Crack Propagation Mechanism and Damage Constitutive Model of Sandstone With Pre‐Existing Flaw Under Multi‐Stage Cyclic Loading and Unloading

ABSTRACT In mining, natural rock joints and fractures significantly impact slope stability. AE technology was employed to monitor the evolution of sandstone samples containing initial cracks under uniaxial multi‐stage cyclic loading and unloading (MS‐CLU), with analyses of mechanical performance, AE parameters, crack propagation, and damage evolution. The results indicate that AE counts, event numbers, and signal intensity rose as the tests progressed, whereas signal frequency and b‐values declined. Sample failure was primarily governed by tensile cracks. Furthermore, with increasing initial crack inclination, sandstone's mechanical properties strengthened, and the proportion of tensile cracks initially rose and then declined. Additionally, this study introduced a new correction coefficient for the unloading stage, applied it in the damage constitutive model, improved model accuracy, and offered dependable theoretical support for assessing the safety of rock masses during staged excavation.