Failure mechanism of tip-to-face roof based on energy method and experimental investigation of support-strata interaction
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摘要:
为研究综采工作面顶板稳定性及其影响因素，结合能量法和“顶板−支架−煤壁”系统模型，建立了端面顶板稳定性力学模型，利用分布式支架顶梁压力监测系统和数字图像监测技术，开展了端面冒顶相似模拟试验，分析了端面冒顶影响因素、顶板破坏形态和支架顶梁压力分布演化特征。研究表明：根据端面顶板稳定性力学模型，距煤壁1 m范围内直接顶稳定性系数小于0，该区域为端面冒顶高发区；距离煤壁越远，顶板垂直位移和水平位移也随之增大；提高支架工作阻力能有效减小顶板下沉量；顶板黏聚力和内摩擦角越大，顶板稳定性越好；相似模型试验中直接顶依次经历了端面冒落、顶板破断、顶板破碎等阶段，液压支架顶梁压力表现为中部>前部>后部；当顶板完整时，模型支架初撑力和支护阻力充足，“支架−围岩”耦合关系良好；当顶板破碎导致支架位态不佳时，模型支架降阻或偏载现象明显，容易造成顶板裂隙发育、端面冒顶、支架压架等事故，“支架−围岩”耦合关系恶化；利用数字图像监测技术获得了端面冒顶阶段直接顶最大剪应变集中于端面顶板附近。研究显示支架与围岩相互作用关系与端面顶板稳定性互相影响，维持良好的“支架−围岩”耦合关系有助于提高工作面顶板稳定性。
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关键词:
- 端面冒顶 /
- 能量法 /
- 相似模拟试验 /
- 支架压力 /
- “支架−围岩”耦合关系
Abstract:In order to study the stability and influencing factors of the end face roof of the full-mechanized mining face, a mechanical model of tip-to-face roof stability was developed in this study with a combination of the energy method and the “roof-support-coal” system. Meanwhile, the load monitoring system on the canopy of the support and the digital image measuring technique were utilized in a physical simulation model to analyze the influence factors of tip-to-face roof fall, the roof failure characteristics and the evolution characteristics of pressure distribution on the canopy of the support. The results showed that the stability coefficient of the immediate roof within 1 m behind the coal wall was less than 0 based on the mechanical model of tip-to-face roof stability, indicating a high risk of roof collapse in this area. In addition, the vertical and horizontal displacement of the immediate roof increased with the increase of the distance behind the coal wall. Enhancing the working resistance of the support can also reduce the roof subsidence, and the higher roof cohesion and internal friction angle can improve the tip-to-face roof stability. On the other hand, the tip-to-face roof caving, roof broken and roof crushing were observed in sequence during the process of the physical simulation experiments. The middle section of the canopy showed the largest measured pressure, followed by the front and rear sections of the canopy in the descending order. When the roof was intact, the support showed adequate setting load and working resistance, and the interaction between the support and the strata was in good condition. As the roof was broken and led to an unfavorable support position, the support showed a loss of working resistance or an unbalanced loading condition, which may easily result in the crack development in the roof, tip-to-face roof cavity, an iron-bound support and an awful support-strata coupling. According to the digital image measuring technique, the maximum shear strain was found near the tip-to-face area during the tip-to-face roof caving stage. Lastly, it can be concluded that the coupling between the support and strata is closely correlated to the tip-to-face roof stability. Thus, maintaining a good support-strata interaction is beneficial to the stability of the tip-to-face roof.
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图 1 端面顶板稳定性力学模型
L—直接顶长度；t—直接顶厚度；l0—支架护顶梁前端距煤壁的端面距；q—上覆岩层作用在直接顶的压力等效；Q—基本顶悬梁部分对直接顶的等效集中力；M—等效弯矩；P—液压支架对直接顶的支护作用
Figure 1. Mechanical model of roof stability in tip-to-face area
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图 4 不同顶板压力作用下直接顶垂直位移
Figure 4. Vertical displacement of immediate roof under different roof loads
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图 5 不同支架支护阻力下直接顶垂直位移
Figure 5. Vertical displacement of immediate roof under different support resistance
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图 6 不同直接顶等效集中力作用下直接顶垂直位移
Figure 6. Vertical displacement of immediate roof under different equivalent concentrated forces
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图 7 不同直接顶等效弯矩作用下直接顶垂直位移
Figure 7. Vertical displacement of immediate roof under different equivalent bending moments
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图 8 不同直接顶黏聚力条件下直接顶稳定性系数
Figure 8. Stability coefficient of immediate roof under different cohesion
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图 9 不同直接顶内摩擦角条件下直接顶稳定性系数
Figure 9. Stability coefficient of immediate roof under different internal friction angles
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图 20 端面冒顶阶段顶板垂直位移
Figure 20. Contour of vertical displacement of immediate roof during roof cavity stage
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图 21 端面冒顶阶段顶板最大剪应变分布
Figure 21. Contour of maximum shear strain of immediate roof during roof cavity stage
表 1 某矿9号煤及岩石物理力学性质
Table 1 Physical and mechanical properties of coal and petrol in a mine No. 9 coal seam
顶底板 岩性 厚度/m 抗压强度/MPa 弹性模量/MPa 泊松比 自然体密度/（g·cm−3） 基本顶 粉砂岩 10.0 27.2 4 800 0.25 2.65 直接顶 泥岩 3.0 7.9 2 180 0.28 2.30 煤层 煤 4.0 7.5 1 460 0.30 1.40 直接底 青灰岩 4.2 39.6 9 600 0.30 2.60 
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