Blasting is a complex process and many variables are involved. Consequently, a model of blasting that predicts fragmentation accurately is necessary to optimize total size-reduction systems. The first theory of blasting was proposed in 1792 and a model based on it was used to design blasts (Drinker 1888), but its objectives, details, and how well it worked were not known. Bond was the first engineer in the 20th century to write a model to predict the sizing of broken products in open cuts, and several engineering models of fragmentation have been developed since then. The more important, listed by developer and data required, follow:
■ Bond (1959): mean block size, energy input
■ Favreau (1970): detonic and physical rock properties, blast design variables
■ Kuznetsov (1973): powder factor, rock mass classification, explosive parameters
■ Harries (1977): blast vibrations, dynamic rock properties
■ Dinis Da Gama (1983): rock structure mapping, energy input, comminution behavior
■ Cunningham (1987): rock mass parameters, mean block size, blast design details
■ Kleine (1988): in-situ block size distribution, energy distribution, breakage characteristics (Scott, Chitombo, and Kleine 1993)
These models were valuable aids in improving blasting practice when they were used by engineers who were familiar with them. The problem was that procedures for determining the composition, fracture pattern, and breakage characteristics of the rock mass being blasted were not well developed, and without this knowledge the interactions between the rock mass and the explosive could not be understood or controlled accurately.
Since the 1990s, there has been an increasing move toward the application of numerical techniques to model the complete blasting process that includes detonation, breakage, fragmentation, and displacement (Preece, Jensen, and Chung 2001; Dare-Bryan, Wade, and Randall 2001; JKMRC 2001). Continued improvements in computing technology will make the future application of these types of models feasible. In addition to the development of these models, the advances being made in other technologies, such as measurement while drilling, blast monitoring systems, and image analyses, are providing the necessary data to validate the new generation of blasting models. The next 10 years should see a significant improvement in our ability to model the blasting process. This progress will enable blasting to fit into the spectrum of size-reduction processes that extends from blasting through crushing and grinding processes to ultrafine grinding.
CONCLUSION
This history of the development of explosives that can be used to break rocks shows the potential of explosives to become a useful means for controlled size reduction in preparing feed for primary crushers and mineral extraction processes. Currently, the mining industry needs methods to best utilize the energy made available from blasting, which requires that methods be developed for describing the structure of the rock formation to be mined. This becomes part of the future for more efficient size reduction of ores.
Copyright © 2005 by the Society for Mining, Metallurgy, and Exploration.
All rights reserved. Electronic edition published 2009.