Open Pit Mine Scheduling Model Considering Blending and Stockpiling

Abstract

Open pit mine production scheduling (OPMPS) is a decision problem which maximizes net present value (NPV) by determining the extraction time and destination of each block of ore and/or waste in a deposit. Stockpiles can be used to maintain low-grade ore for future processing, to store extracted material until processing capacity is available, or to blend material based on single or multiple block characteristics (i.e., metal grade and/or contaminant).

We modify an existing integer-linear program to maximize NPV and provide a schedule and stockpiling strategy for an operational open pit mine, in which the stockpile is used to blend materials based on multiple block characteristics. We compare the schedule of $\left( {\hat{p}^{la} } \right)$ with that produced by $(p^{ns} )$ which does not consider stockpiling, and with $\left( {\tilde{p}^{la} } \right),$ which controls only the metal content in the stockpile and ignores the contaminant level at the mill and in the stockpile. We show that our model improves the NPV of the project while satisfying operational constraints.