Test evaluation of slope deformation and fissure network with different surface shapes under the action of underground mining

The mountainous region of southwest China is rich in mineral resources; however, its complex topography and geological conditions make underground mining susceptible to triggering geological hazards. To comprehensively understand the mechanisms of mining-induced slope instability, generalized models of linear, concave, and concave-convex slopes were developed. The progression from the formation of mining-induced fissure networks to slope failure was analyzed using base friction tests, digital photogrammetry for deformation measurement (DPDM) technology, and fractal theory. The results indicate that an increase in mining area, number of layers, and depth leads to continuous adjustments in fissure networks and formation dislocations, resulting in diverse interactions and developmental trajectories. Fissures propagate toward the surface, increasing the fractured rock mass and decreasing slope stability. The maximum displacement occurring in the direct roof and the upper-middle part of the slope, and the maximum shear strain concentrated in the direct roof, the leading and trailing edges of the slope, and the shear failure zones. Slope shape influences deformation and failure modes: linear and concave slopes undergo creepsliding and fracturing, whereas concave-convex slopes are more prone to bending and fracturing. The fractal dimension is directly proportional to mining depth, while the probability distribution index is inversely proportional to mining depth, indicating that the fissure development mechanism evolves from micro-fissure formation to large-scale fissure. The increasing complexity in the boundaries of fissure networks is accompanied by expansion, compaction, and penetration. These findings provide a foundation for the accurate assessment of mining-induced geological hazards in slopes with similar geometric configurations.