Authors: Khodayari, F; Pourrahimian, Y; Ben-Awuah, E

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Khodayari, F, Pourrahimian, Y & Ben-Awuah, E 2018, 'Application of mathematical modelling for draw control under material flow uncertainty', in Y Potvin & J Jakubec (eds), Proceedings of the Fourth International Symposium on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 815-822.

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Production scheduling is one of the key steps in the decision-making process of any ‎mining operation. In block caving, it is the choice of the amount of caved rock to ‎extract from drawpoints in different periods. One of the main differences between ‎block caving and other mining methods is the influence of the material flow on ‎production, and draw control in general. Achieving an optimum production schedule ‎without consideration of the cave rate and material flow could be unrealistic and impractical as the ‎movements of material between drawpoints will result in unexpected production ‎grades and tonnages. In this paper, a stochastic mixed integer optimisation model is ‎proposed to optimise the production schedule during the life of the mine. The ‎uncertainties of production grades and tonnages are captured by defining a number of ‎scenarios that represent the probable movements of fragmented rock between ‎drawpoints in the same neighbourhood. The decision variables in the formulation are based on the slice model, which means that the mathematical ‎solution determines which slices are extracted from drawpoints in each period of production. The goal ‎is to maximise the net present value of the project during the life of the mine and ‎minimise the deviations of production grades and tonnages from the defined goals in ‎all probable scenarios resulting from the movements of the fragmented rock between ‎drawpoints. Application of the proposed model in caving operations can not only ‎improve the profitability of the project, but also increase the confidence of the ‎production schedule. MATLAB was used for programming and CPLEX for solving the ‎model. The designed graphical user interface, with the capability of adding different ‎technical and operational constraints, will be a flexible tool for mine planners to ‎control the draw based on the company’s goals during the life of the mine.‎

Keywords: block caving, production scheduling, draw control, material flow, stochastic ‎optimisation

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