Pile-top impedance of pile foundation in liquefied soil based on viscous fluid mechanics

Regarding liquefied soil as the fluid and considering its viscosity, the horizontal vibration of the end-bearing pile in viscous liquefied soil is studied. The motion of the liquefied soil layer is simulated by using the viscous fluid motion equation, and the saturated soil layer is simulated by the saturated porous medium model. The analytical solution for the horizontal vibration of viscous fluid is obtained by separating the variables according to the pile-fluid coupling condition. Based on the continuous conditions of displacement, rotation angle and internal force of the interface between the upper liquefied soil and the lower non-liquefied saturated soil, the expression for pile-top impedance under the layered condition of viscous-liquefied-soil saturated soil is obtained. Compared with the FEM results, the correctness of the analysis is verified. A parametric analysis of the pile-top impedance shows that the viscous characteristics of the liquefied soil should be considered when analyzing the impedance of pile foundation in the liquefied soil so as to avoid the overestimation of stiffness impedance and the underestimation of damping impedance.