Numerical simulation on radiation and energy of blast-induced seismic waves in deep rock masses

Abstract

With regard to blasting in deep rock masses, it is commonly thought that an increase in the in-situ stress will change the blast-induced rock crack propagation and ultimately affect rock fragmentation. However, little attention has been given to the change in seismic wave radiation when the fractured zone changes with the in-situ stress. In this study, the influences of in-situ stress on blast-induced rock fracture and seismic wave radiation are numerically investigated by a coupled SPH-FEM simulation method. The results show that the change in blast-induced rock fracture with in-situ stress has a considerable effect on the seismic wave energy and composition. As the in-situ stress level increases, the size of the fractured zone is significantly reduced, and more explosion energy is transformed into seismic energy. A reduction in the size of the fractured zone (seismic wave source zone) results in a higher frequency content of the seismic waves. In a nonhydrostatic in-situ stress field, blast-induced cracks are most suppressed in the direction of the minimum in-situ stress, and thus the seismic waves generated in this direction have the highest energy density. In addition to P-waves, S-waves are also generated when a circular explosive is detonated in a nonhydrostatic in-situ stress field. The S-waves result from the asymmetrical release of rock strain energy due to the anisotropic blast-induced fracture pattern.

Keywords

blasting / in-situ stress / seismic wave / rock fracture / SPH-FEM

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