WorldWide Drilling Resource

35 WorldWide Drilling Resource ® OCTOBER 2018 Staying Safe from Flyrock Compiled by Caleb Whitaker, Associate Editor WorldWide Drilling Resource ® Blasting operations come with inherent risks. One of these risks is flyrock - debris ejected from the blast site. The debris may travel through the air or along the ground, and may be rock or soil. Any size material can damage property or injure people, so flyrock control is essential. Some of the common causes of flyrock are overloaded blastholes with exces- sive amounts of explosives; heavily confined charges; explosives loaded into incompetent materials; burdens and spacings which are too close together; inad- equate stemming material; inadequate delay between holes in the same row or between rows; detonators firing out of sequence, deviation of blasthole detonation from the intended sequence; changing geology or rock type. To prevent flyrock, consider mine conditions and rock strata when designing blasts. Accurately measure the burden for each blasthole, and be aware of the true burden for each hole along the free faces. Be aware of the powder factor and total charge-weight loaded, so holes are not overloaded. Always measure explosive quantities or tape the holes while loading. Use crushed stone for stemming and stem through incompetent zones. Place primer lower in the hole, increase delays between rows, and reduce burden in back rows. It’s important to keep coworkers away from the person doing the blasting. Schedule blasting between shifts or on off-shifts. The blast area should be a minimum of 1.5 times the farthest distance of any previous flyrock. Suitable blast shelters should be used for all personnel at the mine site during blasting, and restricted areas should be implemented for non- enclosed blasting operations. Barricades can be used for access routes to the blasting area to prevent the passage of personnel or vehicles. Effective communication between the drilling crew and the blasting crew is key. This will allow the drilling crew to convey information re- garding unusual conditions, such as mud seams, voids, or other weak layers during drilling. Maintain and use all available methods of communication, such as sirens and radios, to warn personnel of impending blasting operations. In areas of steep slopes, a rock set in motion by the explosive energy may roll hundreds of feet. This rock rolled through a trailer downslope from a mine. EXB