To calculate the charge per hole for optimal fragmentation, the main approach involves determining the amount of explosive needed based on several key mining and rock parameters.
Basic calculation steps
- Determine hole diameter (d) and calculate its cross-sectional area given by the formula: A = (π × d × d) / 4.
- Select explosive density (ρ), typical values depend on explosive type (e.g., ANFO ~850 kg/m³).
- Estimate charge length (L) in the hole, which depends on factors like bench height, rock hardness, desired fragmentation, stemming length, and blasting pattern.
- Calculate charge mass (m) by using the formula: m = A × L × ρ
Considerations for optimal fragmentation
- The charge should adequately match the rock volume to be fragmented in each hole.
- Powder factor (mass of explosive per volume or weight of rock) is adjusted based on rock strength, lithology, and fragmentation objectives.
- Other blast parameters like spacing, burden, stemming, and hole depth also influence optimal charge calculation.
- Advanced methods integrate 3D lithology models to calculate explosive charge for varying rock types within the blast mass for enhanced cost efficiency and fragmentation control.
This approach balances fragmentation quality, cost, and safety. The equation and method are widely adopted in blast design with adaptations based on specific mining conditions and desired blast outcomes.
