Dynamic Response Difference of Single Pile and Pile Group with Variable Section in Variation of Seismic Subsidence Soil Layer

In order to study the difference of dynamic response between large diameter variable section single pile and pile group foundations in seismic subsidence soil with different thicknesses under ground motion, based on the Xiang’an Bridge of Xiamen Second East Channel, a shaking table model test was conducted to study the difference of dynamic response of soil subsidence, horizontal displacement of pile top, acceleration of pile body and bending moment between single pile and pile group foundation when the thickness of seismic subsidence soil layer is 30, 40, and 50 cm. The results show that with the increase of the thickness of seismic subsidence layer, the seismic subsidence, horizontal displacement of pile top, acceleration and bending moment of single pile and pile group foundations increase gradually, and the acceleration and bending moment change abruptly at variable section. In the seismic subsidence layer with the same thickness, the seismic subsidence of soil around pile group foundation is larger than that of single pile, but the acceleration of pile group foundation, horizontal displacement of pile top and bending moment of pile body are smaller than those of single pile. It is suggested that in the design of pile foundation in seismic subsidence site, the difference of dynamic response between variable section single pile and pile group should be mainly considered to ensure the seismic performance of pile foundation.