Pearce, S, Brookshaw, D, Mueller, S & Barnes, A 2019, 'Optimising waste management assessment using fragmentation analysis technology', in AB Fourie & M Tibbett (eds), Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 883-896, https://doi.org/10.36487/ACG_rep/1915_70_Pearce
The blasting and excavation of rock at mine sites generates a heterogeneous waste/ore product with a wide range of particle sizes. The study of the particle size profile generated as a result of mining is typically termed ‘fragmentation analysis’. Although the potential for material geochemical properties to vary with grain size as a result of the mining process has long been known, the concept is not commonly subject to detailed analysis. As a result, it is typical at the mine planning stage for both waste and ore materials to be represented within mine block models and schedules as comprising monolithic blocks with respect to geochemical properties. However, significant changes to material properties that do occur as a result of fragmentation have the potential to significantly alter both the environmental risk profile and economics of the proposed mine plan. This paper discusses the application of modern fragmentation analysis techniques to the characterisation, management and long-term planning of waste rock.
Detailed laboratory-based heterogeneity testing including geochemical, compositional and quantitative mineralogical analysis has been twinned with fragmentation data to assess properties of as-mined waste at two operational sites. The results presented herein highlight the importance of incorporating fragmentation analysis into the process of setting and validating cutoff grades for ore and waste, and in particular the management of low-grade ore. Opportunities are identified for recovery of resources that would otherwise have been discarded and removal of high-risk material from the waste rock stream. The results indicate that, at a high level, the use of a grade-weighted cutoff grade approach to waste modelling requires careful consideration before being relied upon to estimate environmental risks from mining. Further, the study indicates the benefits of the integration of a robust validation program into waste characterisation and grade control systems to both manage risk and optimise project economics.
Keywords: fragmentation analysis, mine planning, waste characterisation
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