Dynamic impedance of pile groups subjected to vertical load in layered transversely isotropic saturated soils

A method to calculate the dynamic impedance of pile groups subjected to vertical harmonic load in layered transversely isotropic saturated soils is proposed. Based on the Biot’s wave theory for fluid-saturated porous media, the general solutions of axial symmetrical dynamic equations for transversely isotropic saturated soils are presented by means of the Hankel integral transform. Then, using the general solutions, the exact dynamic stiffness matrix in the Hankel’s transform domain for a layered saturated stratum and saturated half-space is derived respectively, and the dynamic Green’s function of saturated stratum subjected to internal barrel distributed vertical load is obtained as a result. Furthermore, through a combination of the boundary element method and the finite element method, a system of algebraic equations by satisfying the interface equilibrium and compatibility with pile groups and layered transversely isotropic saturated soils are introduced according to the Kynia’s methodology. The calculated results indicate that the effects of the anisotropy in soil skeleton and the dynamic stiffness in layered saturated stratum on the dynamic impedance of end-bearing pile groups are relatively weak, but are obvious on that of friction pile groups.