Bench height effects on economical parameters at open pit mine

Authors: Hekmat, A; Anani, A; Medina, J; Shademan, M Download Paper

Cite As:
Hekmat, A, Anani, A, Medina, J & Shademan, M 2024, 'Bench height effects on economical parameters at open pit mine', in Daniel Johansson & Håkan Schunnesson (eds), MassMin 2024: Proceedings of the International Conference & Exhibition on Mass Mining, Luleå University of Technology, Luleå, pp. 1444-1460.



Abstract:
The selection of optimal bench height is crucial to the design of open-pit mines. The bench height influences selectivity, dilution, blast design, and equipment selection, which in turn impacts capital and operating costs and the size and value of the final pit. This study investigates the effects of different bench heights (10, 15, and 20 m) on the grades, unit operations, costs, design, and economic value of final pits for different production rates. We used vein and massive deposit types as case studies to gain a comprehensive insight. The results indicate that increasing the bench height for vein deposits leads to an increase in the stripping ratio and reduction in average grade due to low selectivity and high dilution. Conversely, massive deposits exhibit less sensitivity to bench height variations. In both deposit types, larger bench heights are associated with increased blast pattern size and equipment dimensions, which can lead to lower operating costs, with drilling being the unit operation most positively impacted. Blasting costs, on the other hand, experience the least reduction. Regarding production planning, our findings reveal that for vein deposits, the higher capital cost of equipment and the negative impact of dilution from using larger bench heights far outweigh the benefits of lower operating costs. In contrast, for massive deposits, selecting larger bench heights and high-capacity equipment can still be advantageous due to lower operating costs and increased project value at high production rates.