Experimental study on frozen soil-liquefiable soil-single pile interaction during earthquakes

Liquefaction-induced lateral gound spreading can result in excessive lateral displacement, even failure of piles, nevertheless the situation may be somewhat different in frozen ground. Shaking table tests are conducted with the purpose of investigating the corresponding influence. The soil profile, contained in a large flexible box, consists of a horizontally saturated sand layer overlaid with a simulated frozen soil layer. The simulated steel-pipe pile is embeded in these two soil layers, with a supplemental lumped mass at the top. The device is excited through several amplitude-scaled seismic waves with different levels. During the tests the strain of the pile, the displacements of the pile and the frozen-soil layer, and the pore water pressure in the sand are recorded. Some important conclusions can be drawn. When liquefaction occurs, the frozen-soil layer can suppress the pore water drains from the saturated sand soils and make the pore water pressure increase continuously. Hence, the liquefaction has the tendency to accelerate and the lateral displacement of the pile may increase significantly. With the increasing levels of seismic excitation, the position on the frozen crust corresponding to the contact surface of the frozen-soil layer and the pile may be damaged because of squeezing, and thus the contact surface cannot be maintained effectively any longer. The sudden changes in the lateral deformation of the pile occour at the positions corresponding to the bottom and the top surface of the frozen crust, and consequently these positions on the pile can be easily damaged.