The Ceneri base tunnel is an integral part of the New Rail Link through the Alps. Sally Spencer reports.
The Gotthard base tunnel is the world’s longest rail tunnel at a length of 57km, and is part of the Gotthard Alp Transit Project which aims to create a continuous flat rail link between Zurich and Milan, cutting the journey time between the two cities to 3 hours.
As impressive as that tunnel is, these plans could not be realised without its little brother, the 15.4km Ceneri base tunnel.
It’s Switzerland’s second-largest tunnel currently under construction and, along with Gotthard and the Lötschberg base tunnel, forms part of the New Rail Link through the Alps (NRLA). Ceneri tunnel is being built by AlpTransit Gotthard AG, under contract from the Swiss federal government, as is the Gotthard base tunnel. The estimated investment for the Ceneri base tunnel is CHF 2.58bn (USD 2.69bn).
It is anticipated that 270-340 trains per day will be able to travel the new route – up substantially on the 220-260 that were able to run on the previous mountain route. Trains will be able to reach up to 250km per hour. Also, once the NRLA is complete, 2,000t-loads on goods trains will be able to travel non-stop through Switzerland, without the addition of a pushing locomotive and freight transport capacity will increase from around 20 million tonnes per year to 50 million tonnes per year.
Ceneri base tunnel is in the Swiss Canton of Ticino and passes under Monte Ceneri between Camorino in the Magadino Plain and Vezia, near Lugano.
At the request of Ticino, a Locarno-Lugano link is also being implemented to serve regional traffic – travel between these two destinations will reduce from 55 to 22 minutes.
The routes of both the Gotthard and Ceneri base tunnels are curved – determined not just by geology but also by geography, such as the position of dams, access routes to construction sites, depth of the overlying rock and land use.
Despite some hold-ups, breakthrough at the southern end of the western bore was achieved in March 2015 this year, 13 months ahead of schedule and with a deviation of just 20mm horizontally and 10mm vertically from the planned alignment. A short while later, at the end of March, tunnellers broke through on the southbound eastern bore.
Breakthrough of the northern bores was planned for the beginning of 2016 although an area of faulted ground has caused delays.
The original plan in the north section was to line the tunnel after excavation had finished but, to regain time, the contractor has installed the final concrete and foil lining in tandem with excavation.
Another measure, in a shorter section, was to open a third excavation face towards the north while, in the east pipe, the drive was about 400m behind.
A further delay has been caused not by the construction works but by a dispute over the railway system tenders. AlpTransit said that while it believed that the original opening date of December 2019 was still feasible, the risk of failing to meet this target was sufficient that it felt it had to push the opening of the Ceneri base tunnel back to December 2020.
* This is a version of an article that first appeared in Tunnels & Tunnelling: www.tunnelsonline.info