正断层诱发砂土中群桩基础破坏及避让距离研究

地震中发震断层诱发桩基失效，导致上部结构破坏甚至坍塌，相关破坏机制和避让距离缺乏系统研究。通过离心机试验和数值模拟，针对基岩正断层活动诱发上覆砂土中群桩基础的静力破坏展开研究，考察不同群桩断层相对位置下群桩的破坏特征。试验与计算结果均表明，当群桩跨越断层时，正断层活动使群桩向上盘一侧倾斜，并使基桩弯向上盘一侧。基桩桩顶荷载的重分布进一步使基桩形成受拉和受压两种破坏模式。数值参数分析表明，在不同桩位上，群桩的变形响应可划分为5个特征区域。对于埋深为20.0 m的基岩正断层，群桩在上盘和下盘一侧的安全避让距离分别为23.5 m和15.9 m，其中下盘一侧离开断层7.9 m至上盘一侧离开断层4.1 m的区域需要进行重点避让。

Study on failure mechanism and setback distance of a pile group in sand subjected to normal faulting

Pile foundation could be severely damaged by active fault during an earthquake, resulting damage and even collapse of superstructures. The pile failure mechanism and setback distance are not yet investigated systematically. Centrifuge and numerical modeling of pile group foundation in sand subjected to normal faulting were conducted. The influences of pile location relative to the bedrock fault on failure mechanism of pile group were investigated. Centrifuge and numerical results consistently show that when the pile group crosses the bedrock fault, the pile tilts to the hanging wall after faulting and is also bent to the hanging wall. Loading redistribution between piles results in two different failure patterns of tension and compression. Numerical parametric study of pile locations show that five characteristic zones could be classified based on different pile responses. For a soil stratum with thickness of 20.0 m, the setback distances of pile group at the side of footwall and hanging wall are 15.9 m and 23.5 m, respectively. The area within 7.9 m to the fault line at the footwall and 4.1 m to the fault line at the hanging wall is the most critical setback zone.