RESEARCH ON DYNAMIC IMPEDANCE FUNCTIONS OF PILE-RAFT FOUNDATION IN LAYERED SOIL

Dynamic impedance functions of a pile-raft foundation in layered soil are studied by using the thin layered element method and the finite element method. The horizontal, vertical and rocking impedance functions of the pile-raft foundation are compared with those of a pile group and raft foundation. The effects of layered soil on the impedance functions of the pile-raft foundation are also analyzed. The results show that the horizontal impedance of the pile-raft foundation is approximate to that of the raft foundation, but the vertical and rocking impedance are approximate to those of the pile group. The layered soil causes undulations in the impedances of the pile-raft foundation, which are characterized by the increase in the stiffness and the decrease in the damping in the low-frequency range.