聚能药卷的爆炸裂纹定向扩展过程试验研究

应用透射动焦散线试验研究爆炸裂纹定向断裂超动态破坏力学特征。试验结果表明,爆炸主裂纹断口特征为典型的拉伸断裂,爆炸裂纹尖端的动态应力强度因子、裂纹扩展速度、扩展长度的变化趋势几乎相同,爆炸主裂纹主要在60～200μs完成,极限动态应力强度因子很少超过1.5MN/m3/2,爆炸裂纹止裂韧性约为0.3MN/m3/2。聚能药卷具有明显的爆轰波卸载效应和聚能方向爆生气体射流效应,高压爆生气体射流的"气楔效应"是聚能方向压缩径向裂纹进一步扩展的主要驱动力,同时抑制了非聚能方向压缩径向裂纹的发展。双孔点射流聚能药卷、双缝线射流聚能药卷都能实现岩石定向断裂爆破,形成良好的爆破断裂面,多缝线射流聚能药卷适用于高瓦斯煤层增透防突的深孔预裂爆破。

EXPERIMENTAL STUDY OF PROPAGATION OF DIRECTIONAL CRACKS WITH SHAPED CHARGE UNDER BLASTING LOAD

In order to make further analysis of crack propagation for blasting fracture，the paper gives a method to research dynamic mechanical characteristics by the transmitted dynamic caustics. The results indicate that the zone of fracture shows typical tensile fracture. The experiment finds that the trend of the dynamic stress intensity factors，the crack expanding lengths and velocities is almost the same with time. The lengths of blasting main cracks are achieved during 60–200 μs. The ultimate values of dynamic stress intensity factors are smaller than 1.5 MN/m3/2. The tough value of blasting cracks is about 0.3 MN/m3/2. “Gas wedge effect”of the high-pressure gas jet is the main driving force of radial compression cracks，playing a key role in the crack propagation of the cumulative energy orientation cracks under the directional blasting，while restraining the development of the non-cumulative energy directional radial compression crack. It is analyzed the fracture characteristics of the double-point jet with the double-seam thread jet in further，and found that the results of directional fractures and the fine fracture surfaces both can be achieved. Technical ideas are brought forward that both the double thread jet and the multi-seam thread jet cumulative cartridge should be utilized in the directional fracture blasting. The multi-seam thread jet cartridge can be applied to deep-hole presplitting explosion，such as deep-hole presplit blasting，to improve the speed of seam gas drainage and prevent mine gas and coal outburst in high gassy and low permeability coal seam.