Define Prism Framework Troughs

Troughs allow non-rectangular prism shapes, typically used to: Follow ore geometry Reduce dilution Improve recovery near contacts.

In the Prism method, troughs are a supported stope variant where the stope is not a simple rectangular prism, but includes a shaped recess (a “V” or curved feature).

This section of the Shapes screen controls whether trough shapes are allowed, their geometry, and when they should be excluded.

You would use these settings when:

Ore geometry is irregular.
Hangingwall or footwall control is important.
Flat-top stopes would cause excessive dilution.

Overcut and Undercut

You can also choose how (or if) trough-shaped prism stopes can remove material either above or below the main stope envelope.

These controls do not define the trough geometry themselves – they only control where the trough is allowed to operate.

The actual shape is still controlled by the Position, Width, Angle and other geometrical controls on the Shapes screen.

The optimiser may apply trough geometry above and below the stope, subject to other geometric and optimisation constraints. As such, simultaneous overcutting and undercutting is possible.

In summary: Undercut removes ore below the stope, overcut removes ore above it.

A summary of overcut and undercut principles

Note: Trough overcut and undercut options control where trough shapes are applied. They do not guarantee additional extraction, but allow the optimiser to consider these shapes where economically beneficial.

Trough Overcut

Trough overcutting allows the trough to remove material above the nominal stope back or crown. In other words, it allows the trough shape to extend above the stope crown, locally increasing extraction above the nominal stope height.

In mining terms:

The stope crown is locally raised
Additional material is taken from above the stope
Often increases dilution but may improve recovery

This is the logical complement to undercut (see below) and is consistent with the Prism method’s ability to vary crown geometry and apply crown-related refinement.

Why you would use it:

To capture ore near the hangingwall or back
When crown dilution is controlled or tolerated
In wide or irregular orebodies where a flat crown is too conservative

Trough Undercut

Enabling trough undercutting allows the trough to remove material below the nominal stope floor. In other words, it allows the trough shape to extend below the stope floor, locally increasing extraction beneath the nominal stope height.

In mining terms:

The stope floor is locally lowered
Extra material is taken from beneath the main prism
Often used where ore thickens downward or where floor dilution is acceptable

Dilution Risk

Enabling trough overcutting or undercutting allows the optimiser to remove material above or below the planned stope geometry. While this may improve ore recovery in irregular deposits, it can also introduce additional waste and increase dilution. These options should be used only where geological confidence, grade continuity, and economic parameters support the additional extraction.

Specify Trough Settings

Activity steps:

Display the Shapes screen.

Note: The activity outlined below is specific to the Prism framework type. Other framework types present a different screen.
Check Use Trough Undercut if undercutting is required.
1. Choose the Position where the trough is placed relative to the stope (Centre, Left or Right).
2. Specify the Width of the trough feature within the stope.
3. Choose the Angle of the trough relative to the stope orientation.
4. If the Position is either Left or Right, you can also specify an Offset (from the edge of the stope) to position the trough.
Warning: This may increase floor dilution by extending extraction below the stope.
Check Use Trough Overcut if overcutting is required. The settings for this type of cut are the same as for undercutting.

Warning: This may increase crown dilution by extending extraction above the stope.
Optionally, disable troughs entirely by checking Optimise without trough. This can be a useful way to compare optimisation run outcomes without losing trough settings.
Save your settings.