Prediction of gas emission volume from driving face based on seepage mechanics

In order to realize dynamic prediction of gas emission from seam gateway driving face,based on the seepage mechanics method,gas continuity equation,mo vement equation,state equation and gas content equation were applied to establish a gas seepage model of the coal wall.Integration was conducted on the seepage velocit y,the prediction formula of gas emission from the driving face was deduced and obtained and the predicted value accuracy of gas emission value in the site driving process was discussed.Based on the establishment on the gas seepage model of coal wall,a controlled variate method was applied to study the two key factors on the permeability of coal and in-situ seam gas pressure affected to the gas seepage velocity.The study results showed that the predicted value of gas emission volume from the driving face obtained with the predicted formula was basic same with the site actual value and with the seam permeability and in-situ seam gas pressure varied,the gas seepage velocit y would be varied in a negative index relationship. The higher seam permeability was,the higher in-situ seam gas pressure would be.When the coal wall exposed,the gas se epage velocity index would be decayed more obviously.With time increased,the gas seepage velocity would be close to zero unlimitedly.