Mechanical Characteristics and Damage Evolution Law of Sandstone with Prefabricated Cracks Under Cyclic Loading

To study the damage evolution laws of red sandstone samples with prefabricated cracks under cyclic uniaxial compression, physical tests were conducted. In this research, the stress–strain curve characteristics, failure process characteristics, strength, and deformation properties of the cracked sandstone specimens were studied under different cracked geometric parameters (α, β) and cyclic loads. The experimental results revealed that the elasticity modulus, deformation modulus, residual strength, and peak strength increased linearly with the number of loading cycles. Additionally, the failure modes of the samples transition from brittle failure under a small number of loading cycles to ductile failure under a high number of loading cycles. The elastic modulus and peak strength of all the specimens under cyclic loading showed a “strengthening” phenomenon. With increasing crack dip angle (α), the peak strength and crack initiation stress first increased and then decreased. However, with the increase in the crack bridge inclination angle (β), the peak strength and crack initiation stress first decreased and then increased. By using the fitting analysis of the damage evolution equation, it was proven that the damage variable method is suitable for describing the damage evolution characteristics of cracked sandstone.