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ABSTRACT: Sub-level caving (SLC) is a mass mining method that relies on the gravitational flow of blasted ore and the collapse of waste rock. The fine end and the coarse end of blasted particles impact material flow through sublevel interval. Improving blast induced fragmentation has the potential to improve ore recovery, reduce dilution and improve productivity by reducing the remediation of ground support and providing more efficient draw point extraction, while also improving the efficiency of downstream hauling, crushing, and grinding processes. Numerical simulations were conducted using a hybrid finite/discrete element compute engine coupled with a non-ideal detonation model. The model geometries take into consideration the uneven distribution of explosives within each blast due to the fan-shaped rings of blast holes, and the complex environment of blasting into broken ground. The modelling used existing field data from the Ernest Henry Mine to define the blast design, characterize the rock mass, and compare field and modelled fragmentation across a range of explosive densities and burden sizes. Further modelling investigated the influence of discontinuity density in the rock mass on fragmentation. 1. INTRODUCTION The initial step in the comminution process in metalliferous mining involves the fragmentation of the rock mass containing ore. Typically, this is achieved through methods such as drilling and blasting. The fragmentation size distribution after blasting can have a significant impact on the efficiency of downstream processes such as the hauling of the ore, crushing and grinding (Grant et al., 1995), (Campbell & Thurley, 2017), (Jimeno et al., 1995), (Hamdi et al., 2001), (Aler et al., 1996). Within a sub-level caving operation (Figure 1) finer ore is more mobile and flows faster to the draw point, but it can produce sticky mud or slurry in damp circumstances. While larger fragments or boulders can block the flow of material and produce hang-ups, which are a safety hazard and lead to poor ore recovery (Campbell & Thurley, 2017). Determining the optimal fragment size presents a challenge due to the complex interplay of multiple factors associated with blasting parameters, rock characteristics, and operational conditions.
Khodayari et al. (Sun,) studied this question.