Study on overburden damage and prevention of runoff disaster in multiseam mining of gully region

Multi-seam mining in gully region has resulted in serious and complex chain disasters, including fissure development, mountain landslides, river blockage, and intensified water inflow. To prevent and control landslides and water inrush disasters, it is crucial to explore the characteristics and laws of overlying strata failure under the coupling effect of gully terrain and repeated mining in coal seams. This study focuses on the mining of multiseam in the gully terrain of Xiqu Coal Mine. The comprehensive analysis method, integrating surface exploration, InSAR dynamic observation, rainfall-runoff analysis, and numerical simulation, is used to analyze the entire process of spatial expansion of overlying strata failure and surface subsidence caused by downward mining of multiseam in the gully region. The results reveal that after the critical mining of the lower coal seam in the gully region, the lower strata beneath the key stratum in interlayered formations are prone to develop cutting failure and vertical fissure, with tensile cracking being the dominant mode of failure. The proportion of shear fractures in the overburden above the key stratum increases significantly, and the gully slope is prone to shear slip under the effects of mining subsidence and gravity. The connection phenomenon between the downward fractures of the slope and the upward fractures of the overburden can even occur. In addition, if the accumulation formed by mountain landslides due to repeated mining blocks the river channel and forms a barrier lake during the flood season, there is a risk of underground water inflow. To prevent such disasters, high-precision terrain synthesized by UAV tilt photogrammetry is used to simulate the rainfall inundation range and time percentage of different durations in Fanshigou watershed during the “100-year return period” rainstorm in Shanxi Province. The research proposes a comprehensive prevention and control method of surface runoff water disaster based on fissure development and surface inundation range, which provides support for gully water disaster prevention and risk assessment in Fanshigou small watershed. This study can serve as a useful reference for the prevention and control of surface geological disasters and the protection of water resources under the condition of multiseam mining in gully regions.