Abstract: In order to explore the dynamic interaction of the soil−pile group foundation−bridge structure system in saturated sand field overlain by water, a physical similarity model of the vertical (inclined) pile group foundation−bridge structure was designed and manufactured. Centrifuge shaking table tests with seismic wave inputs of different ground motion intensities and characteristics were conducted. The dynamic characteristic indices of pile group foundation−bridge structure were analyzed, and the development of excess pore water pressure in the saturated sand foundation overlain by water and the dynamic response of pile−soil interaction were also investigated. The results indicated that the presence of overlying water had slight influence on the basic cycle and damping of the foundation soil−bridge structure system, but caused a 20% increase in the vibration amplitude of the vertical pile group foundation−bridge structure system and a 10% decrease in the vibration amplitude of the inclined pile group foundation−bridge structure system. The damping ratio of the inclined pile group foundation model was twice as high as that of the vertical pile group foundation model. The overlying water caused the saturated sand foundation to change from a larger liquefaction depth under low-frequency vibration to a larger liquefaction depth under high-frequency vibration. Meanwhile, it promoted the development of excess pore water pressure under small earthquakes and vice versa under strong earthquakes. Furthermore, the overlying water would lead to increases in the dynamic response of the bridge superstructure and the pile bending moment. This study could provide an essential reference for the seismic design of bridge engineering in the sand field overlain by water.

Key words: bridge engineering, seismic performance, centrifuge shaking table test, saturated sand field overlain by water, pile group foundation