不稳定厚煤层回采巷道极软顶板破坏规律及分级控制

Failure law and classification control of extremely soft roof in mining roadway of unstable thickness coal seam

煤层厚度不稳定且其顶板强度远低于煤层本身的条件下,巷道围岩普遍出现围岩大变形、顶板破裂深度大、顶板稳定性区域差异明显等难题。针对此类问题,以敏东一矿16-3煤层回采巷道极软顶板为工程背景,采用理论分析、现场实测、数值模拟等综合研究方法,实测分析不同顶煤厚度条件下回采巷道的矿压显现特点,揭示采动作用下不同顶煤厚度巷道极软顶板的破坏规律。结果表明:采动影响下,顶板的塑性破坏会越过中位坚硬煤层在顶板深部形成隔层扩展破坏区,顶煤厚度越大,隔层破坏范围越小,顶煤厚度超过5.0m,隔层破坏现象趋于消失。大范围隔层破坏区产生伴随剧烈的变形压力,对其下位坚硬煤体产生巨大挤压作用,导致其顶板整体大变形甚至彻底失稳,是薄顶煤区域巷道顶板普遍剧烈变形破坏的内在原因。据此,以隔层破坏隐患区面积为基准,以顶煤厚度为分级指标,将16-3煤层回采巷道顶板分为3级,给出了以注浆锚索、锚索增效锚固为主导的不同级别顶板控制对策,工程应用效果良好。

When the thickness of the coal seam is unstable and the strength of the roof is much lower than the coal seam,The surrounding rock of the roadway generally has problems such as large deformation of surrounding rock,large roof rupture depth,and obvious regional differences in roof stability.For such problems,taking the extremely soft roof of the mining roadway in 16-3 coal seam of Mindong No.1 Coal Mine as the engineering background,the comprehensive research methods such as theoretical analysis,field measurement and numerical simulation are adopted to analyze the characteristics of mine pressure behavior of the mining roadway under different top coal thicknesses,and reveal the failure law of the extremely soft roof of the mining roadway under different top coal thicknesses in the process of mining influence.The results show that the plastic failure of roof will pass through the medium hard coal seam to form the interlayer expansion failure zone under the mining influence.The larger the thickness of top coal is,the smaller the interlayer failure range will be.When the thickness of top coal exceeds 5.0 m,the interlayer failure phenomenon tends to disappear.The large-scale interlayer failure zone generates severe deformation pressure,which has a huge extrusion effect on the lower hard coal body,leading to the overall large deformation and even complete instability of the roof.It is the internal reason for the severe deformation and failure of the roadway roof in the thin top coal area.Accordingly,taking the area of the hidden interlayer failure as the benchmark and the thickness of the top coal as the grading index,the roof of mining roadway in 16-3 coal seam is divided into three levels.The control strategies of different roof levels dominated by grouting cable bolt and cable bolt synergistic anchoring are given,and good engineering application results have been achieved.