Schemes of exploitation in open pit mining

The exploitation of open pit deposits usually takes place through a series of mining phases, commonly known as pushbacks. In open pit metalliferous mining, each pushback considers the extraction of one or more benches simultaneously in a process where the core operational tasks include: drilling, blasting, loading and hauling. In large open pit mines, shovels and front end loaders may be used to carry out loading activities. The type and number of shovels are selected during the planning process and their productivity determines the mining rate of the benches, pushbacks and the mine. The space available for loading is part of the pushback design. This defines the shape and size of the benches where the equipment will be placed. A relevant stage in mine design is the definition of the location and sequence that loading equipment must follow to deplete the benches of each pushback. The deployment of loading equipment in the mine is commonly referred to the scheme of exploitation. This term is widely used in the mining industry but not frequently referenced in the literature. The objective of this paper is to explore the concept of the scheme of exploitation in open pit mining within the context of the strategic mine planning activity. In the first part, the concept is presented through examples where the pushback size is fixed and the number of shovel is changed. The second part includes a discussion of the motivations and constraints that the mine planner may consider in the design. Configurations with several shovels and benches in a same pushback represent a challenge for the scheme design mainly due to the limitation of space for loading. Mathematical and optimisation tools can be useful in these cases; however, the models have to be able to represent the real constraints that will affect the productivity of the shovels in the different levels. In general, aggressive and costly schemes are rarely used by mining companies that seek high performance levels and lower operating costs. However, the selection of an appropriate scheme of exploitation needs to be aligned with the principal objective of the mine planning activity, which is to: create value through the exploitation of a mineral resource