Mining Deformation Characteristics Of Key Aquifers In Overburden Rock Of No.3 Coal Seam In Liuxiang Coal Mine And Evaluation Of Water Conservation Mining

The Yushen mining area in northern shaanxi province of China contains a large number of high-quality coal resources.This area is a coal industry base that is developed and constructed in my country and has a significant impact on the national economy.However,the area is located on the border between the Mu Us Desert and the Loess Plateau in northern Shaanxi,where water resources are scarce and the ecological environment is fragile.The development of coal resources will cause the loss of water resources and the deterioration of ecological environment.Therefore,we must pay attention to the problem of deformation and destruction of the roof rock of the coal seam by mining,as well as the problems of groundwater loss in the aquifer and deterioration of the ecological environment.The overburden rock and soil body of the coal seam roof in Yushen mining area can be generally divided into three major rock groups and six major rock groups,namely loose sand layer group,soil layer group,weathered rock group,coal rock group,siltstone mudstone group and sandstone group;among them,N2 laterite,which is a key water-proof layer in this area,plays a key role in the protection of groundwater resources in mining areas.The thesis is based on the previous research results of N2 laterite in the area,combined with the test results of rock and soil mechanics samples in well fields,to analyze engineering geological characteristics of N2 laterite.N2 laterite is silty clay with good gradation,natural plastic,hard plastic to hard,It has strong expansibility,belongs to low compressibility,saturated soil,weak water permeability and good water barrier performance in natural state.Based on the geological conditions of 30105 working face of Liuxiang Coal Mine,the thesis uses UDEC numerical simulation software to simulate and analyze the mining failure characteristics of overlying rocks and key water-proof soil layers in fully mechanized top coal caving with large mining height.The results show that weathered bedrock and thick soil layer have stronger plastic deformation ability than intact bedrock,which has a certain inhibitory effect on the development of fractured zones.The water-permeable fractured zone basically develops at the bottom of laterite layer after passing through the bedrock.Combined with the measured data of the height of transmission fissure zone,it can be known that the numerical simulation of the height of transmission fissure zone is in line with the actual situation.By analyzing the influencing factors of mining failure in N2 laterite layer,the mining failure evaluation model is constructed to evaluate the mining damage of laterite layer.The height experience formula of water flowing failure zone of full mechanized caving mining is used to predict the maximum height of the aquifer fissure zone.Comparing the distance between coal seam and water in the well site,it can be seen that the maximum height of the water-permeable fractured zone in the Liuxiang mining area is smaller than the distance between coal seam and water.In the normal mining process,the water-permeable fractured zone will not develop into an aquifer,so the entire well site can achieve the purpose of retaining water.The research results of the thesis have certain reference significance for the safe mining of coal and the protection of the surface ecological environment under similar geological conditions in the mining area.