Study on surrounding rock failure characteristics and control technology of gob-side entry retaining in"three hard" thin coal seam
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摘要:
为解决薄煤层沿空留巷应力条件复杂、留巷难度大以及巷道围岩长时稳定性的难题，以陕西汇森煤业凉水井煤矿4301工作面为研究对象，采用理论分析、数值模拟、工程实践等方法，对浅埋“三硬”薄煤层沿空留巷围岩破坏特征及控制对策进行研究，分析巷旁支护体结构参数对于巷道稳定性的影响。结果表明：给顶板提供充足的支护强度以及合适的可缩量，是巷旁充填体整体稳定的前提；高水充填材料单轴加压下的力学行为可分为“均匀压密、弹性变形、动态失稳、劣化破坏”4个阶段；在充填体宽度增加过程中，最大应力表现为先增后减再增的趋势，在充填体1.6 m宽时出现稳定承载应力核；理论计算的切顶最佳高度为10.7 m。工程实践表明，工作面后方60 m范围无大变形和明显应力集中，围岩整体控制效果良好、结构稳定，留巷效果达到设计要求。
Abstract:This study aims to address existing problems of complex stress conditions and difficulties in retaining roadway so as to achieve long-term stability of roadway surrounding rock in gob-side entry in thin coal seam. Specifically, we investigated the 4301 working face of Liangshuijing Coal Mine in Huisen Coal Industry of Shaanxi Province through theoretical analysis, numerical simulation and engineering practice, with an aim to study the failure characteristics and control countermeasures of surrounding rock of gob-side entry retaining in shallow buried "triple hard" thin coal seam, and analyse the influence of structural parameters of roadside support on roadway stability. The results show that 1)maintaining the roadway through roadside filling body requires sufficient support strength and appropriate shrinkage to the roof and ensuring the overall stability of the roadway; 2)the mechanical behaviour of high water filling material under uniaxial compression can be divided into four stages: "uniform compaction, elastic deformation, dynamic instability and deterioration failure". The numerical simulation results show that in increasing the width of the filling body, the maximum stress first increases, then decreases and then increases, and a stable bearing stress core appears at 1.6 m. Theoretical calculation shows that the optimal height of roof cutting is 10.7 m, and it offers the roof cutting scheme and parameters of shaped blasting. Engineering practice shows that there is no large deformation and no obvious stress concentration in the 60 m range behind the working face. The surrounding rock exhibits good overall control effect and stable structure, and the effect of retaining roadway meets the design requirements.
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图 2 充填体-顶板相互作用力学模型
AB—留巷顶板稳定段；BC—破裂顶板弧形下沉段；
α—煤层倾角，(°)；L1—应力极限平衡区宽度，m；
L2—巷道宽度，m；L3—充填体宽度，m；L4—岩块BC长度，m；
ΔL—C处回转下沉量，m；ΔL1—B处回转下沉量，m；
q1—基本顶及上覆软弱岩层自重，N/m；q2—直接顶自重，N/mFigure 2. Mechanical model of backfill-roof interaction
图 3 高水材料单轴压缩实验典型破坏现象
Figure 3. Typical failure of high water material in uniaxial compression experiment
图 4 不同充填体宽度留巷围岩应力分布云图
Figure 4. Stress distribution cloud map of surrounding rock with different filling body widths
图 5 不同充填体宽度最大应力变化
Figure 5. The maximum stress variation of filling body with different width
图 6 充填体不同宽度留巷塑性区分布
Figure 6. Distribution of plastic zone in entry retaining with different filling body widths
图 7 掘巷时期围岩支承应力分布
Figure 7. Distribution of supporting stress of surrounding rock during roadway excavation period
图 8 留巷期间围岩支承应力分布
Figure 8. Distribution of supporting stress of surrounding rock during retaining roadway
表 1 岩石力学参数
Table 1. Parameters of rock mechanics
岩性 厚度/m 密度/(kg·m-3) 体积模量/GPa 剪切模量/GPa 内聚力/MPa 内摩擦角/(°) 抗拉强度/MPa 粉砂岩 1.3 2 689 18.5 2.5 3.1 45 4.2 细粒砂岩 5.2 2 558 20.9 2.8 3.8 52 5.4 4-3煤 1.2 1 600 3.9 1.1 1.0 34 0.98 粉砂岩 5.2 2 689 18.5 2.5 3.1 45 4.2 细粒砂岩 1.3 2 558 20.9 2.8 3.8 52 5.4 
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