Topics and projects

Second tube Gotthard Tunnel: first tunnel boring machine "Carla" at target

Important milestone in the construction of the second Gotthard tube: With its cutting wheel with a diameter of more than seven meters, tunnel boring machine "Carla" has been driving the access tunnel to the north fault zone into the Gotthard massif since August 2022. 3,950 meters deep in the mountain, Carla arrived at its destination on April 23, 2023. A team of 120 people from the Implenia-led consortium "secondo tubo" (Implenia 40%, webuild & CSC SA 40%, Frutiger AG 20%) Lot 243 had worked around the clock for this, in three shifts and without accidents. Together they excavated around 370,000 t of rock for the client, the Federal Roads Office FEDRO.

record of 45.4 m per day

Sometimes Carla, with its trailers, travelled more than 200 m slowly, sometimes much faster than planned, depending on the nature of the rock. On average, Carla covered about 17 m per day. Her record performance is 45.4 m per day, achieved in rather soft gneiss.

Tunneling is teamwork

"It's great that we were able to excavate the northern access tunnel on schedule and, above all, without any significant accidents," says Jacopo Cheda, Senior Construction Manager North at FEDRO. Xavier von Mandach, Implenia's site manager in charge of the project, emphasizes the good cooperation: "Tunnel construction is always teamwork. Our team, consisting of several companies and colleagues from many nations, has a great deal of experience and works in a highly professional manner. Together, we were able to successfully master the technical challenges and achieve this important milestone without incident. The team put in a great performance."

Where to go from here

The excavation of the access tunnel, which runs parallel to the future second tunnel tube, also provided important insights for the other construction work to be carried out in the future, which are important for Carla's "big sister", which will excavate the northern part of the main tube from 2025.

In August 2022, FEDRO awarded the "secondo tubo" consortium with Implenia (60%) and Frutiger (40%) the contract for the northern main lot (Lot 241) of the second tube of the Gotthard road tunnel. The construction period for the 7.9 km long tunnel section up to the lot boundary in the middle of the tunnel is scheduled until 2029.

Construction of the second tube will proceed simultaneously from the north and from the south. A total of four TBMs will be used for this: two smaller ones (Carla and Delia) for the two access tunnels and the two large ones with a shield diameter of over twelve meters for the main tunnel.