Excavation of the second tube of the Pfander road tunnel in Austria is underway with the contractor, a joint venture of Beton- und Monierbau (Bemo) and Alpine Bau, using the modified and refurbished TBM from the A41 Mt Sion project in France.

The use of a TBM to drive a motorway tunnel is a first for Austria which has traditionally used the drill and blast method, said the national roads authority (Asfinag). It awarded the Euro123M (US$157M) contract to the JV in the third quarter on 2007.

The JV is to drive a 6,586m long tunnel through molasses along side the existing, east tunnel that skirts the towns of Bregenz and Lochau at Lake Bodensee in the Vorarlberg region, at the far west of Austria where it meets Germany and Switzerland. The entire length of the new, west tube link for the A14 motorway is 7.5km, and it is due to be completed in mid-2012.

The contractor bought the machine and equipment from Herrenknecht – before the manufacturer rebought the shield from the Bouygues Construction-led JV that was working last year on the twin tube, approximately 3km long Mt Sion tunnel section of A41 in the French Alps, near the Swiss border (T&TI, September 2007, p20-22).

Herrenknecht refurbished and modified the single shield TBM (previously S-333, now S-474) and the diameter remains 11.835m. The shield – named “Angelika” – is expected to advance on average 20m per day and the drive to last less than a year, then another year for completion of concrete lining work.

A key modification was to changeover from a wet grout system used at Mt Sion to the dry grout and follow-on mix for use at Pfander. The back-up system was also modified with approximately 28m added, taking the total length to approximately 200m, to provide additional facilities to work on the tunnel invert.

The existing Pfander tunnel was opened in 1980 and traffic usage is approximately 26,000 vehicles daily (24 hours). While traffic hold-ups are common on the route, which is in the main north-south route in the Rhine valley, the demand on the route is forecast to increase even more – to approximately 46,000 vehicles per day by 2020.

The total budget for the new tunnel, construction of cross passages and ventilation shafts, and refurbishment of the existing tube is Euro218M (US$278M).

Set to bore 2nd road tube at Pfander tunnel, Austria