Simply put, optimization is figuring out the best pit size that meets the company’s goals while also considering engineering, safety, and operational needs. Often, this means finding the pit size that gives the highest net present value within defined engineering, safety and production constraints.
In an open pit mine, you need to remove a lot of waste to get to the valuable minerals (ore). A big pit lets you get more ore, which means more money and a longer-lasting mine, but it also means more waste to remove, which costs more. A smaller pit means you remove less waste, so it’s cheaper and more profitable, but you get less ore, and the mine won’t last as long. Optimization is finding the right pit size that gives you the most revenue by balancing cost and profit distribution.
How do you figure out the best pit size?
After the resource model (a 3D representation of the deposit with details like grade, rock type, and rock properties) is created by resource geologists, it is turned into a planning model by mining engineers by adding and subtracting information. This involves three main activities:
- Resize the model blocks (cells) to a size that can be practically mined. This reduces the grade in each cell while increasing the tonnage.
- Introduce geotechnical parameters like safe slope angles and rock structures. Geotechnical engineers define structures and rock domains important for safe and stable high walls.
- Add necessary planning parameters and remove unimportant ones, like certain grade estimation parameters.
- Define the economic model by adding cost and revenue factors to each block.
This planning model is then imported into optimization software, such as Whittle, Datamine ‘s studio NPVS or Maptek ‘s Vulcan, for optimization.
What does the software do?
These software programs use advanced math to combine production, economic, and engineering factors to create a series of pit shells. Each shell shows the economic value, from the most profitable small pit focused on high-quality ore to the least profitable large pit with more waste.
These algorithms create pit shells for each economic value by looking at geotechnical, operational, and cost factors.
Which pit shell should you pick?
Now you have several pit shells to choose from. Each shell has different benefits: one gives the highest net present value, another has the most reserves (commodity quantity), and another minimizes risks (a smaller pit with high profit).
Which shell and sequence you choose depends on the company’s goals. These might include maximizing the mine’s life, minimizing risk to boost profit, or other objectives. Setting these goals is the first step in planning the mine.
Credits to Martine Mshana
