砂土中垫层隔震基础地震响应离心模型试验及数值分析

Centrifuge Test and Numerical Analysis of Seismic Response of Cushioned Pile Raft Foundation in Sand

摘要:

针对砂土地基中的一种新型基础型式——垫层隔震基础，开展地基-基础-结构动力相互作用的离心振动台试验和三维数值模拟。通过对比不同峰值和类型地震波作用下新型垫层隔震基础与传统群桩基础的动力响应，探讨垫层隔震基础的隔震机理，并结合参数分析垫层厚度等因素对垫层隔震基础地震响应的影响规律。结果表明，与群桩基础相比，垫层隔震基础的上部结构加速度降低，但其峰值及残余位移较大；桩顶约束减弱，筏板与垫层在强震下相对滑动，传递的惯性力降低，导致桩身最大弯矩减小且位置下移；桩身弯矩随垫层厚度的降低而显著增大。

Abstract:

Centrifuge shaking table tests and three-dimensional numerical simulations of dynamic interactions among soil， foundation， and structure are conducted for both a traditional pile group foundation of bridge and a novel cushioned pile raft foundation of bridge in sand. By comparing the dynamic responses of the two kinds of foundations subjected to different peaks and types of earthquake waves， the seismic isolation mechanism of the cushioned pile raft foundation is discussed， and the influences of the thickness of cushion and other factors on the seismic response of the cushioned pile raft foundation are studied based on parameter analysis. The results show that when compared with the pile group foundation， the acceleration of the superstructure of the cushioned pile raft foundation decreases， while its peak and residual displacement increases. The constraint of pile head is weakened， and sliding takes place between the raft and the interposed layer in strong earthquakes， thus reducing the inertial force transmitted to the foundation， which leads to a decrease of the maximum pile bending moment and a moving down of the position of the maximum pile bending moment. The pile bending moment increases significantly with the decrease of the thickness of cushion.