Resilient Decision Making in Open Pit Short-term Production Planning in Presence of Geologic Uncertainty

Short-term production plans are the basis for operational mine production schedules. They concentrate on making long-term mine plans operationally feasible. Furthermore, some variables such as ore grade and tonnage govern mine production systems and cause uncertainty in the supply of raw materials to the mills. Due to the quality variation of material, short-term production optimization is an uncertainty-based problem. Feed quality is a prerequisite for the mill designer. It affects the mill efficiency and the type of measures with respect to environmental regulations. There is a need to control and to predict the quality of feed at the mine site to meet mill requirements, which is a complex problem. To deal with this issue a stochastic optimization model is developed to capture the effects of resource uncertainties on mine planning. In that regard, three performance indicators are defined and an optimized mining schedule is used to simulate the performance of these indicators throughout the mine-life. This will quantify the effects of geological uncertainty on short-term and long-term plans. The objectives of the model also include minimizing the deviation of expected quality and quantity from the required values. The methodology was illustrated using a case study on a surface gold mine in Iran. This approach leads to resilient decisions and better quality control. According to the results, introduced by the new production system, the probability of underproduction is reduced to 13%.