Artificial Stockpiles

Introduction

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

Related common needs

This artifice may be required for cases when the user needs to include into the optimization, any of the following cases:

- 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.

How to incorporate an artificial stockpile into the optimization?

Two main ways to do it:

(1) Modelling the stockpile with its actual geometry.

(2) Creating a simplified artificial stockpile.

Modeled Stockpile

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

- The stockpile and its adjacent areas.
- The stock reclamation.

Step-by-step

For this process, use a modelling software.

1. Use the previous topography for the base of the stockpile.

2. Use the current topography for the top of the stockpile.

3. Create blocks in-between these surfaces. These blocks will have the same size of the block model.

4. Assign an average quality (grade) and density to each block created.

5. Calculate the economic values for these stocked blocks.

6. Import the model back to SimSched to further scheduling.

Simplified Stockpile

For a quicker process, the user can create as many blocks as needed using a spreadsheet application.

This is an alternative useful for cases where you need:

- A quicker process and evaluation.
- Less operational control.

Rows vs Columns

You can model artificial stockpiles as rows or as columns.

Rows

To control a sequence, it may require surface constraints.
A 1-line row will be affected by minimum widths used for the scenario.
Thin rows may cause problems to be mined completely.
Easier setup. Rows don't need geotechnical adjustments.
Multiple rows 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.

Columns

Easier sequence. The precedence is defined by the vertical geometry.
A 1-line column will be affected by minimum widths used for the scenario.
Long columns may affect how deep the scheduling can go in a single period.
Columns require a very vertical slope angle set to them and to the adjacent cells.
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.

Step-by-step (rows)

1. Create rows of blocks above the topography (Figure 1).

2. Assign an average quality (grade) and density to each block created.

3. Calculate the economic values for these new blocks.

4. Import the model back to SimSched to further schedules.

Figure 1: Illustration of a row of 4 blocks created (in green) above a flat topography.

Requirements and observations

Consider checking the following requirements and observations.

Notes on modeling:

- - 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.

Notes 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 parameters to define:
  - - The stockpile base width.
    - 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.

More information (vertical stockpiles)

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.

Figure 2 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.

Figure 2: Example of how to use other constraints to track and control from different sources.

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