Study on reasonable width of coal pillar under water-rock interaction
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摘要: 采空区积水与煤岩作用会弱化区段煤柱强度而引起煤柱逐渐破坏和失效,水岩作用是区段煤柱合理宽度设计必须考虑的关键因素。以内蒙古鄂尔多斯新街矿区某矿31采区与33采区间煤柱留设为工程背景,开展了单轴压缩实验和理论分析,结果表明:水岩作用对煤体强度参数弱化产生显著影响,区段煤柱积水侧塑性区宽度随煤体强度弱化程度的增加而扩大;基于区段煤柱保持稳定的基本条件,计算得到区段煤柱合理的理论宽度为53.62 m。利用FLAC3D模拟了水岩作用的过程,分析了不同宽度煤柱的稳定性特征,结果表明:煤柱宽度较小时,采空区积水弱化作用对较高应力集中的弹性核区具有更强的破坏能力;随着煤柱宽度的增大,弹性核区应力集中程度降低,采空区积水侧垂直应力低于原岩垂直应力的区域范围则有所增大,煤柱两侧应力集中分布趋于均匀,采空区积水弱化作用对弹性核区的影响不再显著。综合理论计算与数值模拟结果,确定区段煤柱宽度为70 m。工程应用结果表明,70 m宽留设煤柱可以有效承载顶板压力,巷道围岩变形小,锚索受力稳定,保障了矿井安全生产。Abstract: The water accumulation in goaf and coal rock interaction will weaken the strength of the coal pillar in the section and cause gradual destruction and failure of the coal pillar. The interaction of water and rock is the key factor that must be considered in the design of the reasonable width of the coal pillar. The uniaxial compression experiment and theoretical analysis are carried out based on the engineering background of the coal pillar design between mining area 31 and 33 of a mine in Xinjie mining area, Ordos, Inner Mongolia. The results show that water-rock interaction has a significant impact on the weakening of coal strength parameters. The width of the plastic zone at the side of the water accumulation in the section coal pillar expands with the increase of the weakening degree of the coal body strength. Based on the basic conditions for the stability of the section coal pillar, the reasonable theoretical width of the section coal pillar is 53.62 m. Using FLAC3D to simulate the process of water-rock interaction, the paper analyzes the stability characteristics of coal pillar with different widths. The results show that when the width of the coal pillar is small, the weakening effect of water accumulation in goaf has stronger destructive capability to the elastic core area with higher stress concentration. With the increase of coal pillar width, the stress concentration degree in the elastic core area decreases. The area where the vertical stress at the water accumulation side of the goaf is lower than that of the original rock increases. The stress concentration distribution on both sides of the coal pillar tends to be uniform, and the weakening effect of water accumulation in the goaf on the elastic core area is no longer significant. Based on the results of theoretical calculation and numerical simulation, the width of coal pillar is determined to be 70 m. The engineering application results show that the coal pillar with width of 70 m can effectively bear the roof pressure. The deformation of the roadway surrounding rock is small, the stress of the anchor cable is stable, and the safety production of the mine is guaranteed.
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表 1 数值计算模型煤岩体物理力学参数
Table 1. Physical and mechanical parameters of coal and rock mass in numerical calculation model
岩层 厚度/m 弹性模
量/GPa泊松比 黏聚
力/MPa内摩擦
角/(°)抗拉强
度/MPa粉砂岩 34 3.51 0.17 5.16 34.58 1.500 细粒砂岩 8 1.61 0.17 4.37 31.83 0.510 粉砂岩 34 5.86 0.15 5.66 36.00 0.890 中粒砂岩 6 3.45 0.09 4.24 31.34 0.480 砂质泥岩 26 5.35 0.19 6.26 37.44 1.080 泥岩 2 6.30 0.19 4.92 33.83 0.670 煤 6 0.99 0.21 3.05 26.09 0.610 煤(浸水) — 0.49 0.21 0.42 9.53 0.004 泥岩 6 6.75 0.18 5.80 31.77 0.680 粉砂岩 26 4.69 0.17 6.46 33.58 0.860 -
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