Study on prediction method of gas emission rate in mining faces of contiguous seams

In the prediction of gas emission rate from the mining face of contiguous seams,the lower coal seam is affected by the mining of multiple upper coal seams,gas will be released many times,and the gas content will be greatly reduced. When using the method described in the industry standard to calculate the gas emission rate of the lower coal seam working face,it will inevitably cause the deviations in the prediction results. In order to accurately calculate the amount of gas emitted from the working face during the mining of contiguous seams,the influence coefficient of gas emission in mining layer to adjacent layer was introduced and the original coal seam gas content and residual gas content in the coal seam in the calculation formula for gas emission from the mining layer in the standard and the gas emission from the adjacent layer have been revised and the revised gas emission calculation formula of the mining layer and the gas emission calculation formula of the adjacent layer were proposed. The revised calculation formula was used to calculate the gas emission of each coal seam mining face under the condition of mining contiguous seams in a mine in Hebei. The calculation examples were analyzed and compared with traditional calculation methods. The results show that calculation results of the gas emission from the first coal seam between the two are basically the same with a deviation value of 0.35 m3/t. The calculated values of the gas emission from the coal mining face in the remaining coal seams have a large deviation the largest deviation value is 3.76 m3/t,and the result calculated according to the method described in the industry standard is 4.45 times of the result calculated according to the revised formula. Combined with the actual situation of gas emission in the working face,the result of gas emission calculated according to the revised calculation formula is closer to the gas emission of the actual working face of the mine,thus verifying the accuracy of the revised calculation formula of gas emission in the mining layer and the calculation formula of gas emission in the adjacent layer.