Blasting Near Crusher Frees 3M Tons of Ore&nbsp;
Document type: Case Study
Categories: Case Study

CASE STUDY

BLASTING NEAR CRUSHER FREES 3M TONS OF ORE

ructures
including two crushers, the conveyor belt drive, and the
thickener. The immediate area around the blast location
had been mined out many years ago prior to the installation
of the structures. Now, in order to open up additional ore
for extraction (over 3 million long tons), it was necessary
to blast out two benches near the mine structures. Mine
management was concerned that flyrock and/or vibrations
from the blasting could damage the nearby structures. The crushers were approximately 250 ft from the nearest
blast hole while the belt drive and thickener were 800
ft and 1300 ft, respectively, from the nearest blast hole. 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 the blasting, the
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.

The blast site with nearby existing structures

$ PROJECT GOALS
 ELECTRONIC DETONATORS AND 3D
 MODELING
 3 MILLION TONS OF VALUE OF $72
 ORE FREED MILLION Several goals for the blast design were established by the
 mine management. A crucial goal was that rock movement from the blast
 SUMMARY should be limited so none of the mine structures would
 be damaged by flyrock. This was considered the most
DYNOCONSULT LEADS TO $72M IN FREED ORE important goal for the blast design. Dyno Nobel’s DynoConsult team worked with a metal The second goal was to minimize the blast vibrations
mine to safely and effectively blast near existing structures at the structures, particularly the crushers. Excessive
to free 3 million tons of ore with a value of $72 million. vibrations could damage the structures, leading to
 extended downtime and costly repairs. The last goal was to produce a muckpile that could be dug
 BACKGROUND easily by the shovels. However, the mine management
 was willing to accept coarse fragmentation if the flyrock
CLOSE-IN BLASTING and vibration goals were achieved. A mine operator wanted to open up ore reserves by
blasting two benches near several mine structures
including two crushers, the conveyor belt drive, and the
thickener. The immediate area around the blast location
had been mined out many years ago prior to the installation
of the structures.

TECHNOLOGY APPLIED
MINIMIZING VIBRATIONS AND FLYROCK
There were two issues that provided an extra challenge
to the blast design. The first was that the blast holes had
to be 16 inches in diameter as that was the only hole
diameter available. The second issue was that the bench
height was short, varying from 34 to 40 ft. From the beginning of the project, it was recognized that
electronic detonators would be required to achieve the
necessary control of the blast. Dyno Nobel’s DigiShot®
detonators were used as the initiation system. UAV
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 3D representation of the free faces
placement of the crest holes and develop a custom
explosive load for each blast hole. Dyno Nobel’s proprietary blast design methodology was
used to determine the burdens, spacings, and explosives VALUE ADDED
loads for each blast hole. The specific equations used
were those designed to minimize rock movement while $72M IN FREED ORE
providing adequate rock fragmentation. This was The results of the blast were what the customer requested.

position of vibration waveforms. The peak vibration level at the crushers was 0.91 in/s at a
 frequency of 15 Hz. There were no flyrock or blast vibration
 issues at any of the nearby mine structures. In fact, the
 rock movement was well contained. 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 $72M, were made available by the blast.

Disclaimer: This case study is provided for informational purposes only. No representation or warranty is made or intended by Dyno Nobel or
its affiliates as to the applicability of any procedures to any particular situation or circumstance or as to the completeness or accuracy of any
information contained herein, and, to the full extent permitted by law, Dyno Nobel expressly disclaims any liability arising from the use of this
document or the information contained herein. User assumes sole responsibility for all results and consequences. © 2020 Dyno Nobel

specific equations used
were those designed to minimize rock movement while $72M IN FREED ORE
providing adequate rock fragmentation. This was The results of the blast were what the customer requested. particularly important given the large diameter blast holes Upon seeing the blast results, the Process Manager for
(16 inches) coupled with the relatively short hole depths Drill & Blast at the operation stated, “You all are awesome
down to 32 ft. This combination of large diameter blast and did an awesome job on the design, loading, and
holes with a short bench provided an unfavorable geometry timing on that shot! We really enjoyed talking and learning
for the goals established by the mine management. with you all. Great job, give your team a pat on the back as
Finally, Dyno Nobel’s proprietary program Dyno42 was they were a large reason why the blast crew was accepting
used to determine the optimum delay times in order to and interested in the DigiShot electronic system and a
minimize the blast vibrations at the nearby mine structures. pleasure to work with. We look forward to working more
Dyno42 is a signature hole analysis software employing with you all.”
linear superposition of vibration waveforms. The peak vibration level at the crushers was 0.91 in/s at a
 frequency of 15 Hz. There were no flyrock or blast vibration
 issues at any of the nearby mine structures.

CASE STUDY