Abstract: In order to explore the dynamic interaction of the soil-pile group foundation-bridge structure system in overlaying water-saturated sand fields, a physical similarity model of the straight (oblique) pile group foundation-bridge structure was designed and fabricated. Centrifuge shaking table tests with seismic wave inputs of different ground motion intensities and characteristics were conducted. The dynamic characteristics indexes of pile group foundation-bridge structure were analyzed, and the development of excess pore water pressure in the overlaying water-saturated sand foundation and the dynamic response characteristics of pile-soil interaction was also investigated. The results indicated that the presence of overlaying water had little 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 straight pile group foundation-bridge structure system and a 10% decrease in the vibration amplitude of the oblique pile group foundation-bridge structure system. The damping ratio of the oblique pile group foundation model was twice as high as that of the straight pile group foundation model. The overlaying 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 led to promote the development of excess pore water pressure under small earthquakes and vice versa under large earthquakes. Furthermore, the overlaying water would lead to an increase in the dynamic response of the bridge superstructure and the pile bending moment. The above research results could provide an essential reference for the seismic design of bridge engineering in overlaying water sand fields.

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