Shaking table test study on seismic responses of pile foundations embedded in liquefiable ground with the frozen crust

The seismic responses of a single steel-pipe pile built in the frozen crust and the liquefiable sand soil were studied by shaking table tests. A flexible soil container was designed and used to construct the soil profile in order to minimize the boundary effect. The frozen crust was simulated through the mortar which was made of cement, sand and water by the mixture ratio. Liquefaction can occur in the saturated sand soil beneath the frozen crust. A lumped mass was exerted at the top of the pile to satisfy the inertia conditions. During the tests, several amplitude-scaled ground motions were chosen as input seismic waves. The liquefying levels of the saturated sand soil and the dynamic responses of the pile can be analyzed via the measured real-time data including strains of the pile, dis-placements between the pile and the frozen crust and pore water pressures in the sand. Experimental results show that before liquefaction occurs, the frozen crust can provide a lateral constraint, and thus improve the load bearing capacity of the pile and suppress its lateral deformation. It is also found that once liquefaction occurs, the frozen crust may further strengthen this tendency and deteriorate the performance of the pile.