Dynamic Pulverization of Rock Under Triaxial Static-Stress and High-Rate Shearing

A long-term opening problem in geophysics and engineering is the generation mechanism of rock pulverization (e.g., fault gouge) within the shear zone when subjected to triaxial stress environment and dynamic loads. A novel triaxial Hopkinson bar is developed to apply quasi-static triaxial confinement and dynamic loads onto the testing rocks and to measure the energy release from the shearing zone. The results elucidate shear strain-rate threshold (i.e., over 125 s −1 ) for granite at the triaxial prestress of (10, 10, 10) MPa is required for fine fragments/gouge generation. The effects of shear and normal pre-stresses on dynamic shear strength and surface energy for rock pulverization are investigated, which will help explain fine fragments formed during the high-rate loading events. It is suggested that, except for the quasi-static cumulative slip attrition and multiple dynamic events, rock pulverization or fault gouge could be generated at relatively shallow depths (low geo-stress) in a single dynamic earthquake processes.