Prediction of coal mine water inflow by different mining methods and environment impact analyses

Improper mining of coal mines can cause damage to water resources and the water environment, especially in areas with relatively fragile ecological environment. At present, the prediction of mine water inflow mainly focuses on the single working face or mining area, and enough attention has not been paid to the influence of long-term mining of coal groups in the gully on groundwater environment. The Toudaoheze gully is selected as the study area. Based on the data of groundwater exploration and coal field investigation, a 3D numerical model of groundwater unsteady flow of the whole gully is constructed. The model is identified and verified with the monitoring data of groundwater and surface water and the long-term data of mine water inflow in coal groups. Taking 9# coal mine as a typical area, the mine water inflow and its influence on water environment under the fully mechanized mining and strip filling mining methods are analyzed. The main results show that (1) under the fully mechanized mining method, the increase of mine water inflow is 0.70×10⁴ m³/d, resulting in the reduction of groundwater overflow of 0.20×10⁴ m³/d and causing groundwater level to drop between 0.21 and 17.92 m in the mining area and region. Under the strip filling mining method, the increase of mine water inflow is 0.11×10⁴ m³/d, resulting in the reduction of groundwater overflow is 0.04×10⁴ m³/d and causing groundwater level to drop between 0.01 and 0.44 m in mining area and region. (2) The water-conducting fracture zone connects with a large area of the Quaternary phreatic aquifer under the fully mechanized mining method, and mine water inflow has a great impact on water environment. If the strip filling method is carried out, the height of the water-conducting fracture zone will be greatly reduced, and the Quaternary phreatic aquifer will not be connected, and mine water inflow will have less impact on water environment. The filling mining method can be adopted when coal mining in the area has small thickness of strata above the coal seam. The results can provide a basis or reference for the formulation of mining schemes in the study area or other similar coal fields, and for scientifically handling the relationship between coal resource mining and ecological environmental protection.