Investigation on the damage accumulation mechanisms of landslides in earthquake-prone area: Role of loading-unloading cycles

Investigating rock damage behavior is crucial for understanding the formation mechanisms of fractured slopes in earthquake-prone areas. However, the current understanding of the nonlinear damage processes and mechanisms of rocks under cyclic loading is insufficient. This study investigated the damage behaviors of metamorphic sandstone, granite, and phyllite under cyclic loading using acoustic emission (AE), infrared thermal imaging, and digital image correlation (DIC) techniques. The experimental results demonstrated that the damage variables based on AE counts, infrared radiation temperature variance (IRTV), and surface deformation variance (SDV) increased with increasing cycles and stress levels. The temperature variation was influenced by lithology and the types of original pores and microcracks. The lag ratio and average lag time of the SDV effectively evaluated the progressive damage process. Specific damage mechanisms were identified, including the “compaction-embedment effect” in metamorphic sandstone, the “crystal incompatible deformation-fracture effect” in granite, and the “defective fracture effect” in phyllite.