Case study: Volvo CE paver adapts to life underground
A Volvo CE tracked asphalt paver has been adapted to suit conditions nearly two kilometres below the frozen Arctic in the world’s largest iron ore mine, writes NATHALIE ROTHSCHILD.
The discovery of a massive iron ore deposit led to the birth of the town of Kiruna, 300km north of the Arctic Circle in Swedish Lapland. It sits atop a giant slab of pure magnetite that plunges 4km into the ground, is 2km deep and has an average width of 80m.
Mining began in 1898, first via open pits. In the early days, miners transported the ore in horse-drawn carts. It was not until the 1960s that Sweden’s state-owned mining company Luossavaara-Kiirunavaara Aktiebolag (LKAB) switched to underground mining.
Today, Kiruna is home to the world’s largest and most modern underground iron ore mines, with railway and road networks that snake their way to a depth of 1,542m below ground level.
More expansion is planned, which means part of Kiruna’s population will have to move relocated to new homes, built around a new town centre, over the next two decades.
Foreman Mathias Enlund leads a team of seven asphalt-paving professionals who are laying the mine’s 400km underground network of roads. The asphalt is mixed at a site 17km away from the mine before being transported underground to the paving team.
Enlund says their task was made easier with the arrival of a Volvo Construction Equipment (Volvo CE) P7820C tracked paver, which has a paving width of 11m.
"We used to work with a wheel-equipped paver," Enlund says. "But now we never get stuck because this machine is track-equipped and very reliable. The work doesn’t get held up and it’s reassuring that it’s equipped with a clean combustion engine with low noise and efficient fuel consumption."
Like the rest of his team, Enlund works four days a week for the entire summer season, from May to October. Asphalt is laid between June and September and it was early this year when the team switched machines. Almost all the paving is uphill, and one immediate benefit the team found was that the new Volvo paver was powerful enough to push 55-tonne mining trucks, delivering asphalt to the tunnel up slopes with a gradient of 7 percent.
When LKAB contracted construction and property development company NCC Roads to carry out underground paving and road repairs in the Kiruna mine, the company contacted Volvo dealer Swecon to check if it could provide suitable equipment.
Volvo CE recommended the P7820C, which was then modified and taken nearly 1.5km below ground – a journey that took several hours since the paver runs at a maximum speed of 4km per hour. Despite this, the whole process – from the first phone call to first asphalting – took just 10 days, which included the time to modify the paver.
"The P7820C had to be adapted to suit the particular conditions that exist down the mine," says Svante Bodare, a product specialist for road machinery at Swecon. "The underground tunnels are dark, the ceilings are low and the roads have a near constant gradient of 7 percent.
"So we removed the roof of the paver, the exhaust pipe was shortened and extra lights were mounted on the machine. In this country, 98 percent of paving is done above ground and with wheel-equipped machines. We also tend to transport those machines between job sites with the help of trucks, but in the mine they drive the P7820C between the paving sites."
NCC Roads site manager Johan Pettersson says the biggest challenge for the team is moving the paver at the end of a work shift because it is a slow process.
Apart from laying this massive road network, the Volvo paver is also being used in the construction of new underground offices, service stations and garages. Iron-ore extraction is currently taking place at around 900m, but the P7820C has been down to 1,480m, where it has literally been paving the way for future operations.
"Around 20,000 tonnes of asphalt has been laid underground this year, which is probably the largest amount ever in the history of an underground mine," Pettersson says.
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