综放沿空留巷顶板下沉及其影响因素研究

Roof subsidence and its influential factors on the gob-side entrying in fully mechanized topcoal caving face

控制顶板下沉是综放沿空留巷成功的关键,为研究综放沿空留巷顶板下沉规律,根据能量守恒和损伤力学的理论,建立了综放沿空留巷顶板下沉损伤力学模型,推导出顶板下沉量的计算公式,并分析了顶板下沉量与其15个影响因素的定量关系。结果表明:直接顶、顶煤、巷旁支护体的有效弹性模量三者耦合,大部分顶板下沉量由有效弹性模量较小者吸收;顶板下沉量随支护体宽度增加而降低,支护体宽度达4 m左右时,下沉量基本保持不变;顶板下沉量随巷道宽度、采高、顶煤厚度和直接顶厚度增加而增加;顶板下沉量随关键块给定载荷的增大而急剧增加。关键块参数对顶板下沉具有决定作用,提高巷旁支护强度,可减小关键块破断长度和回转角,使关键块破断位置靠近巷旁煤壁,有效减小顶板下沉;巷内支护阻力、直接顶容重和顶煤容重对顶板下沉量影响较小。

In order to make a comprehensive study of the surrounding rock deformation regularity of the gob-side entry resistance in the fully mechanized top-coal caving mining face （GEREPTF） , the paper has established a damage and deformation mechanics model to find the GEREPTF roof subsidence based on the energy conservation and dam- age mechanics. For our research goal, we have worked out a calcula- tion formula for the roof subsidence by taking the roof subsidence of Wuyang Coal Mine as a study sample. According to the formula, the roof subsidence of the said coal mine accounts for 331.9 mm, which is well in accord with the actual roof subsidence measured on the spot. In this paper, we have also been trying to find out 15 influential factors of the roof subsidence and their variation range, so as to de- terminate the corresponding influential factors of the roof subsidence and point out which of the said factors is the dominant one or ones. The results of our analysis have shown that the roof subsidence is dominant factor to the success of GEREPTF, while the relationship between the roof subsidence and the effective elasticity modulus should be the main concern when we try to make it out. On the other hand, the effective elastic modulus of immediate roof, top-coal, sup- porting body are coupling, and most of roof subsidence is absorbed by smaller of them. What is more, we have also found that the roof sub- sidence increases with the increase of the width of the supporting bod- ies. But it will remain unchanged until it broadens to 4 m, and, therefore, it wouldn＇t be possible to achieve the goal for reducing such roof subsidence by broadening the width of the supporting bodies ceaselessly. In addition, the roof subsidence tends to go on increas- ing with the mining height, lane width, the immediate roof thickness and the top-coal thickness. On the contrary, the roof subsidence may turn to be dramatically decreasing due to the given load. Therefore, the dominant block parameters tend to play a significant role on the roof subsidence. Thus, it can be seen that the only way to improve the supporting intensity is to reduce the key block length and rotation angle. However, with the increase of the immediate roof and top-coal density, the roof subsidence is likely to increase linearly at the low speed in a range from 328 mm to 336 ram, which makes it little ^- fectcd on the roof subsidence. Therefore, the above results we haw worked out are expected to provide a theoretical hmndation for the ra- tional support for the layout of the GEREPTF.