N-J水电站岩爆区应力释放孔预裂控制的爆破分析
Analysis of pre-splitting blasting in rock burst area of N-J hydropower station

摘要： 为了对N-J水电站引水隧洞岩爆区进行卸压分析,对施工区的SS-1砂岩进行岩爆倾向性试验,采用弹性能量指数作为岩爆倾向判断指标,试验结果表明施工区具有强烈的岩爆倾向,说明了进行钻孔卸压的必要性。运用扩展有限元方法对钻孔预裂爆破进行数值模拟,模拟不同抗拉强度的岩体(4、6、8、10 MPa)在不同钻孔间距(0.5、1.0、1.5、2.0、2.5 m)的孔内预裂爆破情况,分析了爆破过程的能量耗散率、裂缝贯穿最小冲击力等。数值分析结果表明:预裂爆破能量耗散率随卸压孔间距的增加而增大,基本呈指数型增长趋势;岩爆区的计算冲击应力小于岩石极限动态抗拉强度时,爆破不会使钻孔壁产生压碎破坏;在施工现场应对钻孔间距进行合理布局,以保证良好的卸压效果。
Abstract: In order to analyse pressure relief of the rock burst area of N-J hydropower station diversion tunnel in Pakistan, the rock burst proneness test of sandstone SS-1 inconstruction area was presented, and the elastic energy index was used as judgingrock burst proneness. The results showed that the construction area was strong rock burst area.It was necessary torelease the stress of drill hole by presplitting blasting.The numerical simulation of presplitting blasting was presented by extended finite element method(XFEM). Considering spacing and tensile strength, the simulation of borehole stress relief included the results that tensile strength was 4,6,8,10 MPa when spacing was 0.5,1.0,1.5, 2.0,2.5 m respectively. The energy dissipating rates and minimum impact forces to drill hole wall were analysed. The results of numerical analysis showed that the energy dissipation rate of presplitting blasting increased with the spacing of drill hole presenting a trend of exponential form. When the calculated impact stress was less than the rock limited dynamic tensile strength, the blasting wouldnt cause the blasting of the blasting wall. In order to ensure the pressure relief effect, spacing of drill hole should be optimal layout