关键词: 微震监测, 地下洞室, 频率特征, S变换

Abstract: The underground powerhouse of Lianghekou hydropower station is located in the high geostress area. Under the influence of excavation, a series of problems, such as surrounding rock instability and rock burst, are prone to occur. Based on the ESG monitoring system of the underground powerhouse, this paper analyses the laws of micro-seismic (MS) events during excavation by comparing with data from the regular stress monitoring system, to provide timely warning for rock mass instability. The results show that: (1) the excavation of bus tunnels No. 3 and No. 4 has triggered a large number of MS events, and the sudden increase of the number of MS events could be seen as a sign of surrounding rock deformation; (2) during the process of rock deformation, the central frequency of MS events goes down first and then up. These characteristics, indicating the development of micro fractures in rock mass, can be used as an important index for prediction of rock mass damage. The results can provide reference for excavation and support of underground caverns of hydropower stations.

Key words: micro-seismic monitoring, underground cavern, frequency characteristics, S transform