Study on the distribution characteristics of stress deviator in the surrounding rock when mining closely spaced coal seams

In mining closely spaced coal seams, the roadway arrangement for gas drainage in lower coal seams is always a concern. This paper uses mechanical model calculations and numerical simulation postprocessing methods to study the stress deviator distribution characteristics of the surrounding rock in the gob under various conditions. By calculating the distribution of the stress deviator, a reasonable location for the gas drainage roadway in engineering construction is determined, and the rationality of the roadway location selection is verified by the changes in the stress deviator in the surrounding rock during the mining of the lower coal seam. The research includes the following main results. (1) The theoretical formulas for vertical, horizontal, shear and stress deviator under a single gob of an inclined coal seam are derived through the semi-infinite body solution, and the stress deviator distributions in the roof and floor of the coal seam below the gob are calculated. The main factors affecting the distribution of stress deviator are determined by the following parameters: coal seam depth H , horizontal lateral pressure coefficient λ and coal seam inclination θ . (2) Through FLAC3D model calculation and postprocessing, the stress deviator distributions under different conditions are obtained, and the influences of various factors on the stress deviator distribution below a gob are analyzed. (3) Using the calculated theoretical results for the stress deviator and the distribution of the stress deviator obtained by the numerical method, the position of the gas drainage roadway during the mining of the upper coal seam is preliminarily selected; using numerical simulation of mining the lower coal seam, the stress deviator distributions in the surrounding rock during the mining of the lower coal are obtained, thus verifying the scientific basis and rationality of the gas drainage roadway layout.