Abstract: Because of interaction between solid granulae and pore water as well as different permeabilities of pile and saturated soil, the mechanical behavior of a pile in a saturated soil is greatly distinct from that of the pile in single phase soil. Based on the theory of saturated porous media, taking effect of the transversal deformation and inertia of the pile into account and modeling pile as a Rayleigh-Love rod, the dynamical behavior of vertical vibration of the pile in a saturated viscoelastic soil layer is investigated in frequency domain; and the analytical solutions for vertical vibrations of the pile and saturated viscoelastic soil layer are obtained; and an analytical expression of the dynamical complex stiffness of the pile top is presented. The responses of dynamic stiffness factor and damping of pile top against the frequency are shown in figures with the numerical method; and the influences of the soil parameters, modulus ratio of the pile to soil, ratio of the length to radius of the pile and Poisson ratio on the stiffness factor and damping are analyzed. It is shown that the influence of transversal effects on the stiffness factor and damping is much great for the pile with large diameter when the exciting frequency is large

Key words: saturated porous medium, pile-soil interaction, transversal effect, vertical vibration