SHAFT SINKING
Sustainable sinking
Speed and safety are not typically good bedfellows , hence the reason why shaft sinking has historically been considered a dangerous mine development arena . New technology and thinking are changing that , as Dan Gleeson explains
The drive for decarbonised mining operations may lead more mine operators to go down the shaft sinking route if Alamos Gold ’ s example is anything to go by .
Earlier this year , when evaluating a third , even larger expansion of its Island underground gold mine in Ontario , Canada , it said the shaftsupported plan was expected to reduce greenhouse gas emissions by 35 % over the life of mine with the shaft connected to clean , lowcarbon intensity grid power . This would also see Island ’ s already “ industry-low ” GHG emissions per ounce fall by 31 %, Alamos said .
By transitioning from a ramp-supported operation to a shaft-equipped one , the company can skip ore to surface and truck it to the mill circuit . This means even with a 100 % boost in throughput to 2,400 t / d , the operation can remove the required need for 13 42-t-payload haul trucks out of what would be an 18-strong fleet in a ramp-supported operational scenario .
“ This contributes to the lower ventilation requirements , and significantly lower diesel usage ,” it says .
In a sustainability-conscious environment , other miners are also highlighting the benefits of choosing shafts over ramps , with OZ Minerals stating in its Wira Shaft Mine Expansion study that its Prominent Hill operation ’ s Scope 1 emissions were expected to reduce by circa- 20,000 t of carbon dioxide with the introduction of shaft haulage over diesel-powered trucking .
In the case of OZ Minerals , this was more than just a statement , with the company applying a carbon price that factored in such emissions reduction potential in the study .
If future shaft sinking work also becomes electrified – ie uses more cutting / boring technology – one can expect the sustainability tradeoff between the two vertical development methods to fall further into the court of shaft sinking .
Shaft collar construction works are now complete for the 1,329-m-deep , 7.5-m diameter concrete-lined Wira shaft at Prominent Hill
From concept to reality
While Redpath Deilmann is busy with the Shaft Boring Roadheader ( SBR ) sinking work at Woodsmith ( see Woodsmith SBRs re-start cutting process box ), it is also fielding enquiries from across the globe to use the Herrenknechtowned technology .
“ All the discussions are at various stages ,” Jochen Greinacher , Managing Director of Redpath Deilmann , told IM . “ One future deployment may even be in Germany for one of the nuclear storage sites looking at developing a new shaft .”
Other potash projects in Kazakhstan and Brazil are on this list , while the company has had conversations with a silver miner in the Americas where the mechanised sinking technology could have an application .
As mentioned in this same report last year , the company , in tandem with Herrenknecht , is working on bringing mechanised technology to more than just the soft-to-medium rock ( 100 MPa and below ) shaft sinking market .
The Shaft Boring Cutterhead ( SBC ) technology being progressed by the two companies has been
SEPTEMBER 2022 | International Mining 81