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Modeling Mined Out Areas in SurvCADD

This document discusses how to model mined out areas in surface mine planning using SurvCADD. It provides an example of inserting an additional surface/grid into the pre-calc model to represent the void left by previous underground mining. This separate void area is then accounted for separately in reserve calculations and can be subtracted from overburden waste volumes to provide an accurate strip ratio. Grid file utilities (GFU) are used to modify elevation and thickness grids to define the void area based on an inclusion perimeter.

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Eri Sasongko
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71 views4 pages

Modeling Mined Out Areas in SurvCADD

This document discusses how to model mined out areas in surface mine planning using SurvCADD. It provides an example of inserting an additional surface/grid into the pre-calc model to represent the void left by previous underground mining. This separate void area is then accounted for separately in reserve calculations and can be subtracted from overburden waste volumes to provide an accurate strip ratio. Grid file utilities (GFU) are used to modify elevation and thickness grids to define the void area based on an inclusion perimeter.

Uploaded by

Eri Sasongko
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOC, PDF, TXT or read online on Scribd
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SurvCADD Tip: Modeling mined out areas

When a surface mine pit is laid out through underground mine workings, the planner
knows to discount for the coal that has been mined. But to properly calculate the strip
ratio the volume of the void left from underground mining should not be considered
waste volume. In order to account for the void area separately you can simply insert
another surface in your pre-calc that represents the original surface of the floor or roof
grid that was modified with either grid file utilities or limit lines.

Case 1: Using Grid File Utilities

Mined Out Area Example

Drillhole

Void Fence Polyline


Area

Inclusion Perimeter

Grid Limit

The drawing above illustrates a simple test case to show this technique.
The Drillhole Datasheet screen capture below shows the data used to model from:
The Pre-calc grid below shows the additional grid inserted to define the void.

The GFU Macro that zeros out the thickness grid of the C1 strata inside the inclusion
perimeter is:
A=LoadFrom(C:\Carlson\Knowledge Base Articles\C1_THK.GRD);
A=0.0000; PERIM(C:\Carlson\Knowledge Base Articles\Mined_out_area.pln)
SaveAs(A,C:\Carlson\Knowledge Base Articles\C1_Void.grd)

The GFU Macro that updates the precalc grid for the mining void:

A=LoadFrom(C:\Carlson\Knowledge Base Articles\C1_ELV.GRD);


B=LoadFrom(C:\Carlson\Knowledge Base Articles\C1_VOID.GRD);
A=A+B
SaveAs(A,C:\Carlson\Knowledge Base Articles\OB_Mod.grd)

Drawing the Fence Diagram we see that the roof of the coal drops to the floor in the
space of one grid cell:

OB

Void C1
IB
C2

When we run the Surface Mine Reserves against the pre-calc grid with the additional grid
inserted to represent the void we obtain the report below:

Stone Non-key Strip


Strata Tons C.Y. ratio Thick Area S.F.
OB 5330555.9 100.00 1439250.1
OB_VOID 48166.7 5.00 260100.0
C1 235830.0 22.8 5.00 1179150.1
IB 2665278.0 50.00 1439250.1
C2 266527.8 5.00 1439250.1
varies 235830.0 8310528.3 35.2 165.00

As you can see below, there is a separate line accounting for the volume of the void
caused by underground mining. It is added to the other overburden volume in this output
but it can easily be subtracted from the overburden by removing it from the cell, yielding
an accurate strip ratio estimate. I am confident that a similar technique can be used with
Strata Limit Lines where an additional grid is inserted in the pre-calc to account for the
void.

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