Study on width optimization of gob-side entry retaining with flexible concrete in large-height coal seam

Based on the technical requirements of the 22523 large-height working face of Halagou Coal Mine, the section stability control method of large-height coal seam “flexible concrete roadside + anchor rod roadway support” is proposed. Based on the elastic-plastic mechanics, a solid mechanics model is constructed along the open channel, and the stress distribution and displacement evolution characteristics of the surrounding rock of the channel are simulated under different advancing distances and widths, to compare the displacement changes of the surrounding rock quantitatively and filling body of the channel. The results show that: the stress gradually concentrates to the surrounding rock of the roadway as the distance of the working face advances, and the stress of the sandstone overlying the goaf shows a Y-shape as a whole. The vertical stress distribution gradually shows an arch structure. The top of the stress arch is located at the overlying sandstone of the coal seam’s goaf, the toe of the stress arch is located at the surrounding rock and filling body of the coal seam’s side along the open retention lane, and the base of the arch is located at the sandstone of the coal seam’s underlaying sandstone. With the working face advancing distance increases to stay lane surrounding rock displacement gradually increased, the rate of increase in the first increase and then reduce the trend. When the working face advances to 93.8-113.8 m, the displacement of the surrounding rock of the stay lane is basically unchanged. The effect of the working face mining stress disturbance on the perimeter rock along the air stay is within 100 m. As the width of the filling body increases, the displacement of the top of the filling body, the side of the retaining lane, and the side of the hollow area gradually decreases. The displacement of the bottom of the filling body first increases and then decreases. The top plate of the roadway and the surrounding rock on the coal seam side gradually decrease. The displacement of the bottom plate from the side of the coal seam to the side of the filling body shows the change rule of increasing-unchanging-decreasing. After the width is greater than 1.2 m, the amount of displacement reduced by continuing to increase the width of the filling body is significantly lower. Considering the cost, the filling body wall width is selected as 1.2 m.