The value added by a good pit design is often latent in terms of quantification, because you will never know the savings in cost that were achieved. Hence it is often relegated to a less experienced “junior” engineer.
To us, pit design should be completed by an expert. Through experience, an expert will produce a design that is simultaneously safer, more productive, more efficient, and quicker to produce. It is a false economy to give this task to a junior, at least without proper training and guidance.
A poor pit design is jarring to look at. And the further you dig, the more errors you find. Some of the most common errors with pit designs we have seen:
- Ignoring or mis-understanding geotechnical inputs: Safety is of utmost important, and designing a pit to fail introduces unnecessary risks to the project.
- Lack of understanding of access between pit stages: When designing a staged pit design, it is sometimes difficult to track the state of the pit as it progresses. Often access to early ramps will be cut-off by subsequent stages, removing access to a number of benches. If not identified prior to production, this can result in additional waste being mined, or ore not being reached.
- Narrow, impractical mining widths: In trying to follow the pit optimisation shells, often there are segments of the pit that have very narrow widths that cannot be mined. These areas may result in pushing back of walls, taking more waste, or reducing access to ore in production.
- Does not link ramps between stages well: Good pit designs often find opportunities to connect pit ramps to produce multiple pit exit options to provide operational flexibility and mitigate ramp failure risk.
- Does not minimise haulage distances/cost: Pit may exit in the wrong direction and not connect with the ROM, stockpile or waste dump, or not prioritise which contains the majority of the material.
A good pit design is like art: you know it when you see it. And the more you look at it, the more you appreciate the nuances involved. How the pit flows from stage to stage in a way that minimises waste, maximises options for multiple access ramps, and minimises haul distances.
To benefit from our expert pit designs, either to complete design for you, review your existing design or mentor you through the process, contact us at firstname.lastname@example.org.
Click here for more articles like this.