CONTINUOUS CUTTING AND RAPID DEVELOPMENT
Mining companies often need to build infrastructure outside of the mine plan. This is where
conventional TBM technology can come in handy.
In October, Rio Tinto, together with the Cheslatta Carrier and Haisla First Nations, celebrated the
launch of the tl’ughus TBM, which represented a key milestone towards completing the Kemano
Second Tunnel project for the BC Works aluminium smelter in Kitimat, British Columbia.
The 1,300 t machine was named by the Cheslatta Carrier nation after a giant snake that,
according to legend, once bored through the mountains and landscape around the nearby Nachako
Reservoir.
It will dig 7.6 km of tunnel through a mountain as part of a C$600 million ($458 million) project
to ensure long-term clean power supply for the BC Works smelter.
Rio Tinto Aluminium Managing Director Altantic Operations, Gervais Jacques said: “Launching
the tl’ughus in partnership with the Cheslatta Carrier and Haisla First Nations is an important
milestone for our world-class aluminium operations in British Columbia. Our smelter in Kitimat
produces some of the world’s lowest carbon aluminium and this project will enhance the long-term
security of its supply of clean, renewable hydropower.”
Construction of the
Kemano Second Tunnel
project is expected to be
complete in 2020. It will
supply the Kemano
powerhouse with water
from the Nachako
Reservoir, creating a back
up to the original tunnel
built over 60 years ago.
Frontier Kemper Aecon
was selected as the main
contractor for the project,
with Hatch being the EPCM.
Herrenknecht, meanwhile,
supplied the TBM.
The tl’ughus TBM will dig 7.6 km of tunnel through a mountain as
The project will see some part of a C$600 million project to ensure long-term clean power
250,000 m³ of tunnel rock supply for the BC Works smelter
excavated by the tl’ughus, while 8.4 km of an existing portion of the second tunnel (excavated in
the 1990s) will be refurbished.
Phase 1 of the project was completed in 2013 to coincide with the Kitimat Modernisation project
and involved construction of interconnections to the existing portion of the second tunnel.
material in the hardest of rocks can be somewhat
limited, according to Morrison.
And, on top of this, there are some tasks –
such as unblocking ore-passes – where
mechanised cutting cannot currently be used.
This likely means there will always be a place for
the use of explosives in mines, including in ore
production.
This analysis has led CEMI, backed by service
and supply companies, miners, government
agencies, research and academic institutions, to
investigate ways to improve the cost
effectiveness and lean the underground drill and
blast production process.
In the case of drift development, the aim is to
maximise the use of the face and enable
concurrent activities in the heading. This also
means accelerating the rate at which waste is
removed from the face or ore is removed from
drawpoints.
The project aims to do away with the four
sequential activities normally involved in drift
development – removal of blasted rock
(mucking), installation of the ground control
system (bolting), drilling the face holes and
charging them with explosives – and replace it
with one concurrent process.
The RMDP is currently split into two phases:
n The Mine Development Canopy System
(MDCS) – providing a physical barrier to the
rock-related hazards in development headings
in high-stress conditions, enabling
simultaneous activities in the heading and
effectively reducing the development cycle
time, and;
n Mucking cycle reduction – Cutting the duration
of the mucking cycle to remove broken rock
from the heading, allowing face advance
activities to re-commence.
Morrison said the company was currently
negotiating a trial for its prototype canopy
system at an underground mine in Sudbury,
Ontario, hoping it would be in place in the March
quarter of next year. If proven successful, this
should open the doors to a commercial
installation and the building of more such
systems.
Dormant demand
Miners have historically been a very conservative
bunch when it comes to adopting new
technologies, but with orebodies going deeper,
costs increasing and reserves drying up,
companies need new ways to retain their existing
production profiles.
Many of these innovations will eventually be
remotely-, or autonomously-operated, meaning
they remove people from harm’s way in addition
to reducing ventilation needs underground.
They will also enable mining companies to
access remote orebodies faster than previous;
boosting return on investment.
Fortunately for the OEMs, miners in certain
countries are starting to open their eyes to all
types of innovation – mechanical rock excavation
and rapid development technologies included –
according to Lyly.
When asked where demand from these
machines is coming from, he replied:
“Of course, companies within the traditional
mining countries – Australia, Chile, Canada, the
US, Sweden, etc – have approached us.
“Where there is fairly developed mining
methods and customers are looking at
automation or battery-electric vehicles, they also
tend to look at mechanical rock excavation. It is
everything from production machines, to ramp
access, to mine development.”
The more established companies from these
countries are the ones that have been operating
the same mines for decades and are going to
greater depths to continue with these production
rates.
They are also governed by strict regulations in
terms of diesel emissions and safety, making
them ideal candidates for such technologies.
Anglo’s Daley, who said the company’s testing
programme would continue next year and that
Anglo was considering applying mechanised
cutting technology wherever it has hard-rock
underground operations, summed up nicely the
technology business case.
“The value proposition is around speed and
safety – not just cost,” he said.
“Mechanised hard-rock cutting could, for
instance, triple the speed-to-access an orebody.
Reducing access time delivers the financial
benefit of bringing forward cash flow and
reducing the payback time on investments.
“The safety benefit is also clear.
“Besides reducing explosives use in mine
development activity, mechanised hard-rock
cutting eliminates blasting-induced damage to
rock mass, leading to safer and more stable
excavations.” IM
DECEMBER 2018 | International Mining 43