Microseismic monitoring application for primary stability evaluation of the powerhouse of the Tapovan Vishnugad Hydropower Project

Abstract

The study of micro-cracks, shear zone and redistribution of stress after excavation in the rockmass is required for a stability analysis of the underground structure. The powerhouse of the Tapovan Vishnugad Hydropower Project (TVHPP) of NTPC Ltd. is located in the seismic zone V of India and is positioned at the junction of the middle and higher Himalayan region under challenging geological conditions. The powerhouse cavern constructed by drill and blast method encountered a number of rockbursts of various intensities during and after construction. So, a real-time remote microseismic monitoring network was used to evaluate the stability of the powerhouse cavern rockmass. Strata condition, rockburst occurrence during construction and drilling feasibility for sensor installation were studied for an array of designs of the microseismic monitoring network. The primary monitoring period demarcated the micro-crack locations and probable failure zones in the powerhouse rockmass by processing and analysis of various temporal and spatial variations of microseismic parameters to evaluate the underground powerhouse structural stability. Although a large number of microseismic events occurred in the powerhouse which resulted in high displacement in a few areas, due to the low amount of energy released from the events occurring inside the powerhouse, the structure appears to be stable.