School of Energy and Mining Engineering,China University of Mining and Technology-Beijing;Engineering Research Center of Green and Intelligent Mining for Thick Coal Seam,Ministry of Education;Coal Industry Engineering Research Center of Top-coal Caving Mining

Horizontal sublevel top coal caving mining is one of the main mining methods for steeply inclined and extra-thick coal seams. The working face of horizontal sublevel top coal caving mining is relatively short,which leads to a great influence of top and bottom side wall on the top coal drawing law. Based on the BBR theory,the Bergmark-Ro- os (B-R) model was used to analyze the drawing law of top coal and the variation mechanism of the drawing body shape under the influence of inclined side wall. The theoretical model of the drawing body boundary affected by the side wall of the roof and floor was established,and the theoretical equation including the axial dip parameter was derived. The quantitative relationships between the axial angle parameters and the boundary conditions were obtained by the Particle Flow Code numerical calculation,and the physical experiments were used to validate the theoreti- cal model. Some suggestions on reasonable sublevel height interval and the optimization of drawing technique with dif- ferent dip angles ranges were proposed. The results show that the existence of inclined side wall makes granular top coal subject to greater transverse stress,which changes the direction of the acceleration of top coal parti- cle movement. The difference of the filling potential of granular top coal on both sides of the drawing opening leads to the difference of the moving acceleration of top coal particles on both sides of the opening. The change of ac- celeration and direction of top coal causes the axis direction of the drawing body to deviate from the direction of gravi- ty. Under the influence of inclined side wall,the shape of the drawing body is asymmetrical on both sides of the axis, and the drawing body near the roof side is more affected by the boundary than that near the floor side. The β value of axial dip angle increases linearly with the increase of coal seam dip angle. With the increase of the length of non-drawing section,the axial angle of the drawing body near the roof and floor gradually tends to 90°. The physical simulation results validated the accuracy of the proposed theoretical model. The coal drawing method of “ single round near floor,multiple rounds in middle of face” and partially reverse drawing technique can effectively utilize the shape of the drawing body and reduce the loss of residual coal near the roof and floor.

张锦旺,程东亮,王家臣,等.水平分段综放开采顶煤放出体理论计算模型[J].煤炭学报,2023,48(2):576-592.
ZHANG Jinwang,CHENG Dongliang,WANG Jiachen,et al.Theoretical calculation model of top coal drawing body in horizontal sublevel top coal caving mining[J].Journal of China Coal Society,2023,48(2):576-592.