Interaction between pile groups and thrust faults in a physical sandbox and numerical analysis

Abstract

For a bridge that straddles a fault line, its pile group foundation can tilt or even fail during an earthquake event. A small-scale physical sandbox experiment is performed in this study to model a pile group subjected to thrust faulting, and particle flow code (PFC3D) is adopted for numerical analysis. The numerical analysis results are in good agreement with the sandbox test results with regard to the propagation path of the shear zone, displacement of the pile cap, and deformation patterns of the piles. The propagation path of the fault rupture surface (FRS) for the case with a pile group is different from that for the free-field case. The pile cap undergoes substantial rotation and displacement; moreover, adjacent piles can experience different deformation patterns, producing different degrees of axial force and bending moments. The piles in the shear zone can separate, and the pile group can fail with increasing fault offsets. The relative positions of the pile group and the fault show that the position of the pile foundation should be as far from the triangular shear zone as possible. The development of the fault rupture surface is affected by the existence and location of the pile group. The bending moment along the pile shaft is related to the passive earth pressure exerted by soil on the right side of the pile cap. This behavior results in rotation, deformation and displacement of the pile.