Create Dig Lines, Bulk-Mining Grade Control & Dig Line Reporting

Micromine offers a variety of tools to accommodate grade control workflows at the operational level for bulk-mining commodities such as iron ore. The Grade Control tools allow users to:

• Generate first-pass dig lines based on blast boundaries and cut-off grades using a block model as a source.
• Reports block-out physicals based on generated dig polygons or wireframes.
• Adjust dig lines and recalculate reports based on assay data for reconciliation and operational use.
• Merge results from the report (.RPT) file back into the original grade block polygon files (.STR/.DAT).

It is important to understand that the workflow for grade control & reconciliation will be different for other commodities, like gold, which will require small-scale re-estimation due to the nugget effect and levels of uncertainty. 

Block Model Familiarisation and Filtering

Prior to beginning any grade control work:

• Load the block model to be used
• Slice the block model to the elevation and location of the desired blast boundary
• Conduct a visual check to verify anticipated grade zones

For a dataset:

• Load the blast boundary and click on Vizex > Viewpoint > View all
• Load the block model to be used. Apply a filter if required
• Define and slice to an elevation in between a bench (Vizex > Section > Enable Clipping)

Mining > Grade Control > Create Dig Line

When visual inspection of the block model is complete, a first pass set of dig lines can be created using the Mining > Grade Control > Create Dig Line tool. This will create dig block polygons and wireframes based on the block model, grade bins and blast boundaries selected.

• Go to Mining > Grade Control > Create Dig Line
• In the Input Tab
  • Select Input Block Model and assign compulsory fields (Default Density and Element Field)
  • Assign a filter to allow the tool to operate on a limited selection of blocks

• • Define grade bins in the Material Classifications section
  • Define Bench Crest and Heights
  • Define Minimum Mining Width based on Parent Cell Size (only whole numbers accepted)

• Configure Regions tab
  • Select Blast Boundary string file
  • Alternatively, select bench plan string file and use a Key Fields to delineate between shot numbers

• Configure Output tab
  • Enter names for Output String File and Wireframes
    
    

Validating First Pass Dig Line Outputs

After the Create Dig Lines tool has run, two output layers are created:

• Dig Lines
• Wireframes

As a raw output, the constructed dig lines and wireframes will have a single, default colour as per the image below. The output strings will also appear block-like in nature, as they conform to a block model and attempt to adhere to minimum mining widths. First-pass dig lines should always be re-shaped to adhere to blast boundaries.

It is recommended to re-colour all lines/wireframes corresponding with grade bins / material classifications and conduct visual checks on the generated outputs. Modify the wireframe or string formset to create a Colour Set that can be applied to multiple forms.

• To configure a string layer, double click on the layer in the Vizex Layer Display pane
• In the Strings form, navigate to the Display tab
• Select the variable to colour by in the Colour field
• Right-click inside the Colour Set field to create a new Colour Set
• In the Edit Colour Set form, assign grade bin cut-offs and colours.
• Click on the Save and Close button to save the Colour Set as a Formset

• Back in the Strings form, select the formset that was just created.
• Wireframes can be coloured by the created Colour Set
• Navigate to the Display tab and enable 3D Colour Coding
• Select the Wireframe Attribute to colour by. This attribute should be present in the string file (ie. Grade)
• Select the Colour Set previously created

Either layer can be used to do grade control reporting and have their own use cases. Polygons dig lines are best used for creating dig maps and can be easily modified to re-run reports. Wireframes need more work to re-adjust boundaries but can be carried through / imported into a scheduling package.

Mining > Grade Control > Setup (Polygon/Wireframe)

When dig line validation is complete, run Mining > Grade Control > Setup to configure reporting inputs and outputs. Note that the Setup form has two options; Polygon and Wireframe

• In the Input/Output tab
  • Enter the Input Data Source. This can be a block model or an composited assay file (ie. 3D Points)
  • Select input file and apply the same filters used in the Create Dig Lines command
  • Configure source of density information, default densities and density fields where applicable

• In the Grade Fields tab
  • Configure any grade fields to report on
  • Specify grade and mineral/metal units

