Dynamic behavior of pile foundations under cyclic loading in liquefiable soils

Abstract

In this paper, a fully coupled three-dimensional dynamic analysis is carried out to investigate the dynamic behavior of pile foundations in liquefied ground. A critical state bounding surface plasticity model is used to model soil skeleton, while a fully coupled ( u– P) formulation is employed to analyze soil displacements and pore water pressures. Furthermore, in this study, variation of permeability coefficient during liquefaction is taken into account; the permeability coefficient is related to excess pore water pressure ratio. Results of a centrifuge test on pile foundations are used to demonstrate the capability of the model for reliable analysis of piles under dynamic loading. Then, the verified model is used for a parametric study. The parametric study is carried out by varying pile length, frequency of input motion, fixity of the pile head, thickness of the liquefying soil layer and relative density of liquefying soil layer. Three different soil profiles have been considered in this study. In general, parametric studies demonstrate that fixity of the pile head, thickness of liquefying soil layer and frequency of input motion are the most critical parameters which considerably affect piles performance in liquefied grounds.