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Construction of HS2 Northolt Tunnel cross- passages completed
TELT Italian side sees first TBM FAT ITALY, FRANCE - The first TBM for excavating the Italian section of the Mont Cenis base tunnel for the Lyon-Turin high speed rail project (TELT) recently passed its factory acceptance test (FAT). The 10.6m-diameter Herrenknecht machine,
built for the UXT consortium of Itinera, Ghella, and Spie Batignolles, is the first of two shields that will operate on the Italian section of the Lyon-Turin rail line. It is scheduled to be launched from the Chiomonte construction site in the Susa Valley in 2027. The TBM will construct the second access
shaft before continuing with the excavation of the southern tube of the base tunnel, works for which are already under way on the French side of the bi-national transport project. At peak, seven TBMs are to work on the project simultaneously, carrying out approximately 75% of excavations for the base tunnel. The dual-mode TBM is expected to
Construction of the 34 cross-passages for HS2’s Northolt Tunnel has been completed. PHOTO CREDIT: HS2/SCS JV
UK - HS2’s London Tunnels contractor, Skanska Costain Strabag joint venture (SCS JV), has completed construction of the 34 cross-passages for the Northolt Tunnel. The 13.5km-long tunnel runs
underground between West Ruislip and Victoria Road in Ealing, west London – just outside HS2’s Old Oak Common station. At its deepest point, the tunnel is 35m below ground. Northolt twin tube tunnel was
constructed using four TBMs and excavation was finished in mid-2025. The mined cross-passages
linking the twin tubes range from 6m-20m in length. Linking the northbound and
southbound main tunnels, the cross passages were constructed using sprayed concrete lining (SCL) and some required artificial ground freezing (AGF). AGF was used on 11 of the cross-
passages because of the presence of water-bearing soils with a high water table in the western section of the tunnel. This work required the team to insert freeze pipes through special tunnel segments to create a 2m-thick freeze wall to stabilise the ground before excavation could take place.
With construction of the cross-
passages completed, reinforced concrete secondary collars will be installed to form the permanent openings for doors and enable the installation of permanent fire- rated sliding doors. It is expected that all structural
works on Northolt Tunnel – the second longest on the 225km- long HS2 route between London and the West Midlands – will be completed in late 2026. The tunnel will then be readied for installation of the rail systems, such as tracks and overhead power in the coming years. HS2’s project client, Malcolm
Codling, said completing the construction of the cross- passages was an important step towards finishing the civil engineering on the tunnel. Booth Industries in Bolton is
manufacturing the doors for all the tunnels on the HS2 route. High-speed trains will pass within metres of the doors which will be capable of withstanding constant 14KPa pressure cycles, along with two-hour integrity and two-hour insulation against fire. They are being manufactured using mainly UK-made steel.
make an average daily advance of 10m. It is equipped with a hyperbaric compression/ decompression chamber for closed mode operation. The specification chosen because of varied geological conditions, high overburden, high temperatures at these depths, and tight curves in both plan and profile.
NY’s first CSO award UK - The New York City Department of Environmental Protection (NYCDEP) has selected Newtown Creek CSO Partners to provide construction supervision services for the city’s first combined sewer overflow storage tunnel and pump station project. The JV - which comprises Aecom, Parsons
and EPC Consultants - is to oversee the delivery of approximately 5.2km of tunnel and related facilities, including underground storage and conveyance tunnels, a tunnel dewatering pump station and connections to the Newtown Creek Wastewater Resource Recovery Facility.
Hochtief on Swedish rail SWEDEN - Hochtief has been awarded a contract to design and expand a 26km section of Sweden’s East Link railway line, including a series of tunnels. The OL31 Vagnhärad project, with an
estimated value of up to around SEK9.5bn (US$1bn) is being developed in collaboration with the client Trafikverket – the Swedish Transport Administration – as part of a partnership agreement. The construction phase is scheduled to
run until 2034 and the line is scheduled to open in 2035.
June 2026 | 7
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