Air-Decking Technique in Bench Blasting

1 Introduction The air-decking technique (Fig.1) has been ap- plied in mining industry abroad. Melniokov and other experts1–5]* thought that the existence of the air layer causes the second loading waves and a series of sub- sequent loading waves stirred up in the process of the explosion, and also causes further breakage of the fractured rock mass resulting from the previous pres- sure wave. Although the average pressure on the borehole resulting from the air-decking structure is lower than…

Air-Decking Technique in Bench Blasting

The mechanism and the design parameters of blasting with air-decking are studied. The theory of detonation waves is used to investigate the processes of the one-dimensional plane detonation wave within a borehole. The interaction of the rarefaction wave with an interface and reflection on a rigid wall is also analyzed. The same courses of the shock wave are also investigated. This decides the distribution of the pressure of the explosion products changing with time along the borehole. Based on the above theoretical analysis, two conditions should be met for a reasonable range of values of the air-decking ratio in blasting rock. First, the rarefaction wave from the contact interface between detonation products and air reaches the bottom earlier than that of the reflected shock wave from the end of the stemming. Second, the reflected shock wave reaches the contact interface between the detonation products and air earlier than that of the reflected rarefaction wave from the bottom of the borehole. Finally, the reasonable value of the air-decking ratio must be decided theoretically in air-decking blasting. For different explosives, the reasonable range of air-decking ratio varies from 0.15 to 0.4. This result is well consistent with what was obtained by previous researchers.