Exceptional under ground

12 May 2008

Almost invisible to the public is one of the largest construction projects in Europe in full swing deep down under the Swiss Alps.

As part of a project to improve rail transport facilities throughout Europe AlpTransit Gotthard Ltd is constructing the Gotthard section of the new rail Link through the Alps with base tunnels through the Gotthard, Zimmerberg and Ceneri mountains. It is said to be the centrepiece of the new future-orientated railway connection through the Alps that will lead to a striking improvement in the transport opportunities in the heart of Europe.

The biggest challenge on the project is to dig the new Gotthard tunnel. On completion in 2016, the 57 km long tunnel will be the longest underground structure in the world. Before that becomes reality, however, it is one of the world’s biggest construction challenges. To cut the twin tunnel through the geologically complicated rock structure, four tunnel boring machines (TBMs) are deployed.

The construction of the Gotthard tunnel is divided into five projects. Two of these, the Bodio and Faido stretches, respectively 15 and 14 km long, have been awarded to the Swiss TAT construction consortium. After completion of part of the Faido stretch, one of the TBMs had to be moved back to an underground service facility, a vast cavern cut inside the mountain, for it to be overhauled and prepared for its next assignment in the project. That required the expertise of heavy and special transport specialist Riga Baumann from Germany.

Restricted space

The Riga Baumann team had to move the heart of one of the TBMs, weighing 360 tonnes and measuring 7.60 m tall, the same wide, by 23 m long, back to the service facility through the previously cut tunnel. The restricted space and lack of manoeuvrability inside the tunnel left only some 0.50 m between the tunnel wall and the TBM for manoeuvring. It was a good application fit for the Scheuerle self propelled modular transporter (SPMT) operated by Riga Baumann.

To fit the TBM, a 22-axle line configuration was required, equipped with one power pack. Mobilising the SPMT modules was an operation as such, with the Swiss road transport weight restrictions.

Five trailer loads were required. Moving the SPMT modules deep inside the tunnel required another transfer operation on to special purpose transport vehicles used in the construction of the tunnel.

Once inside, the 22 lines of SPMT were assembled and manoeuvred underneath the TBM, which could lift itself by means of its built-in hydraulics. Once on board the Riga Baumann team needed three hours to move the 360 tonne TBM back through the tunnel, a distance of about 2.5 kilometres. Tight locations required the utmost concentration of the SPMT operator and crew. Without problems, the TBM arrived safely at its destination. The trailer hydraulics were used to discharge the machine and to put it on a higher level for the required increase of the tunnel boring diameter.

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