MECHANISMS OF SHEAR WAVE GENERATIONS DURING UNDERGROUND EXPLOSIONS IN JOINTED ROCK

Shear wave generation observed in underground explosions has been an area of research during the last few decades. Various mechanisms were proposed to explain this ground motion such as source imperfections and emplacement conditions, rock mass anisotropy and in situ stress relaxation after creation of the cavity. One of the main goals of Source Physics Experiment conducted recently in Nevada was to understand the mechanisms of the shear wave generation by conducting a series of chemical explosions in a well characterized geologic settings. We have performed analysis of this experiments using computational models based on geological site characterization to understand the main mechanisms behind the shear wave generation. After we were able to reproduce the observed non-radial motion in our calculations, we have conducted a computational study to investigate possible mechanisms of shear wave generation for underground explosions at various depth, in Situ stresses, explosion yields etc. Results of this study is an extrapolation of SPE data to different conditions which may be encountered in practice. We hope they will provide benefits to monitoring programs.

This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.