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Liebherr's tunnel vision

Liebherr puts its machines to work at Austria’s Pfander Tunnel

Scheme: Pfander Tunnel (western tube)
Client:Asfinag BMG
Contract value: £162 million

As the excavation of the second tube of Austria’s Pfander motorway tunnel undoubtedly proves, boring your way through 6.5 km of rock and soil requires some ambitious kit.

This is where Angelika comes in – an admittedly saccharine name for a 2000 metric tonne tunnel boring machine with a total installed power of 4,800 kW and a cutter head 11.92 m in diameter.

The refurbished machine was supplied by Herrenknecht and is advancing around 20m per day, creating a passage that will run alongside the existing east tunnel, which skirts the towns of Bregenz and Lochau at Lake Bodensee in the far west of Austria.

The project, which is a joint venture between contractors Beton- und Monierbau and Alpine Bau, is due for completion in mid-2012, and includes a year’s worth of concrete lining work. South German construction company Glass is supplying 19,500 lining segments over a period of 15 months. The precast elements are produced from C40/50 concrete by a Liebherr Compactmix 1.0 mixing plant 100 km away from the tunnel. Formulations include high performance flow agents and high grade cement.

Bringing methods bang up to date, the Liebherr Type RIM-M circular pan-type mixer features a mechanical agitator system, which was used in conjunction with the Litronic-MPS II microprocessor control system – an inhouse development by Liebherr-Mischtechnik.

Crawler loaders

Unsurprisingly, space within the tunnel is at a premium and a certain level of agility is required from specified plant. Liebherr’s Generation 4 crawler loaders, which can be programmed up to 10 km/h, feature a spot-turn function with contra-rotating tracks which is performed automatically in situations when a particularly tight turn is required.

In the main, the machines are removing limestone scree embedded in a compacted, silty sand. For air management, automatic dust extraction systems, particulate filters and special cab air-supply filters were applied to crawler loaders.

The stability of earth moving equipment is a core consideration within underground conditions. According to Liebherr, a weight-optimised main frame and a well-planned internal component layout ensure their crawler loaders are up to the challenge. The vehicles are equipped with a Z-pattern linkage, designed to permit high breakout forces during loading work.  

Following the completion of the western tube, the Pfander Tunnel’s eastern counterpart is set to benefit from an extensive refurbishment project. When all is complete, it is estimated that 46,000 vehicles will pass through every single day; truly a feat to be proud of.

 Number crunch:

790,000 cu m total spoil volume

7.5 km total length (including 6.5 km bored tunnel)

26,000 passage of vehicles per 24 hours in 2007 (east tunnel)

46,200 expected passage of vehicles per 24 hours in 2020 (east and west tunnels, following refurbishment of eastern tube)

2012 opening of new western tube

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