Damage mechanism evolution of red sandstone under drying-wetting cycles: experiment and discrete element modeling

Repeated rainfall usually results in the weakening of the strength characteristics of the engineered rock masses, which can induce engineering accidents. To explore the effect of water-induced rock strength damage under the repeated action of saturation and drying, this study conducted compression experiments on red sandstone. Laboratory experiments were combined with numerical simulations aimed at analyzing strength damage patterns and crack evolution characteristics. The results show that drying-wetting cycles have a strong deterioration effect on the physico-mechanical properties, particularly during the initial cycle, which causes the greatest damage. As the number of cycles increases, the number of tensile cracks decreases, the number of tensile-shear cracks increases, and the number of compression-shear cracks is stable. The particle contact force chain becomes thicker and denser, and the particle displacement direction gradually changes from "center to both sides" to "center to top and bottom." The crack evolution process under uniaxial compression was divided into four stages: crack-free, crack emergence, crack propagation, and crack sharp increase stage. When the cracks progressed to the crack propagation stage, macroscopic fracture of the rock was imminent. This may be an indicative precursor of rock damage.