Aggregates Manager Digital Magazine
Issue link: http://read.dmtmag.com/i/594078
Understanding the Root Causes of Flyrock OPERATIONS T he issue of fl yrock in aggregates blasting is di- minishing. "Our practices, the products we use, and our understanding of the process are all getting better," notes Frank Sames, corporate manager of blaster development for Austin Powder Co. "At the same time, though rarely, fl y- rock still does occur," he says, add- ing that three aspects that continue to present problems in surface and underground blasting are fl yrock, misfi res, and fumes. As these incidents occur, the producer or contractor must look at what the cause might be. Was it human error? Was it a problem with explosives initiation through product failure? Was there an error made in the planning phase, resulting in a systems failure? Or was it Mother Nature? "The best planning can still result in a failure, due to some un- certainty with nature," Sames says. According to Bob Archibald, pres- ident of Archibald Consulting Group, most fl yrock incidents can be traced to four root causes. 1. Insuffi cient burden: Burden is the space between blasthole rows. If there is not enough burden between the face and the front row of blastholes, fl yrock can occur. "An irregular face often will contribute to this," Archibald says. 2. Improper stemming: Stemming is material loaded into the blast- hole, on top of the explostive. Too little stemming will result in rocks launching upwards. If the blasthole is not perfectly vertical, the rocks may launch up and out toward personnel, businesses, and homes. 3. Improper timing: Timing is the sequence at which the blast oc- curs. "If, for instance, a hole in the second row shoots before the hole in the fi rst row, there is no relief for the energy, except for rock to go straight up," he says. 4. Geology: Irregularities and discon- formities in the geology, such as a clay seam, can create a fl yrock incident. "The blaster needs to know if there is a clay seam, so that he can stem through that section," Archibald says. These four top causes of fl yrock can, alternately, be addressed by experienced drilling and blasting professionals. Understanding the geology of a site means knowing the native stone structure or type in the region, and how to design a blast accordingly. The blast pattern must take into account the amount of burden, es- pecially at the face, to ensure proper blasthole placement and loading. The driller must know the exact parameters of the blast pattern — in- cluding hole depth, burden, spacing, diameter, and angle. The blaster must know the proper products to use and the correct timing of the shots. "It all speaks to the human element — with experience and communication at the top of the list," Sames says. AGGREGATES MANAGER The issue of fl yrock in quarry blasting is diminishing, due to a number of reasons, but it still can happen. Practices, products used, and the overall understanding of the process have all improved over the years to make blasting a safer undertaking. When fl yrock incidents do happen, the common perception is that the rock launch- es vertically. In reality, most damaging fl yrock launches horizontally from the face. Producers who contract their drilling and/or blasting do so because the contractor brings experience, expertise, equipment, and materials to the shot that the producer might not be able to provide in-house. That said, it is important to designate someone on staff who under- stands the best practices to monitor your contractor(s) and ensure there is the correct documentation and communication between the parties involved. 1 Prevalence is dropping 4 Monitor your contractors