Shaking table test and theoretical analysis of the pile–soil–structure interaction at a liquefiable site

Pile foundations are widely used to support high‐rise buildings, in which piles transmit foundation loads to soil strata with higher bearing capacity and stiffness. This process alters the dynamic characteristics of the pile–soil–structure system in seismically active areas, especially at a liquefiable site. A series of shaking table tests on liquefiable soils in pile group foundations of tall buildings were performed to evaluate the liquefaction process and dynamic responses of the pile, soil, and structure. The soil was composed of two layers: the upper layer was a clay layer and the lower layer was saturated sand. These layers were placed in a flexible container that was excited by El Centro earthquake events and Shanghai Bedrock waves at different levels. The test results indicate that the pore pressure ratio is gradually enhanced as the amplitude of the input acceleration increases. The liquefied sand has a filtering effect on the vibration with a high frequency and an amplified effect on the vibration with a low frequency. With increased excitation, contact pressure and strain amplitudes of the pile increase, whereas the peak acceleration magnification coefficient decreases. The seismic responses of a structure with pile–soil–structure interaction are generally smaller than those on a rigid foundation.