空气间隔装药爆破机理研究

Research on mechanism of air-decking technique in bench blasting

利用爆轰波理论分析了空气间隔装药炮孔内一维不定常激波的相互作用及其在炮孔堵头、孔底的反射过程,同时分析了孔内各点的压力随时间的变化过程,介绍了空气间隔装药爆破的机理及设计参数。基于此,认为应充分利用空气间隔爆破结构的优势,并在梯段爆破中满足以下两个条件:(1)在设计过程中要尽量使稀疏波及从孔底反射的稀疏波传播过程能在整个孔内每一断面都作用到,即稀疏波到达孔底的时间要比从堵头反射的压力波到达孔底要早;(2)反射压力波应该到达空气与爆生气体接触面的时间比从孔底反射的稀疏波到达空气与爆生气体接触面的时间要早。由此通过计算得到了在梯段爆破工程中合理的空气层长度比例值约为30%～42%。计算结论与已有实测成果基本一致。

The mechanism and the design parameters for blast with air-decking is studied. The theory of detonation waves is adopted to investigate the processes of the one dimension expanding of the detonation products and motions of plane detonation waves within borehole. Interactions of a rarefaction wave with a interface and reflection on a rigid wail are also analyzed. The same courses of a shock are investigated. It decides the distribution of the pressure of explosion products changing with time along blast hole. Based on the up theory analysis, two conditions should be meeting for a reasonable range of the value of the air-decking ration in blasting rock. First, the ratio adopted should assure that the rarefaction wave from the contact interface between detonation product and air should reach to the bottom earlier than that of the reflected shock wave from the end of the stemming. Second, it also should assure that the reflected shock wave should be reach to the contact interface between detonation products and the air earlier than that of the reflected rarefaction wave from the bottom of the blast hole. Finally, a reasonable value for the air-decking ratio is decided theoretically in air-decking blasting. For different explosives, the reasonable range for air-decking ratio varies from 0.15-0.4. This result is well consistent with the values obtained from site carried out by previous researchers.