Restrict mining is used to prohibit access to any area (Figure 1) in a specific time-frame. This feature is responsible for making MiningMath ignore what is outside the surface inserted, which means that only the material above it is available to be extracted, whether is ore or waste. Thus, this feature could be also understood as a maximum depth that could be mined at a specific timeframe.
Keep in mind that these surfaces might be adjusted during the optimization to respect the slope angles (Figure 2), which has a higher priority order on the algorithm, while the optimization is done. Therefore, less material can be mined either to correct the overall slope angle or to increase the NPV, since mining, useless waste material does not increase the revenue.
This functionality is commonly used to refine/optimize the mining amount of a previous surface in any period, restrict depth to a specific value which the deposit could achieve, extract the best ore in custom advances. It locks/prohibits an area due to concession rights, environmental issues, or even due to an already built stockpile, waste dump or structure in general, etc.
As MiningMath aims to assist the users to apply their project knowledge to guide the algorithm into the best decisions, that is why surfaces are one of the most important constraints hierarchy, which enables the implementation of custom geometries and operational parameters based on this smart hints imposed. To sum up, the material above a Restrict Mining imported surface will be available to be mined until the specified period of time and what is inside could be mined if the blocks respect all the constraints and generate profitable results. Regarding what is outside, it will not be mined whether profitable or not.
2. Practical example
The image aside illustrates an example as the standard scenario scn21-PriceUp-RampUp-Protection300 available on optimizing scenarios. It is possible to identify that in the free case (left), the pit limit advanced beyond the limiting surface on the west portion, defined by the higher elevations of the cells (equal to the topography). On the other hand, applying the limiting surface (right) to restrict mining until the last period, a new pit limit is obtained and obeying the constraint imposed by the surface, as shown in Figure 3.
The second example is based on the attempt to extract the best material inside the Mining_Front-FM.csv, which mapped high-grade ores in the first period (Figure 4 to 6), as mentioned on this page. Using the suitable surface file, in a scenario of Exploratory Analysis was run using the set up disclosed in Figure 4. Note that a scenario without Force Mining (Figures 7 and 8) was also run to have a good comparison.
As a result, the Restrict Mining surface mined the best material within the area available (Figure 9), which generates different sequences (Figures 10 and 11) and illustrates how powerful could be user assumptions to generate suitable results or explore possibilities.