荒沟抽水蓄能电站地下厂房开挖过程微震活动特征与围岩稳定性研究

牡丹江荒沟抽水蓄能电站地下厂房具有典型的“大跨度、高边墙、多洞室交叉”的工程结构特点，在陡倾结构面、中等地应力等复杂地质条件和强卸荷开挖的影响下，洞室围岩片帮、掉块等局部稳定性问题突出。针对此问题，构建荒沟抽水蓄能电站地下厂房微震监测系统，对地下厂房开挖卸荷过程进行实时监测，揭示围岩内部岩石微破裂的萌生演化过程及其对围岩稳定性的影响。结果表明： 1）开挖卸荷的强施工扰动引起的围岩高能量释放，导致主厂房上游边墙围岩内的断层破碎带局部损伤加剧，诱发大量微震事件； 2)微震事件在主厂房上游侧拱肩区域沿断层走向呈条带状分布,且在厂房下游侧边墙与3#支洞交汇的洞室结构薄弱部位聚集； 3）识别主厂房上游边墙桩号厂左0+20 m至厂左0+80 m段是围岩潜在失稳区域。

Microseismicity and Stability of Underground Powerhouse at Huanggou Pumped storage Power Station Subjected to Excavation

The underground powerhouse at Huanggou pumped storage power station is characterized by large span, high sidewalls and multi cavern groups. Under the influence of complex geological conditions and strong excavation unloading, serious rib spalling and falling of blocks occurred in local parts of surrounding rock mass. Hence, an ESG microseismic monitoring system for powerhouse of Huanggou pumped storage power station is established to carry out real time monitoring of excavation unloading of the powerhouse, and the stability of the surrounding rock mass and the tempo spatial evolution laws of microseismic events in the underground caverns are revealed. The results show that: (1) The large energy releasing induced by strong excavation disturbance of excavation unloading would lead to local damage increase of broken and fractured zone in sidewall surrounding rock upstream main powerhouse, and further cause a large number of microseism. (2) The microseismic event at arch shoulder upstream main powerhouse along fracture zone direction presents belt shape distribution, and which meets sidewall downstream main powerhouse and branch cavern No. 3 at weak point of cavern structure. (3) It is indentified that the section of Changzuo 0+20 m - +80 m is a potential unstable section upstream main powerhouse.