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Abstract The underground powerhouse of Houziyan hydropower station is a typical deep-buried powerhouse with the depths of 280–510 m horizontally and 400–660 m vertically. The ground stress is high and the geological conditions are very complicated. In order to monitor and analyze the surrounding rock mass stability during continuous excavation of underground powerhouse and locate the potential instability failure areas，an ESG (engineering seismology group) microseismic monitoring system manufactured in Canada was installed in April，2013. The wave velocity range of rock mass in underground powerhouse was measured by digital acoustic instrument. The overall equivalent wave velocity of P wave was 5 700 m/s in monitoring system which was determined through several blasting tests. The seismic source location error was less than 10 m. The microseismic event waveforms were manually processed to acquire high position accuracy and the interference events were filtered out. On the basis of geological conditions and field observation，micro-fracture clustering areas of surrounding rock mass and the potential instability risk areas in the underground powerhouse of Houziyan hydropower station were revealed and delineated by the tempo-spatial evolution laws of microseismicity. Results could provide some references for later excavations and supports in the underground powerhouse of Houziyan hydropower station. Furthermore，a new research idea is opened up for the stability analysis of deep-buried underground powerhouse subjected to excavation-induced unloading.
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Received: 18 July 2013
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2014, Vol. 33 
