基于微震监测的锦屏二级水电站深埋隧洞岩爆孕育过程分析

Nucleation process of rockbursts based on microseismic monitoring of deep-buried tunnels for Jinping Ⅱ Hydropower Station

为研究锦屏二级水电站深埋隧洞岩爆孕育及发展过程,利用构建的微震监测系统对#3引水洞的TBM掘进过程进行全天候连续实时监测。通过获取大量微震监测数据,分别从微震事件的时空序列分布、事件活动率、微震能量、能量密度及视体积对隧洞岩爆前各参数变化特征进行分析,并从动态裂纹扩展角度揭示了岩爆孕育过程中微破裂的萌生、发展、扩展直至相互贯通的宏观破坏机制,初步探讨了微震活动演化规律与岩爆间的时空内在联系。监测与分析结果表明:多数岩爆都存在有可被微震监测定位的微破裂前兆,微震活动率、微震能量及累积视体积均有不同程度的上升趋势。部分岩爆的驱动源由本地岩爆能量与转移能量之和获得,即E驱动=E本地+E转移,强岩爆可再次诱发邻近位置产生岩爆。研究结果,初步证明了利用微震监测系统对深埋隧洞岩爆进行实时监测的可行性。

To study the rockburst nucleation and evolution process in deep-buried tunnels for Jinping Ⅱ Hydropower Station,a microseismic real-time monitoring system is established to monitor diversion tunnel No.3 during TBM excavation.Based on a great deal of microseismic monitoring data,the characteristics of spatiotemporal distribution,activity rate,exhausted energy,energy density and apparent volume of microseim are comprehensively considered before occurrence of rockbursts.What's more,the initiation,propagation,extension and inter-coalescence mechanisms of microcracks during progressive nucleation process of rockbursts at Jinping Ⅱ Hydropower Station are revealed.The spatial relationship between evolution rules of microseismic activities and rockbursts is discussed.The monitoring results show that precursory microcracking exists prior to most rockbursts,which can be captured by the microseismic monitoring system.The event rate,microseismic released energy and accumulated apparent volume have their different increase tendencies before rockbursts.The energy source of some rockbursts is composed of local energy and transfer energy,namely Edrive source =Elocal+Etransfer,and a portion of rockbursts can be induced by certain adjacent violent rockbursts at the same time.It is feasible to monitor and predict rockburst events by using the microseismic monitoring technology for deep-buried tunnels.