Abstract
The gas emission zone is an important parameter for the space–time effect of coal excavation and gas emission. In this paper, according to the effect of roadway excavation, a numerical model of gas emission zone based on the evolution of stress and permeability was established to obtain the width of gas emission zone with different pressure and permeability coefficient. Then the numerical simulation results were verified by measuring the gas content at different depths. Through numerical simulation and field measured data, the theoretical calculation formula is established on the basis of comprehensive consideration of the influencing factors of gas emission zone. The results showed that the gas emission zone increases with the increase of coal seam gas pressure and permeability coefficient when the roadway section and exposure time are the same. The measured gas emission zone, when taking gas content as the index with the same logistic function growth curve, matches the measured results with a relative error of 1.3 to 6%. The validity of the model is also verified by field experiments. The results can provide guidance for mine gas emission and gas drainage design.
Highlights
The gas emission zone is an important parameter for the space–time effect of coal excavation and gas emission
Determining the width of a gas emission zone after coal excavation allows mine engineers to estimate the intensity of gas emission more accurately; on the other hand, a reasonable sealing depth and length can be determined according to the width of gas emission zone to improve the gas drainage e ffect[3,4,5]
Coal seam gas content is one of the most direct parameters to determine the width of gas emission zone, which can be determined by testing the gas content of coal seam with different exposure time and different depth
Summary
The vertical initial geostress can be expressed as the product of the overburden rock bulk density and buried depth, and the horizontal geostress is the product of the vertical stress and the correction coefficient used in elastic mechanics t heory[24]. According to the relationship betweenthe volume of drilling cuttings, coal seam gas pressure and effective stress, it can be concluded that:. There is a good corresponding relationship between coal seam permeability and stress. The change in permeability with depth in the coal body can be obtained by fitting the effective stress and permeability[26]:.
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