竖向荷载对高承台群桩基础侧向位移影响规律的振动台试验

Shaking table tests aiming at the analysis of the effects of vertical load on lateral displacement of pile group foundation with high-cap in liquefiable soil

基于大型振动台模型试验,以高承台群桩为研究对象,模拟了地震作用下高桩承台基础的振动响应,通过超静孔压比(简称孔压比)、加速度和地基土位移研究饱和砂土液化场地竖向荷载对桩基侧向位移的影响规律。结果表明:近桩区域受桩基竖向荷载影响最为显著,孔压比与竖向荷载呈负相关关系,桩基两侧孔压比差值与地基土浅层加速度是造成桩基侧向位移的主要原因;地基土对台面输出加速度主要起放大作用,且随着竖向荷载的增加,加速度放大系数显著减小;在振动输入与竖向荷载相同的条件下,地基土在地震动作用下引起的侧向流动及显著变形极大影响了桩基的侧向位移;竖向荷载为9%桩基极限承载力条件下,桩基倾斜角为4.80°,侧向位移较小,结合地基土抗液化能力,桩基抗倾覆能力最优。

Large-scale shaking table model tests on a group of piles with elevated caps were used to simulate the vibration response of pile group foundations under seismic action.Excess pore pressure ratio(pore pressure ratio for short),acceleration,and foundation soil displacement were used to study the effects of vertical load on the lateral displacement of pile foundations in saturated sand soil liquefaction sites.The findings indicate that the near-pile region is most significantly impacted by the pile foundation’s vertical load.Specifically,the pore pressure ratio decreases as the vertical load increases.The shallow acceleration of the foundation soil and the difference in pore pressure ratios between the superstates on either side of the pile foundation are the primary causes of the pile foundation’s lateral displacement.Moreover,the acceleration output of the table surface is mostly amplified by the foundation soil,and the acceleration amplification coefficient falls noticeably as the vertical load increases.The lateral flow and considerable deformation of foundation soil brought on by ground vibration has a major impact on the lateral movement of the pile foundation under the same input and vertical load conditions.Under the condition of a 9%vertical load,the tilt angle of the pile foundation is 4.80°,and the lateral displacement is small.Furthermore,the best overturning resistance can be expected if combining with the liquefactionresistant ability of the foundation soil.