Chang Zechao, Wang Xufeng, Qin Dongdong, Sun Yongxin, Yue Yanpeng, Chen Xuyang, Wang Jiyao
School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu, 221116, PR China.
School of Mines, Shanxi Institute of Technology, Yangquan, Shanxi, 045000, PR China.
Heliyon. 2024 May 4;10(10):e30705. doi: 10.1016/j.heliyon.2024.e30705. eCollection 2024 May 30.
Due to the large mining area, the fully-mechanized top-caving mining with thick-hard roof is easy to form cantilever structure on the lateral roof of the working face, which on the one hand causes high stress level of adjacent roadway and serious deformation of roadway, on the other hand causes gas accumulation in corners, which brings severe challenges to safe and efficient mining of the mine. In this study, a mine facing such problems in Jincheng, China was taken as the research object. Based on the mechanical characteristics of coal and rock, the characteristics of overlying strata activity in the mining process of working face are mastered, and the dual effects of controlled transformation of lateral overlying strata structure on stress field and gas field were revealed. On this basis, roadway reinforcement and gas drainage schemes were put forward and applied. The results showed that the strength of the hard rock stratum was high in the triaxial stress environment, and it was not easily destroyed. However, once the strata exceed their strength threshold, they break down. In addition, the strength of coal is relatively low, and it is continuously deformed when the force exceeds its strength. The overlying strata structure after thick-hard roof fully-mechanized top-caving mining evolves in the following manner: "long cantilever length formed by the main roof being broken in the initial stage, voussoir beam formed by the upper hard roof being broken in the middle stage, and double cantilever beam formed by overlying strata compaction." The stress carried by upper hard rock stratum is transferred to coal pillars, which is the main reason for the high stress environment of multi-purpose roadway with large coal pillars. The controlled transformation of lateral overlying strata structure by pre-splitting and roof cutting can realize the "transfer-unloading" of coal pillar stress and the "plugging and driving" of corner gas. Based on the hydraulic fracturing reconstruction of lateral overburden structure, the grouting reinforcement scheme of roadway and dynamic gas drainage scheme were put forward. The results demonstrated that after roof cutting, the maximum deformation of the surrounding rock in the multi-purpose roadway was reduced by approximately 90 %, and the maximum concentration of corner gas was decreased by 15.28 %. This approach successfully achieved a collaborative control effect on roadway surrounding rock stability and gas emission well within the safety limits.
由于采区面积大，厚硬顶板综放开采在工作面侧向顶板易形成悬臂结构，一方面导致相邻巷道应力水平高、巷道变形严重，另一方面造成隅角瓦斯积聚，给矿井安全高效开采带来严峻挑战。本研究以我国晋城一个面临此类问题的矿井为研究对象。基于煤岩力学特性，掌握了工作面开采过程中上覆岩层活动特征，揭示了侧向覆岩结构控制改造对应力场和瓦斯场的双重作用。在此基础上，提出并应用了巷道加固和瓦斯抽采方案。结果表明，硬岩地层在三轴应力环境下强度高，不易破坏。然而，一旦地层超过其强度阈值，就会破裂。此外，煤的强度相对较低，受力超过其强度时会持续变形。厚硬顶板综放开采后的覆岩结构按以下方式演化：“初期老顶断裂形成长悬臂梁，中期上部硬顶断裂形成砌体梁，后期覆岩压实形成双悬臂梁”。上部硬岩地层所承受的应力转移到煤柱上，这是大煤柱多用途巷道高应力环境的主要原因。通过预裂切顶对侧向覆岩结构进行控制改造，可实现煤柱应力的“转移-卸压”和隅角瓦斯的“封堵-驱替”。基于侧向覆岩结构的水力压裂改造，提出了巷道注浆加固方案和动态瓦斯抽采方案。结果表明，切顶后多用途巷道围岩最大变形量降低了约90%，隅角瓦斯最大浓度降低了15.28%。该方法成功地在安全限度内实现了对巷道围岩稳定性和瓦斯涌出的协同控制效果。
