The dynamic programming optimize method and its application of cutoff grade

Selection of cutoff grade in a metal mine has a profound effect on the overall economic gain of the mining operation, especially, when the boundary between ore body and waste rock is not clear cut. Many researchers have devoted their effort to cutoff grade optimization. However, Cutoff grade selection is still by and large an unsolved problem mainly due to the fact that the variation in local grade distribution in different zones of the deposit has not been fully considered. This paper presents a newly developed model to overcome this shortcoming. In this model, the deposit or portion of it under study is divided into "optimize units" based on the mining method and sample data. The statistical grade distribution and the grade tonnage relationship of each optimize unit are then computed based on the sample falling in the unit. Each optimize unit with its grade-tonnage relationship is considered as a stage in a Dynamic Programming scheme and the problem us solved by applying a Dynamic-Programming based algorithm. A software package has been developed for the model and successfully applied to a copper mine in Africa.