ABSTRACT
The group of controllable parameters least known by engineers and operators is the one that comprises the initiation sequences and the delay timings between the charges of a blast. The parameters indicated do not only have influence upon the fragmentation, but also upon other basic aspects such as displacement and swelling of the rock, overbreak and intensity of vibrations. Fragmentation is better than in instantaneous blastings, because the heave energy is used in vertically shearing the burden and extending the cracks and the strain wave has a larger field of action. Except in those rock formations where single-row blasts produce a large overbreak with positive effects on the breakage costs, multi-row rounds are recommended as they give better fragmentation. As to the delay timing in between blastholes, it has been proven that the interaction of the first shock waves does not contribute in a significant way to the rock fragmentation.
