Analysis Of The Development Law Of The Induced Water Fracture Of Overlying Strata In Close Coal Seam

Based on the Yanjiahe coal mining geological conditions,this paper used physical simulation,numerical simulation and industrial test analysis methods to study the migration and water diversion of overlying strata of 5"1,5"2,and 8 coal seams in coal mines.The development of cracks has been systematically studied.The upward mining of 8 coals,5-1 coals and 5-2 coals was carried out separately,and the development of water-splitting cracks in overlying strata under the condition of different mining sizes was adopted for down mining of 5-1 coal,5-2 coal and 8 coal.The study has obtained the characteristics of the development of water-guiding fissures for mining of overlying strata under different mining conditions and determined the reasonable size of the 8 coal working face.The main research results are as follows:(1)The physical simulation shows that the initial pressure step of 8105 working face is 54m,and the step pressure step is 20m.8 During the coal seam mining,the water-splitting cracks in the overlying strata at the mining boundary have developed significantly.On the basis of the 8th coal mining,the 5-1 coal and 5-2 coal overlying the 8th coal were simulated in ascending order.The development height of the water-guiding fissure of the 8th coal overlying strata was 98.4m and 5-1 The development height of water-guiding fissures for coal overlying strata is 118.4m,and the development height of water-guiding fissure for 5-2 coal overburdens is 126m.After the 5-2 coal mining,the water-flooding cracks developed from the overlying strata developed to the Zhiluo aquifer..(2)Numerical simulation analysis shows that different mining sequences have obvious influence on the development of water-guiding fissures in overlying strata.Affected by the spacing between layers,the final development height of the water-guiding fissure is 129.2m after the ascending mining.At this time,the water-guiding fissure enters the Zhiluo Formation aquifer.In the downstream mining process,the final development height of the water-guiding fissure is 145.3m.Water cracks penetrate the Zhiluo Formation aquifer;downward mining overlying strata and mining waterflooding cracks developed more than upstream mining.(3)The numerical simulation analysis shows that the working face mining size has asignificant influence on the development of water-guiding fissures in overlying strata.The width of the water-spreading fracture is obviously increased from Om to 200m;when the depth is 200-300m,the development height of the water-guiding fissure tends to 95m;the mining height is from 3m to 7m,and the height of the water-guiding fissure grows linearly;but the overburden mining water diversion The cracks did not enter the aquifer of the Zhiluo Formation,and the reasonable width of the working face was determined to be 200m and the mining height was 7m.(4)The results of industrial tests show that,at the early stage of mining,the height of water-guiding fissures did not enter the aquifer of Zhiluo Formation,and the amount of water inflow was small;as the working face progressed,the water-guiding fissures of the overlying rock were developed and increased,and entered.After the aquifer of Zhiluo Formation,the amount of water inflow increased significantly;when the working face was fully mined,the cracks in the overlying strata gradually compacted and closed,and the water inflow from the working face decreased and stabilized.