Application of Microseismic Monitoring in Analysing the Stability of Underground Cavern

Long term stability of an underground cavern is significant for construction engineers. For structures constructed in the geologically active regions of the Himalayas, continuous monitoring is required to ward off the sustained threats due to seismic activities and associated local geological hazards. Underground powerhouse of Tapovan Vishnugad Hydropower Power Project (TVHPP), Chamoli, Uttarakhand is one such powerhouse that encountered various types of rockmass failures both during and post construction. The project area is located about 2.0 km north of the Main Central Thrust (MCT) and the rockmass cavern has numerous joints, shear and seam zones and fractures. This pose threat to the long term stability of this underground powerhouse cavern. To analyse the rockmass stability of the powerhouse, real time microseismic monitoring system was installed in this underground cavern. Spatio-temporal variation of the recorded seismic events has been analysed for microseismic events distribution in terms of seismic energy, displacement, cumulative apparent volume and various other contours led to the identification of potentially hazardous zones in the underground rockmass structure.