Evolutionary characteristics of the fracture network in rock slopes under the combined influence of rainfall and excavation

Analysis of fracture propagation, evolution mechanisms, and failure characteristics is crucial for investigating the stability of rock slopes under the combined effects of rainfall and excavation. The novelty of this study lies in the comprehensive investigation of crack propagation and final failure modes of high steep rock slopes at different angles (ranging from 45° to 65°) under the coupling effect of rainfall and excavation. These investigations were based on conventional rock mechanics tests, large-scale laboratory similar model experiments, and theoretical analysis of fractal fractures. Herein the experimental results revealed that: (1) During the open-pit excavation stage, the rock masses gradually moves towards the mining area, resulting in vertical cracks during the mine-room stage. These cracks exhibit a semi-elliptical shape as they continuously develop through combination. Moreover, separation cracks appear in the overlying rock area after pillar mining, which is followed by the large-scale collapse of the overlying rock due to continuous pillar extraction. (2) The fractal dimension of the fracture connected zone is found to be the highest among the “three zones” within different slope angles, followed by the collapse zone, while the fracture extensive zone exhibits the lowest fractal dimension. (3) The fractal dimension and percolation rate initial decrease, followed by an increase, as the slope angle increases from 45° to 65°. Notably, among these angles, the highest value is demonstrated by 65° when compared to 45°, 50°, 55°, and 60°. Hence, this study can provide theoretical guidance for safe and efficient mining in the coupled rainfall-mining environment.