20 DECEMBER 2024 WorldWide Drilling Resource® Blasting Near a Crusher Adapted from Information by Dyno Nobel A mine operator wanted to open up additional ore for extraction (over 3 million long tons), by blasting two benches near several mine structures including two crushers, the conveyor belt drive, and the thickener. The crushers were approximately 250 feet from the nearest blasthole while the belt drive and thickener were 800 feet and 1300 feet, respectively, from the nearest blasthole. The crushers were identified as critical structures as they were the production lifeblood of the mine. If the crushers were shut down due to any damage from blasting, revenue of the mine would be adversely affected. DynoConsult® was contacted by the local distributor to provide recommendations on how to drill and load the blastholes so there would be no flyrock and minimal blast vibrations. Several goals for the blast design were established by the mine management. A crucial goal was that rock movement from the blast should be limited so none of the mine structures would be damaged by flyrock. This was considered the most important goal for the blast design. The second goal was to minimize blast vibrations at the structures, particularly the crushers. Excessive vibrations could damage the structures, leading to extended downtime and costly repairs. The last goal was to produce a muckpile that could be dug easily by the shovels. UAV (unmanned aerial vehicle) flyovers of the blast area were conducted to provide a 3D representation of the free faces and bench surface. The 3D point cloud produced from this was used to measure the shape of the free faces. Once the shape of the free faces was quantified, it was possible to establish proper placement of the crest holes and develop a custom explosive load for each blasthole. There were two issues which provided an extra challenge to the blast design. The first was the blastholes had to be 16 inches in diameter as it was the only hole diameter available. The second issue was the bench height was short, varying from 34 to 40 feet. From the beginning of the project, it was recognized electronic detonators would be required to achieve the necessary control of the blast. Dyno Nobel’s DigiShot® detonators were used as the initiation system. Dyno Nobel’s proprietary blast design methodology was used to determine the burdens, spacings, and explosives loads for each blasthole. The specific equations used were those designed to minimize rock movement while providing adequate rock fragmentation. This was particularly important given the large-diameter blastholes (16 inches) coupled with the relatively short hole depths down to 32 feet. This combination of large-diameter blastholes with a short bench provided an unfavorable geometry for the goals established by the mine management. Finally, Dyno Nobel’s proprietary program Dyno42 was used to determine the optimum delay times to minimize the blast vibrations at the nearby mine structures. Dyno42 is a signature hole analysis software employing linear superposition of vibration waveforms. Upon seeing the blast results, the Process Manager for Drill & Blast at the operation stated, “You all are awesome and did an awesome job on the design, loading, and timing on that shot! We really enjoyed talking and learning with you all. Great job, give your team a pat on the back as they were a large reason why the blast crew was accepting and interested in the DigiShot electronic system and a pleasure to work with. We look forward to working more with you all.” There were no flyrock or blast vibration issues at any of the nearby mine structures. As a result, the mine was able to maintain its production with no downtime. The muckpile was well fragmented with reports from the shovel that it dug well. Three million long tons of ore, with a value of $72 million, were made available by the blast. EXB 3D representation of the free faces. Groundwater Week See You at Booth 780 Merry Christmas and Happy, Prosperous New Year wishes to each and everyone ~ from the WWDR Team.
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