Deformation and failure mechanisms of deep fractured karst slopes induced by underground mining

Deep karst fractures significantly drive rock strata movement induced by mining and are one of the key factors causing slope failures. Understanding the disaster formation mechanisms of mining-induced slopes controlled by deep karst fractures is crucial for geological hazard prevention and mitigation. Existing research on slope failure mechanisms under the coupled influence of deep karst fractures and underground coal mining remains limited and insufficiently developed. Consequently, this study establishes a coupled geomechanical model of mining–karst interaction for layered reverse-dip slopes in southwestern China. By integrating field investigations with discrete element simulations, this study explores the deformation characteristics and failure mechanisms of deeply fractured karst slopes subjected to underground mining, along with their impacts on slope stability. The main findings are as follows: (1) Deep rock karst fractures dominated the spatial distribution of tensile fracture zones, forming a dynamic stress arch effect above the goaf; (2) The mining process dynamically induced a three-stage destruction mode of the slope, namely, the bending effect caused by the dynamic stress arch, arch migration, and the evolution of the unlocking of the locking rocks; (3) Significant spatiotemporal variability existed between the tensile zone at the top of the slope and the shear zone on the slope surface, leading to the gradual overturning of the cantilever beam structure along the dominant structural surface. It indicates that deep rock karst fractures are the primary factor controlling the disaster of the cantilever beam structure, exacerbating the degree of rock fracture and surface subsidence induced by coal mining. This study reveals the chain disaster mechanism of layered anti-dip rock karst fracture slopes in southwestern China, namely, fracture penetration, rock stratum movement-induced failure, unlocking of key rocks, and final tensile overturning destruction, profoundly elucidating the critical role of rock dissolution fissures in mining-induced slope disasters.