跨越走滑断层黏土地层动力响应离心机试验研究

Abstract

地震中基岩走滑断层活动引起跨断层地下结构物破坏,上覆土层的非一致响应机制尚不明确,隐伏裂缝影响规律认识不足。基于可模拟走滑断层活动的层状剪切箱,针对黏土地层展开两个离心机振动台试验,对比上覆土体中隐伏裂缝的影响。试验结果表明,当地层中不存在隐伏裂缝时,基岩走滑断层错动对两盘地层的非一致振动的影响不显著。当地层中存在隐伏裂缝,错动盘一侧土体的振动加速度幅值随振动循环次数的增加逐渐减小,固定盘和错动盘两侧土体出现非一致振动响应,固定盘一侧土体产生的超静孔压大于错动盘一侧。隐伏裂缝对土体非一致振动响应的影响范围受限于其在地层中的分布范围,探明隐伏裂缝上断点的埋深具有重要工程意义。 Underground structures are severely damaged when subjected to strike-slip faulting during an earthquake. Mechanism behind inconsistent dynamic responses in soil stratum is not yet fully understood. The influence of pre-existing fracture in soil stratum on the dynamic response of the soil is still not clear. Based on a newly designed laminar box with simulation of strike-slip fault, two dynamic centrifuge tests were conducted on clay stratum to investigate the influences of the pre-existing fracture. Centrifuge test results show that inconsistent dynamic responses for the soil crossing bedrock fault is not obvious when there is no pre-existing fracture. With a pre-existing fracture, however, the magnitude of seismic wave at the moving block decreases with time during shaking. Inconsistent dynamic responses between the stationary and moving blocks are then observed. In addition, the excess pore water pressures developed at the stationary block are larger than what are observed at the moving block. The effects of distribution of the pre-existing fracture on the inconsistent dynamic responses in the soil stratum are also demonstrated. It is of significant importance to identify the tip depth of the pre-existing fracture in soil stratum. © 2018, Science Press. All right reserved