Shock airwaves in short-delayed blasting for open pit mining

Abstract

1. During a short delayed blasting with a delay interval between groups of 50 m/sec, a complete separation of SAW pulses produced by individual charges is observed. The weight of the charge in a group in that case can be taken equal to the weight that would be safe for an instant blasting. When the delay is 30 m/sec, the charge weight in a group should not exceed two-thirds, and for a delay of 20 m/sec a half, of the maximum admissible weight for instant blasting. These recommendations are applicable at distances not greater than 2000 m from the explosion site. 2. When blasting a linear string of charges, the delay interval at which SAW pulses are fully separated depends on the direction at which detonation propagates along the block and is defined by relations (13) and (14). With this position of charges, they should be detonated in the direction away from the object to be protected.