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煤层群开采遗留煤柱效应及跨掘巷道围岩控制研究

Study on effect of residual coal pillar in coal seam group mining and surrounding rock control of cross-excavation roadway

  • 摘要: 针对采区边界遗留煤柱下侧跨掘巷道存在特殊破坏段问题,以灵新煤矿沿空侧051606回风平巷为背景,采用现场调研、理论分析、数值模拟及工业性试验的综合分析方法,通过研究巷道特殊破坏段现场矿压显现情况,基于半平面体理论建立的遗留煤柱效应影响力学模型以及跨掘巷道和回采期间精细化数值模拟,确定了巷道特殊破坏段的修复支护设计方案。研究结果表明:遗留煤柱效应影响下跨掘巷道围岩在遗留煤柱中轴线正下方主要受垂直应力影响,此处垂直应力大小为13.0~15.0 MPa,而在遗留煤柱两侧边缘位置下方主要受剪切应力集中影响,此处剪切应力大小为-6.5~-5.0 MPa和5.0~7.0 MPa;051606回风平巷跨掘期间顶板位置处最大垂直应力为14.4 MPa,底板位置处最大垂直应力为13.6 MPa,顶板位置处最大剪切应力为6.5 MPa,底板位置处最大剪切应力为5.3 MPa,且最大垂直应力位于遗留煤柱中轴线正下方,最大剪切应力位于遗留煤柱两侧边缘位置下方;051606工作面回采期间对于巷道特殊破坏段围岩的扰动影响分为无应力影响段(距遗留煤柱边缘大于16 m),超前应力影响段(距遗留煤柱边缘0~16 m)和叠加应力影响段(距遗留煤柱中轴线0~17.5 m)3个阶段,且受回采扰动影响护巷煤柱和顶板靠近护巷煤柱侧偏应力集中程度较高,煤岩体更易变形发生非对称性破坏;巷道特殊破坏段采用非对称锚索桁架支护系统修复后,后续051606工作面回采期间矿压监测到顶底板收敛量为143 mm,两帮收敛量为109 mm,较巷道原始断面尺寸收敛率分别为4.3%和2.2%,整体控制在5%以内,能够很好地满足行人、通风等需求。

     

    Abstract: In view of the problem of special damage section in the cross-excavation roadway at the lower side of the residual coal pillar at the mining area boundary, taking the No.051606 tailentry along the gob-side of Lingxin Coal Mine as the background, the comprehensive analysis method of field investigation, theoretical analysis, numerical simulation and industrial test was adopted to study the on-site rock pressure behavior in the special failure section of the roadway. Based on the mechanical model of the influence of the residual coal pillar effect established by the half plane theory and the fine numerical simulation during the cross excavation and mining period, the repair and support design scheme of the special damaged section of the roadway was comprehensively studied and determined. The research results show that: under the influence of the legacy coal pillar effect, the surrounding rock of the cross-excavation roadway is mainly affected by the vertical stress below the axis of symmetry of the residual coal pillar, where the vertical stress is about 13.0-15.0 MPa. While the shear stress is mainly affected by the shear stress below the edge of the residual coal pillar, and the shear stress is about -6.5--5.0 MPa and 5.0-7.0 MPa; the maximum vertical stress at the roof is 14.4 MPa, the maximum vertical stress at the floor is 13.6 MPa, the maximum shear stress at the roof is 6.5 MPa, and the maximum shear stress at the floor is 5.3 MPa. The maximum vertical stress is directly below the central axis of symmetry of the residual coal pillar, and the maximum shear stress is located below the edge of both sides of the residual coal pillar; the disturbance effect on surrounding rock of special damaged section in No.051606 working face can be divided into non-stress influence section (more than 16 m away from the edge of residual coal pillar) and the advanced stress affected section (0 to 16 m away from the edge of residual coal pillar) and superimposed stress influence section (0 to 17.5 m away from the axis of symmetry of residual coal pillar). Due to the influence of mining disturbance, the concentration degree of deviatoric stress in coal pillar and roof close to the coal pillar is higher, and the surrounding rock is more prone to deformation and asymmetric damage; after the special damaged section of roadway was repaired by asymmetric anchor cable truss support system, the convergence of roof between floor and two ribs were 143 mm and 109 mm respectively, which were 4.3% and 2.2% respectively compared with the original section size of roadway. The overall control was within 5%, which could meet the needs of pedestrians and ventilation.

     

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