Research On The Gas Extraction Radius Of Multi-coal Seam Drilling In Qinglong Coal Min

My country’s coal mining environment is getting worse and worse,especially most coal mines in Guizhou Province have complex geological conditions,high gas content,and high gas pressure,which increases the difficulty of mine gas extraction,and also easily causes gas dynamic disasters.This paper takes M16,M17 and M18 of Qinglong Coal Mine in Guizhou as the research objects.In order to solve the problem of gas extraction in this mine,the gas extraction radius and extraction ratio of this mine are studied through theoretical analysis,numerical simulation and field test and other methods.The main research results are as follows:Based on the coal seam gas seepage equation and the coal body deformation control equation,a fluid-solid coupling mathematical model for gas drainage was constructed.Combined with the COMSOL simulation software,the influence laws of different borehole diameters(75mm,94 mm,113mm)on gas pressure and different drainage time were simulated respectively.(30d,60 d,90d,120d)influence law on gas pressure,and change law of gas flow velocity with extraction time.The results show that:(1)As the diameter of the borehole increases,the range of the disturbed coal body increases,resulting in more fractures in the coal(rock),providing more migration channels for the gas,thus improving the coal(rock).)permeability,and the effective gas drainage radius increases.Therefore,the hole diameter of 113 mm is better than75 mm and 94 mm,but because the diameter is too large,it will increase the cost and the difficulty of sealing the hole,so the diameter of the hole is 94 mm.Under certain conditions,when the extraction time is longer,the effective extraction radius is larger,but when the extraction reaches a certain time,it will not increase,indicating that there is a limit extraction time for gas extraction.Combined with the simulation results,Qinglong Coal Mine The limit drainage time is 120d;(3)Under the condition of the negative drainage pressure of 25 k Pa and the borehole diameter of 94 mm,as the drainage time increases,the gas flow velocity presents three stages: a fast rising stage and a slow falling stage In the stable and constant stage,the influence effect of measuring points closer to the drilling hole is more obvious,and the effect of measuring points farther away is less.According to the measurement principles of the pressure drop method and the content method,the field test was carried out in the 21605 bottom extraction tunnel of Qinglong Coal Mine.Through the analysis of the data,it was concluded that the effective radius of the M16 coal seam extraction was 1m when the extraction was 98 d,2m when the extraction was 108 d.When the mining time is 121 d,it is 3m,and the limit mining time is 121d;the effective radius of the M17 coal seam is: 1m when the mining is 49 d,2m when the 63 d is mining,3m when the 96 d is mining,and the limit mining time is 111d;the M18 coal seam is 1m.The effective radius of extraction is: 1m for 22 d extraction,2m for 40 d extraction,3m for 94 d extraction,and the limit extraction time is 110 d.Judging by the effect of gas extraction,the effect of eliminating bursts has been achieved.When multi-coal seam through-bed drilling is used to simultaneously extract M16,M17,and M18 coal seam gas,M16 accounts for 41.37% of the total drainage,M17 coal seam accounts for 13.22%,and M18 coal seam accounts for 45.41%.The extraction ratio of each coal seam is mainly related to the thickness of the coal seam.For areas where the thickness of the coal seam changes,the extraction ratio can be calculated approximately by the thickness of the coal seam.In this paper,through the field test,the mining radius and mining ratio of M16,M17 and M18 of each coal seam in Qinglong Coal Mine are obtained,and the influencing factors are analyzed,which has important practical significance for the safe mining of the coal seam group in the mine.