For Week 1 of Safety Month, ISEE focuses on the critical role of precise drilling in safe blasting. The article outlines how drilling mistakes like poor spacing, burden, or depth can lead to serious hazards. It stresses the value of detailed drill logs and strong driller/blaster communication to prevent issues before loading begins.
There is an old saying in the Explosives Industry that says: “The best blaster cannot make up for bad drilling and the best driller cannot make up for a bad blaster.”
In other words, good drilling practices go hand in hand with good blasting practices.
Imprecise drilling can create serious safety and operational issues:
- Improper spacing - If holes are too close together, it can lead to sympathetic detonation and pose a flyrock hazard. If they are too far apart, you’ll get poor fragmentation and not enough relief for the next row.
- Incorrect burden - Too little burden results in poor confinement and can cause forward-moving flyrock. Too much burden offers poor relief and increases the risk of vertically moving flyrock.
- Angled face holes - These reduce burden at the toe and floor, leading to too much face movement and likely flyrock.
- Holes drilled too long - These cause an uneven floor and excessive vibration, which may lead to License to Operate issues.
- Holes drilled too short - These also result in an uneven floor and can cause toe problems, which may require secondary blasting and reduce heave.
A good drill log is crucial. It should note actual hole depths, how much broken material is below the collar, and any voids or mud seams. This information must be reviewed with the blaster before explosives loading begins, so the blaster can make any needed adjustments to the plan.
It’s always harder, and riskier, to fix problems after a poor blast. It’s much safer and leads to better outcomes if issues are addressed before the yelling “Fire in the Hole.”
