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坚硬顶板走向与倾向爆破断顶防冲机理与卸压效果差异性研究

Study on differences in rockburst prevention mechanism and pressure relief effect between strike and dip blasting for hard roofs

  • 摘要: 为揭示坚硬顶板条件下走向与倾向爆破断顶防冲机理与卸压效果差异性,以新巨龙6305工作面为工程背景,采用3DEC数值模拟与理论分析相结合的方法,系统研究2种爆破布置方式下围岩应力演化规律、顶板结构响应特征与防冲作用机制。结果表明:走向爆破主要作用于回采巷道煤柱及侧向顶板区域,煤柱应力峰值随参数优化逐步降低,爆破深度45 m、角度80°时最佳,应力峰值降低20.49%;倾向爆破主要作用于工作面前方上覆岩层,超前支承压力峰值随爆破高度增加先降低后趋于稳定,最优参数下峰值降低20.60%。在此基础上,分别构建了侧向悬臂梁力学模型与倾向铰接结构力学模型,走向爆破通过切断侧向悬臂梁、缩短悬臂长度,使顶板储能与悬臂长度的五次方成正比降低;倾向爆破则通过扇形弱面分割关键层,使顶板破断步距减小、单次释放能量与破断步距的三次方成正比降低。2种爆破方式存在较显著差异:走向爆破适用于沿空侧向悬顶大、煤柱应力集中明显的高静载控制条件,倾向爆破适用于超前支承压力大、周期来压强烈的动载控制条件。现场工程实践表明,合理选择爆破方式可取得良好卸压防冲效果。研究结果可为深部矿井坚硬顶板爆破断顶防冲设计提供理论依据。

     

    Abstract: To reveal the differences in rockburst prevention mechanism and pressure relief effect between strike and dip blasting for hard roofs, the stress evolution law of surrounding rock, the structural response characteristics of the roof, and the rockburst prevention mechanism under two blasting layouts are systematically studied by combining 3DEC numerical simulation and theoretical analysis, with the Xinjulong 6305 working face as the engineering background. It is shown by the results that strike blasting mainly acts on the coal pillar of the mining roadway and the lateral roof area. The peak stress of the coal pillar is gradually reduced with the optimization of blasting parameters, and the optimum is achieved at a blasting depth of 45 m and an angle of 80°, where the peak stress is reduced by 20.49%. Dip blasting mainly acts on the overlying strata ahead of the working face. The peak advance abutment pressure first decreases and then tends to stabilize with the increase of blasting height, and under the optimal parameters, the peak value is reduced by 20.60%. On this basis, a mechanical model of the lateral cantilever beam and a mechanical model of the dip hinged structure are established, respectively. By strike blasting, the lateral cantilever beam is cut off and its length is shortened, so that the roof stored energy is reduced in proportion to the fifth power of the cantilever length. By dip blasting, the key stratum is divided through a fan-shaped weak surface, so that the roof breaking interval is reduced and the energy released in a single event is reduced in proportion to the third power of the breaking interval. Significant differences are found between the two blasting methods. Strike blasting is suitable for high static load control conditions characterized by a large lateral hanging roof along the gob side and obvious stress concentration in the coal pillar. Dip blasting is suitable for dynamic load control conditions characterized by high advance abutment pressure and strong periodic weighting. It is demonstrated by field engineering practice that satisfactory pressure relief and rockburst prevention effects can be achieved through reasonable selection of the blasting method. The research results can provide a theoretical basis for the design of blasting for hard roofs in deep mines.

     

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