Energy analysis for damage and catastrophic failure of rocks

The development history and current state of studies on the characteristics and mechanisms of deformation and failure of rock materials were briefly reviewed from the viewpoint of energy. The main scope and the achievable objectives of the energy-based research system were expatiated. It was validated by experiments that the damage process of rocks can be well described by the rock damage evolution equation established based on energy dissipation. It was found from the uniaxial compression and biaxial compression tests that only a small proportion of the total input energy in hard rocks is dissipated before peak load and a large proportion in soft rocks is dissipated before peak load. For both hard and soft rocks, the energy dissipated after peak load accounts for a greater proportion. More energy would be required for rock failure under equal biaxial compression than under unequal biaxial compression. The total absorbed energy is different for rock failure under high-rate loading and low-rate loading. More fragmented failure pattern usually corresponds to higher energy absorption. The mesoscopic analysis on the damage and failure of bedded salt rocks showed that the energy dissipation is prominent and the total absorbed energy for rock failure is low when cracks propagate in the weak mud interlayer while it is contrary when cracks propagate in the salt rock. The energy accumulation, transfer, dissipation and release during the failure process of tunnel with impending failure under disturbance were analyzed theoretically based on the elastoplastic mechanics theory. Furthermore, the spatial distribution of energy dissipation and energy release of fractured rocks under unloading was simulated numerically. It was demonstrated that energy is likely to be released from the weakest surface under compression, which triggers the global failure of rocks.