砂质泥岩巷道顶板定向爆破不耦合装药系数优化与应用

Optimization and Application of Uncoupled Charge Coefficient for Directional Blasting of Sandstone Roadway Roof

聚能爆破技术在沿空留巷工程项目中有着重要的作用,装药结构问题一直是目前讨论的热点及难点。对于目前沿空留巷顶板超前预裂装药长度尚没有明确的指标情况下,以孟津煤矿二_2-11031工作面轨道顺槽为研究背景,提出了等长装药顶板预裂技术,为明确最优装药结构,本文通过LS-DYNA数值模拟软件建立了三维定向聚能爆破模型,改变轴向药柱的长度,以裂纹扩展长度和应力衰减速率为分析指标,通过数值模拟可知,轴向不耦合系数在1.25~1.7之间径向切缝距离约为40 cm,轴向切缝距离约为80 cm,相比轴向不耦合系数在2~3之间,切缝距离分别提高了25%和12.5%;轴向不耦合系数在1.25~3之间,应力衰减速度均小于1,能量利用最为合理;将轴向不耦合系数α=1.25~2的装药结构在孟津煤矿二_2-11031工作面轨道顺槽进行顶板定向爆破实验,对预裂爆破后的两炮孔中线进行钻孔窥视,观察到4种爆破方案,两炮孔之间沿切缝方向裂纹均已经完全贯通,裂纹光滑平整,现场应用效果良好,结合经济性、安全性两方面考虑,不耦合系数α=1.7为最优;研究结果表明等长装药结构可以代替传统的三段式装药结构。研究结果可以为今后类似的项目提供参考。

Shaped charge blasting technology plays an important role in goaf retaining roadway engineering,and the charge structure is always a hot and difficult issue in current discussions.At present,there is no clear indicator of the pre-splitting charge length of goaf-retaining roof.Taking the track groove of No.2-11031 working face of the Mengjin Coal Mine as the research background,an isometric charge pre-splitting technology is proposed.Firstly,a three-dimensional directional shaped charge blasting model is established by LS-DYNA numerical simulation software to determine the optimal charge structure.By changing the axial cylinder length and taking the crack propagation length and stress decay rate as the analysis indexes,the numerical simulation shows that the radial slit distance is a-bout 40 cm,and the axial slit distance is about 80 cm per meter when the axial uncoupling coefficient is between 1.25 and 1.7.Additionally,the slit distance is respectively increased by 25%and 12.5%compared with the axial uncoupling coefficient between 2 and 3.Furthermore,the energy utilization is the most reasonable as the stress atten-uation rates are all less than 1 when the axial uncoupling coefficients are between 1.25 and 3.Finally,a roof direc-tional blasting experiment with an axial uncoupling coefficientα=1.25~2 was carried out on the track groove of No.2-11031 working face of the Mengjin Coal Mine.After the pre-split blasting,the middle line of the two holes was drilled and peeping.It is found that the cracks along the cutting seam direction between the two holes have been com-pletely connected,the cracks are smooth,and the field application effect is good.Considering economy and safety,the uncoupling coefficientα=1.7 is the best.The results show that the isometric charging structure can replace the tra-ditional three-stage charging structure.