The consortium of Implenia (40%), Webuild & CSC SA (40%) and Frutiger (20%) launched TBM Carla in August last year to drive the access tunnel to the north fault zone into the Gotthard massif.

The group also has the Lot 241 contract for the main northern section of the Gotthard road tunnel’s second tube. It includes a 7.3km-long, 12.3m-diameter tunnel to be excavated by a TBM with tubing. The tunnel connects to a 160m-long stretch at the start, which will be excavated conventionally.

The contract also includes 430m of conventional tunnel through the northern disturbance zone, which will be excavated from the 4km-long northern access tunnel completed by TBM Carla.

The new Gotthard Tunnel runs 70m to the east of the existing road tunnel, which opened in 1980 and carries traffic in both directions. Once the new tunnel is completed, the older tunnel will be refurbished and each tunnel will have a single lane of traffic.

TBM Carla, which has a diameter of just over 7m, made an average daily advance of 17m, with a daily record of 45.4m, achieved in rather soft gneiss.

“It’s great that we were able to excavate the northern access tunnel on schedule and, above all, without any significant accidents,” said Jacopo Cheda, senior construction manager north at FEDRO.

Implenia said excavation of the access tunnel, which runs parallel to the future second tunnel tube, provided important insights for construction of the northern part of the main tube, due to start in 2025.

The joint venture will deploy four TBMs on the project. Carla and Delia are building the access tunnels, while the two larger TBMs will dig the main tunnel, working simultaneously from the north and the south.