The mining industry is often challenged with the task of evaluating narrow vein open pit deposits. A realistic mineable solution from optimisation needs to accurately represent mining dilution and the practical limitations of mining equipment. Open pit dilution is driven according to mining method and fleet selection as this dictates the ‘selective mining unit’ (SMU) that can be practicably mined.
Common evaluation methods represent dilution by:
- a mathematical dilution assumption
- addition of a dilution skin
- reblocking of the model to an appropriate SMU.
This paper will explore an alternative method of applying dilution by adapting an underground stope modelling tool. By considering an SMU as a stope, automatic stope shape creators such as Datamine’s Mineable Shape Optimiser (MSO) can be used to create wireframes for each mining unit over the entire deposit. Using these wireframes, the model can be subblocked and assigned as either ore (inside the wireframe) or waste (outside the wireframe) prior to optimisation.
The MSO process considers SMU geometry and a depth specific value-based cut-off. The result is an optimised solution for the deposit based on practical and achievable mining constraints rather than one based on generalised modifying factors.
To evaluate the economic impact of the methods above, results have been costed and scheduled and a comparison of operating cash flows made.
Swapp, S and Mann, C, 2016. Optimisation Improvements for Narrow Vein Open Pit Deposits Using Mineable Shape Optimiser, in Proceedings Ninth AusIMM Open Pit Operators’ Conference 2016, pp 50–59 (The Australasian Institute of Mining and Metallurgy: Melbourne).