Feasibility Study on the Construction of Underground Reservoirs in Coal Goaf-A Case Study from Buertai Coal Mine, China

The construction of underground reservoirs in coal goaf is a new technology aimed to realize the sustainable development of coal mining-water storage-surface ecology in arid areas of northwest China. The key to the feasibility of this technology is that underground coal mining cannot affect the near-surface aquifer, and the amount of water entering the underground reservoir must meet the needs of the coal mine. Taking Buertai Coal Mine, one of the largest underground coal mines in the world, as an example, this article used similar simulation, numerical simulation and in-situ test methods to study the height of the water-conducting fracture zone of overlying strata and water inflow of underground reservoirs. The results show that, under the repeated mining of the 22- and 42-coal seams, the maximum height of the water-conducting fracture zone is 178 m, and the distance between the near-surface aquifer and the 42 coal is about 240 m, so the mining has little effect on the near-surface aquifer. During the mining period of the 22-coal seam, the groundwater of the Zhidan and Zhiluo Formations was mainly discharged vertically, while the groundwater of the Yanan Formation was mainly a horizontal flow during the period of the 42-coal mining. In this way, the total water inflow of Buertai Coal Mine reaches 500 m3/h, which not only meets the needs of the mine, but also, the rest of the water can irrigate about 98 hectares of farmland nearby. Underground reservoirs in coal goaf could achieve sustainable development of coal mining, groundwater storage and surface ecology in semi-arid areas.