Effect of Type of Explosive and Blast Hole Diameter on Boulder Count in Limestone Quarry Blasting

Rock fragmentation due to blasting depends upon many parameters. The properties of the explosive are one of them. In limestone quarries, ammonium nitrate–fuel oil (ANFO) or site mixed emulsion (SME) are generally used for rock fragmentation. Both these explosives cause substantial changes in the breakage mechanism of rockmass thereby affecting the fragmentation. This paper reports the effect of type of the explosive and blast hole diameter on the boulder count in limestone quarry blasting. In all, 264 blasts using ANFO or SME explosives have been conducted in nearby limestone quarries. The blasts have been conducted for 152 mm diameter and 115/100 mm blast holes. The analysis of the results indicates that the SME explosives are more suitable explosive in limestone quarries than ANFO for reducing the boulder count. SME has caused a reduction in generation of boulders for both 152 and 100 mm diameter blast holes when compared to ANFO. Moreover, the blasts with larger diameter blast holes charged with SME have resulted in less boulders than smaller diameter blast holes charged with the same explosive.