Abstract: To investigate the dynamic response characteristics of pile groups in liquefaction sites under strong earthquakes as well as the laws between soil resistance and pile-soil relative displacement (p-y), a shaking table model test associated with the project of Haiwen Bridge was conducted. The dynamic responses of sand pore pressure ratio, pile bending moment and p-y curve under different embedded depths of saturated silty sand encountered by 0.15g-0.35g seismic action were studied. The results show that when the seismic intensity reaches 0.25g, the pore pressure ratio of saturated silty sand under different embedded depths is larger than 0.8 and the liquefaction phenomenon occurs. As the embedded depth increases, the increased time of the pore pressure ratio is obviously delayed. At different embedded depths, the maximum bending moment of the pile appears at the interface between liquefied soil layer and the non-liquefied soil layer. At the same embedded depth, the area surrounded by the p-y curve increases gradually with seismic intensity, and its overall slope decreases, indicating that the dynamic energy dissipation of pile-soil interaction increases gradually and that the stiffness of soil around the pile decreases gradually. As the embedded depth increases, the area enclosed by the p-y curve gradually decreases and its overall slope gradually increases, indicating that the dynamic energy dissipation of pile-soil interaction gradually decreases and the soil stiffness around the pile gradually increases. Therefore, when performing the seismic design of bridge pile groups at liquefied sites, the relationship between liquefied soil layer and pile foundation should be considered comprehensively to ensure the bending bearing capacity of the pile foundations at the boundary between liquefied and non-liquefied soil layers.

Key words: bridge pile foundation, strong earthquake action, shaking table test, liquefaction site, dynamic response, p-y curve