Field studies of an instrumented model pile in clay / M. R. Coop in Géotechnique, Vol. 39 N°4 (Decembre 1989)  

Public ISBD [article]  inGéotechnique > Vol. 39 N°4 (Decembre 1989) . - pp. 679 –696 Titre : Field studies of an instrumented model pile in clay Type de document : texte imprimé Auteurs : M. R. Coop, Auteur ; C. P. Wroth, Auteur Année de publication : 2007 Article en page(s) : pp. 679 –696 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Piles Offshore geotech-nits Field tests Research Model Résumé : An instrumented model pile was used to investigate the fundamental behaviour of driven cylindrical steel piles, in clay soils. Data are described from two test-bed sites, one with heavily over-consolidated clay, and one with normally consoli-dated clay. These confirm that a residual shear surface is formed adjacent to the pile shaft during installation. Comparisons with other site investigation data and cavity expansion theoretical predic- tions suggest that stress relief immediately behind the pile tip during installation gives rise to total radial stress and pore pressure measurements on the shaft which are lower than the simple cavity expansion model predicts. However, the data did indicate that the radial effective stress might be successfully predicted. During reconsolidation, the radial effective stress drops initially, followed by a slow recovery, which was insufticient in the two clays investigated for the final value to reach that during installation. On undrained loading, the clay adjacent to the pile did not reach a critical state as many current theories assume, as failure occurred on the residual surface created during installation. The generation of negative excess pore pressures on the shear surface during undrained loading caused an increase in the radial effective stress. In the normally consolidated clay this was solely responsible for the large set-up of pile shaft capac-ity by comparison with that during installation. The same capacity increase may not be seen in these clays if loading were drained. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.4.679 [article] Field studies of an instrumented model pile in clay [texte imprimé] / M. R. Coop, Auteur ; C. P. Wroth, Auteur . - 2007 . - pp. 679 –696. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 39 N°4 (Decembre 1989) . - pp. 679 –696 Mots-clés : Piles Offshore geotech-nits Field tests Research Model Résumé : An instrumented model pile was used to investigate the fundamental behaviour of driven cylindrical steel piles, in clay soils. Data are described from two test-bed sites, one with heavily over-consolidated clay, and one with normally consoli-dated clay. These confirm that a residual shear surface is formed adjacent to the pile shaft during installation. Comparisons with other site investigation data and cavity expansion theoretical predic- tions suggest that stress relief immediately behind the pile tip during installation gives rise to total radial stress and pore pressure measurements on the shaft which are lower than the simple cavity expansion model predicts. However, the data did indicate that the radial effective stress might be successfully predicted. During reconsolidation, the radial effective stress drops initially, followed by a slow recovery, which was insufticient in the two clays investigated for the final value to reach that during installation. On undrained loading, the clay adjacent to the pile did not reach a critical state as many current theories assume, as failure occurred on the residual surface created during installation. The generation of negative excess pore pressures on the shear surface during undrained loading caused an increase in the radial effective stress. In the normally consolidated clay this was solely responsible for the large set-up of pile shaft capac-ity by comparison with that during installation. The same capacity increase may not be seen in these clays if loading were drained. ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.1989.39.4.679

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