Rheology of two-dimensional crushable granular materials

The rheology of two-dimensional crushable granular materials under shear is numerically studied using the discrete element method. We find that the mean fragment size changes as the shear strain increases while the shear stress is almost independent of this mean size. The fragment size distribution is found to follow a power law. In particular, the exponent in the intermediate fragment size regime becomes approximately – 11/6, which is almost independent of the shear rate.

Prediction of rock fragmentation using the Kuznetsov-Cunningham-Ouchterlony model

SYNOPSIS Assessment of blast fragment size distribution is critical in mining operations because it is the initial step towards mineral extraction. Different empirical models and techniques are available for predicting and investigating the consequences of blasting, one of which is the Kuznetsov-Cunningham-Ouchterlony (KCO) model. In this paper we summarize the advances in the empirical models from inception until now, and explore the improvements that have been made so far with particular emphasis is on the most recent KCO model. Utilization of the model and the errors that arise between expected and the actual outcomes are analysed. The results indicate that the KCO model remains useful for predicting the blast fragmentation at limestone mine sites, despite the availability of other advanced prediction models. It is also a valuable instrument for pre-surveying the impact of varying certain parameters of a blast plan. Keywords: blasting, rock fragmentation, modelling, prediction.

Stemming zone fragmentation analysis of optimized blasting with top-column air decks

Trial application of air decks on a production shot improved fragmentation (32% reduction in x50). Empirical fragmentation models and digital image processing software were used to estimate fragment size distribution of the blasted muck pile. The x20, x50, and x80 passing fractions, and top size were 42, 265, 683, and 1,455 mm, respectively. Air-deck application reduced explosives load in blast-holes, lowering total charging cost by US$20/hole (15% decrease) and the powder factor to an average of 0.86 kg/m3 (12% decrease). Blast results were 443,624 t of blasted material from the block (90% of total muck pile) was smaller than 900 mm.