This paper introduces an engineering approach to estimate the proportion of fines generated during the blasting process. The proposed framework is based on the combination of two Rosin-Rammler based distribution functions to model the full range of fragments expected to be produced during this process. This particular approach, which has been successfully applied for a number of years by the Julius Kruttschnitt Mineral Research Centre (JKMRC), has been improved with the introduction of a new model to predict the potential volume of crushed material resulting from the crushing and shearing stages of blasting. Other sources of fines including liberation of infilling from discontinuities, particle collisions and post-blast processes have been excluded to simplify the modelling process. Validation analysis of the proposed framework has shown that there is good agreement between model predictions and the measured distribution of fines. In three distinct cases, results verified the hypothesis that a single index of uniformity can be used to describe the distribution of fragments in the range of 1 mm through to the expected post-blast mean fragment size (x 50 ). Although some limitations have been noted, the approach appears to provide useful approximations for I. Onederra (for correspondence -I.Onederra@ uq.edu.au), S. Esen and A. Jankovic are at the Julius Kruttschnitt Mineral
Reactive flow cylinder code runs on six explosives were made with rate constants varying from 0.03 to 70 μs−1. Six unconfined/steel sets of original ANFO and dynamite data are presented. A means of comparing confinement effects both at constant radius and at constant detonation velocity is presented. Calculations show two qualitatively different modes of behavior. For Us/Co≥1.2, where Us is the detonation velocity and Co the zero‐pressure sound speed in steel, we find a sharp shock wave in the metal. The shock passes through the steel and the outer wall has a velocity jump‐off. For Us/Co≤1.04, we find a pressure gradient that moves at the detonation velocity. A precursor pulse drives in the explosive ahead of the detonation front. The outer wall begins to move outward at the same time the shock arrives in the explosive, and the outer wall slowly and continuously increases in velocity. The Us/Co≥1.2 cylinders saturate in detonation velocity for thick walls but the Us/Co<<1.04 case does not. The unconfined cylinder shows an edge lag in the front that approximately equals the reaction zone length, but the highly confined detonation front is straight and contains no reaction zone information. The wall thickness divided by the reaction zone length yields a dimensionless wall thickness, which allows comparison of explosives with different detonation rates. Even so, a rate effect is found in the detonation velocities, which amounts to the inverse 0.15–0.5 power.
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