强震作用下桩-土-断层非线性动力响应特性

Nonlinear dynamic response characteristics of pile-soil-fault under strong earthquake

为研究强震作用下桩-土-断层非线性动力响应特性,依托海文大桥实体工程,选取4种类型(5010波、5002波、Kobe波和El-Centro波)地震波,通过建立桩-土-断层相互作用模型,利用MI⁃DAS/GTS有限元分析软件,研究断层上、下盘桩基加速度响应、桩顶水平位移、桩身弯矩以及剪力响应情况。结果表明:4种类型地震波作用下,断层上盘桩基响应程度相对于断层下盘较大,呈现出显著“上盘效应”;覆盖层土体对桩身加速度放大作用和滤波作用明显;上盘桩顶峰值加速度响应具有滞后性;桩顶加速度及其放大系数在El-Centro波作用时较大;桩顶水平位移峰值在5010波作用时较大;桩顶永久位移、桩身弯矩以及剪力峰值在Kobe波作用时较大。在桥梁桩基抗震设计时,应着重考虑断层上、下盘差异和地震波类型对桩基承载特性的影响。

In order to study the nonlinear dynamic response characteristics of pile-soil-fault under strong earthquake,based on the solid project of Haiwen Bridge,four types of seismic waves(5010 wave,5002 wave,Kobe wave and El-Centro wave)are selected,and the finite element analysis software MIDAS/GTS is used to establish the pile-soilfault interaction model to study the acceleration response of pile foundation,horizontal displacement of pile top,bending moment and shear response of pile.The results show that under the action of four types of seismic waves,the response degree of pile foundation in the upper wall of the fault is larger than that in the lower wall of the fault,show⁃ing a significant“upper wall effect”.The overburden soil has obvious magnifying and filtering effect on the accelera⁃tion of pile body.The response of the peak acceleration at the top of the upper pile has hysteresis.The acceleration of pile top and its magnification coefficient are larger under the action of El-Centro wave.The peak value of horizontal displacement at the top of pile is larger under the action of 5010 wave.The permanent displacement at the top of the pile,the bending moment of the pile and the peak value of shear force are larger under the action of Kobe wave.In the seismic design of bridge pile foundation,the influence of the difference of pile foundation between the upper and lower wall of fault and the type of seismic wave on the bearing characteristics of pile foundation should be considered.