Evaluation On Safety Of Preventing And Controlling Water Before Mining In Extra-thick Coal Seam Of 61303 Working Face

The thesis uses the 61303 working face of Tangjiahui Coal Mine as the engineering background for the study of water safety before mining.The main coal seam thickness of this working face is 23.1m,which is an extra-thick coal seam,and there is a thick sandstone aquifer on the coal seam and Ordovician limestone strength below it in aquifers,water inrush and well flooding accidents have occurred.In order to ensure the safe and efficient mining of 61303 fully mechanized caving face,it is very necessary to conduct water safety evaluation before mining.On the basis of reviewing the top and floor water hazard detection and treatment frontier technologies and research results of ultra-thick coal seams at home and abroad,this paper analyzes the main water-filling factors that affect the safe mining of the surface;predicts the mining-induced damage for the thick roof sandstone water.The height of the water fissure zone is developed,the roof water exploration hole is designed and the pre-mining drainage is carried out;the geophysical exploration,hydrogeological drilling,grouting reinforcement and geophysical abnormal area exploration verification and treatment are designed for the limestone water of the floor,and the mining is calculated.Water inrush coefficient of moving floor.An engineering geological model was constructed,and numerical analysis and technical and economic safety analysis were compared and selected.Obtained the following results:(1)The main water-filling factors of 61303 working face are roof sandstone fissure water and floor Ordovician water.Roof sandstone water is the net reserve.Drainage drilling is designed.The use of advanced dredging will have little impact on the safety of coal mining;Grey water is rich in water and is the key research object of the thesis.(2)For the roof sandstone water,112 roof sandstone drainage holes were designed and constructed according to problems such as advancing speed and deteriorating working environment,with a total engineering volume of 1,8063.5m.The inspection and verification holes for 4 abnormal drainage areas were completed,with a footage of 523m.The cumulative water discharge is 686801.1m3.(3)Aiming at the aquifer water of the Ordovician limestone floor with strong water richness,groove wave,sliding wave and other geophysical exploration methods were used to detect the working face,and 9 abnormal areas of geophysical prospecting were found,and exploration,grouting reinforcement treatment and verification holes were designed and constructed.65,the engineering volume is 4969.5m,the perforation is 220 times,the engineering volume is 16584m,the grouting through the layer is completed 285 times,and the grouting volume is 666.57t.Twenty-three drilled holes(9 main holes and 14 branch holes)were drilled along the bedding,with a cumulative footage of 13155.5m,a sweeping footage of 2046m,and a total of 218.2t of cement.Transient electromagnetic was used to test the effectiveness of the treatment.(4)The rock samples were taken during the construction of the underground exploration hole,and the rock mechanics and hydraulic performance test and thin slice identification were carried out in the laboratory.The tensile strength was 1.00MPa?5.19MPa,the compressive strength 1.30MPa?89.50MPa,and the poisson Ratio 0.10?0.40,porosity 3.69?14.45,water absorption rate 0.96?6.24,elastic modulus5.08GPa-38.13GPa,deformation modulus 3.68GPa?29.85GPa.It has typical damage evolution characteristics such as large porosity,low tensile strength,high quartz content,poor water resistance and regeneration water resistance.(5)Based on the rock physical mechanics test data of each rock layer in the 61303working face of Tangjiahui Coal Mine,an engineering geological analysis model was created,and the software FLAC^3Dwas used for numerical simulation to simulate the deformation and failure of the surrounding rock during the horizontal advancing process of the 6 coal seam roof and floor along the coal seam.In order to study the mining process of the 61303 working face under the aquifer,the vertical displacement of the working face along the longitudinal mining direction of 40m,80m,120m,160m,200m,240m,280m,300m during mining was obtained Vertical stress,plastic zone and other surrounding rock changes.(6)According to the empirical formulas in the"Detailed Rules for Water Prevention and Control in Coal Mines"and other relevant regulations,it is estimated that the height of the water-conducting fissure zone during mining is 163-206.4m,and the floor damage depth zone is 26m;6 the distance between coal floor and Aquifer is 43.5?80.25m,the maximum confined water pressure is 1.0MPa,and the calculated floor water inrush coefficient is 0.022?0.043MPa/m,which is less than 0.06 MPa/m.It meets the requirements of the"Detailed Rules for Water Prevention and Control in Coal Mines"and has safe mining conditions.(7)Using the"big well method",it is estimated that the normal water inflow at the61303 working face is 453m³/h,the maximum water inflow is 571m³/h,and the designed comprehensive drainage capacity is 1100m³/h,with strong disaster resistance.And formulated 61303 working face water hazard prevention and control safety control technical measures and emergency plans.In summary,61303 working face has been equipped with safe mining conditions.When the thesis is completed,the working face has been safely mined,and the actual water inflow of the working face is about 5m³/h,and no water inrush accident has occurred,indicating that the water damage control method adopted in the thesis is that the roof sandstone water is dredged in advance and the floor limestone water grouting is modified.And the methods have high applicability and popularization to Tangjiahui Coal Mine.Figure[58]Table[14]Senate[71]...