Pit and Stope Optimization

This section explains how to configure and run pit and stope optimization from the Block Model > Optimization menu.

Optimization menu commands

• Pit Optimization Settings…: Opens the pit optimization setup dialog (algorithms, economic parameters, slopes, limits, and output options).
• Optimize Pit: Runs pit optimization on the selected block model using the current pit settings.
• Optimize Pit With Reblocked One…: Refines a pit optimization using a selected reblocked model (requires Dressed Cones settings and compatible block-size factors).
• Generate Pit Profit Blocks: Creates a profit-focused block model for pit-related workflows.
• Generate Pit Surface From Block Model…: Builds a pit surface from an existing block model.
• Optimize Pit Profit: Runs optimization using profit-based inputs.
• Stopes Optimization Settings…: Opens stope optimization setup (shape, orientation, 4D options, and economics).
• Optimize Stopes: Runs stope optimization on selected block model(s).

Pit Optimization

Purpose

Pit optimization creates:

1. A new optimized pit block model (economic pit shape), and
2. A pit surface in the envelope tree.

The optimized pit block model represents the pit shell with optimization values. If you need resources physically extracted from the original block model, use the extraction workflow afterward (for example, extraction from pit surface).

Before you start

• Select the block model to optimize.
• Prepare a valid topography surface (required).
• If needed, prepare an overburden surface (optional).
• Ensure required economic inputs are available, either as fixed values/formulas or predefined block model variables.

Open and configure pit settings

Go to Block Model > Optimization > Pit Optimization Settings….

General

• Algorithm
  • Dressed Cones: generally lighter in memory usage.
  • Max Flow: often more memory-intensive;
• Use Profit Variable: uses a precomputed Profit variable already stored in the block model. This option allows you to pass to the algorithm a complete block model which already has a “Profit” field already correctly calculated. Otherwise, this profit will be calculated according to the profit calculation parameters.
• Pattern Size: applies to Max Flow; controls slope pattern resolution.
• Type
  • Geostat 3D: generates one optimal pit.
  • Geostat 4D: generates staged/economic sequencing outputs depending on algorithm.
• Output Folder: destination for generated optimization outputs.
• Cone Only: generates cone surface output without topography extent.

Note: There are two optimization algorithms, the “Max Flow” and the “Dressed Cones”, these two algorithms allow to mutually validate the optimization. We recommend performing a Max Flow with a high reblocking and the Dressed Cones with a low reblocking or even without reblocking, it is much faster and less memory intensive.

Block model and density parameters

• Topo: mandatory topographic reference for pit generation.
• Overburden (optional): identifies overburden volume between surfaces.
• Overburden Mining Cost and Overburden Density: used when overburden is defined.
• Fixed Waste Density and optional Variable Waste Density formula: used for waste-cost calculations.

Commodities

• Commodities
  • Using Block Model: expects a Commodity variable in the model.
  • Fixed: uses the Formula field.
• Formula: ore value expression (for example, grade × price).
• Minimal value / Maximal value / Step value: 4D value factors for applicable 4D runs.

Cost

• Mining Cost
  • Using Block Model: expects MiningCost variable. Defined in the block model schema
  • Fixed: uses Fixed Mining Cost.
• Processing Cost
  • Using Block Model: expects ProcessingCost variable.
  • Fixed: uses Fixed Processing Cost.

Recovery and dilution

• Mining Recovery: fraction in [0,1].
• Process Recovery: fraction in [0,1].
• Mining Dilution: fraction in [0,1].

Reblocking

Reblocking is useful when optimization (especially Max Flow) is heavy in memory/time.

• Reblock: enables automatic reblocking for optimization.
• X size / Y size / Z size: must be greater than zero and should be multiples of the original block dimensions.

If optimization runs out of memory, cancel the run and restart with reblocking enabled.

