Block Model Reblocking, Regularisation & Reporting

Block Models can be regularised to dilute a resource model for mine planning use.

Prior to regularisation, a user will need to check for the following block model and planning properties:

1. The Origin and the Parent Cell Size of the resource model
2. The Selective Mining Unit (SMU) for the diluted model
3. Knowledge of the fields to carry through the regularisation process

Furthermore, it is important to understand the difference between the Block Model Reblocking tool & and Regularisation tool despite the similar sounding names. 

The workflow below demonstrates an example of using the Block Model Reblocking & Regularisation tools and highlights where each tool is intended to be used.

Checking the Origin and Parent Cell Size of the Resource Model

Open the Resource Model in the File Editor via the File > Open command.

In the File Editor, click on the Properties button to view the Minimum Centres (Origin) and the Block Size (Parent Cell Size) for the model.

Reblocking / Redefining Origin

If the parent cell size is going to be changed, run the Block Model > Reblock command to set the new parent cell size and alter the block model origin.

A user needs to ensure that the block model origin aligns properly with the new SMU to prevent the regularised model from forming a halo around the resource model as per the image below.

Ideally, the regularised model block extents should cleanly encapsulate the extents of the resource model except in areas where there is a insitu/air contact zone.

Running the Regularisation Tool

When a resource model is ready for regularisation, use the Block Model > Reblock Model > Regularise command.

Ensure that the correct block size is set and that key fields (grades, rock types etc.) are configured to be aggregated by the correct method.

• Grades can be aggregated using Weight Average (Volume) or Weight Average (Volume x Density)
  • Density field is required to use the Weight Average (Volume x Density) option
• Character fields should be set to Dominant

After Micromine regularises the block model, visually inspect the resulting diluted model with the resource model to ensure obvious errors are not present.

Dilution Reporting

Micromine offers functions that allow a user to quantify dilution & ore loss through their own processes and logic. One process to quantify dilution and ore loss will require:

1. Flagging block model using simple values or expressions
2. Using the Block Model > Reblock > Combine command
3. Using Expression Calculate to flag a dilution & ore loss code into the combined model
4. Use the File > Report > Report Generator to run a custom report based on the dilution code

Flagging the Resource and Diluted Model

• Use the File > Open command to open the resource model and the diluted/regularised model in the File Editor.
• Use the File Editor > Edit Fields > Calculate (Expression) command to open a dialogue box and assign a flagging value to a new field that will designate what block belongs to what block model. This step is crucial prior to combining
• For the resource model, assign a value of 1 to a new field called RESFLAG
• For the diluted model, assign a value of 1 to a new field called DILFLAG

Combining Block Models and Block Definition Selection

• Run the Block Model > Reblock > Combine command
• Select the resource model as Model 1 and the regularised model as Model 2
• Use the Output Block Definition for Model 2
  

Dilution Code Flagging

• Open the combined model in the File Editor
• Use Calculate Expression to insert a value of 0 for the RESFLAG and DILFLAG fields.
• Additionally, create a new dilution/ore loss code field (DIL in the example image below) with a default value of 0.
• Using the appropriate combination of the RESFLAG and DILFLAG, assign a code to designate material that is:
  • Always Waste (DIL=0)
  • Always Ore (DIL=1)
  • Dilution (DIL=2)
  • Ore Loss (DIL=3)

Use the Report Generator to create a Dilution Evaluation Report

• Use the File > Report > Report Generator command
• Configure the form to run a report of the combined block model
• Set Grouping to the dilution / ore loss code
• In the Field Mapping section, configure the fields to be accumulated and reported on (tonnes, grades, metal content)
• Validate the dilution evaluation report by running report on the resource model and comparing the ore tonnes and contained metal
  • Both models should have the same amount of contained metal
  • Block tonnes should vary to account for dilution unless and ore-only model is used
  • To account for block tonnage values for dilution, waste blocks need to be generated around the ore-only block model.

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