Tunnelling : Road tunnels

Frejus tunnel

FRENCH-ITALIAN BORDER

FRENCH SIDE
Excavation of a 6,543-metre-long emergency tunnel parallel to the existing road tunnel. The tunnel starts on the French side of the border near Modane (Maurienne) and emerges on the Italian side of the border in the middle of the mountain range. Drilling and blasting was used for the first 653 metres, then for the following 5,890 metres a 9.2 metre diameter TBM (inner tunnel diameter 8 metres) was employed. No less than 18 shelters, 4 technical centres and 2 by-pass tunnels link up to the existing road tunnel, an average of 40 metres away.

ITALIAN SIDE
Excavation of a 6,332-metre-long emergency tunnel, 8 metres in diameter, parallel to the existing road tunnel. Two excavation techniques are being used: drilling and blasting for the first 120 metres, then a 9.2 metre diameter TBM for the following 6,212 metres. The structure also includes 19 shelters and 4 technical centres linking up to the existing road tunnel, an average of 40 metres away.

Highlight: The tunnel is being excavated using a tunnel boring machine through areas of high convergence. Cross passages are to be used to connect the emergency tunnel under construction with the existing tunnel in operation.

Contracting authority: Société Française du Tunnel de Fréjus (SFTRF)
Project management: I3S - Inexia/SNCF Ingénierie/SWS/SEA Consortium

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