Experimental and numerical study on rockburst triggered by tangential weak cyclic dynamic disturbance under true triaxial conditions

The excavation and/or dynamic disturbance induced critically stressed (stress close to the strength of the rocks) rocks near the excavation boundary of deep openings are highly unstable, and they may fail violently in the form of rockburst triggered by weak dynamic disturbance in the maximum principle stress direction (tangential). In this paper, true triaxial coupled static and dynamic loading tests and a 3D discrete element method (DEM) simulation were carried out to investigate the characteristics and the mechanisms of rockburst triggered by tangential weak dynamic disturbance. Test results indicate that, compared to self-initiated rockburst under corresponding test conditions, the weak dynamically-triggered rockburst has much longer development duration, much lower kinetic energy, and the failure of the specimen is dominated by tensile splitting. The DEM simulation results show that, the occurrence of tensile cracks generally precedes that of shear cracks, and shear cracks are mainly result from the slipping displacement dipping in the free face direction after the tensile cracks accumulated to a certain extent. The tangential weak dynamic disturbance significantly increases the cracking and damage degree, and the dissipated energy of the rocks. The released kinetic energy accounts for a very small proportion (0.27%) of the dissipated energy due to the dynamic disturbance. In conclusion, the mechanism of rockburst triggered by tangential weak dynamic disturbance can be summarized as the “activation” (activating cracks), “magnification” (driving dynamic propagation of cracks), and the “inducing energy release” (inducing release of the stored strain energy of the rocks) effects of the weak dynamic disturbance.