Study on Energy Evolution and Damage Constitutive Model of Sandstone under Cyclic Loading and Unloading

In order to strengthen disaster prevention control under deep resource development and space utilization, it is necessary to construct a damage intrinsic model under complex stress states to predict the mechanical behavior of deep-rock mass under cyclic loading. An indoor uniaxial cyclic loading test on sandstone was carried out in this paper. By analyzing the mechanical properties and energy transformation of the failure process, it was assumed that the failure of rock micro-units follows a Weibull density function, and the damage intrinsic relationship was constructed using the Mogi–Coulomb strength criterion. The constitutive rationality was verified via the nonlinear fitting of the experimental curve and theoretical curve, and the model parameters were analyzed. This study indicates that the cyclic loading procedure has a strengthening effect on the elastic modulus. The brittleness of the rock increases with the cycle amplitude, the axial strain accumulates continuously, and the hysteresis loop area increases gradually and moves to the right. The energy conversion of the loading process is mainly split into the energy storage phase before the damage and the release phase at the time of damage, and the dissipation energy percentage curve shows the groove evolution law. The damage intrinsic model based on the Mogi–Coulomb strength criterion accurately reflects the ontological relationship of sandstone under cyclic loading, and the model parameters have clear physical significance. This study has important theoretical and engineering meaning for predicting the deformation and destruction of rocks.