Calculation And Forecast Of Mine Hydraulic Discharge In Hebi Siwan

Lower Permian Taiyuan Formation undergroup coal is one of the main seams of Siwan mine, including Upper floor coal (122 or seam 6) and Lower floor coal (111 or seam 8). Karst water of upper plane coal bed is the second layer limestone Karst and gets water recharge from Ordovician system limestone. Seam floor is water-resisting layer belonged to Benxi group, and about 30m below this floor is limestone Karst aquifer of Ordovician system. Kast crack is developed in Ordovician aquifer, the water quantity is extremely abundant and water pressure is high. The aquifer is the indirect water filling layer of undergroup coal seams'floor. In order to mine safely. It is necessary to drainage and decrease pressure of the second layer limestone karst water in advance. At present, the water level of the second layer limestone karst water is +127m. It is necessary to drainage it to +20m. But now the capability of mining drainage is insufficient, and water coal storehouse is so small that it can not satisfied with the requirement of drainage the second layer limestone karst water in the future. Carried on dewatering and tracing test in order to realize the effect of drainaging, forecast normal water yield when the level of the second layer limestone karst water falls to +20m, and look into the hydraulic link between the karst water of the second layer limestone and the Ordovician limestone karst water.The test had lasted for 240 hours, including three dropping stages of unsteady flow and a period of water level recovery. At the same time, proceed tracing test in two Ordovician limestone observing wells on the ground through pouring into KI and NaF. In the centre of dewatering, samped water at intervals of two hours and carried out water quality analysis.According to analyzing water quality data, we can conclude that the Ordovician limestone karst water is recharged by the second layer limestone karst water through faults. Based on the dewatering test data and comprehensive analysis of the hydrogeologic conditions of Siwan mine, applying correlated extrapolation of Q～f(S)and using Visual MODFLOW software to build a numerical simulation model, successfully fitted the flow field and the water level during test processes, the predicted normal water yield is 1400m3/h. The research shows that the maximum water yield is 1.2 times of the normal water yield when mining +50m undergroup coal seams in NO.1 coal mine. The maximum water yield is 1680m~3/h.