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猴子岩水电站地下厂房水平埋深280~510 m,垂直埋深400~660 m,属于典型深埋地下厂房,山体地应力高,地质条件复杂。为监测和分析地下厂房开挖过程围岩的稳定性,识别和圈定围岩潜在的破坏失稳区域,2013年4月安装加拿大ESG微震监测系统。采用声波仪测定地下厂房岩体波速的范围,并结合爆破试验方法计算得到微震监测系统整体等效P波波速为5 700 m/s,系统定位误差小于10 m。对拾取的微震事件波形手动处理,提高定位精度,并剔除干扰事件。通过地质资料分析和现场踏勘,微震活动性时空分布演化规律揭示并圈定猴子岩水电站地下厂房围岩微破裂集中区域及其潜在失稳风险区域。研究结果可为猴子岩水电站地下洞室群后期开挖和支护提供参考,也为类似开挖强卸荷作用下深埋地下洞室围岩稳定性评价提供一条新的研究思路。
The underground powerhouse of Houziyan Hydropower Station is buried at a depth of 280-510 m horizontally and vertically at a depth of 400-660 m. It belongs to a typical deep underground powerhouse with high ground stress and complicated geological conditions. In order to monitor and analyze the stability of surrounding rock during excavation of underground powerhouse and to identify and delineate the potential rupture zone of surrounding rock failure, ESG microseismic monitoring system in Canada was installed in April 2013. The range of rock mass velocity of underground powerhouse is determined by sonic meter, and the total effective P wave velocity of the microseismic monitoring system is calculated to be 5 700 m / s. The system positioning error is less than 10 m calculated by the blasting test method. Pick up the microseismic event waveform manually, improve the positioning accuracy, and eliminate interference events. Through the geological data analysis and scene reconnaissance, the temporal and spatial distribution of microseismic activity evolution rules reveal and delineate the micro-rupture concentrated area and the potential instability risk area of the surrounding rock of the underground powerhouse of the Houzhipan Hydropower Station. The results provide a reference for late excavation and support of the underground caverns at the Houzhipin Hydropower Station and provide a new idea for the evaluation of the surrounding rock stability of the deep underground caverns under the similar excavation and unloading.