Stockpiles are a post-processing unit of the algorithm. Therefore, after the optimization, which generates mining surfaces, the algorithm does its analysis among the discarded blocks. MiningMath checks if the block’s values (Revenue – Fixed Mining Cost – Rehandling Cost) is higher than the cost of discarding it, with the respective discount rates applied at the period of extraction and period of processing. Therefore, the stocks are considered as an optimization of the blocks that initially went to the dump.
When choosing the destination, the same logic of maximizing the project value is used and MiningMath will define which discarded blocks will be reclaimed, complementing production shortfalls over time, Figure 1 shows the process.
To enable the stockpiles on the interface the first step is on the General tab (Figure 2) where two inputs are required:
Fixed Mining Cost: value used to decompose the economic value while considering stockpiles;
Rehandling Cost: represents the cost to reclaim blocks from the stockpile to the process.
After that, on the Destinations tab, you can define stockpile limits (Figure3) for each processing plant added, remembering that this limit is based on the life of mine, not in a period timeframe.
Defining a Fixed Mining Cost is required because MiningMath does have an interface to enter these parameters when calculating the economic values. It is only used to decompose the block value so that the algorithm can make proper calculations to adjust values considering that part of its costs will occur when mined, while others may be charged when processed.
The Rehandling Cost is the cost to reclaim a block from a stockpile. Therefore, it is the way to break the Economic Values into parts and apply the discount rate at the time a block is processed.
Disclaimer: stockpiles and total tonnage
Since stockpiles are a post-processing unit of the algorithm, total tonnage restrictions might be violated when the stockpiles are processed. Total tonnages restrictions are only considered during the processing unit of the algorithm.