爆破开挖诱发的地下交叉洞室微震特性及破裂机制分析

白鹤滩水电站右岸地下多洞室间相互施工扰动，使得母线洞等交叉洞室围岩的微震活动规律及破裂机制十分复杂。引进南非IMS微震监测系统，研究高地应力、多面临空卸荷应力环境下交叉洞室围岩的微震特性及破裂孕育机制。根据地下厂房区围岩岩性、错动带及断层分布，选取监测效果较佳的传感器并合理布置；通过定点敲击试验进行波速反演，分析震源定位的精度；以10#母线洞掉块案例为工程背景，分析爆破开挖诱发的交叉洞室岩体破裂微震事件与能量释放时空演化规律，并基于S波和P波的能量比（ES /EP），归纳、总结了掉块发生过程中岩体破裂演化机制：大量张拉事件发生（爆破冲击诱发）→拉剪、压剪事件发生→张拉事件、剪切事件交替发生（集中应力和节理综合影响）→掉块发生（重力和节理综合作用）。研究结果有利于优化白鹤滩水电站右岸地下洞室群交叉部位的开挖方案，同时对类似工程的开挖和支护具有重要借鉴意义。

Analysis of microseismic characteristics and fracture mechanism of underground caverns induced by blasting excavation

Mutual construction of underground caverns on the right bank of Baihetan hydropower station caused complex microstructures and rupture mechanism of surrounding rock of intersecting caverns. In this study, the IMS system was introduced to investigate microseismic characteristics of surrounding rock of caverns and rupture mechanisms under high stress, multi-faceted unloading stress conditions. According to the lithology, fault zone and fault distribution in the underground powerhouse area, the sensors with perfect monitoring effect were chosen and rationally arranged. The accuracy of the source location was analyzed by using the velocity inversion through the fixed point percussion test. Based on the case of failure of the #10 omnibus cave, this study analzsed the spatial-temporal evolution of microseismic events and energy release of the intersected chambers. Meanwhile, according to the energy ratio (ES/EP) criteria, the evolution mechanism of rock mass rupture was discussed, which included a large number of tension events (blasting shock caused), pull-shear and pressure-shear events, tension and shear events alternately (the effect of concentrated stress and joint) and failure (the effect of gravity and joint) in the order of occurrences. This study is helpful to optimise the excavation scheme of the underground section on the right bank of Baihetan hydropower station, and it is of significance for the excavation and support of similar projects.