Development of a New Model to Predict Uniformity Index of Fragment Size Distribution Based on the Blasthole Parameters and Blastability Index

Uniformity index n represents the range of fragment size distribution and it is applied to evaluate fragment size by Rosin and Rammler cumulative distribution function for a muck pile. The uniformity index n of fragment size distribution has been assessed by digital image analysis technique using Split-Desktop for several blasthole parameters and different zones of in-situ rock mass conditions in five mines having a wide range of blastabilty index (BI). Rosin and Rammler equation has been determined by a new procedure using a software entitled Pixler to delineate images the same as manual method for achieving a proper fragment size distribution by Split-Desktop. The obtained values of n had significant differences with estimated n by the former equations. Relations between n and several blasthole parameters, BI and mean fragment size X50 of the results and their various combinations have been analyzed. Finally, a new empirical model having a good correlation has been developed to predict n value for using 25 ms electric delay detonators.