Reserve Calculation Techniques

Using Grid Masks

Often it is necessary to calculate reserves on mineable horizons. This will usually mean burdens outside the subcrop of a seam will be mined and assigned as waste to that seam. Also, it may be practical to report burden to a seam even if that seam is missing due to some geological feature (for example a "want" or area where coal thins to below recoverable mining thickness).

In this case, Grid Calc and Rsvute allow you to specify how "masked" grids are to be treated in reserve calculation and reporting. A technique for calculating vertical reserves with burdens using grid masks is shown in Diagram 1.

Diagram 1 - Burden Calculation Using Grid Masks

The prerequisite for this reserving method is a mining model created in Grid Calc. The burden grids created are:

• all waste material called Overburden
• seam floor used even if masked
• assume no coal if masked
• carry seams to topo or grid edge

The Set Mask Mode panel should have the Ignore Grid Mask option selected. The No variables and Burden check boxes on the Report Reserves panel should also be enabled. Note that the variables list should contain all the quality variables to be included in the reserves report.

Diagram 2 shows the resulting report for Strip 01 Reserves calculated from mining burden grid (OB).

Diagram 2- Standard Report Output for Strip 01 Reserves