Abstract: In order to study the dynamic response and the avoidance distance of pile foundation of cross-fault bridge in strong earthquake area, four types of seismic waves were selected to establish the pile-soil-fault interaction model, which was based on the physical project of Haiwen Bridge. The four types of seismic waves included 5010 wave, 5002 wave, Kobe wave and El-Centro wave. The finite element analysis software MIDAS/GTS was adopted to study the variation laws of the peak acceleration response of pile foundation in the upper and lower walls of the fault, the horizontal displacement response of pile top and the bending moment response of pile. And the influence of the safe avoidance distance between pile foundation and fault on the mechanical deformation characteristics of pile foundation was also studied. The results show that the response degree of pile foundation in the upper wall of the fault is larger than that in the lower wall of the fault under the action of the four seismic waves, showing a significant “upper wall effect”. The overburden soil has obvious amplification and filtering effect on the peak acceleration of the pile body, and the peak acceleration response of pile top has hysteresis. In comparison, the peak acceleration and amplification factor of the peak acceleration at the pile top under the action of El Centro wave are the largest, the peak value of horizontal displacement at the pile top under the action of 5002 wave is the largest, and the peak value of pile body bending moment under the action of Kobe wave is the largest. It is suggested that in the seismic design of bridge pile foundation, the influence of the difference between pile foundation upper and lower walls of fault and the type of seismic wave on the bearing capacity of pile foundation shall be taken into account emphatically. It is recommended that the safe avoidance distance of the pile foundation of cross-fault bridge in strong earthquake area is 20 m (10D).

Key words: bridge engineering; dynamic response; cross-fault bridge; the safe avoidance distance

摘要： 为研究强震区跨断层桥梁桩基动力响应及避让距离，依托海文大桥实体工程，选取4种类型地震波——5010波、5002波、Kobe波和El-Centro波；采用MIDAS/GTS有限元分析软件，建立了桩-土-断层相互作用模型，研究了断层上下盘桩的峰值加速度响应、桩顶水平位移响应和桩身弯矩响应的变化规律，以及桩基与断层之间的安全避让距离取值对桩基础力学变形特性的影响。结果表明：4种地震波作用下，断层上盘桩基的动力响应均较断层下盘的大，呈现显著的“上盘效应”；覆盖层土体对桩身峰值加速度有明显的放大作用和滤波作用；桩顶峰值加速度响应具有滞后性；比较而言，El-Centro波作用时桩顶峰值加速度及峰值加速度放大系数最大，5002波作用时桩顶水平位移峰值最大，Kobe波作用时桩身弯矩峰值最大。建议在桥梁桩基抗震设计时，应着重考虑断层上、下盘桩基的差异和地震波类型对桩基承载力的影响；推荐强震区跨断层桥梁桩基安全避让距离值为20 m（10D）。

关键词: 桥梁工程；动力响应；跨断层桥梁；安全避让距离