Study On Gas Drainage Technology With Large Diameter High Level Sector Boreholes Of The Goaf In High Gas Mine

Large diameter drilling is the future development trend of the gas extraction and the research emphasis of gas extraction technology of full-mechanized caving mining face in the future. Based on this, this paper chooses the Shaqu mine as the background, analysis the gas drainage technology with large diameter highlevel sector boreholes.Using Flac3D to simulate and analyzes the movement regularity of roof strata in24207working face. Through the analysis of the Z direction displacement isoline, learned in goaf in60m behind the strata movement reached the equilibrium state, and can clearly judgement the location of the main key strata distribution in46m and18m above the working face. Finally using the empirical formula method to calculate the MaoLaDai and fissure zone maximum height of16.88m and16.88m respectively, calculated using the key strata combination analysis MaoLaDai and fractured zone height of17.56m and44.96m respectively, using the results of the numerical simulation analysis of18m and50m. To minimize the error, take average as the final result, namely MaoLaDai, fissure zone of the maximum height of17m and47m, respectively. Systematic analysis the goaf gas migration rule and its concentration distribution in goaf spatial features under "U" type,"U+L" and "Y" type ventilation. Analysis that under the same conditions using the "Y" type ventilation working face gas in upper corner within10m behind the concentration between0.26%～0.33%, only "U" type ventilation when1/8,"U+L" type ventilation of3/4. Predict the gas emission during the face mining, calculate to know rely on ventilation to dilute gas, gas concentration is as high as2.24%, in return for gas extraction is imperative.The basic principles of borehole extraction gas are discussed; formula of pressure distribution around the borehole is unstable seepage and seepage. The pressure range drilling more far less, and decreases with the increase of drainage time conclusion drop co-located pressure. And using Fluent software main factors effect of extraction of borehole are analyzed in detail, learned that drainage effect by negative pressure drainage hole, and coal seam permeability very boring; drilling and drilling of drainage quantity increases with decreasing negative pressure drainage; increases with the increase of the hole; and increases with the decrease of permeability of coal seam. This conclusion is consistent with the formula, and proves the feasibility of mining of large diameter borehole gas treatment.Based on the migration characteristics of roof strata and the distribution law of gas migration, put forward the layout plan of large diameter high borehole, determine the high drilling’s parameter value scope that21°<θ<39%reasonable spacing drill field should be40m-45m. Through drilling and tendency of the extraction from data of high lane were analyzed, and the average five borehole drilling field extraction scalar12.2m3/min, effective drainage time of63days; Decorate in the same side alley, the tendency of high extraction from scalar to an average of10.05m3/min, effective drainage time43days. Prove the large diameter drilling high extraction effect is more ideal at the end, it can replace high level tilt direction suction roadway perfectlly, and this drainage technology has highly reference value in methane control to other mines in our country.