Mechanism of Bed Separation Water Inrush during the Mining of Extra-Thick Coal Seam under Super-Thick Sandstone Aquifer

The bed separation water inrush disasters in the Jurassic coalfield of Huanglong, China occur frequently, and they seriously threaten the safety of coal mining. This study systematically collected data from multiple instances of bed separation water inrush (BSWI) in the Cuimu coal mine and summarized the characteristics of BSWI. Through the analysis of hydrogeological conditions, hydrochemical characteristics, field detection of a water-conducting fractured zone (WCFZ), and groundwater level monitoring, the water inrush source, water-conducting channel, and the dynamic response of the aquifer water level were studied. The results showed that the water inrush source was mainly Cretaceous groundwater. The height of WCFZ in the extra-thick coal seam mining in the study area was 239.62 m, forming a water-conducting channel of water accumulation in bed separation. There was a strong correlation between water level changes in the Luohe Formation and BSWI. On this basis, we have proposed that four conditions must be met simultaneously for BSWI, and a hydrogeological-mining coupling conceptual model was established to reveal the evolution process and the mechanism of BSWI. The research results are crucial for the prevention of BSWI disasters and for ensuring the safety of coal mine production.