Influence Of Coal Mining On The Groundwater In Eastern Ningxia Hui Autonomous Region

Eastern Ningxia Hui Autonomous Region coal base with the expected yield of coalaccounting about100,000,000tons in2015is one of fourteen large-scale coal bases accordingto China’s Planning Construction. In the region where Eastern Ningxia Hui AutonomousRegion coal base locates, with the fragile eco-environment and the relative short waterresources, it is significant to make clear the influence of coal mining on the groundwater inthis region, which would provide some scientific guides to the coal mining, the conservationof water resources and the sustainable development of the mining area.In this work, we selected21mine fields in the7mining areas and1independent minefield of Eastern Ningxia Hui Autonomous Region coal base as the research area. Based on thewidely collected former data on the coal geological exploration, the data on the relatedmining geology and mapping analysis, we analyzed the hydrogeological condition and theoccurrence features of the first coal seam which illustrated that a) the main aquifers relativelystronger water yield property in the roof of the first coal seam in mine areas ofCarboniferous-Permian and Jurassic are the Cenozoic aquifer and sandy aquifer in the lowerZhiluo Formation of middle Jurassic, respectively; b) the thickness of the fist coal seam withthe general trend of “Northern part is thicker while the southern part is thinner” and unable toexploit in part regions varied greatly from several meters to several thousands meters; c) thecombination relationships between first coal seams and the aquifers accounts almost7types.Through the comparative analysis between calculated results on the caving zone and fracturedzone, of the first coal seams of different mine fields in the research area by the formulas in theregulations and standards and the observation data of3working faces, we made sure of theestimated methods on the heights of the caving zone and fractured zone; we pointed out thatwhen the thickness of the coal seam is greater than3m, the values calculated by the formulas of the caving zone and fractured zone would be smaller; besides, we should use the height ofcaving zone(fractured zone)/mining ration between of observation values to estimate theheights of the caving zone and fractured zone, and when the thickness is smaller than3m, themaximum values calculated by the formulas could be utilized to estimate the heights of thecaving zone and fractured zone.Though the work on the estimation and mapping on theheights of the caving zone and fractured zone in the first coal seams, we hold that the heightsof the caving zone and fractured zone in the mine field namely Qingshuiying and Hongliu inYuanyanghu mining area and Lingwu area developed much higher while the height in othermining areas and mine fields developed much lower.Through the comparative analysis on theheights of the caving zone and fractured zone and the distance between first coal seams andmain aquifers, we regarded that, in the most research mine fields of the mine area ofCarboniferous-Permian, the mining of the first coal seam would bring little influence to themain aquifer of Cenozoic while in the most research mine fields of the mine area of Jurassic,the mining of the first coal seam would bring great influence to the main aquifer of lowerZhiluo Formation; besides, in part regions, the secondary aquifer would also be influenced.We adopted the district overlay analyzing methods between watery and safety on combiningthe influence analysis on the coal exploration to the moving direction of groundwater andsupply-runoff-recharge conditions to predict the influence level on the coal mining togroundwater resources.The results showed that the influence level in the mine area of Carboniferous-Permian isslight with median and relative serious levels in some parts while in the mine area of Jurassic,there existed serious, relative serious, median and slight levels in different regions.