Mechanism and practice of rock control in deep large span cut holes

Deep large span cut holes are difficult to stabilize. The 7801 cut hole in the Lu'an Wuyang Mine was used as this project's background. The main factors affecting large span cut hole stability are analyzed. Pre- stressed bolting theory was used to design a roof control method for a large span roadway. By reducing the span and applying equal strength coordinated supports the rock could be stabilized. The control prin- ciples and methods are given herein along with the analysis. A double micro arch cross section roadway is defined and its use in solving the current problem is described. Beam arch theory was used to build a model of the double micro arch cross section roadway. A support reverse force model for the arch foot intersection was also derived. A support method based upon reducing the width of the large span in the cut hole is presented. These results show that the reduced span of the roadway roof plus the use of cable anchors and single supports gives an effective way to control the large span cut hole. On site monitoring showed that the reduced span support from the double micro arch cross section roadway design had a significant effect. The roadway surface displacement was small and harmful deformation of the cut hole was effectively controlled. This will ensure its long term stability.

大断面泥质巷道顶板离层突变垮冒演化相似模拟实验研究

针对大断面泥质软弱夹层巷道掘进顶板离层失稳垮冒控制难题和现有离层相似模拟实验装置存在的不足,根据精密位移传感原理自主研制了巷道顶板离层模拟实验监测装置,并对该监测装置进行可靠性综合测试。结果表明:位移传感器监测形变量与相似模拟巷道开挖离层量呈良好线性关系,测量误差控制在±2%。通过平朔矿区大断面泥质巷道掘进顶板离层相似模拟实验,研究了顶板离层渐进发育至突变致灾演化全过程并提出离层安全临界值节点判据,研究表明:1)离层划分为渐变趋稳型离层和突变致灾型离层2类;2)离层渐进发育至突变致灾演化全过程可划分为裂隙发育离层孕育、离层急剧扩展、离层渐进趋稳和离层突变垮冒4个阶段;3)离层值达到渐变趋稳临界值之前,即刻进行合理补强支护能维持巷道围岩稳定,若仅依靠现有支护方式,当离层值达到突变致灾临界值后,巷道将发生失稳垮冒事故。巷道顶板离层模拟实验监测装置及实验结果为潜在失稳巷道离层突变失稳判据及合理补强支护时机的确定提供了实验条件和决策参考。