切顶沿空留巷卸压机理及支护技术研究

Pressure relief mechanism and support technology of immediate roof cutting gob-side entry retaining

云驾岭矿9号煤上覆厚硬岩层,采场矿压显现强烈,采用传统的沿空留巷方法围岩控制难度大。以云驾岭矿19103工作面运巷为背景,分析了切顶沿空留巷厚硬直接顶力学平衡条件,得出巷旁需提供不小于1046 kN的支护阻力。采用数值模拟的方法对比了沿空留巷在厚硬直接顶条件下切顶与不切顶时围岩变形及应力、塑性区的分布规律,结果表明:切顶后采空区顶板更容易垮落,留巷顶板稳定时下沉量仅为同期不切顶时的28.2%,切顶后留巷侧顶板垂直应力变小、水平应力增大且围岩塑性区向顶底板深部转移,揭示了预裂切顶卸压的机理为阻断工作面动压的传递以及诱导采空区顶板提前冒落接顶承压,水平应力增大的原因为切缝两侧形成的长、短“悬臂梁”变形的结果。提出了针对厚硬直接顶切顶留巷的顶板控制理念为集中支护切缝端、适当让压和形成“组合悬臂梁”,采用了“长、短锚索+单体液压支柱+可缩性U钢梁”的综合支护技术及挂网喷浆的密闭措施。现场工业性试验效果良好,切顶后留巷顶板锚索受力峰值在350 kN左右,围岩稳定后巷道规格满足二次复用的条件。

The No.9 coal seam of Yunjialing Mine is under thick and hard rock strata,and the mine pressure in the stope is strong,and it is hard to control the surrounding rock using the traditional gob-side entry retaining method.Taking the engineering background of the transportation roadway of 19103 working face in Yunjaling Mine,the mechanical equilibrium conditions of thick and hard immediate roof of gob-side entry retaining with roof cutting are analyzed,and it is concluded that the support resistance of no less than 1046 kN should be provided beside the roadway.The numerical simulation method was used to compare the deformation and stress of surrounding rock and the distribution of plastic zone of gob-side entry retaining with and without roof cutting under thick and hard immediate roof.The results show that the roof of goaf is more likely to collapse after roof cutting.The subsidence of the roof of the retaining roadway is only 28.2%of that without roof cutting in the same period.After roof cutting,the vertical stress of the roof on the side of the retaining roadway becomes smaller,the horizontal stress increases and the plastic zone of the surrounding rock transfers to the deep part of the roof and floor.It is revealed that the mechanism of pre-splitting roof cutting pressure relief is to block the transmission of dynamic pressure in the working face and induce the roof of the goaf to fall in advance to meet the roof pressure.The increase of horizontal stress is caused by the deformation of the long and short cantilever beam formed on both sides of the slit.The roof control idea for gobside entry retaining with thick and hard immediate roof is proposed as centralized support of the cutting end,appropriate pressure relief and formation of combined cantilever beam.The comprehensive support technology of long and short anchor cable,single hydraulic prop and yielding U steel beam is adopted,and the sealing measures of hanging mesh shotcreting are adopted.The field industrial test results are good,the peak stress of the anchor cable of the roadway roof after cutting the roof is about 350 kN,after the surrounding rock is stable,the specifications meet the conditions of secondary reuse.