Second tube of the Gotthard tunnel: first tunnel boring machine “Carla” at its destination

Important milestone in the construction of the second Gotthard tube: With its cutting wheel with a diameter of more than seven metres, tunnel boring machine "Carla" has been driving the access tunnel to the north fault zone into the Gotthard massif since August 2022. 3,950 m deep in the mountain, Carla arrived at its destination on 23 April 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.

Sometimes Carla, with her followers more than 200 m long, came 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.

TUNNEL CONSTRUCTION IS TEAMWORK
“It’s great that we were able to excavate the northern access tunnel on time and, above all, without any significant accidents,” says Jacopo Cheda, head of northern construction at FEDRO. Xavier von Mandach, Implenia’s site manager in charge, emphasises 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 reach this important milestone without incident. The team did a great job.”

WHAT’S NEXT
The excavation of the access tunnel, which runs parallel to the future second tunnel tube, also provided important findings for the other construction work that will be carried out in the future, which are important for Carla’s “big sister”, which will excavate the northern section 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.

The construction of the second tube will be driven 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 metres for the main tunnel.

Source: implenia.com