Shake table test for seismic response of pile foundation and bridge structure in liquefiable ground

The shake table test for studying the pile-soil-structure seismic interaction in liquefiable ground was carried out, and the characteristics of seismic response of the structure were investigated. Results show that under small seismic input, the dynamic response of foundation is relatively small, while the pore pressure reaches its peak within several seconds after the peak input acceleration time and then, almost immediately, begins to dissipate. Slight liquefaction occurs in the upper sand layer, and the difference of peak pore pressure between far-pile area and near-pile area is very little. The dynamic deformation of pile-pier manifests specific elasticity, and the confinement effect of foundation on the seismic response of the pile cannot be neglected. The dynamic strain of pile in sand is larger than that in clay. On the other hand, the dynamic strain of pile in clay is much larger than that of pier, due to the co-action of confinement effect of upper clay on the pile and counterweight inertia effect of the pier top. While inputting the large seismic wave, complete liquefaction, accompanied by strong shear flow, occurs in a short time. The pore pressure increases immediately after the peak input acceleration time, then increases to its peak gradually, and the dissipation rate is also very low. The peak pore pressure of near-pile area, different from the case of small seismic input, is much larger than that of far-pile area. Dynamic response of pile-pier is quite violent, and the fixing point of pile greatly moves upwards, as a result of large counterweight inertia effect together with complete liquefaction in sand. A large range of damage locates around the interface of sand and upper clay layers, and the pile breaks in the clay layer.