Evaluation Of Water Abundance Of The Fourth Aquifer In Qidong Mine And Study On Law Of Deformation And Breaking Of Overlying Strata

The coal measure strata in North China coal field are generally covered by thick loose layers.There is a layer of confined aquifer which is composed of non-cemented sand and gravel which poses a serious threat to the safety production of coal mine.Through the research and analysis of a lot of water pollution accidents in this area,many water inrush accidents are closely related to the water-rich aquifer,the damage law of the overburden and the influence factors of overburden.Therefore,based on the geological and hydrogeological data of Qidong Coal Mine in Suzhou,this paper firstly analyzes the spatial distribution of the aquifer at the bottom of the loose bed in the study area.Then select multiple aquifer water influence factors are analyzed,utilize the geographic information system（GIS）,the powerful spatial analysis function and fuzzy analytic hierarchy process to Qidong well four containing water in the coal mine.Finally,the structure of 2713 borehole 71 seam and its roof and floor sedimentary rock mass on the 26-27#exploration line of Qidong.Coal Mine is selected as the object,and the numerical simulation software FLAC^3Dis used to simulate the structure of the rock mass.The stress-displacement-failure law and the controlling factors of deformation and failure of overburden rock mining under loose confined aquifer are studied in this paper.The specific research results are as follows:（1）Five main water-rich control factors,including effective thickness,structural development density,consumption of drilling fluid,permeability coefficient and unit water inflow are selected.By using fuzzy analytic hierarchy process,the weight coefficients of five main control factors for water-rich zoning are obtained which are respectively 0.18.0.19.0.2 15.0.2.0.215.（2）The four water-rich grades of Qidong Coal Mine are reevaluated which can be summarized as follows:the strong water-rich area is located in the southern and eastern areas of Qidong Coal Mine.The middle water-rich area is located in the south of Qidong Coal Mine except for the remaining area with strong water-rich area and the sporadic area in the north direction of Qidong Coal Mine.The water-rich and weak area is located in the middle of Qidong Coal Mine,straddling the east-west direction and adjacent to the strong water-rich area.The extremely weak water-rich area is located at the northern boundary of Qidong Coal Mine.The distribution area is narrower and the boundary of the water-rich weak area divides into two.（3）Accelerating the speed of the working face can effectively reduce the displacement and deformation of top floor rock strata and effectively improve the structural integrity of mining overburden.Increasing the slanting length and mining height will increase the difficulty of surrounding rock control,the requirements of stope support system will become higher and the risk of water inrush will be increased.The larger the pressure,the more serious the overburden deformation.The fault will increase the height of roof failure and the scope of plastic zone in goaf and the water separation capacity of overburden rock will be decreased to different degrees which will increase the risk of roof water inrush.