ABSTRACT
The Bureau of Mines is conducting research to develop methods for controlling fragmentation in surface mine blasting. The application of fractal concepts offer a new and perhaps useful method to help analyze fragmentation mechanisms in blasting. Turcotte has shown that if the fragmentation exhibits a statistical dependence according to a Weibull distribution, then a fractal dimension can be obtained if certain other conditions are met. Thirty-five test blasts in rock, using a bench-type geometry, were studied and the fragment distributions were found to exhibit a strong Weibull dependence. The fragmentation data reflects the effects of differing explosives, rock types and shot configurations, including a wide range of bench sizes, with burdens ranging from a few inches (small scale) to ten feet (production scale). Fractal dimensions were calculated for each test blast and ranged from D = 1.66 to D = 2.20 with a mean for all thirty-five shots of DA = 2.00 ± 0.17. These values were obtained with the assumption that the entire distribution of fragments will exhibit a Weibull dependence. The overall results suggest that the blast fragmentation process is not greatly affected by the size or scale of the blast designs studied here. This supports the claim by Turcotte that the fragmentation process is scale invariant since the zones or planes of weakness along which materials fail occur at all scales.
