Seismic Subsidence Characteristics of Soft Soil and Dynamic Response of Pile Group with Variable Cross Section

To study the dynamic response characteristics of large-diameter variable cross-section pile group foundations under different types of seismic waves in soft soil site conditions，the shaking table test was carried out based on the solid project of Xiang-An Bridge. The synthetic 5010 and 1004，Kobe，and El-Centro waves with a ground motion intensity of 0.15g were selected in the test. The dynamic response characteristics of the pile group foundation，such as the seismic settlement of soil around the pile，acceleration of the pile body，horizontal displacement of the pile top，and bending moment of the pile body，are studied experimentally. The test results show that under the action of the earthquake，the soft soil layer has seismic subsidence，and the amount of seismic subsidence is in the range of 0.16 ~ 0.22 cm，which is related to the spectral characteristics of the input seismic wave. The acceleration time history response curve of the pile end is more“dense”，and the soft soil has an amplification effect on the acceleration. The peak acceleration of the input seismic wave appears earlier than the pile end，the pile top，and the variable section. The acceleration of the pile and the horizontal displacement of the pile top reach the maximum under the action of the 1004 wave and Kobe wave，respectively. Under the 5010 and 1004 waves，the pile top produces permanent lateral displacement. Under the Kobe wave，the peak bending moment of the pile is the largest，and the peak bending moment appears the latest. Therefore，in the seismic design of pile group foundations，different seismic wave types can be selected for different pile foundation characteristics. © 2023 Hunan University. All rights reserved.