SHOTPlus™ Tunnel - Powder Factor


SHOTPlus™ Variant:
KBA Summary:
This KBA describes how SHOTPlus™ Tunnel calculates powder factor in that is reported in Loading Sheets. 


Powder Factor is an expression of how much explosive is used to break a volume or mass unit of rock, as shown in the equation below. SHOTPlus Tunnel calculates uses the following units:

  • kilograms of explosive for mass, and
  • bank cubic metre (in-situ volume) for volume.

Powder factor = quantity of explosives / volume of rock

As powder factor is calculated on a hole-by-hole basis for the Blast Loading Sheet, the quantity of explosives is the charge weight specified in the design. It considers only the mass of the bulk explosive.

The volume for the hole is calculated at the point in time the hole is considered to be moving, which means holes must be timed in order to get a powder factor calculation.

SHOTPlus Tunnel uses hole timing (inclusive of surface tube delay for pyrotechnic blasts) and a breakout angle calculation that considers the void created by previously fired holes. As shown in the breakout visualisation below, the different colour areas are indicative of the variation in hole volumes used in powder factor calculations. 

As a result, this method:

  • will result in powder factor values that vary across the designed face, and
  • may calculate different powder factor values for holes with similar charge weights and geometry due to the sequence.
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