Investigation on the ultimate load bearing capacity of U-shaped steel arch support in coal bursting mine
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摘要: 煤矿巷道围岩的冲击破坏程度与支护形式密切相关，探究冲击地压矿井巷道U型钢的极限承载能力，是研究深部煤炭资源安全开采的重要课题，对矿井冲击地压的防治具有重要意义。本文以义马煤田典型冲击地压矿井为工程背景，建立均匀围压条件下U型钢支护变形的力学模型，给出U型钢变形量的解析解，对比分析均匀和不均匀荷载作用下U型钢和巷道的变形规律，研究了荷载增加时U型钢支护可承受的上覆岩层极限荷载和极限埋深。通过现场监测巷道不同U型钢支护条件下顶底板移近量、移近速度的变化，分析了提高U型钢承载能力来控制巷道变形和冲击地压的机理。研究结果表明：随着荷载增加，巷道变形量和应变能均将出现一个急剧加速点，该点可用来确定应用U型钢支护的极限埋深均匀荷载下为1 600 m，非均匀荷载下为1 400 m，当达到极限埋深时，U型钢将完全处于失效状态，巷道变形激增；在冲击地压矿井巷道进行U型钢支护设计时，改善围岩支护接触条件、对U型钢边界施加均匀荷载，对提高U型钢的支护性能具有重要作用。采用承载能力更大的U型钢支护方式能吸收更多来自围岩释放的能量，对巷道顶底板移近量的控制较为稳定，使得巷道变形无法瞬间激增，保证巷道的稳定性，实现对巷道冲击地压的有效控制。Abstract: The damage degree of the surrounding rock in the coal mine roadway is closely related to the support form, thus to carry out research on the ultimate bearing capacity of U-shaped steel support in coal bursting mine is of important guiding significance for the prevention and control of coal burst.Taking a typical coal bursting mine in Yima Coalfield as the engineering background, a theoretical calculation mechanical model of U-shaped steel deformation under uniform loading is established and the analytical solution of the overall deformation is given, then deformation of U-shaped steel and roadway under the action of uniform and non-uniform load is compared, and the affordable ultimate load from overlying strata and applicable ultimate depth of U-shaped steel support is studied when the load increases.The change of approach amount and speed of the roadway roof and floor through on-site monitoring is obtained, and improving the bearing capacity of U-shaped steel support to control the deformation of roadway and coal burst is analyzed.The results show that: with the increase of load, there will be a sharp acceleration point in the deformation and strain energy of roadway, which can be used to determine the applicable ultimate depth of U-shaped steel support.The applicable ultimate depth of U-shaped steel under uniform loading is 1 600 m, and the value is 1 600 m under the non-uniform loading.When the ultimate depth is reached, U-shaped steel will be completely in failure state, and the deformation of roadway will increase rapidly.When designing U-shaped steel support for the roadway of coal bursting mine, it is very important to improve the contact condition of surrounding rock support and apply uniform load to the U-shaped steel support boundary to ensure good contact between surrounding rock and U-shaped steel, and improve the bearing capacity of U-shaped steel.U-shaped steel support with greater bearing capacity can absorb more energy released from surrounding rocks, and better control the approach amount between the roof and floor of the roadway, preventing the deformation of the roadway from increasing rapidly, thus the stability of the roadway is ensured and the coal burst in the roadway is effectively controlled.
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Key words:
- U-shaped steel arch /
- ultimate depth /
- bearing capacity /
- roadway deformation /
- strain energy
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图 1 均匀荷载下U型钢力学计算模型
Figure 1. Theoretical model of U-shaped steel arch under uniform loading
图 5 FLAC3D中数值模型及其施加边界条件示意图
Figure 5. A sketch of FLAC3D mesh showing the model and boundary conditions of roadway and U-shaped steel arch
图 6 均匀荷载下U型钢两帮位移曲线
Figure 6. Results of the sidewall displacement of steel arch under uniform loading
图 7 均匀荷载下U型钢塑性铰的变化情况
Figure 7. Results of the plastic hinge of steel arch under uniform loading
图 8 巷道顶板和两帮位移随上覆荷载变化曲线
Figure 8. Displacement of the roof and two walls of roadway versus the overburden loading
图 9 围岩松动圈体积随埋深变化曲线
Figure 9. Result of the volume of plastic zone with different depth
图 10 巷道围岩应变能分布云图
Figure 10. Distribution of strain energy in roadway surrounding rock masses
图 12 顶底板移近量变化曲线
Figure 12. Variation curves of convergence quantity curve of the roof and floor
图 13 顶底板移近速度变化曲线
Figure 13. Variation curves of convergence rate of the roof and floor
表 1 U型钢截面参数表
Table 1. The cross-section parameters of U-shaped steel arch
型号 横截面尺寸/mm 横截面面积/cm2 惯性矩/cm4 横截面弯曲模量/cm3 抗拉强度/MPa 屈服强度/MPa B1 B2 B3 B4 H Iy Wx Wx Wy 25U 135.0 101.5 40.0 47.0 120.0 31.79 495.81 551.97 79.77 81.77 530 335 29U 150.5 116.0 44.0 53.0 124.0 37.00 612.00 771.00 92.00 102.00 530 335 36U 171.0 128.0 50.5 60.5 138.0 45.69 928.65 1 244.75 128.55 145.59 530 350 40U 171.0 128.5 50.5 60.5 141.9 51.02 1 064.07 1 366.98 141.22 159.94 580 390 
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表 2 数值模拟中U型钢截面参数表
Table 2. Parameters of U-shaped steel arch in the numerical simulation
类型 杨氏模量/GPa 泊松比 横截面面积/cm2 惯性矩/cm3 Ix Iy 25U 200 0.3 31.79 495.81 551.97 29U 200 0.3 37.00 612.00 771.00 36U 200 0.3 45.69 928.65 1 244.75 40U 200 0.3 51.02 1 064.07 1 366.98
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表 3 数值模型中岩层物理力学参数
Table 3. Mechanical parameters of rock strata used for numerical model
杨氏模量/GPa 泊松比 抗压强度/MPa 抗拉强度/MPa 内聚力 摩擦角 剪胀角/(°) 初始值/MPa 软化率/% 残值/MPa 初始值/(°) 软化率/% 残值/(°) 7.13 0.25 4.0 0.04 3.06 5 0.306 36.0 0.5 30.0 6.0
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表 4 理论计算与数值模拟对比
Table 4. Comparison between theoretical calculation and numerical simulation
围压/MPa 36U型钢变形量/mm 40U型钢变形量/mm 理论值 模拟值 理论值 模拟值 15.0 73 70 68 65 17.5 89 85 82 78 20.0 97 94 89 86 22.5 110 106 101 97 25.0 115 112 109 104 27.5 124 120 115 112 30.0 136 131 127 123 32.5 149 145 141 138 35.0 171 168 160 155
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