Technology Research On The Through Beds Hole With Improving Permeability And Relieving Pressure At High Drainage Roadway In Pan Ⅱ Coal Mine

In order to explore outburst prevention technology of improving permeability andrelieving pressure at high drainage roadway, taked11223high drainage roadwaysheltering coal roadway drivage in the group A coal seam of Pan II coal mine asengineering practice, the pressure relief and permeability increase effects of hydraulicfracturing and were researched by using the methods of theoretical analysis, numericalsimulation and field test inspection. The results showed that the extent of hydraulicfracturing could reach to10m, but the effects of gas extraction were not improvedevidently. Based on the analysis, the main reason was that cracks formed under highfield stress fracturing re-closed due to high ground stress. Therefore, hydraulicfracturing technology is not suitable to the pressure relief and permeability increase ofPan II soft coal seam.Through theory and numerical analysis of the hydraulic flushing and combinedwith field trials, got investigation conclusion as follows:①Under the same extractiontime, the effective influence radius increased with the increase amount of flush-out coalin per-meter, and the increase amplitude had a attenuation trend, proposed taking1t offlush-out coal in per-meter or slightly larger than1t as the flush-out amount coalstandards in group A Pan II coal mine, test results showed that can achieve the goalbasicly by adopted nozzle of2Φ2.8mm and established the pump pressure at14~16MPa.②Under the same amount of flush-out coal, the effective influence radius increasedwith the increase of extraction time and the increase amplitude decreases gradually,identified the quantitative relationship between the effective drainage radius y andextraction time x, and reasonable extraction time was determined as90days after usedhydraulic flushing measures in group A Pan II coal mines.③Resolve the problem oflow efficiency extraction caused by accumulated water in next to the hole after adoptednew automatic water-drainage sealing process, and pure gas extraction increased by2times than used conventional sealing process.④To inspected the hydraulic flushingradius used the methods of gas pressure, gas content, hydraulic flushing radius and puregas extraction, when the amount of flush-out coal was about2.94t/m and drainage timewas determined as15days, effective influence radius could reach more than6m.⑤ Compared the results of field test study and numerical simulation, the accuracy of thenumerical simulation was confirmed. Three kinds of hole arrangement distance ofhydraulic flushing were designed according to the results of numerical simulation andthe practical situation of Pan II coal mine. And it showed that the measure of hydraulicflushing was fit for the improving permeability and relieving pressure in coal seam of Agroup in Pan II coal mine at last.