A Numerical Model for Seismic Analysis of Piles in Liquefying Soil

Abstract

Liquefaction of the soil is one of the major factors affecting the behaviour of piles founded on seismically active areas. Although methods are available for dynamic analysis of pile foundations, many of them are purely elastic methods or consider only the non-linearity of the surrounding soil. Here a numerical model is presented which takes into account the reduction in stiffness and strength of the soil due to pore pressure build up and subsequent soil liquefaction, in addition to the non-linearity of the soil and pile material. Soil in the far field is represented by the displacements calculated from a ground response analysis based on the effective stress method. The interaction between pile and the surrounding soil is modelled using the Mindlin's fundamental solution with appropriate extensions to account for the soil radiation damping. Interaction coefficients and ultimate lateral pressure of soil at the pile-soil interface are calculated by taking into account the reduction in effective stresses due to build-up of pore water pressures. The non-linearity of the soil at the pile-soil interface is modelled via an iterative procedure which ensures that no where along the pile-soil interface, soil pressure will not exceed the ultimate lateral pressure of the soil. Results given by the numerical model are compared with the data recorded during centrifuge tests and the 1995 Hyogoken-Nambu earthquake. It is demonstrated that the new method gives results in agreement with the recorded data despite its relative simplicity.