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基于薄板理论的复合坚硬顶板深–浅孔协同爆破预裂技术研究

Research on the pre-splitting technology of composite hard roof with deep-shallow hole coordinated blasting based on the thin plate theory

  • 摘要: 晋东南矿区复合坚硬顶板呈现低位大跨度悬顶和高位大范围离层的覆岩垮落特征, 容易诱发巷道蠕变变形或冲击动力灾害, 以改善采场边界形态促进顶板回转下沉为切入点, 提出了深–浅孔协同爆破促使高–低位顶板互馈垮断的护巷消冲技术。研究结果表明: 采空区边界由固支端转变为简支端, 解放了顶板的边界束缚; 借助深–浅孔协同导向机制、聚能管控制聚能流的作用和高–低位顶板互馈机制, 爆破裂隙在巷道轴向方向发育长度被大幅度延长, 为固支端转变为简支端创造基本条件。通过理论计算和现场工程案例确定了开切眼和回采巷道顶板预裂爆破施工参数。工程实践结果表明: 开切眼爆破孔促使工作面开采初期顶板由四端固支向三固一简转变, 开切眼顶板预裂爆破工作面初次来压步距降低28%; 13132巷道内深–浅孔协同爆破在煤层上方18~40 m形成了裂隙密集区, 改善运输巷顶板边界条件, 弱化了顶板蓄能属性, 13132巷区域内88%微震事件能量降低至12 500~27 500 J, 1312工作面周期来压步距和动载系数降至9.5 m和1.27, 来压步距和来压强度均有所降低。表明深–浅孔协同爆破预裂可有效改善复合坚硬顶板在采场边界的形态, 在开采工作面起到了护巷消冲的作用。

     

    Abstract: The composite hard roof in the southeastern Shanxi mining area exhibits characteristics of low-level large-span suspended roof and high-level extensive delamination, which can easily induce creep deformation or impact dynamic disasters in the roadways. To improve the stope boundary morphology and promote roof rotation and subsidence, a technique for maintaining roadway integrity and mitigating impact disasters by using deep-shallow hole cooperative blasting to induce mutual feedback and collapse of high-low level roofs is proposed. Research indicates that the transformation of the goaf boundary from a fixed end to a simply supported end liberates the boundary constraints of the roof. Leveraging the deep-shallow hole cooperative guidance mechanism, the role of the shaped charge tube in controlling the shaped charge flow, and the mutual feedback mechanism between high-low level roofs, the development length of blasting fractures in the axial direction of the roadway is significantly extended, creating basic conditions for the transformation of the fixed end into a simply supported end. The construction parameters for pre-splitting blasting of the roof in the cutting and extraction roadways have been determined through theoretical calculations and field engineering cases. Engineering practice shows that the blasting holes in the cut-off tunnel prompt the initial roof of the working face to change from a four-end fixed support to a three-fixed and one-simplified support. The initial pressure step distance of the working face is reduced by 28% after the pre-splitting blasting of the cut-off tunnel roof. The deep and shallow hole coordinated blasting in the 13132 roadway forms a dense fracture zone 18 to 40 meters above the coal seam, improving the boundary conditions of the roof of the transport entry and weakening the energy storage property of the roof. The energy of 88% of the microseismic events in the 13132 roadway area is reduced to 12500 to 27500 joules. The periodic pressure step distance and dynamic load coefficient of the 1312 working face are reduced to 9.5 meters and 1.27 respectively. Both the pressure step distance and pressure intensity are decreased. This indicates that deep-shallow hole cooperative blasting pre-splitting can effectively improve the morphology of the composite hard roof at the stope boundary and play a role in maintaining roadway integrity and mitigating impact disasters during extraction work.

     

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