Research on the evolution mechanism of water inrush disasters in coal seam roof karst pipelines under multi-field coupling effects

Water inrush from karst pipelines within coal seam roofs is a critical hazard constraining safe coal production in karst mining areas, yet its catastrophic evolution mechanism remains poorly understood. Taking the No. 21606 working face of Qinglong Coal Mine in Guizhou, China as the engineering prototype, this study independently developed fluid–solid coupling similar materials tailored for karst coal measure strata, and systematically explored the multi-field evolution patterns of the roof under mining disturbance through a combination of three-dimensional physical simulation and fluid–solid coupling numerical simulation. Physical simulation results demonstrate that the total development height of the caving zone and water-conducting fracture zone in overburden strata reaches 54.8 m. The roof stress exhibits a trend of initial increase, subsequent decrease and eventual stabilization, with a maximum roof displacement of 16.1 mm. Both pore water pressure and electrical conductivity remain stable at first, followed by a sharp rise and an abrupt drop, with peak values of 39.79 kPa and 87 ppm respectively. Numerical simulation results show that the roof plastic zone connects with the karst pipeline at a mining advance of 100 m. The maximum stress increment in strata near the coal seam reaches 2.65 MPa, and the maximum roof displacement is 52.80 mm. Pore water pressure peaks at 1.86 MPa at the location closest to the karst pipeline. This study identifies the ‘karst pipeline—lower-right fracture channel—working face’ as the dominant water inrush pathway, and reveals that the water inrush process follows a three-stage evolution law of stable stage—accumulation stage—water inrush stage. The findings can provide a theoretical basis and technical support for the prevention and control of roof water inrush in karst mining areas.