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Biel Tunnel East Branch

Photo: Biel Tunnel East Branch: Group picture with workers in front of the TBM at the breakthrough
Facts and Figures
Company PORR Bau GmbH and PORR SUISSE AG in a consortium
PrincipalCivil Engineering Authority of the Canton of Bern
LocationBern - Switzerland
Type Tunneling
Runtime10.2007 - 11.2015

New table-type bridge structure allows rail operations to continue uninterrupted

With the new link between Solothurn and Neuchâtel, the Biel motorway bypass closes one of the last gaps in the Swiss road system. The new section of tunnel around Biel connects the A5 motorway with the A16 Transjurane and T6 in the direction of Bern.

A passage had to be built under the railway tracks of the Swiss federal railways in Bözingenfeld. This was achieved with the help of an innovative, table-type bridge structure. This supported the tracks, which are just three metres above the road tunnel and involves pipe-roofing constructed with the drive-pipe method, the sides of which rest on diaphragm walls.

Once all of the open-cut sections were completed, the tunnel boring machine was installed. The rear back-up units were made to slide down to the tunnel level, on a slipway from the previously constructed Bözingenfeld waterproof concrete tank. After the breakthrough of the Büttenberg Tunnel, the complete TBM was transferred to the nearest portal of the Längholz Tunnel by means of special lift and pulling equipment. 

Finally, the eleven cross-cuts linking the two tunnel tubes were driven with the support of watertight ground blocks, and artificial ground freezing in zones of unconsolidated sediments.

Construction facts:

  • Expansion of the two twin tunnels using hard-rock and earth-pressure tunnelling with segmental lining and final lining using a multimode shield (diameter: 12.60m, cross section: 124.69m²)
  • Tunnel lengths: Büttenberg Tunnel: two times 1,230m, Längholz Tunnel: two times 2,330m
  • Building four open-cut excavations and tunnels at the tunnel portals