• In the Polygon tab
  • Confirm polygon position and define bench thickness based on position.
    • If polygon boundaries are Crest lines, set position to Front
    • If polygon boundaries are Toe lines, set position to Back
    • If polygon boundaries are mid-way into a bench, set position to Middle
      • Set bench Thickness to half of the bench height
    • In the Wireframe Output tab
      • Configure an output .TRIB (Triangle Database) for wireframe outputs after reporting.
        • This allows for wireframes previously created to be renamed in line with the material classification.
      • Define an Ore and Waste material prefix or use a Wireframe’s Naming Field to configure wireframe reclassification in case new sources are used.
      • Note that reclassifying wireframes is optional in the Setup (Polygon) command

The Setup (Wireframe) form is similar to the polygon setup form. As the form only deals with Wireframes, there is no Polygon tab and the Wireframe Output only deals with writing densities, void attributes and material classification labels.

Tagging and Reporting using Block Model Source

Once the Grade Control Setup form has been set up, use the Tag Ore and Tag Waste buttons to assign the Ore/Waste flags to either:

1. The Dig Line Polygons or;
2. The Dig Line Wireframes

Note that if a polygon is tagged, wireframes will not be able to be tagged and vice versa.

When the set of polygons/wireframes are tagged as Ore and Waste, clicking on the Mining > Grade Control > Report button to generate a report seen in the image below.

The report will tabulate volumes, densities, tonnages, grades, contained metal/mineral and names for each dig block defined.

Void statistics are only reported if voids / gaps in block models are present. In open pit environments, use void statistics as a diagnostic tool to find gaps and potential issues in the block model, unless cavities or old UG workings are actually present.

Tagging and Reporting using Assay Data Source

Any created dig line or wireframe can be dynamically re-reported using a different Input Data Source. If assay data from production drilling has been obtained, it can be used to re-report the grades for blocks.

• When assay data is received, ensure that a collar file for the assayed holes is available.
• Create a new Drillhole Database (.DHDB file) using Drillhole > Database > New
  • Select the collar file containing the collar coordinates for the assayed holes
  • Select the assay file containing the grade information for the assayed holes
    • Ensure the assay file is populated properly with From/To Depths
    • From/To Depths should be interval lengths, not RLs / bench levels
  • In the Output Database tab, specify a database name and enable all sorting options
• Use Drillhole > Generate > XYZ Coordinate to generate XYZ coordinates for your assay files.
• Once coordinates have been created for the assay file, open the Grade Control Setup tool
• Specify the Input Data Source to 3D Points File and select the assay file. Define a new name for the Assay-based report
• Re-tag the Ore and Waste polygons/wireframes and click on the Report tool.

Assay data will usually be different from block model data. It is expected that dig block boundaries are adjusted to ensure waste isn’t unintentionally mined as ore.

When redefining dig block boundaries, ensure that any newly made polygons are assigned an ID. This will be necessary for re-assigning updated material classifications and properties from the report (.RPT file) to the string (.STR) file.

Redefining Dig Block Polygons and Reclassifying Material

When reports are re-run on different grade boundaries, the aggregate grades for dig blocks may change. However, at this time, running the Report command only re-calculates physical properties (volume, tonnage, grade etc.) in the .RPT file. In order to reclassify the material/grade bin, an expression will need to be performed on the .RPT file.

• Modify the grade block boundaries, redo Ore & Waste tagging and update the .RPT file if required.
• Use File > Open to open the .RPT file. If the report window is open in the Calculation Results Pane, click on Open File in File Editor
• Use File Editor > Edit Fields > Calculate (Expression) to open the next formset
• Use conditional statements & expressions to construct a formula in the Input column. Click on the fx icon to open the Expression Editor to help with constructing the expressions. Ensure that expressions are checked/verified.

• When the expression has been configured, designate an output field in the Result column (ie. Material Classification)
• Run the tool and verify the results.
• If properties in the .RPT file need to be written back into the .STR file or polygons, use File > Actions > Merge and set the ID field as a key field.
  • Set the Grade Control .RPT file as the source
  • Set the adjusted Dig Block .STR file as the target
  • Configure ID as the key field
  • Configure the fields from the source file that will be merged into the target file

• • Verify the results of the file merge

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