Mechanism and prevention of bed separation water hazards in karst coal mining areas of Northern Guizhou Province, China

This study used the Tenglong Coal Mine in northern Guizhou as a case study to prevent or control bed separation water disasters caused by complex hydrogeological conditions in karst mining areas. A systematic research approach integrating theoretical modeling, quantitative monitoring, and on-site prevention and control was used to analyze the dynamic evolution of overburden separation in karst areas and establish a prevention system. The rock mechanics theory was used to identify the location of bed separation and establish a mechanical model of the roof containing a conical funnel-shaped karst cave. The cusp catastrophe theory was applied to derive a safety distance criterion between the karst cave and the separation zone. The box-counting fractal dimension (D) was used to quantify the dynamic evolution of the separation. It was 1.1881 after the working face reached 240 m, and the maximum separation was 2.64 m. A similarity simulation was conducted, and fiber Bragg grating (FBG) sensors and digital image correlation (DIC) were employed to measure the separation space. A site-specific system was developed to analyze bed separation water disasters, perform spatiotemporal prediction, and prevent or control them. The following was observed. (1) The higher the karst water pressure, the higher the load, and the thinner the rock layer, the more prone the area was to water inrush disasters. (2) The fractal dimension accurately described bed separation. Bed separation became critical when D exhibited a sudden step-like increase above 1.15. (3) A strong positive correlation existed between the strain and the separation ratio F. The maximum subsidence of high-level separation derived from DIC was 10.5 mm, and the highest bed separation position occurred beneath the thick Changxing Formation limestone. (4) The proposed surface and underground drainage approach improved the drainage efficiency. This research provides theoretical support and technical guidance to prevent or control bed separation water disasters in karst mining areas.