Model Updating with Flitch Polygons

Intelligent Mining Software “Solutions” IMS - Model Updating with Flitch Polygons

Table of Contents

CREATING FLITCH BARS AND FLITCH INTERPRETATIONS

Generating Flitch Bars

Interpretation of Flitch Polygons

Change to Plan View

Draw Flitch Interpretation Polygons

WRITE OUT DRILLHOLE DATA THAT LIES WITHIN PODS

MODELLING PROCESS

Concept

Using Flitch Plans

Setting the Region

Model Processes

CREATING FLITCH BARS AND FLITCH INTERPRETATIONS

The interpretation of the orebody in section view needs to be transferred to a plan view interpretation for block model interpolation. This is done by creating horizontal drillhole(flitch) bars that represent the intersection of your sectional polygons at a particular plan view elevation. The following example leads you through the procedure.

Generating Flitch Bars

Load the CAD file 'pods.svy' by dragging in to 3D view.

Make sure that the front view is shown. This is easily achieved by selecting<Section View - Front> from the toolbar.

Select <Show All Data> from the toolbar to display all your drillholes and sectional ore outlines.

Select theDrillholes<Generate<Flitch Bars…from the menu to display the flitch bar dialog box (seeFigure 1).

Figure 1: Parameters for flitch bar generation

Here we are creating a IMS drillhole file called ‘bars.dhl’.

Enter “427.5”for the minimum elevation (our lowest bench was nominated as 430 in model definition, ‘gold.mod’).Note that the flitch bars must be created at the mid-bench elevation.

Enter “5.0” in the increment field, which will result in the drillhole bars being created from the 427.5m elevation, every 5.0m, within the sectional polygons.

Load the new drillhole file ‘bars.dhl’ by dragging in to 3D view.

Interpretation of Flitch Polygons

Once you have created the horizontal drillhole bar file (‘bars.dhl’) and are satisfied that it is correct, you need to interpret flitch polygons on each bench. This is done in plan-view for every bench level at which you want to interpret your orebody.

This is done at every 5.0m, viewing in plan-view, and polygons will be drawn enclosing the drillhole bars, representing the interpretation of the ore zones on that particular 5m bench.

You will need to create a polygon(s) for each bench level starting at the 527.5m RL, to the 437.5m RL, every 5m.

Change to Plan View

If you are still in section view from the previous exercise, select <Plan View- Up>from the toolbar.
Select<Show All data> from the toolbarto make sure all drillholes are displayed.
Select <View<Viewing Slice<Setup and Use Plan View Slice… from the menu to display the slice parameters dialog box (see Figure 2)

Figure 2: Parameters for plan view slice

Enter 527.5 for the RL, a search distance of 2.5 and a translation distance of 5. This ensures that the view plane is on the 527.5 RL and data that is 2.5m either side of the RL will be displayed. Whenever you press the slice in or out buttons, the window will move in or out by the translation distance.

Draw Flitch Interpretation Polygons

Right-click in the Loaded Files Pane and select <New CAD Layer…from the context menu.
Rename the file to “flitches”.
Select<Strings<New…from the menu.
Choose the Polygonradio button in the resulting dialog box. All the other fields in the dialog box can be left as is.
Create the polygon in the 3D Pane. Start with free hand drawing, then use <Tools<Snap< To a Drillhole> to accurately define the perimeters of the ore zones (see Figure 3).

Figure 3: Flitch polygon around the ore zone

Once you have finished outlining the ore for this bench save the flitch interpretation by selecting<Save> from the context menu in theLoaded Files Pane.
Move the viewing slice down to the next plane by selecting <Move Viewing Slice In> from the toolbar.
Repeat steps 3 to 7 for all the remaining flitches. You will then have a CAD file with flitches from 517.5m RL to 437.5m RL.

WRITE OUT DRILLHOLE DATA THAT LIES WITHIN PODS

The modelling processonly requires drillhole data that lies within your interpreted sectional polygons. Data outside these polygons is classified as “waste”while the data inside the polygons is classified as “ore”.

