环向切缝药包爆破块度分布特征及其机理研究

Study on blasting fragmentation and characteristics of circumferential slit charge

为研究环向聚能作用对爆破块度的改善效果,采用标准混凝土试块开展了环向切缝药包爆破与常规爆破试验。对两种不同爆破方式得出的爆破块度进行了筛分统计,试验结果表明:相同装药量下环向切缝药包爆破得到的平均块度和大块率较低;与常规爆破相比,环向切缝药包爆破平均块度可降低2~15 mm,大块率可减少0.66%~30.74%。针对环向切缝药包爆破时,其减小平均块度的程度随装药量的增加出现先增加后降低现象,选取3种典型药量(4、10和14 g)构建了数值模型进行裂纹扩展特征分析,对比了切缝药包爆破时切缝处孔壁爆破压力与常规爆破时相应位置的爆破压力。结果表明:常规爆破时孔壁裂纹均匀向外发展,且裂纹长度基本相同;环向切缝药包起爆后,在切缝与非切缝交界处先形成裂纹并扩展,其他位置的裂纹后形成且长度较短。对切缝处孔壁的爆破压力进行模拟分析,结果表明:3种不同药量情况下环向切缝药包与常规爆破的压力峰值之差分别为0.62、1.25和0.41 GPa,从应力分布角度解释了环向切缝药包可通过改变爆破能量在被爆体内的分布规律进而降低爆破块度的作用机理。

In order to investigate the improvement effect of annular energy accumulation on blasting fragmentations,the experiments of circumferential slit charge blasting and conventional blasting were carried out with the standard concrete specimens.The blasting fragments obtained by those two blasting methods were screened and statistically analyzed,and the testing results showed that the average fragments and bulk percentage obtained by the annular slit charge blasting were relatively lower under the same charging amount.Compared with conventional blasting,the average fragments of annular slit charge blasting could be reduced from 2 to 15 mm,and the bulk fraction could be reduced by 0.66%-30.74%.With respect to the annular slit charge blasting,the reduction degree of the average fragments increased first and then decreased with the increase of charge amount.A numerical model with three typical charge dosages(4 g,10 g,and 14 g)were established to analyze the characteristics of crack growth,and the blasting pressure on the hole wall at the slit blasting point was compared with that at the conventional blasting.The results showed that the cracks in the hole wall developed uniformly and the length of the cracks was basically the same in conventional blasting.However,after charge detonated in the annular slit blasting,cracks formed and expanded innitailly at the junction of slit and non-slit,and the cracks at the other positions were delayed to some extent with a relatively smaller length.Base on the numerical simulation analysis on the blasting pressure of the hole wall at the slit,the difference of pressure magnitude between the annular slit charge and conventional blasting under three different dosage conditions was 0.62 GPa,1.25 GPa,and 0.41 GPa,respectively.Furthermore,the mechanism that the annular slit charge could reduce the blasting fragments by changing the distribution characteristics of blasting energy in the blasted body was explained from the point of view of stress distribution.