This article is to help explain how blast volumes are calculated in BlastIQ™ Insights, the most common cause of incorrect blast volume calculations, and how to remedy the blast volume calculation in SHOTPlus™.
Background
The most common cause of incorrect blast volume calculations between design vs actual is due to blasts being designed without a bench surface, and designed to the default elevation of 0m.
The Single Blast - Quantities Dashboard KBA details how the blast volumes are calculated in BlastIQ™ Insights. Briefly, the calculation uses the voronois tessellation algorithm for the surface area at the hole collars (actual) and the grade point of the hole (design length - subdrill). The grade point is determined from the design location of the holes.
When holes were designed at an elevation of 0m, the grade used for the volume calculation is actually below this. When drilling actuals are imported against a blast, and the hole collars are set to the actual elevation, the actual hole collar is generally much higher than 0m, and this is why the calculated blast volume is ending up much larger than expected.
Solution
In SHOTPlus, create a new bench surface from the collars of the holes with drill actuals
- Import actuals into SP
- Make sure Hole collar Actual is checked in the Visibility Manager
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- Select all blast holes then go to Tools -> Surfaces -> Create surface
- With Bench surface selected, select OK
- With the newly created surface selected, go to the Surface Manager, make sure Drill bench surface is selected, and select Register Surface
With the bench surface now created and registered, it is time to re-project the design of the holes onto the new bench surface. This will place the hole grade at the correct RL, and make the volume calculation in Insights more accurate.
- Select all holes, right-click and select edit.
- Go to the Drilling Tab, and ensure Drill from bench surface is selected
- Select the Loading Tab (1), select Clear actuals (2), and just select Drill collar and toe (3). Select OK (4). Select Apply (5).
All holes will now have their design collar RL, and Grade RL set correctly. You will now have to export the blast back to BlastIQ. This will update these values in BlastIQ, and the blast volume calculation will correct itself.