Bidirectional reinforcement of narrow pillar with inflatable lock-type anchor experimental investigation and its application
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摘要: 针对沿空掘巷窄煤柱非对称变形问题，提出了对穿锚索双向加固窄煤柱技术，设计了伸长型和胀锁型两种对穿锚索结构及工艺，开展了对穿锚索拉拔试验，试验表明两种锚索结构均满足抗拉要求，从锚索破坏形态、施工便捷性和材料经济性等方面对比分析，确定胀锁型对穿锚索为窄煤柱双向加固的首选。进一步通过相似模型试验与数值模拟研究了不同加固方式下煤柱承载变形规律和对穿锚索受力特征。结果表明：双排紧密型对穿锚索加固试件较未加固试件峰值荷载提高了96.04%，且随着锚索排数及数量的增加，窄煤柱双向加固稳定性越来越高，胀锁型对穿锚索提高了煤柱破坏前的能量储存量和临界破坏点。最后，在济宁三号煤矿123下04工作面运输巷开展胀锁式对穿锚索加固窄煤柱工程试验，监测显示对穿锚索锚固力超过220 kN，锚索加固区煤柱帮鼓量降低70%，窄煤柱整体稳定性好，窄煤柱双向加固技术可行，为沿空掘巷工程提供了新技术途径。Abstract: This study targets at asymmetric deformation of narrow coal pillar in gob-side entry driving.We put forward the bidirectional reinforcement of narrow pillar with opposite-crossing anchor cable.Specifically, we designed two types of anchor cable structure: the byelongation type and the expansion lock type, and carried out the pull-out test of opposite-crossing anchor cable, the test shows that both anchor cable structures could meet the tensile requirements.We conducted comparative analysis on the morphology of anchor cable failure, construction convenience and the economic aspect of material selection, where the expansion lock type crossed anchor was selected for narrow coal pillar bidirectional reinforcement.Furthermore, we investigated the bearing deformation patterns of coal pillars and the stress characteristics of anchor cables under different reinforcement methods through similar model tests and numerical simulation.Results show a 96.04% increase of peak load in the specimen reinforced by the double-row tight opposite-crossing anchor cable compared with that of the not reinforced specimen, and higher stability of the narrow pillar reinforced by the double-row tight opposite-crossing anchor cable as the rows of the anchor cable increases in number.The expansion lock anchor type crossed cable improved the energy storage and the critical failure point before the coal pillar was destroyed.Finally, the engineering test of expansive lock type crossed anchor cable to reinforcing narrow coal pillar was carried out in the transportation roadway of 123 lower 04 working face of Jining No.3 Coal Mine.The monitoring show that the anchoring force of the anchor cable exceeded 220kN, with 70& reduction of the coal pillar in the reinforcement area and good overall stability of the narrow coal pillar.It proves the feasibility of the bidirectional reinforcement technology of narrow pillar and provides new technical way for gob-side entry driving.
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图 1 对穿锚索双向加固窄煤柱示意图
Figure 1. Bidirectional-reinforcement of narrow coal pillars with opposite anchor cables
图 9 胀锁型对穿锚索荷载-位移曲线
Figure 9. Load-displacement curve of inflatable lock-type anchor cable
图 14 对穿锚索加固窄煤柱模拟结果
Figure 14. Simulation results of narrow coal pillar reinforced by anchor cable
图 20 对穿锚索加固窄煤柱实施过程
Figure 20. Implementation of reinforcing narrow coal pillar with inflatable lock-type anchor cables
图 21 围岩表面位移随采面推进变形曲线
Figure 21. Surrounding rock surface displacement curves with the advance of mining face
图 22 对穿锚索锚固力随采面推进变化曲线
Figure 22. Variation of the anchoring force of anchor cables with the advance of the mining face
图 23 对穿锚索加固窄煤柱应用效果
Figure 23. Application of reinforcing narrow coal pillar with inflatable lock-type anchor cables
表 1 锚索规格参数
Table 1. Anchor cable specifications
直径/mm 截面积/mm2 抗拉强度/MPa 质量/(kg·m-1) 最低破断荷载/kN 21.6 285 1 770 2.24 504 
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表 2 对穿锚索结构分析比选
Table 2. Comparison of anchor cable structures
类别 最终破坏形态 施工便捷性对比 材料经济性对比 伸长型 高强套管自身强度、挤压锚及固定头螺纹综合作用力大于锚索破断力，最大抗拉力即锚索破断力 在上采面施工后，下采面回采巷道不易找到锚索后置段；需完成上采面钻孔和新掘回采巷道侧锚索伸长2次施工 材料成本较高，施工成本高，可实现性较差 胀锁型 在囊袋包裹力、胀锁体自身强度及其对锚索的握裹力综合作用下，胀锁型对穿锚索最大锚固力可达430 kN 沿新掘巷道侧煤柱施工，不存在寻找的问题；仅需在巷道侧进行1次施工 材料成本相当，施工成本低，可实现性较强
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表 3 对穿锚索布置方案
Table 3. Layout plan of inflatable lock-type anchor cables
编号 布置方式 锚索数量/根 间距/mm 排距/mm A1 未加固 — — — A2 单排大间距 3 100 — A3 单排紧密型 6 50 — A4 双排大间距 6 100 60 A5 双排紧密型 12 50 60
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表 4 试件各阶段变形量[20]
Table 4. Deformation of the specimens at each stage
试件编号 压密阶段 裂隙发育阶段 破坏阶段 累计变形 轴向位移/mm 水平位移/mm 临界荷载/kN 轴向位移/mm 水平位移/mm 临界荷载/kN 轴向位移/mm 水平位移/mm 临界荷载/kN 轴向位移/mm 水平位移/mm A1 2.02 2.27 10 4.20 4.68 80 4.34 4.88 87.89 10.56 11.83 A2 2.04 2.20 14 2.78 3.19 88 4.40 5.12 103.72 9.22 10.51 A3 1.16 1.35 15 3.32 4.04 110 3.17 3.21 133.55 7.65 8.60 A4 0.95 1.09 18 4.11 4.85 100 2.01 2.02 112.93 7.07 7.96 A5 0.40 0.60 15 3.51 3.87 149 1.77 1.89 172.30 5.68 6.36
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表 5 煤体力学参数
Table 5. The mechanical parameters of coal
弹性模量E/GPa 泊松比ν 容重γ/(kN·m-3) 黏聚力c/MPa 内摩擦角φ/(°) 1.64 0.24 14.5 1.5 30
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表 6 材料参数
Table 6. Parameters of materials
材料名称 弹性模量E/GPa 泊松比ν 容重γ/(kN·m-3) 对穿锚索 210 0.24 78.5 锚杆 210 0.20 78.5
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