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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

Dynamic centrifuge model tests on clay embankments / B. L. Kutter in Géotechnique, Vol. 39 N°1 (Mars 1989) 

Public ISBD [article]  in Géotechnique > Vol. 39 N°1 (Mars 1989) . - pp. 91 –106 Titre : Dynamic centrifuge model tests on clay embankments Type de document : texte imprimé Auteurs : B. L. Kutter, Auteur ; R. G. James, Auteur Année de publication : 2007 Article en page(s) : pp. 91 –106 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Stability  Centrifuge  modelling  Slopes  Clays  Earthquakes  Deformation Résumé : Centrifuge modelling is a valuable means for obtaining data to study the response of geotech-nical structures to infrequent or extreme events such as earthquakes. The results of a study of five clay embankments subjected to 23 simulated earthquakes on the Cambridge geotechnical centrifuge are presented and analysed. The influence of earthquake intensity on dynamic magnification, the existence of a yield acceleration, and a delayed failure were observed in this test series. Deformation patterns observed by X-ray radiography are presented. The stress history and soil shear strength data for the models are presented to enable other researchers to test their ability to predict the observed embankment response. The mechanisms of deformation and failure of the embankments are observed and discussed. Well-documented data of this type are not available from natural earthquakes, since large earthquakes are infrequent and unrepeatable, and it is difficult to predict where they will strike. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.1.91 [article] Dynamic centrifuge model tests on clay embankments [texte imprimé] / B. L. Kutter, Auteur ; R. G. James, Auteur . - 2007 . - pp. 91 –106. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 39 N°1 (Mars 1989) . - pp. 91 –106 Mots-clés : Stability  Centrifuge  modelling  Slopes  Clays  Earthquakes  Deformation Résumé : Centrifuge modelling is a valuable means for obtaining data to study the response of geotech-nical structures to infrequent or extreme events such as earthquakes. The results of a study of five clay embankments subjected to 23 simulated earthquakes on the Cambridge geotechnical centrifuge are presented and analysed. The influence of earthquake intensity on dynamic magnification, the existence of a yield acceleration, and a delayed failure were observed in this test series. Deformation patterns observed by X-ray radiography are presented. The stress history and soil shear strength data for the models are presented to enable other researchers to test their ability to predict the observed embankment response. The mechanisms of deformation and failure of the embankments are observed and discussed. Well-documented data of this type are not available from natural earthquakes, since large earthquakes are infrequent and unrepeatable, and it is difficult to predict where they will strike. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.1.91