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Moving in the mountains

One British contractor has broken into the lucrative Swiss tunnelling market with a £200M contract. Steve Turner reports.

For years British contractors have been sent abroad to work on major international projects.

But few contracting staff can ever have been sent to a more idyllic setting than this.

And when one of the tunnel team leaders says his foreman is a ski instructor who owns a vineyard, you realise why Balfour Beatty is happy to be here.

Balfour Beatty is part of the Arge MaTrans joint venture constructing the near 10 km Steg/Raron section of the 34.6km Lotschberg tunnel.

In 1998 the Swiss electorate voted in a referendum to spend more than £12bn to upgrade the railways. The Lotschberg tunnel formed £1.2bn of that.

Running from Frutigen in the north to Raron in the Valais region, the tunnel aims to provide a faster route for both passengers and freight through the Alps. It is also intended to reduce the growing amount of heavy traffic on the region's roads and connect Switzerland to the European high speed rail network.

BLS Alptransit has been commissioned by the Swiss government to implement design and construction of the project.

Andreas Siegrist of BLS explains: 'At present there is only a slow railway to serve that region. The train has to snake its way through the mountains. We needed a fast route for traffic travelling north-south across Europe to take the heavy lorries off the road.'

Of the tunnel sections Balfour Beatty is involved with, two will be driven by tunnel boring machine and one, the shortest, by traditional drill and blast.

At Steg, work on the 8.5km length got under way at the start of October. The massive 9.4m diameter TBM is getting into its stride and edging toward 20m of drilling a day. Nearly 150m long, the machine is of the gripper type, where transverse hydraulic rams act against the rock walls and push the monster forward.

A system of conveyors transports the hewn rock out of the tunnel to a processing plant where stone is recycled for use as aggregate in concrete.

A team of 15 tunnellers man the TBM, working round the clock in eight hour shifts.

Balfour Beatty shift engineer Dietmar Reuter explains that the TBM uses laser guidance to work to a tolerance of 110mm.

The tunnel is being driven at a relatively low altitude to keep gradients to a minimum and enable higher train speeds. But this means the temperatures in the tunnel are gradually rising and will rise past 35degreesC, believes Reuter. An efficient air conditioning system has therefore had to be put in place to make working conditions bearable.

Geologically, the area is good for tunnelling, the rock being a mixture of granite, granodiorite and limestone. The TBM at present is cutting through this 'like cheese', Reuter explains, leaving a smooth finish to the rock surface, a characteristic he hopes will continue.

Water expandable rock bolts are being used to strengthen the tunnel, with steel support mesh bolted onto the tunnel lining to protect the miners underneath.

Sprayed concrete is then used as an initial lining to support the tunnel integrity.

A permanent 250mm concrete lining will be cast in situ along the tunnel length, once all the tunnelling is complete in approximately two and a half years time.

Just a few hundred metres to the east work on Raron's double portals is still in the early stages.

The shorter length will be constructed using traditional drill and blast methods starting next February. Meanwhile, a second TBM is being brought in for the 10km length due to start in April.

Blasting into the mountainside has begun at the start of the shorter length, while support beams are being cast at the entrance to the 10 km section.

Space is the biggest constraint at the Raron portals, as Balfour Beatty team leader Mike Grace explains. 'The working area is tight. The River Rhone acts as a very tight border to the site and the privately owned concrete plant on the site has to remain in operation.'

So although there can be no excuses for the late delivery of concrete, careful planning is essential.

Balfour Beatty is in the process of tendering for further work on the longer Gotthard tunnel further to the east. Malcolm Lorimer, Balfour Beatty commercial manager, is hopeful that further work will be won, explaining: 'we are very actively tendering for further contracts'.

The client seems happy with Balfour Beatty and the staff are more than keen to stay. It is easy to see why.

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