Green coal mining and water clean utilization under Neogene aquifer in Zhaojiazhai coalmine of central China

Coal plays an important role in the high-quality development of national economy and society, and overburden movement caused by coal mining has also caused groundwater loss and eco-environment damage. Under the national strategic goal of emission peak and carbon neutral, green mining and low-carbon clean production have become the mainstream production mode of coal enterprises. In this study, the overlying unconsolidated layer is divided into four aquifer groups in Zhaojiazhai coalmine of central China based on its characteristics and water yield coefficient of pumping experiment. According to the coal seam thickness, the damage range of the aquifer under the mining influence and the maximum hydrostatic reserves are accurately determined, and a combined up-down well drainage technology is proposed, which solves the water hazard threat of the safe mining under Neogene aquifer. Considering that the loss of groundwater resources will aggravate the surface subsidence, the distribution characteristics and formation mechanism of surface cracks under fully mechanized top coal caving mining are analyzed, the angular parameters of surface dynamic movement and deformation are obtained, the damage degree of mining subsidence area is divided into regions, and land reclamation measures are implemented. Combined with the clean production concept of waste heat utilization, and based on the life cycle theory, the life cycle cost model of mine heat supply mode is established. It is analyzed that the waste heat utilization of mine water and air compressor is the best way of heat supply in Zhaojiazhai coalmine, and has been successfully applied. The engineering application shows that the dewatering and drainage not only liberates the coal resource under water of 5.99 Mt, but also provides rich waste heat of mine water for coalmine clean production. The waste heat utilization saves 7000 tons of standard coal for the mine every year, which has the characteristics of low operation cost, high efficiency, energy conservation and green environmental protection. Meanwhile, using the surface movement parameter to guide the land reclamation in the subsidence area not only improves the land productivity, but also effectively improves the eco-environment of the mining area, speeds up the construction process of green mines, and provides a reference for the green mining and low-carbon production of coal enterprises.