Dahuangshan Mine Mechanized Top Coal Caving Face Gas Drainage Technology Research And Evaluation

Gas disaster is one of the five major coal mine disasters. ConstrainingChina’s coal mine production safety in a long-term, especially in high gas coalseam with thick, gas prevention and control work is particularly important.Because the thick coal seam generally uses the technology of top coal cavingmining, the mining process determines the coal goaf more residual coal gas, therelease will increase dramatically, more easily lead to the occurrence of fullymechanized working face gas overrun problem. Therefore, extraction oftreatment technology for thick coal seam gas in high gas is very important.In this paper the high gas coal mine, coal mine in Mount HuangshanXinjiang Yuxin, is used for practical engineering background, the mine miningworking face of fully mechanized top coal caving face+735as the researchobject, the research of gas drainage recovery treatment measures, in order tosolve the problem of face gas overrun. The main research contents of this paper are as follows:First, coal samples were collected of eight feet in the big groove to do therelated experiments. Research on basic parameters of the occurrence of gas, gascontent, obtained the original coal gas pressure, gas adsorption constant a, bvalue and the gas emission from borehole; natural attenuation coefficient andpermeability coefficient of coal etc..Second, the study of mining in fully mechanized top coal caving workingface roof overburden movement, on the distribution of roof "three belt" to do aquantitative analysis of the top plate, the calculation of the height of caving zoneis between9.8~14.2m, using numerical simulation, get the roof fracture zoneheight is about30m. For gas drainage has important significance to determinethe production parameters and drilling hole position.Third, in sub level caving mining working face gas source were analyzed,on the gas emission source term and the contribution degree is analyzed andcalculated, draw the goaf gas emission accounted for61%, accounted for39%ofgas emission of coal wall, the gas control in735working face should be mainlycarried out goaf gas governance, to provide a theoretical basis for the selectedextraction scheme.Fourth, to carry out the study on mathematical theory model of the gaspumping drilling practical. Using numerical simulation software COMSOLMultiphysics, to wear layer drilling as an example, simulation of gas flowaround a borehole, gas flow rate and gas pressure obtained contours nephogram and stress. The simulation results show: from the borehole distance, stable gasflow velocity, gas pressure distribution is uniform, consistent with Darcy’s law;close to the borehole at the center, the largest gas velocity. Along with thedrainage borehole gas in coal seam, surrounding pressure gradually reduced, thegas in the near borehole in the coal seam at the center of the pressure gradient islarge, reduce speed is very quick, in the more distant gas pressure gradient isrelatively small, the gas pressure reduces slowly.Fifth, the fully mechanized coal face gas drainage treatment effect wereevaluated, respectively from the residual gas drainage gas residual content,pressure, gas desorption quantity and coal face gas extraction rate, the mine totalgas extraction rate and other indexes were calculated and analyzed, combinedwith the number according to the field measured data, standard and the rules toallow comparison, arrive at a decision+735in fully mechanized coal face gasdrainage management of specified requirements, the drainage effect is good.Sixth, the hole diameter of the gas drainage effect is very large, under thecondition of different borehole diameter (94mm,180mm,300mm), with theincrease of the hole, gas low pressure area was increased, showed that theeffective drainage radius increased significantly and the theory on large diameterdrilling in favor of735working face after gas drainage. But the pore diameterincreased from180mm to300m when the gas flow velocity distribution aroundthe borehole temperature distribution did not change significantly, and increasethe contribution of the hole diameter on gas flow relative to the large diameter borehole operation and maintenance costs, has little significance. In this paper,we should work on the+735surface borehole after gob gas drainage with180mm aperture.