The Ceneri Base Tunnel completes the flat rail route through the Alps for passenger and goods traffic. After the Gotthard and Lötschberg base tunnels, the Ceneri Base Tunnel, with a length of 15.4 km, is the third-largest construction project of the New Rail Link through the Alps (NRLA) as well as Switzerland's fifth-longest railway tunnel. On 4 September 2020 the Ceneri Base Tunnel was ceremonially opened.
The portals of the Ceneri Base Tunnel are located in the north at Camorino (Bellinzona) and in the south at Vezia, near Lugano. The tunnel comprises two single-track tubes approximately 40 metres apart which are linked to each other by 48 cross-passages. With this length of tunnel, no track crossovers or multifunction stations are needed. In the area of the north portal at Camorino several bridges were constructed and, with the «Bretella», a new, direct rail connection between Locarno and Lugano was created.
The construction of the century was put into operation with scheduled train services by Swiss Federal Railways on 13 December 2020.
Except for the access adit at Sigirino, the Ceneri Base Tunnel was excavated entirely by drilling and blasting. Most of the driving was performed simultaneously in both directions from the intermediate heading at Sigirino. Inward drives were also cut from the portals at Vigana and Vezia.
Driving to the south progressed faster than forecast. In the west tube, breakthrough to the inward drive from Vezia took place on 17 March 2015, which was around 13 months ahead of the construction schedule.
In the northward drive, the miners encountered more difficulties with the rock. AlpTransit Gotthard Ltd therefore contracted the consortium of the main lot with acceleration measures. On 21 January 2016, the miners and many invited guests could celebrate the final breakthrough of the Ceneri Base Tunnel in the west tube. This took place with great accuracy: the vertical deviation was 2 cm, horizontally 1 cm.
Following completion of driving and lining of the Ceneri Base Tunnel, work began on installation in the concrete shell of the mechanical, electrical and ventilation systems without which the tunnel cannot be operated.
In order to simplify spare-parts management as well as the acceptance processes, wherever possible the same components were used for the tunnel infrastructure systems in the Ceneri Base Tunnel as in the Gotthard Base Tunnel. This related particularly to the doors, the ventilation systems, and the technical floors in the 48 cross-passages.
In two areas of the tunnel infrastructure systems there are, however, major differences compared to the Gotthard Base Tunnel: one of these is the operational ventilation, the other is the water supply and drainage. In contrast to the Gotthard Base Tunnel, in the Ceneri Base Tunnel no ventilation centre was installed. Fifty jet fans, which are mounted near the portals and in the middle of the tunnel, provide the necessary ventilation of the tunnel during maintenance and in the event of incidents. Moreover, as opposed to the Gotthard Base Tunnel, in the Ceneri Base Tunnel the groundwater and soiled water are not drained separately. Here, the much smaller volume of groundwater allows a mixed drainage system. The water-processing systems are located by the north portal at Vigana.
Railway operations in the Ceneri Base Tunnel only become possible with the railway infrastructure systems. These integrate the new track systems into the existing railway network.
Installation of the railway infrastructure systems started in summer 2017. They comprise the track, overhead conductor, electric power supply, telecommunication and safety systems, and control systems. To comply with revised Swiss Federal Railways standards for overhead conductors in tunnels, a new type of overhead conductor system was used. Instead of conventional overhead wires as in the Gotthard Base Tunnel, in the Ceneri Base Tunnel overhead conductor rails were installed.
Before scheduled train services could travel through the Ceneri Base Tunnel, all of its systems had to be thoroughly tested, test kilometres with trains carried out, and personnel trained. In autumn 2019, commissioning of the full length of the Gotthard Base Tunnel began.
First, in numerous test runs, all of the tunnel components and systems were exhaustively tested. On 29 April 2020, incremental speed tests with the ICE-S began. In the early hours of 1 May 2020, the first travel at 275 km/h – the highest speed that was tested in the Ceneri Base Tunnel – was performed. Up to the end of August 2020, 2,310 test runs with a total travel distance of 40,972 km were completed.