The velocity of detonation (VOD) is an essential parameter for assessing and comparing the performance of explosives in blast holes. Explosives with lower VOD tend to have less impact on rock fragmentation compared to those with higher VOD (Chiappetta, 1988; Heit, 2011).
According to Cooper (1996), VOD is commonly used to estimate the detonation pressure and, consequently, the shock energy of an explosive.
This detonation pressure is influenced by the explosive’s density, VOD, and the ratio of specific heats of the detonation product gases (Eugie, 2017). A reduction in VOD leads to a decrease in both detonation pressure and shock energy (Tete et al., 2013).
VOD measurements provide real-time data on the explosive’s performance. There are two commonly used VOD measurement techniques: the point-to-point system and the continuous system.
Pradhan and Jade (2012) investigated the performance of bulk emulsion explosives in watery blast holes using in-hole VOD measurements, finding poor performance due to reduced VOD and incomplete detonation of the explosive column.
Žganec et al. (2016) studied the influence of three different primer types on the VOD of ANFO and ANFO blends using continuous in-situ measurements. They concluded that even with identical emulsion percentages, densities, and borehole diameters, the VOD differed based on primer properties.
Mendes et al. (2014) compared emulsion explosives sensitized with hollow glass micro-balloons and hollow polymer micro-balloons, concluding that the type of sensitizer did not significantly affect the detonation behavior.
Accurately measuring explosive properties and evaluating fragmentation performance is critical. Often, design adjustments or changes to the explosive may be necessary to meet the energy demands for optimal rock breakage.
By Blessing Olamide Taiwo.