Although the modelling and interpretation of the orebody takes place in plan-view (flitches or benches), the ellipsoidal algorithm (set in the model definition) searches in all three dimensions for drillhole data to calculate the grade of a cell. To ensure the samples outside the orebody interpretations made in section view are not included (which would result in the down grading of cell values) the drillhole, or ore,data inside the polygons must be written to a new drillhole file.

Load ‘gold.dhl’ and ‘pods.svy’.The drillholes and the polygons representing your orebody for the first section should now be displayed.

Make sure you are in plan-view.

Select<View<Viewing Slice<Setup and Use Section View Slice> and draw a line to roughly indicate the required section. The section slice dialog box will then ne displayed (see Figure 4).

Refine the section slice by modifying the values in the section slice dialog box.Here we select the section at 3650N.

Figure 4: Parameters for section view slice

Select<Drillholes<Write Within Polygon… from the menu and fill in the dialog box (see Figure 5).

Figure 5: Selecting condition for samples

Select the required polygon(s) in the 3DPane. The drillholes within the polygons will be written to the drillhole file you specified.

Move the viewing slice to the next section selecting <Move Viewing Slice In> from the toolbar.

Repeat steps 6 and 7 for all remaining sections.

To end the process and finalize the drillhole file press the ‘Esc’ key.

MODELLING PROCESS

Modelling takes place in plan-viewusing the subset of drillhole data (‘ore.dhl’) within the interpolated sectional polygons and flitch plans.The combination of these two sets of data is used to update cell in an empty block model (‘gold.mod’)using the ‘ellipsoidal IDW’algorithm.

Concept

The concept of block modelling is to create regular mining units (ie. cells) that represent the oredeposit. Since the deposit has been delineated between widely spaced drillholes (25m spaced sections) the selective mining units (in this case 2.5 x 5.0 x 5.0m blocks) will have their values changed fromthe nominated waste values to an algorithmically interpolated value.

The flitch polygon interpretations of the orebody on each flitch will determine which cells will be updated by the algorithm. The subset of drillhole data, (ie. the drillhole data that lies withinthe ore zones in section) will be the database from which the algorithm will calculate the value for thecells.

Using Flitch Plans

Load ‘flitches.svy’, ‘ore.dhl’ and ‘gold.mod’ to the 3D Pane.
Select <Plan View – Top>from the toolbar.
Select <Show All Data> from the toolbar to show all flitches and drill data in the 3D Pane.
Select <View<Viewing Slice<Setup and Use Plan View Slice> from the menu and set the plane of elevation to the mid bench of the top flitch interpretation (527.5m) with a window of 2.5m. Set a translation distance of 5m (see Figure 6).

Figure 6: Parameters for plan view slice

Setting the Region

If you have more than one polygon visible then you need to define a region so that multiple polygons can be modelled in one operation. Here we require all visible polygons so choose RegionScreen Areafrom the menu.

Model Processes

Select <Model<Update Cells<Setup>to display the update parameters property sheet (see Figure 7).

Figure 7: Parameters for stratigraphy updating

Here we are operating on the 530 bench since you have set up the viewing slice for this level.

We are also operating on theblock model directly. Surface files are only used with laminar models.

Select theMethodtab and set the grade calculation method for the bench (see Figure 8).

Figure 8: Selecting grade calculation parameters

Here we specifyAll samples, length weighted, triangles weighted by area (the default grade calculation method).This ensures that the grade calculation (Ellipsoidal IDW) will search for all drillhole data displayed on the screen, irrespective of whetherthe data lies inside or outside of the polygons. This is done because you have previously written out thedrillhole data subset of ore data (ie. only data within the sectional interpretation polygons) tomodel using the quasi wireframe method of modelling.

Commence the updating process by selecting <Model<Update cells<Update> from the menu.

Move the viewing slice by selecting <Move Viewing Slice In>from the toolbar.

Select <Model< Update Cells <Setup> to change the updating bench & select only “525” from the list.

Select <Model<Update Cells<Update> to update the model cell values for that bench.

Repeat steps 4 through 6 for the remaining benches.

NOTE: The modelling process is an integration of three file formats: the IMS CAD file (‘fliches.svy’)which defines which cells for that bench will have their values changed; the drillhole data subset (‘ore.dhl’) which determines what drillhole data is used to interpolate the cell’s value; and the model file itself (‘gold.mod’).

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