On prevention and mechanism of bed separation water inrush for thick coal seams: a case study in China

Bed separation can occur in overlying strata, especially in hard and soft interbedded roof strata. If these strata prone to form bed separation are rich aquifers, water can accumulate into bed separation and maybe cause a serious water hazard under the condition of water inflow passages existence. Therefore, studying these types of roof water inrush mechanisms, forecasting roof water inrush, and formulating preventive and control measures in advance are extremely important to a mine. In this paper, we takes the typical case of water inrush in the workface number 1121 at Hongliu coal mine as an example, and study the mechanism of water inrush in detail. Primarily, field drilling with water leakage and color TV observations showed that the maximum height of the water conducting fractured zone was 12.50 times the thickness of the coal seams, which spread to the overlying coarse-grained sandstone aquifer. Secondly, the numerical simulation indicated that bed separation storage space was prone to form under the combination of coarse-grained sandstone and mudstone geological structure. The detection using UWTEM revealed that the groundwater accumulated in this bed separation and formed a water bag (bed separation water). When the water bag reached a certain degree, water bursting happened with the main roof collapsing. Finally, prevention, effective drainage methods, and successful experiences with bed separation water have been summarized, and it will have a major significance to coal mines suffering from bed separation water inrush.