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Shock and Vibration
Volume 15 (2008), Issue 6, Pages 665-685
http://dx.doi.org/10.1155/2008/149031

Dynamic Instability of Pile-Supported Structures in Liquefiable Soils during Earthquakes

S. Adhikari1 and S. Bhattacharya2

1University of Wales Swansea, Swansea, UK
2University of Bristol, Bristol, UK

Received 12 April 2007; Revised 18 September 2007

Copyright © 2008 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Piles are long slender columns installed deep into the ground to support heavy structures such as oil platforms, bridges, and tall buildings where the ground is not strong enough to support the structure on its own. In seismic prone zones, in the areas of soft soils (loose to medium dense soil which liquefies like a quick sand) piles are routinely used to support structures (buildings/ bridges). The pile and the building vibrate, and often collapse, in liquefiable soils during major earthquakes. In this paper an experimental and analytical approach is taken to characterize this vibration. The emphasis has been given to the dynamic instability of piled foundations in liquefied soil. The first natural frequency of a piled-structure vibrating in liquefiable soil is obtained from centrifuge tests. The experimental system is modelled using a fixed-free Euler-Bernoulli beam resting against an elastic support with axial load and tip mass with rotary inertia. Natural frequencies obtained from the analytical method are compared with experimental results. It was observed that the effective natural frequency of the system can reduce significantly during an earthquake.