煤矿巷道顶板锚索受力特征与分区锚固机理
Stressed characteristics and regional anchoring mechanism of cable bolts in coal mine roadway roof
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摘要: 锚索是煤矿巷道围岩控制的主要支护材料,随着开采深度增加,巷道围岩应力环境恶化,顶板锚索破断问题较为突出,极易引发冒顶事故,严重影响生产安全。为解决煤矿巷道顶板锚索破断率高,层状顶板难以实现稳定控制等难题,综合采用数值模拟、理论分析和现场试验等方法,研究了巷道顶板不同区域锚索的真实受力特征和长短锚索对顶板的支护效应,分析了不同区域锚索对顶板的锚固机理。研究结果表明:布置在顶板不同区域的锚索受力具有显著的差异性,锚索在下位顶板岩层中受力较为复杂,同时承受拉伸荷载和剪切荷载,越靠近顶板中部其受到的轴向拉力越大,而越靠近巷帮其受到的横向剪切荷载越显著;提高锚索的预紧力有利于实现顶板的稳定控制,使锚索受力趋于均匀,减小有害受力;锚索的长度增加有利于扩大顶板的支护范围,但短锚索对其锚固范围内围岩的支护刚度优于长锚索;巷道顶板在横向可分为三区,即一个中心区和两个肩角区,长锚索优先布置在中心区,主控顶板的挠曲离层,短锚索布置在肩角区,主控顶板的层间剪切错动;巷道顶板在竖向可分为三层,即非稳定层、亚稳定层和稳定层;基于顶板锚索分区锚固机理,提出了以长短锚索为主导的多层次支护技术,并在现场取得了良好的工程应用效果。Abstract: The cable bolts are the main supporting material for controlling the surrounding rock of the coal mine roadway. As the mining depth increases,the stress environment of the surrounding rock of the roadway deteriorates,and the roof cable bolts breaking problem is more prominent,which can easily lead to roof collapse accidents and seriously affect production safety. To solve the problems of the high breaking rate of cable bolts in coal mine roadway roof and difficult to realize stability control of layered roofs,numerical simulation,theoretical analysis and field test are comprehensively adopted. In this paper,the real stressed characteristics of cable bolts in different areas of roadway roofs and the supporting effect of long and short cable bolts in the roof are studied. Moreover,the anchoring mechanism of the cable bolts in roof in different areas is analyzed. The results show that there is a significant difference in the force distribution of the cable bolt arranged in different areas. It sees that the cable bolt force in the lower roof strata is more complex and bears both tensile and shear loading at the same time. The closer to the middle of the roof,the greater the axial tension on the cable bolt,and the closer to the roadway corner,the more significant the shear load on the cable bolt. It can be concluded that increasing the pretension force of the cable bolt is beneficial to realize the stability control of the roof and uniformity of forces on cable bolts,reduce the disadvantageous force. The increase of the cable bolt length is beneficial to expand the supporting range of the roof,but the surrounding rock supporting stiffness in the anchoring range of the short cable bolt is better than that of the long cable bolt. The roadway roof can be divided into three areas laterally,that is,a central area and two shoulder corner areas. The long cable bolts are preferentially arranged in the central area,which mainly control the deflection and separation of the roof. The short cable bolts are arranged in the shoulder corner areas,which mainly control the interlaminar shear dislocation of the roof. The roadway roof can be divided into three layers vertically,namely,the unstable layer,sub-stable layer and stable layer. Based on the regional anchoring mechanism of roof cable bolts,a multi-level support technology dominated by long and short cable bolts is proposed,and it has achieved a good engineering application effect in the field.