Discrete element calculations of the top-coal drawing process for different gangue-coal density ratios were conducted to investigate the effect of the gangue-coal density ratio on the drawing mechanism in longwall top-coal caving. The effects were analyzed for the drawing body, the top-coal boundary, and the recovery of top coal. The results show that for increasing density ratio, the initial drawing body on the goaf side is farther away from the drawing support and its width and volume gradually increase. The upper part of the sickle-shaped drawing body extends near the initial drawing body with increasing density ratio in the normal cycling stage, and the distance from the drawing body to the initial drawing body is its maximum width. The larger the density ratio, the smaller the height of the top coal above the goaf at the end of the initial drawing process. The height of the top-coal boundary decreases with increasing density ratio, until it reaches a limit. In a normal cycle, due to hysteretic development, the top-coal boundary moves toward the goaf until the density ratio is approximately 2.0, which is consistent with the physical experiment results. Finally, increasing the advance length of the working face is beneficial for increasing the overall recovery of top coal.

对不同矸煤密度比的顶煤抽采过程进行离散元计算，研究矸煤密度比对长壁放顶煤抽采机理的影响。分析了牵引体、顶煤边界和顶煤回收率的影响。结果表明，随着密度比的增加，采空区的初始牵引体离牵引架越来越远，其宽度和体积逐渐增大。在正常循环阶段，镰刀形拉丝体的上部随着密度比的增加在初始拉丝体附近延伸，拉丝体到初始拉丝体的距离为其最大宽度。密度比越大，在初始抽采过程结束时，采空区上方的顶煤高度越小。顶煤边界的高度随着密度比的增加而减小，直到达到极限。在正常循环中，由于滞后发展，顶煤边界向采空区移动，直到密度比约为2.0，这与物理实验结果一致。最后，增加工作面的推进长度有利于提高顶煤的整体采收率。