Seismic behavior of pile group-supported bridges in liquefiable sloping ground covered with crusts: Insights from experimental observations

Pile group-supported bridges in liquefied sloping ground with crust are prone to severe damage. However, there remains a limited comprehension of the intricate interactions among pile group, soil, and superstructures, as well as the associated failure mechanisms. To address this issue, this paper presents large-scale shaking table tests conducted on pile group-supported bridges in sloping liquefiable ground with crust to uncover the intricate interaction mechanisms. Firstly, the dynamic characteristics and interaction of the pile-soil-superstructure system were explored. Then, the lateral displacement and acceleration of the superstructure and pile were presented. Next, the curvature and damage characteristics of the pile group-supported bridge were discussed. Finally, through cross-correlation analysis, the study revealed the inertia and kinematic effects, focusing on how the effects influenced the seismic demands. Results indicate that significant differences are observed in pile-soil interactions during strong seismic events depending on the depth and liquefaction stage. As earthquake intensity increases, peak displacement in the superstructure rises linearly while residual displacement grows exponentially. Moreover, the pile group effect becomes more pronounced, especially at the pile head, with the trailing piles showing greater curvature than the leading ones. Due to significant soil lateral spreading and the shadowing effect within the pile group, the leading piles experience prominent kinematic effects from the surface down to the intermediate layer of saturated sand compared to the trailing piles. These findings contribute valuable insights for improving the seismic design approach for bridges with pile groups in sloping liquefied soils.