ABSTRACT
In air-deck blasting, the presence of air gap allows the explosion product gases to move and expand into the air gap, thus decreases the initial bore hole pressure. The shock waves oscillate in the bore hole, interact mutually and also with stemming column and/or hole bottom. The repeated interactions result in the generation of reinforced secondary shock front and allow shock waves to act over the surrounding rock mass for a longer period (Mel’Nikov & Marchenko, 1971, Fourney et al., 1981 and Moxon et al., 1993. Since the shock waves oscillate repeatedly within an air-gap, their velocities and pressure at the wave front are governed by the length they travel within the air column. Air-deck length is, therefore critical to the fragmentation. The effectiveness of this technique is also controlled by the rock mass structure and its strength (Jhanwar, 2011).
