What is the minimum delay between holes when blasting one hole per delay?

What is the minimum delay between holes when blasting one hole per delay?

• A. 8 milliseconds
• B. 8 seconds
• C. 0.8 milliseconds
• D. 80 milliseconds

Answer: (A)

Staggering initiation between holes is used to control how the blast energy arrives in the rock, reducing peak ground vibration and improving fragmentation. When you blast one hole per delay, the delay must be long enough so the detonation of the first hole is already underway and its energy can start to dissipate before the next hole fires. Eight milliseconds is the minimum that achieves this balance: it’s short enough to keep the blast sequence efficient, but long enough to prevent near-simultaneous detonation that would produce higher shock and greater vibration. If the delay were much longer, you’d slow the sequence unnecessarily and potentially lose fragmentation efficiency. If it’s shorter, the blasts can behave almost as a single impulse, increasing vibrations and flyrock risk. Therefore, eight milliseconds is the best choice for the minimum delay in this setup.

Staggering initiation between holes is used to control how the blast energy arrives in the rock, reducing peak ground vibration and improving fragmentation. When you blast one hole per delay, the delay must be long enough so the detonation of the first hole is already underway and its energy can start to dissipate before the next hole fires. Eight milliseconds is the minimum that achieves this balance: it’s short enough to keep the blast sequence efficient, but long enough to prevent near-simultaneous detonation that would produce higher shock and greater vibration. If the delay were much longer, you’d slow the sequence unnecessarily and potentially lose fragmentation efficiency. If it’s shorter, the blasts can behave almost as a single impulse, increasing vibrations and flyrock risk. Therefore, eight milliseconds is the best choice for the minimum delay in this setup.