By Ashley Karen
The Second Tube JV has completed its first breakthrough on Lot 243 of the Second Gotthard Tunnel.
The consortium of Implenia (40%), Webuild & CSC SA (40%) and Frutiger (20%) launched the tunnel boring machine Carla in August last year to move the access tunnel to the north fault zone into the Gotthard massif.
The joint venture also has the Lot 241 contract for the key northern section of the Gotthard Road tunnel’s second tube. It comprises a 7.3km-long, 12.3m-diameter tunnel to be bored by a machine with tubing. The tunnel links to a 160m-long stretch at the beginning, which will be bored conventionally.
In addition, the contract contains 430m of the conventional tunnel via the northern disturbance zone, which will be bored from the 4 km-long northern access tunnel, achieved by TBM Carla.
The new Gotthard Tunnel runs 70m to the east of the existing road tunnel, which opened in 1980 and bears traffic in both directions. When the new tunnel is completed, the older tunnel will be refurbished, and each tunnel will have a single lane of traffic.
Tunnel boring machine Carla has a diameter of just more than 7m and made an average daily advance of 17m, with a daily record of 45.4m, acquired in a relatively soft gneiss.
Jacopo Cheda, senior construction manager north at FEDRO, stated: “It’s great that we were able to excavate the northern access tunnel on schedule and, above all, without any significant accidents”.
Implenia declared boring the access tunnel, which runs similarly to the future second tunnel tube, delivered significant insights for the construction of the northern part of the central tube, due to begin in 2025.
The JV will use four tunnel boring machines on the project. Carla and Delia are constructing the access tunnels, while the two larger machines will excavate the main tunnel, simultaneously working from the north and the south.
