Behavior of Pile Groups Subject to Excavation-Induced Soil Movement in Very Soft Clay
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VIEW THE REPLYPublication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 135, Issue 10
Abstract
A series of centrifuge model tests was conducted to investigate the behavior of pile groups of various sizes and configurations behind a retaining wall in very soft clay. With a 1.2-m excavation in front of the wall, which may simulate the initial stage of an excavation prior to strutting, the test results reveal that the induced bending moment on an individual pile in a free-head pile group is always smaller than that on a corresponding single pile located at the same distance behind the wall. This is attributed to the shadowing and reinforcing effects of other piles within the group. The degree of shadowing experienced by a pile depends on its relative position in the pile group. With a capped-head pile group, the individual piles are forced to interact in unison though subjected to different magnitudes of soil movement. Thus, despite being subjected to a larger soil movement, the induced bending moment on the front piles is moderated by the rear piles through the pile cap. A finite element program developed at the National University of Singapore is employed to back-analyze the centrifuge test data. The program gives a reasonably good prediction of the induced pile bending moments provided an appropriate modification factor is applied for the free-field soil movement and the amount of restraint provided by the pile cap is properly accounted for. The modification factor applied to the free-field soil movement accounts the reinforcing effect of the piles on the soil movement.
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Acknowledgments
The writers wish to acknowledge the able assistance of laboratory officers in the Geotechnical Centrifuge Laboratory of the National University of Singapore in the conduct of centrifuge model tests presented in this paper.
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© 2009 ASCE.
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Received: Apr 17, 2008
Accepted: Feb 1, 2009
Published online: Feb 27, 2009
Published in print: Oct 2009
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