A Volvo paver was adapted to suit conditions nearly two kilometres below ground in the world’s largest iron ore mine.
The discovery of a massive iron ore deposit led to the birth of the Arctic town of Kiruna. Located 300km north of the Arctic Circle in Swedish Lapland, Kiruna 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 largest and most modern underground iron ore mine in the world. A railway and road network snake their way to a depth of 1,542m below ground and Kiruna is literally a town on the move. Over the next two decades, part of the town’s population will be relocated to new homes, built around a new town center to allow the mine to expand.
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 located 17km away from the mine before being transported underground to the paving team. According to Enlund, their task was made easier with the arrival of a Volvo Construction Equipment (Volvo CE) P7820C tracked paver.
“We used to work with a wheel-equipped paver,” says Enlund. “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 through 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 the new Volvo paver is powerful enough to push 55-tonne mining trucks, delivering asphalt to the tunnel up slopes with a gradient of 7%.
When LKAB contracted NCC Roads – one of the leading construction and property development companies in the Nordic region – to carry out underground paving and road repairs in the Kiruna mine, the company contacted authorized Volvo dealer, Swecon, to check if they could offer suitable equipment.
Volvo CE immediately provided 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. 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,” explains 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%. 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% 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 claims the paver made all the difference to his team’s work. “When the equipment is unreliable, it really raises everyone’s pulse. This paver provides a whole different sense of confidence that we can carry out the work efficiently and without disruption.”
Whilst the operators are pleased with the paver, the biggest challenge, says Pettersson, is moving it at the end of a work shift because that is a slow process. And since the paver is being used in unusual and tough conditions, proper maintenance is imperative.
“We’re currently leasing the machine from Swecon and since they have a workshop here in Kiruna, the service is excellent. They can send out specialist service personnel fairly quickly which makes a huge difference. In the past, we used older machines and the closest service staff were located in Umeå, seven hours away.”
Apart from laying a 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 under-ground this year, which is probably the largest amount ever in the history of an underground mine,” says Pettersson. “We would like to keep using the Volvo paver as it will be useful for road maintenance and there is a constant market underground.”
By Nathalie Rothschild / photographs by Jonathan Nackstrand.
Picture 1: The P7820C paves the underground network.
Picture 2: Manoeuvring around tight corners and tunnel entrances.