开挖扰动下地下交叉洞室错动带岩体微震演化规律

错动带具有“历史上多次剪切错动、延伸范围广、遇水易软化、力学强度低”的软弱特性，致使其在开挖卸荷作用下极易诱发不同程度的变形和破坏，进而严重影响地下洞室的稳定性。针对白鹤滩水电站右岸9#母线洞（地下交叉洞室）发生的错动带岩体塌方破坏，借助高精度、实时微震监测系统，系统地研究了塌方孕育过程中的微震活动性，包括微震事件时空演化规律、震级和视应力分布特征。采用矩张量理论，反演塌方孕育过程中的微震事件破裂机制（张拉、剪切或混合），归纳、总结其演化过程为：表层围岩卸荷张拉破裂→裂纹渐进向围岩深部扩展→破裂沿错动带方向萌生、扩展（张拉破裂为主，伴随剪切或混合破裂）→裂缝与错动带交汇，切割出不稳定楔形体→爆破振动或重力作用下，错动带岩体塌方。该研究结果可为高应力地下交叉洞室错动带岩体的开挖、支护提供参考，同时对类似工程的施工具有重要借鉴意义。

Microseismic evolution of rock mass with staggered zone of underground intersecting chambers under excavation disturbance

Staggered zones have the properties of “multiple shear dislocation in history, wide range, easy to soften when exposed to water and low mechanical strength”, which cause rock masses with staggered zones to easily induce varying degrees of deformation and failure under excavation unloading. It seriously affects the stability of the underground caverns. In order to study the collapse of rock masses with staggered zones in the underground caverns on the right bank of Baihetan hydropower station, we adopted microseismic (MS) system to study the microseismicity in the process of collapse, including spatiotemporal evolution of MS events and distribution characteristics of magnitude and apparent stress. We analyzed the fracture mechanisms (tension, shear or mixed) of rock masses through moment tensor theory, and summarized the evolution process: surrounding rock tension fracture → fractures gradually extend deeper → fractures initiate and expand in the direction of staggered zones (mainly tensile fractures, accompanied by shear or mixed fractures) → the fractures merge with the staggered zones, then unstable wedges are cut → the rock masses with staggered zones collapse under the blasting vibration or gravity. This paper provides references for the excavation and support of rock masses with staggered zones in underground intersecting chambers under high geo-stress, and also provides guidance for the construction of similar projects.