The 53km-long Terzo Valico dei Giovi rail line connecting Genoa and Milan comprises 90km of tunnelling through the mountains of northern Italy. Once completed, the new high-speed/high-capacity rail corridor will connect Genoa’s port with Europe, cutting journey times for passenger travel and freight transportation alike. It will also be home to Italy’s longest rail tunnel.
NATM is being used for a portion of the tunnelling to cope with the Argille a Palombini formation, a claystone schist with limestone lenses that features highly variable rock mass behaviours and squeezing ground among other geotechnical challenges.
Crews used Dramix® 3D 65/35BG steel fibres at a dosage of 30kg/m3 for temporary shotcrete, sprayed 15-25cm thick, as part of the tunnels’ excavation.
Opting for NATM rather than TBM excavation in this portion of the tunnel alignment enabled the construction to advance much faster in such complex geology.
Crews could work on several tunnel faces along the entire route, allowing for parallel advancement on more than 30 excavation fronts, through 24/7 uninterrupted activity.
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