近距离煤层群下煤层主应力差演化及巷道合理布置研究

    Evolution of principal stress difference and reasonable roadway layout of the lower coal seam for close-distance coal seam group

    • 摘要: 为解决近距离煤层群下煤层巷道合理布置问题,以合盛煤业五采区2#煤层开采后3#煤层回采巷道布置为工程背景,采用理论计算与FLAC3D数值模拟相结合的方法开展研究。通过理论计算分析2#煤层保护煤柱下方煤岩层的垂直应力、水平应力、剪切应力及主应力差分布规律,明确不同空间位置下各应力的演化特征;借助FLAC3D数值计算深入研究底板煤岩层主应力差的分布形态,重点剖析主应力差与主应力差变化率随层间距变化的演化特征。研究发现,随着层间距增加,主应力差峰值逐渐减小,且主应力差趋于稳定的位置与保护煤柱的距离增大,主应力差变化率呈现先增后骤降再趋于稳定的特征。基于上述研究结果,综合理论计算的水平错距理论值与数值模拟中应力稳定临界距离,并考虑安全系数,确定五采区3516工作面回采巷道布置的水平错距为15 m。依据层间距差异提出分区支护方案:层间距处于4.5~6.5 m范围时,采用“顶板长、短锚索+两帮左旋高强锚杆”支护方案;层间距在6.5 m以上时,采用“顶板新型长锚索、锚杆+两帮左旋高强锚杆”支护方案。现场监测结果显示,实施分区支护方案后,巷道自稳时间约20 d,顶底板移近量83 mm,两帮移近量82 mm,未出现锚杆锚索支护失效及巷道大变形失稳等情况,围岩控制效果良好,验证了巷道布置位置与分区支护方案的合理性,可为类似近距离煤层群下煤层回采巷道布置及围岩控制提供实践借鉴。

       

      Abstract: To solve the problem of reasonable layout of lower coal seam roadways in close-distance coal seam groups, research is carried out by combining theoretical calculation and FLAC3D numerical simulation, with the layout of 3# coal seam mining roadways after the mining of 2# coal seam in the fifth mining area of Hesheng Coal Industry as the engineering background. Theoretical calculations are used to analyze the distribution laws of vertical stress, horizontal stress, shear stress and principal stress difference of the coal and rock layers under the protective coal pillar of 2# coal seam, clarifying the evolution characteristics of each stress at different spatial positions. FLAC3D numerical calculation is employed to deeply study the distribution pattern of principal stress difference in the floor coal and rock layers, focusing on analyzing the evolution characteristics of principal stress difference and principal stress difference change rate with the variation of interlayer spacing. The study shows that with the increase of interlayer spacing, the peak value of principal stress difference decreases gradually, the distance between the position where principal stress difference tends to be stable and the protective coal pillar increases, and the principal stress difference change rate presents the characteristics of first increasing, then dropping sharply and finally tending to be stable. Based on the above research results, the horizontal offset of the mining roadway layout in the 3516 working face of the fifth mining area is determined as 15 m by synthesizing the theoretical value of horizontal offset from theoretical calculation and the critical distance of stress stability in numerical simulation, while considering the safety factor. Partition support schemes are proposed according to the difference of interlayer spacing: when the interlayer spacing is 4.5-6.5 m, the support scheme of “roof long and short anchor cables + two ribs left-handed high-strength rock bolts” is adopted; when the interlayer spacing is more than 6.5 m, the support scheme of “roof new long anchor cables and rock bolts + two ribs left-handed high-strength rock bolts” is adopted. On-site monitoring results show that after the implementation of the partition support scheme, the roadway self-stabilization time is about 20 days, the roof and floor convergence is 83 mm, the two ribs convergence is 82 mm, and there are no failures of anchor bolts and cables or large deformation and instability of the roadway. The surrounding rock control effect is good, which verifies the rationality of the roadway layout position and partition support scheme, and can provide practical reference for the layout and surrounding rock control of lower coal seam mining roadways in similar close-distance coal seam groups.

       

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