Reblocking in this workflow is applied to calculated profit values (used by the optimizer), not directly to grade variables. This generally produces more consistent optimization behavior than grade-only reblocking.

Keep in mind that block size controls the final pit resolution: larger reblocked cells produce a coarser pit shape.

Slopes

Define slope by azimuth sectors.

• At least one main/waste slope is required.
• Azimuth must be between 0 and 360.
• Slope angle must be between 0 and 90.
• If overburden is used, define overburden slopes as well.

Example for variable azimuth slopes:

• 0° → 60° slope
• 20° → 50° slope
• 150° → 60° slope

For a constant slope (for example 50° everywhere), one active slope entry is sufficient.

Limits

• Prism Inclusion Limits: constrain optimization inside selected prism boundaries (for example concessions).
• Prism Exclusion Limits: exclude areas from optimization (for example lakes or protected zones).

Run pit optimization

1. Select the input block model.
2. Open and validate settings.
3. Run Optimize Pit.
4. Review generated block model(s), surface, and optimization log.

Interpreting results and practical guidance

• Compare algorithm outputs and prioritize the solution with the better economic result.
• In practice, teams often use:
  • Max Flow to cross-check pit position, and
  • Dressed Cones for practical result comparison and 4D sequencing use.
• If needed, a pit result can be refined by running Optimize Pit With Reblocked One….

4D pit behavior

• Dressed Cones 4D adds an extraction order field to support sequencing analysis.

• Max Flow 4D can generate multiple pit scenarios from value-factor ranges.
• Yield analysis can be reviewed from View > Geostat Chart > Operation > 4D Pit Profit….

Stope Optimization

Purpose

Stope optimization creates a new block model where optimized stopes are identified and sequenced.

Before you start

• Select one or more block models.
• Confirm economic settings (commodities, costs, recovery, dilution).
• Choose realistic stope dimensions relative to block size.

Open and configure stope settings

Go to Block Model > Optimization > Stopes Optimization Settings….

Algorithm Control

• Use Best Fit Plane: uses the block model mean plane as orientation reference.
• Step Over Blocks: speeds up scanning by skipping according to stope fraction (faster, less precise).
• Step Factor: controls the skip fraction.
• Create Disjoint Stopes: creates separate stopes instead of nested/imbricated stopes.
• Use Exact Stope Volume: available with disjoint stopes; uses geometric stope volume instead of block-sum approximation.
• Waste Limit Fraction: available with disjoint + exact volume; controls minimum dilution handling on stope surfaces.
• Waste Density: used in waste cost computation.
• Create Multiple 4D Stopes: runs multiple optimizations using factor-based economics.
• Minimal 4D factor / Maximal 4D factor / Step for 4D factor: define the 4D factor sequence.

Use a positive, non-zero 4D step. A zero step does not create a valid progression.

Size

All sizes are entered in project units and converted to block dimensions.

• X Stope Size
• Y Min Stope Size
• Y Max Stope Size
• Z Stope Size

Use dimensions compatible with the block model resolution. Stope dimensions must not be smaller than block size in corresponding directions.

Orientation

• Minimal Azimuth / Maximal Azimuth
• Minimal Dip / Maximal Dip

If Use Best Fit Plane is enabled, variation is applied around the best-fit orientation.

Economic settings

Stope optimization uses the same economic framework as pit optimization:

• commodities,
• mining and processing costs,
• mining recovery,
• process recovery,
• mining dilution.

Run stope optimization

1. Select one or more block models.
2. Configure settings.
3. Run Optimize Stopes.

For 4D mode, one output model is generated per factor step.

Stope outputs

Generated optimized stope models include additional optimization fields for:

• block profit,
• extraction sequence,
• stope zone grouping.

4D stope analysis

As with pit workflows, yield curves can be reviewed from:

• View > Geostat Chart > Operation > 4D Pit Profit…

Provide interest-rate and production assumptions to evaluate schedule sensitivity and profitability across scenarios.