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Centrifuge modeling of seismically induced uplitt for the BART transbay tube / J. C. Chou in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 8 (Août 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 8 (Août 2011) . - pp. 754-765 Titre : Centrifuge modeling of seismically induced uplitt for the BART transbay tube Type de document : texte imprimé Auteurs : J. C. Chou, Auteur ; B. L. Kutter, Auteur ; T. Travasarou, Auteur Année de publication : 2011 Article en page(s) : pp. 754-765 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Tunnel  Centrifuge  modeling  Liquefication  Buried  structure  Sand  Gravel  Clay  Earthquake  Uplift  mechanisms  Seismic  performance Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The BART Transbay Tube (TBT) is an immersed cut-and-cover subway tunnel that runs from Oakland to San Francisco, California. The loose sand and gravel backfills placed around the tunnel are considered to be liquefiable, and the clays under the backfill are soft in some zones along the alignment. These conditions could potentially result in uplift of the tunnel during strong earthquake shaking. This paper describes centrifuge model tests performed to verify numerical methods used to assess the stability and to evaluate the potential uplift mechanisms of the TBT. The observed mechanisms of uplift were a ratcheting mechanism (sand migrating under the tunnel with each cycle of relative movement), a pore water migration mechanism (water flowing under the tunnel), and a bottom heave mechanism, involving soft soils below the base of the trench. A fourth potential mechanism, viscous flow of liquefied soil, was not observed. The volume of the tunnel relative to the volume of the trench and the densities and permeabilities of the nonhomogeneous backfill were important parameters affecting the uplift of the tunnel. From the experiments reported here and analyses reported by the designers, it was concluded that the magnitude of uplift is limited and, hence, that an expensive ground improvement project to densify the backfill was unwarranted. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i8/p754_s1?isAuthorized=no [article] Centrifuge modeling of seismically induced uplitt for the BART transbay tube [texte imprimé] / J. C. Chou, Auteur ; B. L. Kutter, Auteur ; T. Travasarou, Auteur . - 2011 . - pp. 754-765. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 8 (Août 2011) . - pp. 754-765 Mots-clés : Tunnel  Centrifuge  modeling  Liquefication  Buried  structure  Sand  Gravel  Clay  Earthquake  Uplift  mechanisms  Seismic  performance Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : The BART Transbay Tube (TBT) is an immersed cut-and-cover subway tunnel that runs from Oakland to San Francisco, California. The loose sand and gravel backfills placed around the tunnel are considered to be liquefiable, and the clays under the backfill are soft in some zones along the alignment. These conditions could potentially result in uplift of the tunnel during strong earthquake shaking. This paper describes centrifuge model tests performed to verify numerical methods used to assess the stability and to evaluate the potential uplift mechanisms of the TBT. The observed mechanisms of uplift were a ratcheting mechanism (sand migrating under the tunnel with each cycle of relative movement), a pore water migration mechanism (water flowing under the tunnel), and a bottom heave mechanism, involving soft soils below the base of the trench. A fourth potential mechanism, viscous flow of liquefied soil, was not observed. The volume of the tunnel relative to the volume of the trench and the densities and permeabilities of the nonhomogeneous backfill were important parameters affecting the uplift of the tunnel. From the experiments reported here and analyses reported by the designers, it was concluded that the magnitude of uplift is limited and, hence, that an expensive ground improvement project to densify the backfill was unwarranted. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i8/p754_s1?isAuthorized=no