Abstract: Regarding the seismic liquefied field deposit as being composed of a non-liquefied crust layer at the ground surface, non-liquefied base layer and a sandwiched liquefied layer, based on the nonlinear Winkler model for pile-soil interaction and taking both the nonlinear bending moment-curvature constitutive relationship and geometric nonlinearity of the pile, the fundamental governing equations for nonlinear large deflection deformation of the pile undergoing soil layer’s lateral spreading are formulated and are solved numerically with the shooting method. At the same time, the analytical solutions of the pile are presented for the case of small deformation and linear elasticity. The validity and reliability of the shooting method presented in the paper are verified by comparing the results of the shooting method with those of the nonlinear finite element method and analytical solutions. The influence of the lateral spreading of the soil layer on the mechanical behavior of the pile is investigated numerically. The results show that the effects of nonlinear interaction between the pile and soil as well as material nonlinearity of the pile are much stronger than that of the geometric nonlinearity of the pile. The effect of the geometric nonlinearity is increased with the lateral spreading increasing of the liquefied soil layer. And it’s necessary to analyze the mechanical behavior of the pile with fully nonlinear model.

Key words: nonlinear bending moment-curvature relationship, geometric nonlinearity, nonlinear pile-soil interaction, soil liquefaction, Winkler model