Research on distribution characteristics and water filling modes of mine water inflow in western mining areas of China

The characteristics of Chinese energy endowment determine that coal is the main energy source for long-term stability in the future. With the depletion of coal resources in the eastern region, the northwest coal rich area has become the core area for coal resource development. In the past 30 years, continuous and in-depth geological and hydrogeological exploration and underground mining in western mining areas had revealed significant differences in the geological structure and hydrogeological conditions of different mining areas/mines, resulting in significant differences in mine water inflow. Based on the analysis of the water inflow of major coal bases in western China, combined with the geological and hydrogeological conditions of the mining area, a water filling mode of the roof aquifer under mining disturbance is proposed. The Inner Mongolia East Coal Base mainly mined Cretaceous coal resources. Poor diagenesis of the coal seams and their roof strata and high porosity of the aquifers provided good conditions for the storage and transportation of groundwater. The Inner Mongolia East Base had the highest average water yield coefficient (2.09 m³/t) and the highest total water inflow (5.54×10⁸ m³/a). Other coal bases mainly mined Jurassic coal resources. The average water yield coefficients were around 0.60 m³/t (except for the Shaanxi part of Huanglong Base, which had an average water yield coefficient of 1.85 m³/t). The DM, ZNH, YBS and other coal mines in the Mengdong Base were adjacent to large rivers, with water inflows exceeding 4000 m³/h. The JJ coal mine in the northern Shaanxi base had shallow coal seam burial, large thickness of the Quaternary aeolian sand layer, and strong water abundance. The water conducting fracture zone of coal mining communicated with the Quaternary aquifer, and the water inflow of the mine was more than 3000 m³/h, even exceeding 6000 m³/h during peak periods. The NTT, XW and other coal mines in the northern Shaanxi base were affected by the burnt rock aquifers, with a water inflow of about 1000 m³/h. The surface of the border area between Inner Mongolia and Shaanxi was the Maowusu Desert. The thickness of the Quaternary and Cretaceous strata was over 400 m, which continuously replenished the bedrock aquifer and formed a multi-layer superimposed composite aquifer structure. The water inflows of most mines were more than 1500 m³/h. The rivers in the Binchang mining area cuted through the Cretaceous bedrock, and the thickness of the Cretaceous aquifer was large (500–700 m), forming a “sponge type” thick aquifers. The development of water conducting fracture zones connected the middle and lower sections of the Cretaceous aquifer, and the water inflow of GJP coal mines in the area exceeded 7000 m³/h. The coal seam fractures in the northern area of Yuheng were relatively developed, with a wide range of coal seam aquifers. The static reserves of coal seam water were large, and the mine water inflow was more than 1000 m³/h. The conventional water filling modes of the coal seam roof and floor aquifer was summarized, and three water filling modes were proposed, including the “strong filling type” shallow aquifer water filling modes, the “sponge type” thick aquifer water filling modes, and the coal seam aquifer water filling mode. The study could provide scientific basis for active protection of groundwater resources and coordinated utilization of mine water in western coal bases.