Space time evolution characteristics of stress transfer path of surrounding rock in longwall mining of steeply dipping seam

The spatial distribution pattern and the transmission path of mining stress in the roof of a steeply dipping seam are more complicated than that in a horizontal coal seam affected by the angle of the coal seam during the mining process of steeply dipping coal seams. Discovering and revealing the macroscopic distribution of mining stress and the evolution characteristics of the stress transfer path are the cornerstones for the safe and efficient mining of this type of coal. Taking 25221 working face of a mine as engineering background，this paper adopted the comprehensive research methods of simulation experiment，numerical simulation，and theoretical analysis. On the basis of determining the macroscopic structural evolution law of the surrounding rock of the coal seam，the spatial distribution of the principal stress enveloped arch shell in the surrounding rock space was quantified，and the spacetime evolution characteristics of the mining stress transfer path of surrounding rock were revealed. The results show that the shape of surrounding rock failure archshell increases first and then tends to be stable in height during the mining process of the steeply dipping seam. With the increase of the advancing distance，the shell base at the headgate Tjunction and tailgate Tjunction of working face shifts to the deep coal pillar and then tends to be stable. The surrounding rock stress envelope arch shell presents an asymmetric arch shell with the top in the middle and upper part of the working face and the base in the coal body around the stope. The evolution of the abutment pressure peak can be divided into growth area and stable area. The principal stress first increases and then decreases in front of the coal wall under the influence of mining，while in the middle of the minedout area，the three all decrease，and the first principal stress decreases the most. The transfer path of the first principal stress affected by mining can be divided into three areas: original area，increasing area，and decreasing area. In the increasing area，the first principal stress increases most in the Zaxis component，and its direction rotates perpendicular to the Yaxis plane. The research results reveal the evolution mechanism of macroscopic stress arch shell and stress transfer path of the roof，which enriches the strata control theory of steeply dipping coal seam.