Create Ratio and Burden Grids
Use Create Ratio and Burden Grids to create midburden, overburden and strip ratio grids making reserving simpler and faster. It is the only way to force Rsvute to calculate burden values outside of coal regions, such as areas where a strip extends beyond the edge of coal because of mining considerations.
Instructions
On the Grid Calc menu, point to Composite Models, and then click Create Ratio and Burden Grids to display the Burden Grids panel.
Horizons
All horizons
Select this option to consider all seams when calculating burden grids.
Ignore unspecified horizons
Select this option to ignore unspecified horizons. It will be as if they were not part of the stratigraphic sequence. If this option is not selected, the thickness will be calculated using the unspecified seams.
Select this option if you want to ignore all seams in the calculation of burden grids.
Horizons
Enter the horizons. This section is only applicable when you have chosen to ignore unspecified horizons.
Roof variable
Specify the roof variable (usually SR).
Floor variable
Specify the floor variable (usually SF).
Topography horizon
Specify the horizon for the topography (usually TOPO).
Topography variable
Specify the variable for the topography (usually TP).
Burdens
Call all material overburden
Select this option if the separation between midburden (interburden) and overburden is unnecessary. Material isn't classified and all burden for a seam (whether it is midburden or overburden) is grouped into one thickness grid called OB (overburden).
Midburden/Overburden Distinguished
All Material Called Overburden
Make burdens mutually exclusive
Select this option to force Midburden and Overburden thickness values to zero where they are masked, that is, outside their regions. If this option is not used, then the grids are 'continuous' and the values in the masked areas are not zero. Keep in mind, that having zero values in the masked region may cause smooth contouring problems. Smooth contouring expects a grid to be continuous (that is, have no sudden and dramatic value changes) throughout the unmasked area and between the masked and unmasked regions. Also, depending on the options used, Rsvute may report overburden values even if the overburden grid is masked. To prevent unwanted reserves, select this option if you are distinguishing between midburden and overburden values.
None
Select this option if you don't want to specify a method for handling midburden and overburden. Burden grids are still created when using this option.
Use seam floor even if masked
In the default mode of operation, burdens are carried upwards to the first unmasked surface. If a seam has 'holes' (washouts, burnouts etc.) the waste in these masked regions is assigned to a lower seam as burden. You can overwrite this default by checking this check box.
The burden material is then limited by the masked portion of the upper seam. You must be sure that the masked portions of your grids have valid interpolated (or extrapolated) values. If you do check this check box, then you can choose to treat the coal thickness in those regions as zero (see the Assume no coal if masked option).
Default Burden Calculation
Use Seam Floor Even if Masked
Assume no coal if masked
Select this check box to set the coal thickness values in the masked portions of grids to zero. If this check box is not checked, then there may be an overall material loss - depending on how the reserves are reported.
Default Burden Calculation if Seam Floor is Used
Assume No Coal if Masked
Carry masks to topo or grid edge
Select this check box to extend the burden masks beyond the coal seam mask. This is important if the seam floor is used and the mine plan extends beyond the edge of coal
. 
Default Burden Extent
Burden Extent if Carried to Topo or Grid Edge
To reserve overburden grids that extend beyond the seam limit, use the Set Masked Nodes to Zero mode in Rsvute.
Create strip ratio grids
Select this check box to create grids of 'volume/tonnage'. Two factors are required to generate the strip ratio: (1) Coal Density, and (2) Volume Ratio. If the strip ratio grids will be contoured, make sure that Grid Fill is applied to each grid beforehand.
Global coal density factor
Enter the coal density factor. This is a number that converts raw volumes to tonnages. In metric units this will be commonly set to 1.4. In imperial units, the density will typically be measured in tons per cubic foot for which 0.04 is a suitable density.
Volumes are always multiplied by the density to give tonnages.
Coal density variable
This optional field, which is only available when using the Create strip ratio grids check box, to specify the variable that will be used when trying to obtain a density at a grid point. Density grids must have the same dimensions and spacing as the roof of the segment being implemented.
Strip ratio volume to raw unit volume
Enter the ratio to be used to convert raw volume units to a suitable volume for the stripping ratio. In metric units this will be set at 1 for cubic metres. In imperial units the volume ratio is 27. There are 27 cubic feet per cubic yard - the standard stripping ratio volume.
Raw volumes are divided by the volume ratio.
Coal thickness variable
Specify the thickness variable to use (usually TK).
Cumulative ratios
Select this option to calculate the cumulative stripping ratio grids.
Cumulative Ratio
Assume overlaying seams mined
Select this option to calculate the incremental ratio grids.
Incremental Ratio
Click OK.
The grids are then calculated. We recommend that you save the modelling parameters used when creating the burden and strip ratio grids.
