These rules provide a first estimate in the absence of any better data.
→ Blasthole diameter in mm ≤ 15 x Bench height (BH) in metres
→ Bench height (BH) in metres ≥ (Blasthole diameter (D) in mm)/15
→ Burden (B) = (25 to 40) x (D)
→ Spacing (S) = 1.15 x B (This gives an equilateral pattern)
→ Subdrill = (3 to 15) x D
→ Charge length (C) ≥ 20 D
→ Stemming ≥ 20 x D or (0.7 – 1.2) x B
→ Burden stiffness ratio = BH/B: 2 to 3.5 good fragmentation
→ Stemming material size = D/10 to D/20 (Angular material with minimum fines)
Author: Dyno Nobel
