MANAGEMENT OF OPEN PIT MINING OPERATIONS WITH ORE STOCKPILES

An open pit mining operation consists of mining, processing, and refining stages. The mining stage is responsible for provision of required amount of ore of pre-defined grade to the processing plant. The heterogeneity in the ore grade in various parts of the deposit leads to the definition of cutoff grade. The material below cutoff grade is sent to the stockpiles for utilization in later years when it becomes economical. The cutoff grade optimization theory maximizes the Net Present Value (NPV) of a mining operation with a declining effect as the deposit leads toward exhaustion. This declining effect of NPV defines dynamic cutoff grades i.e. higher cutoff grades in the early years of mine life and lower cutoff grades in the later years. However, this precisely defines the amount and grade of material sent to the stockpile for processing in the later years. The management i.e. supply of material from the mine to the stockpile and from the stockpile to the processing plant is an issue that is addressed in this paper by developing a cutoff grade optimization algorithm with option to stockpile. The benefits of methodology are elaborated in a case study.