Abstract:The vertical vibration analysis of a pile embedded in soil has been applied in machinery foundations,structures exposed to seismic excitation and dynamic pile testing. In past several decades,some models have been developed. But in many cases,the soil was viewed as a monophasic medium. In this paper,a simplified method for analyzing axisymmetric elastodynamic problem of a single pile in single-layer saturated soil is developed. The soil is viewed as a poroelastic solid saturated with fluid;and its motions is governed by field equations originally presented by M. A. Biot. The pile is dealt with one-dimensional bar. By means of elastodynamic and variable separation methods,the traction between pile and soil is obtained considering the perfect contact;and then the analytical solutions of the pile-soil system are finally derived. The complex stiffness of the pile in frequency domain is computed for illustrating the dynamic responses of the pile-soil system in a wider frequency range. Numerical results show that the effects of the moduli ratio of pile and soil on the pile dynamic stiffness are significant at lower frequency as well as the reaction parameter of pile toe. By comparing numerical results of present solution with the poroelastic half-space solution,it can be concluded that the two solutions agree well with each other when reasonable reaction parameters of pile toe are chosen. Furthermore,when the present solution degenerates to a monophasic solution,the result compared with that of finite element also shows that the former can agree well with the latter.