Analysis of overlying aquifer water inrush above mining seam in Yushen Mining area

Yushen mining area is an important part of the coal base in Northern Shaanxi.Aiming at the problems of insufficient research on water inrush of aquifer above the coal seam being mined in Yushen mining area,the overlying strata of the coal seam being mined is divided into four aquifer groups:loose pore,bedrock and weathering fissure,cave fissure aquifer in burnt rock,as well as the main and sub 2 water proof soil layers according to the typical geological and hydrogeological structure characteristics of the mining area,Three types of aquifer water inrush modes are proposed and named as “shallow lateral direct water inrush mode”,“medium deep lateral and vertical combined water inrush mode” and “deep buried lateral and vertical weak water inrush mode” respectively according to the water inrush characteristics of aquifers under different combinations of water conducting fissure zone and aquifer groups.The water inrush analysis models of three coal mining modes on the scale of coal mining face are constructed,which shows that under the lateral direct loss type of shallow seam condition (Liangshuijing coal mine),the main mineable coal seam is No.4-2,because of the water conducting fissures directly develop to loose aquifers,the top aquifer of the mining face is dried,the total water inrush is 47 m3/h,and the mining effect on groundwater flow field is significant.In the deep buried composite water proof protection micro loss type (Xiaohaotu No.1 coal mine),the main mineable coal seam is No.1-2,the total loss of water in the aquifer is 21.87 m3/h,it is mainly in the form of lateral water inrush,although the water conducting fissures develop into bedrock aquifers,the groundwater flow of the loose pore aquifer is basically unchanged under the protection of main and sub soil layers.In the medium deep lateral and vertical composite water inrush type (Caojiatan coal mine),the main mineable coal seam is No.2-2,and the average thickness of No.2-2 coal seam is about 11 m，water conducting fissures develop to the interior of bedrock aquifer under the condition of stratified mining of coal seam which leads to a lateral water inrush of aquifer with 23.17 m3/h and a vertical water inrush with 12.67 m3/h,the groundwater flow of loose aquifer changes little.The total water inrush increases to 131 m3/h which has a great influence on the loose aquifers when the water conducting fissures break through the sub aquifer and develop to the bottom of the weathered bedrock aquifer under the condition of full mining height.In addition,the total amount of water inrush increases slightly with the increase of the height of the water conducting fissures when the height of water conducting fissure zone is less than 180 m and does not extend to the weathered bedrock aquifer.However,the water conducting fissures expose weathered bedrock aquifers with better water rich when the height of the water conducting fissures is greater than 180 m,which leads to a larger increase in the water inrush of aquifers.It can be seen that it is an important measure to control the water inrush by restraining the contact relationship between the height of water conducting fracture and the overburden aquifer with significant water yield.The research results of this paper provide a scientific basis for the prevention and control of roof water disaster and the coordinated protection of water resources in the arid and semi arid mining areas of Western China.