Abstract: Based on a 3-dimensional finite element method(3D FEM),the behaviors of lengthy pile in two-layer soil have been studied.The stress-strain relationships of pile concrete are simulated by a linear elastic model,and that of the soil is simulated by a nonlinear elastic model developed by Duncan and Chang.A special thin-layer element model developed by Hohai University is used to simulate the non-linear displacement between pile and soil.The calculated results show that,for the hard-soft two-layer soil structur...