Palabora Lift 1 block cave: understanding the grade behaviour

Abstract

Palabora Mining Company commenced mining of the Lift 1 block cave in 2001. Lift 1 is now nearing completion, and this paper will discuss the challenges around the reconciliation and forecasting of grades during the life of Lift 1. Particular emphasis will be placed on the impact of the open pit failure which took place in 2004 and its impact on the grades later on in Lift 1. The paper will look at the different caving mechanisms which have contributed to, and impacted on, the recovered metal from the block cave. It will also look at how the cave management was impacted by the coarse fragmentation of the cave, which was a first worldwide at the time, and the interaction between practical mining constraints and idealised caving strategies. In the latter stages of the mine, some particularly surprising grade behaviour was experienced, and plausible explanations for this behaviour will be presented relating to the open pit failure material and cave back shapes. Concluding remarks will discuss how the experiences learned from Palabora Lift 1 can potentially benefit Palabora Lift 2 and other future caving operations.