Hydrological effects of the underground hydraulic curtain with different design parameters based on numerical modeling for a co-exploitation of coal and uranium

Abstract

Coal is both the most widely utilized traditional energy resource and a raw material for chemical industries. Uranium is an important nuclear fuel used to produce clear electric energy. The coal mine is widely distributed, while the uranium deposit is scarce. However, a large storage of both the two ore deposits, with the uranium deposit lying above the coal seam, was found in the Tarangaole coalfield in Ordos Basin, China, which caused a co-exploitation of coal and uranium with a high risk of radioactive pollution. A hydraulic curtain approach was proposed to realize the safe co-exploitation; the hydrological effects of separately mining the two ores and different-design hydraulic curtain, including different shapes (polyline, straight and arc), different locations (100 m, 300 m and 500 m from uranium deposit), number of injection wells (167, 207 and 247), spacing between injection wells (50 m, 100 m and 150 m), single well injection rates (50, 75, 100 m3/d), and injection positions (Zhiuo-Yanan Formation and Zhiluo Formation), were quantified by numerical simulation. The water level of groundwater dropped from 72 to 300 m with separately mining Plan A-D at the end of the 20th year. The drawdown in the uranium deposit of the polyline curtain shape was only 99.49 m, which was half that of separating coal mining and also smaller than that of the straight and arc-shape curtains. 167 injection wells, 50 m injection well spacing, 100 m3/d single well injection rate, and injection location in Zhiluo-Yanan Formation were the best combination to reach a high injection efficiency of water and protect from the minimum rise of water level (8.69 m). The hydraulic curtain of the polyline, 8300 m length, and 100 m distance to the uranium deposit had a high feasibility for the two resources recovery together. Compared with separate mining plans, the advantages of the hydraulic curtain method could make the two ore deposits not influenced by each other in the co-exploitation of the same time. This study offers a new way to make combined uranium and coal mining practicable, and the findings and methods could be applied to other places with similar problems.