Water Inrush Modes Through a Thick Aquifuge Floor in a Deep Coal Mine and Appropriate Control Technology: A Case Study from Hebei, China

Water inrush disasters caused by confined aquifers under high pressure below the mine floor are a major problem in China, restricting the safe and efficient mining of deep coal seams. We have classified the stress disturbance modes acting on the floor area in such mines into two types based on the water yield changes of a thick aquifuge floor in a deep longwall mine and the underground pressure behavior of deep longwall faces during water inrush events, and they are the dynamic load of the main roof instability from the far field of the longwall face and the static load of the abutment pressure from the near field, respectively. The water inrush modes include mining-induced cracks indirectly connected with the Ordovician limestone aquifer and through-going faults directly connected with the same aquifer. In order to control water inrush from thick aquifuge floor, grout was used to block off the cracks in the strata just above the Ordovician limestone on the site; decreasing the mining width also decreased the stress disturbance intensity caused by the dynamic and static loads; while presplitting the roof relieved the underground pressure and effectively weakened the dynamic load; and the confined water was drained to lower the water pressure and cut off the source of water flowing into the longwall face. Finally, the combined effectiveness of these control technologies was verified by micro-seismic monitoring, and further water inrush disasters were prevented through the thick aquifuge floor of a deep longwall mine in the Xing-dong coal mine in north China.

Automated summary

Water inrush disasters caused by confined aquifers under high pressure below the mine floor are a major problem in China. This study proposes a combination of control technologies including grouting, reducing mining width, pre-splitting the roof, and drainage to prevent further water inrush disasters and ensure safe and efficient mining.