Artificial stockpiles

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Artificial Stockpiles is an advanced operation to incorporate external sources of material to your model and use them as an input on your scheduling.

Common use cases

This technique is especially useful when you need to incorporate the following scenarios into the optimization process:

Pre-existing stockpile from ongoing operations.
Underground material to be blended with open-pit material.
Ore bought from third-part companies to fulfill production shortfalls.

There are two main ways artificial stockpiles can be incorporated into the optimization: 1) modelling the stockpile with its actual geometry; or 2) creating a simplified artificial stockpile. These are detailed next.

Modelling the stockpile with its actual geometry

Modelling an existing stockpile with its actual geometry is the best alternative to include it into the scheduling for cases where you need an operational control over:

The stockpile and its adjacent areas.
The stock reclamation.

For this process, use a modelling software to perform the following steps:

Use the previous topography for the base of the stockpile.
Use the current topography for the top of the stockpile.
Create blocks in-between these surfaces. These blocks will have the same size of the block model.
Assign an average quality (grade) and density to each block created.
Calculate the economic values for these stocked blocks.
Import the model back to MiningMath to further scheduling.

Creating a simplified artificial stockpile

To speed up the process, users can create multiple blocks as needed using a spreadsheet application. This method serves as a useful alternative in scenarios where you require:

Faster processing and evaluation.
Reduced need for operational control.

Rows vs Columns

You can model artificial stockpiles as rows or as columns. A comparison between each choice is listed below.

Rows	Columns
To control a sequence, it may require surface constraints.	Easier sequence. The precedence is defined by the vertical geometry.
A 1-line row will be affected by minimum widths used for the scenario.	A 1-line column will be affected by minimum widths used for the scenario.
Thin rows may cause problems to be mined completely.	Long columns may affect how deep the scheduling can go in a single period.
Multiple rows will give more flexibility and reduce conflicts with the operational constraints from the open-pit scheduling.	Multiple columns will give more flexibility and reduce conflicts with the operational constraints from the open-pit scheduling.
If you opt for multiple stockpiles, create them with a 2-cell distance to avoid overlapping interference.	If you opt for multiple stockpiles, create them with a 2-cell distance to avoid overlapping interference.

Step-by-step (rows)

Create rows of blocks above the topography.
Illustration of a row of 4 blocks created (in green) above a flat topography.
Assign an average quality (grade) and density to each block created.
Calculate the economic values for these new blocks.
Import the model back to MiningMath to further schedules.

Requirements and observations

Consider checking the following requirements and observations.

Notes on modelling:

The blocks created must have the same size of the ones from original model.
Consider increasing densities for the blocks created to represent more material with a few blocks. The trade-off is a reduced selectivity.
The more blocks you have, the more selective is the algorithm.

Note on operational needs:

The blocks created will be subject to the operational constraints, such as widths and vertical advance, from your scenarios. This means you need to consider these two parameters to define them: 1) the stockpile base width; and 2) the stockpile height.

Notes on the placement within the model:

The artificial stockpile should be placed in a peripheral area of your model to not affect the open-pit schedule.
Avoid borders to prevent any geotechnical issue, which will impede mining the artificial stockpile completely.

Additional information

The following video shows more information on artificial stockpiles.

Additional control over sources

Use Other Constraints to have additional control over different sources of material, whether they come from the original model or from a modeled stockpile. The figure below shows an example on how to setup your model to track and material from different sources and control them by inputting minimum and maximum limits.

MiningMath

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