortunately, our current understanding of these anchors is unsatisfactory, and the underlying theoretical framework adopted by engineers has proven to be largely inappropriate and inadequate. A better understanding of helical anchor behavior will lead to increased confidence in design, a wider acceptance as a foundation alternative, and more economic and safer designs. The primary aim of this research is to use numerical modeling techniques to better understand multiplate circular anchor foundation behavior in clay soils. A practical design framework for multiplate anchor foundations will be established to replace existing semiempirical design methods that are inadequate and have been found to be excessively under- or overconservative. This framework can then be used by design engineers to confidently estimate the pullout capacity of multiplate anchors under tension loading. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i7/p704_s1?isAuthorized=no