Study On The Influence Factors Of U Style Ventilation On Air Leakage From Working Face To Gob

Air leakage in gob is not only one of the main causes that lead to spontaneous combustion of the residual coal in gob,but also has great influences on gas aggregation and gas emission in gob.So it is significant to study air leakage from working face to gob.In this paper,the influences of different ventilation and gas extraction conditions on air leakage are studied.And the influences of the different factors on air leakage are analyzed respectively.According to the analysis result,the suitable measures are made.According to the theory of "O" type circle and the nonlinear seepage equation,the numerical model of air flow field in gob is established.The commercial CFD software,Fluent,is used to simulate the air leakage flow field of the working face 151305 in Liuzhang mine.And the actual situation of the working face is combined to obtain the model of permeability distribution in the gob.The permeability distribution and the flow field distribution of the working face are analyzed.The results show that the flow field is in accord with the feature of "O" type circle.And the range of air leakage is the zone of 0～160m at working face,and the air leakage in the zone of 0～20m at working face is the most serious.The permeability in the central section of the gob is small relatively,but it is large relatively in the other section of the gob.The change of the permeability in the gob is the quickest in the zones of 0～10m from open-off cut and the coal walls of the intake side and the return air side,followed by it in the zone of 0-70m after the working face,and the permeability is unchanged basically in the other zone of the gob.In the gob,the dangerous zone of spontaneous combustion is the zones of 25～95m from the working face at the intake side,15～120m from the working face at the return air side and 0～20m after the fully mechanized mining supporter.On the basis of the simulation of the air leakage situation of the working face,the influences of air volume of intake roadway,wind resistance at working face and gas extraction volume of high drainage roadway on air leakage are simulated respectively and analyzed.According to the simulation results,it is obtained that the relationships of the air leakage volume with the air volume of intake roadway,the wind resistance at the working face and the gas extraction volume of high drainage roadway are respectively third-order polynomial,linear function and exponential relation.The results show that the air volume of intake roadway and the gas extraction volume have the respective critical values for their influences on air leakage volume,and the critical values of this working face are obtained.When the air volume and the gas extraction volume are smaller than the respective critical values,the influence of the wind resistance at working face on air leakage is the largest,followed by the influence of the air volume,and the influence of the gas extraction volume is smallest.When the air volume and the gas extraction volume are larger than the respective critical values,the influence of the air volume of intake roadway on air leakage is the largest,followed by the influence of the gas extraction volume,and the influence of the wind resistance is smallest.The range of air leakage is also studied.All the air volume,the wind resistance and the gas extraction volume affect the range of air leakage,and the larger the values of them are,the larger the range of air leakage is.The influence of the gas extraction volume on the range of air leakage is the largest.