水平和竖向地震作用下液化场地群桩基础动力响应试验研究

为研究水平和竖向(双向)耦合地震作用下液化场地群桩基础的动力响应,设计了可液化地基-群桩基础-框筒结构动力相互作用体系振动台模型试验。选取不同类型模拟地震波作为振动台试验激励,通过对比水平地震作用和双向耦合地震作用下土体加速度、超孔隙水压力和群桩应变等试验结果,进而分析双向耦合地震作用对可液化地基和群桩基础动力响应的影响。研究结果表明:双向耦合地震作用下,液化场地土体竖向加速度峰值随土体埋深高度的减小而逐渐增大;饱和砂土的液化效应与双向耦合地震作用和输入地震波的类型有关;相比水平地震作用,不同种类波双向耦合地震作用下群桩基础桩身中部和底部的应变峰值增大,桩顶应变峰值变化略有不同;双向耦合地震作用加剧了建筑结构群桩体系的摇摆和倾斜。研究结果对可液化地基上群桩基础的抗震设计和防灾减灾具有十分重要的研究意义。

Experimental investigation on dynamic response of pile group foundation on liquefiable ground subjected to horizontal and vertical earthquake excitations

To investigate the dynamic response of pile group foundation on liquefiable ground subjected to horizontal and vertical(bidirectional)coupling earthquake excitations,a shaking table model test for a dynamic interaction system with liquefiable groundpile group foundation-frame tube structure was conducted.Different types of earthquake motions were selected as the excitations for the shaking table test,and then the influence of bidirectional coupling earthquake excitations on the dynamic response of liquefiable ground and pile group foundation were analyzed by comparing the test results of soil acceleration,excess pore water pressure and pile group strain subjected to horizontal unidirectional and bidirectional coupling excitations.The results indicate that under the bidirectional coupling earthquake excitations,the vertical peak acceleration of liquefiable soil gradually increases with the decrease of buried depth;the liquefaction effect of saturated sand is related to the bidirectional coupling earthquake excitations and the type of input earthquake motions;besides,compared with the horizontal earthquake excitation,the peak strain in the central and bottom of pile group foundation are larger than those under the bidirectional coupling earthquake excitations,the variation of peak strain of pile top is different;also,the swaying and tilting of the pile group system of the building structure are exacerbated by the bidirectional coupling earthquake excitations.The research results are of great significance to both the seismic design of pile group on liquefiable foundation and disaster prevention and mitigation.