Bigger blasts better for mines, says consultant
BIG BLAST Large-scale blasting allows for the mining process to start sooner as only one blast has to be performed
EMPHASIS ON BULK EMULSION Over 90% of Blast Consulting Services’ blasts are conducted with bulk-emulsion explosives
To ensure that mining pits are cleared in one blast, instead of being cleared before several smaller explosions are required, mining companies need larger volumes of explosives, in the region of 75 t to 150 t, says local specialist blast consulting firm Blast Consulting Services.
MD Marco Olivier tells Mining Weekly that larger blasts are significantly more cost-effective to undertake, as the logistics required for smaller blasts are equal to the logistics required for large blasts.
“The difference is that multiple smaller blasts have to go through the same procedures as with just one large blast,” highlights Olivier, adding that large-scale blasting therefore allows for the mining process to continue for much longer intervals between blasts, not requiring the clearing of the pit and the evacuation of all production machinery numerous times for the same amount of blasted material that would be available from numerous smaller blasts.
He adds that, if a mine is based near a community that is unhappy with a mine, particularly regarding its blasting activities, then that mine should ensure that larger blasts are undertaken to avoid unnecessary additional blasting.
“Sending out blast notifications to the community every day has a much bigger negative reception from the community than receiving a blast notification maybe once a week, or once every second week,” says Olivier.
Blasting Technology Patterns
Olivier tells Mining Weekly that 90% of the blasts the company performs are conducted using bulk-emulsion explosives. For shallow holes and presplitting blasting, Blast Consulting uses blasting cartridges, even though Olivier says contractors are increas- ingly starting to use bulk emulsions in shallow holes.
He explains that cartridges are significantly more expensive than bulk emulsions, but says there will always be a market for cartridges in the blasting sector, particularly mines with shallow holes that are between 1 m and 2.5 m deep, such as in coal and reef blasting.
“Still, the use of cartridges is more time consuming for blasters and labour intensive, as all cartridges have to be loaded separately and 25 kg cartridge boxes need to be carried to the blasting block, which is another reason why bulk emulsions are increasingly being used for shallower holes,” he states.
Industry Development
Over the past ten years, the use of seismographs to accurately record ground vibrations and airblasts during a blast has become standard practice for blasting contractors, owing to increased levels of environmental impact awareness, says Olivier.
He adds that the use of seismographic information is important, as many people living near mine sites claim that their houses are being damaged by the blasting activity at the mine site.
“The readings on the seismograph will show whether the structure could have sustained damage from a particular blast,” says Olivier.
Blast Consulting
Olivier says many civil blasters that undertook mine projects in the past are no longer willing to take the risk of performing mine blasting, “as they recognise that mine blasting requires specialised skills sets, which are much different from blasting trenches and civil projects”.
As a result, Olivier does a significant amount of blast-pattern-design consulting for mines.
He says mining companies often ask him to consult on a project when they have specific challenges, such as rock fragmentation or high-wall instabilities.
However, over the past three years, the majority of Blast Consulting Services’ project work has revolved around production blasting.
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