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Deposit variability |
Department of Mining and Mineral Engineering, University of Leeds, Leeds LS2 9JT, UK
This paper discusses two important, and often overlooked, aspects of optimum open pit design: the information and support effects. Pit designs are ultimately based on estimated block grades and, as such, their optimality can only ever be approximate; as the errors of estimation of the block grades increase the pit design will deviate more and more from true optimality. Estimation errors depend on the amount of data available (information effect) and on the size of the block to be estimated (support effect). There is a lower limit to the block size used in grade and revenue block models for pit design and this lower limit is determined by the drilling grid. The use of blocks which are significantly smaller than the drilling grid will produce block models which will yield erroneous pit designs. Geostatistical simulation is used to quantify these effects for a particular case and to demonstrate the most effective way of dealing with small selective mining units at the planning stage.
