Optimization About Gas Controlling Technique At Upper Corner Of High Gas Fully Mechanized Mining Face Containing Single Thick Coal Seam

The N1101 working face of Yu Wu coal industry is a single thick coal seam containing high gas fully mechanized coal caving face,and the ventilation way is"U+high level suction roadway".The accumulation and overlimit of gas in the upper corner are the important factors that threaten the safe of the working face.The main reasons are:large differential pressure between intake and return air lane,low concentration and low flow of high pumping alley,and low gas drainage efficiency of goaf buried tube.By theory analysis,field measurement,similar simulation and numerical simulation,the law of air leakage and gas migration in the goaf is revealed.The coherent combination mechanism of the air leakage flow field in the goaf,the extraction flow field of the high pumping alley and the flow field of the goaf buried tube is clarified,and the technical measures of the original upper corner gas controling are optimized.The specific research results are as following:(1)Using the unit method and tube monitoring technology,it is found that the leakage in area in goaf is the 30m range of inlet air side in goaf,the leakage out area in goaf is the 10m range of outlet air side in goaf.Air leakage and gas emission in goaf are smaller because of the existing of the high pumping alley and the effective action range is 20m on both sides of the high pumping roadway.The distribution range of"Three Zone of gas"in the deep direction of the goaf is analyzed and determined,and combined with the"O"ring theory of goaf,it is determined that the area suitable for gas extraction in the goaf is the fast accumulation area of gas(20 to 70m in the depth of the goaf).(2)based on the similarity theory,a three dimensional gas flow field test platform about the goaf is set up,and the similar simulation experiment of the gas flow field of"U+high pumping lane"ventilation is carried out.The experiment shows that the expansion of the air leakage range in the goaf is larger and that is bad for the prevention and control of the spontaneous combustion of the coal in the goaf,the wind discharge capacity is weakened when the level of the high pumping level is far away from the return airway.The air leakage range of the inlet side is smaller,the air leakage is slightly increased,and the pressure converge point in the deep mining area is moved deeper,when the level of the high pumping alley rised.the air leakage range of the goaf is not changed,the air leakage intensity is enhanced,and the pressure point moves deeper,when the pressure increases.(3)A physical model reflecting the working face of N1101 is established.the changing rules of the flow field,gas concentration field,oxygen concentration field and the distribution range of compound disaster area are studied through the FLUENT numerical simulation software.The optimal level of high level suction roadway is 20m from the coal seam floor and 20m in the distance from the return airway.The optimum extraction range of the buried pipe is 30 to 40m and the rate of flow is 50m~3/min.It is found that the supporting measures for improving the extraction efficiency of gas extraction methods and reducing the gas emission in the goaf are as follows:using foam cement to block the upper and lower corner of the goaf to reduce the pressure between the inlet and the return air lane.Through the above research,the optimization system of gas accumulation and exceeding limit controlling technology in the upper corner of a single thick coal seam high gas fully mechanized caving face is formed,which is of great significance for ensuring the safe and efficient mining of the mine.