微差爆破的爆生裂纹扩展特性试验研究

Tests for blasting induced crack propagation characteristics of short-delay blasting

以有机玻璃为模型材料,采用新型数字激光动态焦散线实验系统,研究了延时为20μs和40μs的微差爆破爆生主裂纹扩展特性,比较了试件破坏形态和破坏过程的差异,分析了爆生主裂纹扩展过程中的偏转角度、扩展速度和动态应力强度因子等物理量随时间的变化关系。结果表明,延时为20μs的爆生主裂纹的竖向偏移值明显大于延时为40μs的情况。延时时间的不同对爆生主裂纹动态应力强度因子的第一次峰值没有明显影响,但对其第二次峰值影响显著。此外,两个或多个切槽炮孔同向并排起爆会使得爆生主裂纹的扩展偏离切槽方向,影响定向断裂效果,应尽量避免。

Using the model material of PMMA,adopting the new type test system of digital laser dynamic caustics,the blasting induced main crack propagation characteristics of short-delay blasting with time delay of 20 μs and 40 μs were studied. Failure modes and destruction process discrepancies of specimens were compared. Time histories of blasting induced main crack deflection angle,propagation speed,dynamic stress intensity factor and other physical quantities were analyzed. Results showed that vertical off-set value of blasting induced main crack with time delay of 20 μs is obviously larger than that with time delay of 40 μs; time delay value has little effect on the first peak of blasting induced main crack's dynamic intensity factor,but has a remarkable effect on the second peak; furthermore,homodromous and abreast detonation of two or more grooved boreholes makes propagation of blasting induced main crack deviate from grooving direction,and then affects effects of directional fracture,this case should be avoided as much as possible.