Evaluation of Destress Blasting Effectiveness Using the Seismic Moment Tensor Inversion and Seismic Effect Methods

Abstract

The effectiveness evaluation of long-hole destress blasting in an underground hard coal mine was made via the seismic effect method and the seismic moment tensor inversion. The seismic effect method is based on the difference between seismic and explosive energies, indicating that additional processes appeared to change the stress state in the rock mass, however, the seismic effect does not consider the focal mechanism. Therefore, the seismic moment tensor inversion was applied. Tremors that were an effect of long-hole destress blasting during the extraction of coal seam No. 507 in one of the hard coal mines localized in the Polish part of the Upper Silesian Coal Basin were analyzed. The results of the preceding applied methods were compared. High values of seismic effect indicate stress relaxation and thus the occurrence of additional processes, leading to a new stress equilibrium state in the rock mass. It has been shown that in analyzed cases, achieving such a state corresponded to the presence of a nonexplosive mechanism, with a large share or domination of the double couple component in the full seismic moment tensor solution. The reverse slip mechanism was present in the foci of provoked tremors, which can be associated with the displacement of rock blocks under conditions of high horizontal stress. Convergent results of the methods used confirm that the appropriate design of blasting parameters in relation to specific geological and mining conditions make it possible to provoke additional geomechanical processes in the rock mass.