Effect of Initial Freeze–Thaw Damage on Sandstone Failure and Energy Dissipation Mechanisms Under Triaxial Loading

To determine the damage nature of cyclic freeze–thaw rock under triaxial stress, the triaxial compression test and freeze–thaw test were performed on sandstone. Based on the energy principle, the energy dissipation mechanism in the process of freeze–thaw rock deformation and failure under the action of surrounding rock is analysed. The experiments show that the confining pressure influences not only promotes the conversion of absorbed energy to elastic energy, but also inhibits the release of elastic energy. The energy storage rate of rocks gradually downscales with freeze and thaw cycle. When the confining pressure increased, the influence level of freeze–thaw on the energy storage capacity increases. The impact of freeze–thaw on the extreme of rock elastic energy represents a changing tendency that first increases and then decreases under low and high confining pressures, and keeps increasing under medium confining pressures. Freeze–thaw reduces the storage efficiency of elastic energy. But the confining pressure promotes the effective conversion of elastic energy. The elastic limit of energy is a comprehensive manifestation of the effects of the freeze-thaw and confining pressure.