Analysis of the influence of mining thickness on the stability of surrounding rock of goaf-side roadway driving

At present, in most coal mines, the coal pillar width of goaf-side roadway driving is determined by the average mining thickness. However, the thickness of the same coal seam could be varied greatly by various factors during the formation process. The large variation of mining thickness in the fully mechanized working face leads to large difference of surrounding rock deformation and complex damage mechanism of the goaf-side roadway driving. In order to solve the above problems, FLAC3D software is used to establish a roadway model so as to analyze the surrounding rock deformation and damage law under the average mining thickness, and determine the reasonable coal pillar width. When the average mining thickness is 18 m, on the side of the solid coal, the peak supporting pressure in the coal is positively correlated with the coal pillar width. Moreover, when the coal pillar width is greater than 8 m, the growth rate of the supporting pressure slows down. Therefore, the reasonable coal pillar width should be 8 m. This paper studies the influence of mining thickness on the stability of the surrounding rock of goaf-side roadway driving in the context of determined coal pillar width. The results show that when the coal pillar width is 8 m, with the increase of mining thickness, the shear damage area of roof increases, and the rock deformation range and the roof subsidence increase. However, the shear damage area of two sides and the distance between the two sides decrease. When the mining thickness is less than 18 m, the peak support pressure in the coal pillar is negatively correlated with the mining thickness. When the mining thickness is greater than 18 m, the peak support pressure in the coal pillar is positively correlated with the mining thickness, but the growth is small. According to the simulation analysis results, it is concluded that the increase of mining thickness is beneficial to the control of the surrounding rock along the two sides of the goaf roadway, but not beneficial to the roof maintenance. For areas with large mining thickness, anchor rods should be added to strengthen support in time. The actual application on site verifies the reliability and validity of the research in this paper.