Precursory monitoring of impending rockbursts in Kolar gold mines from microseismic emissions at deeper levels

摘要

Microseismic emissions generated by deformation and cracking of the rock around an opening inside a mine as the rock tends to achieve equilibrium in a new geometry under changing stress conditions have been found to provide useful clues to an impending major rockburst in the mine. Since the spatio-temporal patterns of occurrence of such microseismic emissions are known to be intimately related to stress changes within the rock mass, the typical characteristics of these emission patterns are shown to be of diagnostic value in sensing in advance major rockburst events that invariably follow such emissions. Among several parameters investigated, the three reliable short-term precursors are found to be the rate of change of microseismic event count, strain energy release and predominant signal frequency. The extent of predictive utility of these parameters is illustrated by extracting them from the microseismic emission data of major rockbursts in the Champion Reef mine of the Kolar gold fields (KGF) in southern India, of which two representative examples out of several similar ones studied are discussed here.