竖向荷载对液化群桩基础的动力响应影响

Dynamic Response Law of Pile Group Foundation in Liquefiable Ground Under Different Vertical Loads

摘要

为研究竖向荷载对液化群桩基础的动力响应影响,以高承台群桩为研究对象,分别取桩基竖向极限承载力的5%、10%、15%、20%作为竖向荷载,在地震强度为0.20g、0.34g、0.50g的工况下进行振动台试验。从超静孔压比时程、加速度时程、桩承台位移时程和桩身弯矩时程4个方面来分析不同竖向荷载对砂土液化和动力响应的影响。研究结果表明:随着竖向荷载增加,超静孔压比峰值减小,砂土液化程度降低;而桩顶加速度、桩承台位移和桩身弯矩随着竖向荷载增加,峰值先减小后增大,竖向荷载为15%时峰值最小。竖向荷载的增加能够抑制砂土液化,同时也会增加结构惯性力。在砂土液化和结构惯性力的共同作用下,竖向荷载为15%时液化群桩的动力响应效果最优。

Abstract

In order to study the influence of vertical loads on the dynamic response of pile group foundation in liquefiable ground, the high cap pile group is taken as the research object. The shaking table test is used to take 5%, 10%, 15% and 20% of the ultimate vertical bearing capacity of the pile foundation as the vertical load, and the test is carried out under the seismic intensity of 0.20g, 0.34g and 0.50g. The effects of different vertical loads on sand liquefaction and dynamic response are analyzed from aspects of pore pressure ratio time history, acceleration time history, pile cap displacement time history and pile bending moment response time history. The results showed that with the increase of vertical load, the peak pore pressure ratio and the liquefaction degree of sand decreased. The peak values of pile top acceleration, pile cap displacement and pile bending moment decreased first and then increased with the increase of vertical load, and the values were the smallest when the vertical load was 15%. The increase of vertical load can inhibit the liquefaction of sand and increase the inertial force of the structure. With the combined influence, the dynamic response effect of pile group in liquefiable ground is optimal under the vertical load of 15%.

关键词

群桩基础 / 竖向荷载 / 地震液化 / 振动台试验 / 动力响应

Key words

pile group foundation / vertical load / earthquake-induced liquefaction / shaking table test / dynamic response

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基金资助

国家自然科学基金资助项目(U21A20164)

国家自然科学基金资助项目(51825904)