Deformation theory and energy mechanism of cyclic dynamic mechanical damage for granite in the diversion tunnel under cyclic loading-unloading

The diversion tunnel is frequently subjected to cyclic dynamic loads during blasting and mechanical excavation. To explore the theory and mechanism of cyclic dynamic mechanical damage for granite in a diversion tunnel under cyclic loading-unloading, the incremental cyclic loading-unloading test and numerical simulation were conducted on granite samples from the diversion tunnel. According to the mechanical and deformation characteristics of rock samples in the process of cyclic loading-unloading, the stress-strain normalization theory evolution model based on viscoelastoplasticity was established, and the cyclic dynamic damage evolution mechanism of rock samples was revealed. The evolution characteristics of stress-strain curves of rock samples under cyclic loading-unloading were effectively described, and the loading-unloading two-stage constitutive equation of rock samples under cyclic loading-unloading was established. The energy and damage evolution mechanism of the final full stress-strain curve and the influence mechanism of shrinkage and expansion of rock particles on the mechanical properties of granite were discussed.