Research On The Influence Of Coal Mining On Groundwater In Caojiatan Coal Mine

The impact of coal resource mining on groundwater is a key basic issue that needs to be resolved in coal resource development decision-making and water resources protection in mining areas.This thesis takes Caojiatan coal mine as the research area,comprehensively using field investigation,theoretical analysis of key layers of overburden failure,FLAC^3D numerical simulation,Visual Modflow numerical simulation of groundwater flow field,fuzzy analytic hierarchy process of water richness,independent weight coefficient analysis and other methods.The development height of the water-conducting fissure zone in the 2^-2 coal seam in the study area,the law of the influence of coal mining on the groundwater flow field,and the degree of influence of coal mining on the groundwater are studied.The research results have important guiding significance for coal mining and groundwater resources protection.Based on the analysis of the meteorological and hydrological relationship,the spatial combination of aquifer-bearing layers,and the hydrogeological test results in the study area,it is believed that the aquifers with strong water richness in the area are Quaternary phreatic aquifers and Jurassic weathered bedrock aquifers.In the study area,there is a stable distribution of Neogene Baode Formation soil water barrier between the two,and the hydraulic connection is poor.Based on the theoretical analysis of key strata and FLAC^3D simulation,the heights of the water-conducting fissure zone in the 2^-2 coal mining at the 122109 working space are 197.14m and 209.97m,respectively,and the corresponding crack-to-production ratios are 19.71 and 20.99,respectively.Combining with the actual drilling data of the 122109 working space,it is comprehensively determined that the height of the water-transmitting fissure zone of the fully mechanized caving mining in Caojiatan minefield can be predicted according to the fracture-to-production ratio of 20.13.2^-2 The water-conducting fissure zone formed by the full height of coal mining at one time will break through the bottom boundary of weathered bedrock in most areas of the minefield,and there is no conduction in a small area of the northern and northwestern boundary of the minefield;the water-conducting fissure zone of the entire minefield does not break through the red soil The top boundary is calculated according to the relevant formula in the "Detailed Rules for Water Prevention and Control in Coal Mines".The critical value of the minimum safe thickness of the critical aquifer is 18.95m.Comparing this value with the distance between the water-conducting fissure zone and the top boundary of the red soil,it is found that only a small area in the south of the minefield The mining of inner 2^-2 coal seams will affect diving,and the rest of the areas are safe areas;The conceptual hydrogeological model and mathematical model of the study area were established,and the model was identified and verified using Visual Modflow software.The results showed that the established model basically conformed to the actual situation.The groundwater flow field of the phreatic aquifer and weathered bedrock aquifer after mining at the 122106 working space(mining height of 6m)and the 122109 working space(mining height of 10m)are simulated,and the disturbance of the phreatic flow field caused by the mining of the 122106 working space and the 122109 working space is obtained.The water level is lowered by about 0.1m,and no large drop funnel is formed;the water level drop of the weathered bedrock aquifer at the 122109 working space is 5m larger than the water level at the 122106 working space,because the coal seam mining thickness of the 122109 working space is greater than the 122106 working space mining thickness of coal seam.The thickness of weathered bedrock,permeability coefficient,brittle-plasticity ratio,and core selection rate are selected as indicators for evaluating the water richness of weathered bedrock aquifers,and fuzzy analytic hierarchy process and independent weight coefficient method are used to divide the water richness of weathered bedrock aquifers.It is found that the water richness of the small area at the northwest boundary of the mine field is relatively strong,and the water richness of the northern,central,and eastern regions is relatively weak.Combined with the conduction of the weathered bedrock aquifer by the water-conducting fissure zone,a regional prediction of the extent of the influence of 2^-2 coal mining on the weathered bedrock aquifer is carried out.The results show that the middle to north boundary of the well is a very small to moderately affected area,accounting for 61.2%of the area of the well,and the area with the greatest degree of influence is located in the southern part of the well and has the smallest area,accounting for 17.4%of the area of the well.