| With the continuous extension of mining depth in China,coal seam gas content and gas pressure increase gradually.Combined with the use of comprehensive mechanized coal roadway excavation and caving mining method,the upper corner and the mining roadway heading face and other areas of frequent gas overload.Gas control production"bottleneck"problem is more and more prominent.In this paper,in view of the problem of gas exceeding limit in some areas during the mining roadway production and the fully mechanized caving face during the mining in the Changcun Coal Mine.Using the method of field investigation,theory analysis,numerical simulation and industrial test.The coal seam methane can be solved by using the drilling hole.The high suction roadway can solve the problem of gas exceeding limit in goaf and upper corner of fully mechanized caving face during mining.In order to resolve the problem that gas frequently exceeded in some areas of the mining face and caving face,the technology of drilling gas extraction was studied,The main research contents and results are as follows:(1)By fitting the monitoring data of geological exploration,the relationship between coal seam gas content and buried depth in Changcun Coal Mine is obtained.The relation between coal seam gas content and buried depth is:W=0.042H–10.96,The buried depth of coal seam(491~533m)in the 23 mining area was substituted into the equation of fitting equation.The range of coal seam gas content in this mining area is 9.71~11.43m~3/t.The accuracy of the formula is verified by measuring the coal seam gas content in different areas of 2301 transport roadway.(2)Through theoretical calculation,the range of collapse zone is about 0~21.4m,the height of fracture zone is about 80m,and five different simulation schemes of roadway layout are given.It is obtained that the gas concentration in the roadway is26-28%and the gas concentration in the upper corner is only 0.6-0.7%when the high drainage roadway is located in the position of the second project(S=29m?H=30m),and the gas drainage effect is better.The supporting scheme of the high drainage roadway is given.(3)By analyzing the theoretical calculation results of effective extraction radius and COMSOL simulation results,the effective extraction radius is determined to be2.5m,and the influence of suction negative pressure and drilling diameter on effective extraction radius is analyzed.The results show that the best negative pressure is15KPa and the diameter of drilling is 94mm.The gas extraction simulation of the 65m wide seam strip near the mining roadway shows that the gas pressure of coal seam is reduced below 0.74MPa,the gas drainage effect is better.(4)The layout scheme of drilling in high drainage roadway is given,and the parameters such as length and inclination angle of each drilling are determined,and the distance between the final drilling is 5000mm.The industrial test of gas extraction in coal seam with high drainage layer is carried out on the 2301 fully mechanized caving face of Changcun Coal Mine.The results of field monitoring show that the residual gas content in coal seam is reduced to 4.7m~3/t,and the application effect of drilling drainage is better.The maximum gas concentration in the upper corner is0.76%and the maximum gas concentration in the return air roadway is 0.7%.The application effect of the high drainage roadway in the four stages is good,which ensures the safe and efficient production of the fully mechanized caving face. |
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