Final TBM launched for HS2 Northolt Tunnel

TBM Anne will bore 5.5km from Victoria Road in Ealing, near HS2’s Old Oak Common station, to Greenpark Way in Greenford, alongside TBM Emily which launched in February. The 13.5km Northolt Tunnel will run from Victoria Road in Ealing to West Ruislip in Hillingdon

The other 8km of twin-bored tunnels has been under construction since 2022, with TBMs Sushila and Caroline both over halfway through their journey between West Ruislip, on the outskirts of London, and Greenpark Way. The four TBMs are all set to complete their journeys in 2025.

TBM Anne – an EPBM manufactured by Herrenknecht – weighs 1,700 tonnes, is 170m long and has a 9.11m diameter cutterhead. It was lowered in parts into the 25m-deep crossover box at the end of last year.

It will install rings with an external diameter of 8.78m, an internal diameter of 8.10m, each made up of seven segments. Each segment weighs approximately 7 tonnes. The concrete tunnel ring segments are being manufactured in Hartlepool by Strabag. A new factory has been established in Hartlepool, and the segments are being transported to London by train, after Strabag reopened a freight line at the Hartlepool Dock.

TBM Anne is named after Lady Anne Byron, an educational reformer and philanthropist. In 1834 she established the Ealing Grove School – England’s first co-operative school which provided education for the working classes.

HS2’s London tunnels contractor, Skanska Costain Strabag (SCS) joint venture, has delivered an extensive programme of work for the TBM to launch at the Victoria Road Crossover Box, excavating the caterpillar-shaped box where eventually the trains will cross tracks on their way in and out of Old Oak Common station.

TBM Anne is the eighth TBM to be launched to date across the HS2 project. In all, almost half of the 105km worth of twin-bored tunnels has now been excavated.

The London clay excavated by TBM Anne will be taken away from the Victoria Road Crossover Box site via a conveyor, removing the need for local lorry movements. From there, it is transported to HS2’s London Logistics Hub at the Willesden Euroterminal site where it is sorted, before being taken by train for reuse across the UK.

In total, 10 machines are building the HS2 tunnels. Two remaining TBMs, which will eventually be used to dig the final tunnel between Old Oak Common and Euston, in central London, once the government gives approval, are still being built. They are set to be delivered to the UK later this year and lowered into the underground station box at Old Oak Common ready for launch.

SCS JV managing director James Richardson said the launch of TBM Anne was a milestone in a year of peak activity for the HS2 London Tunnels project.

“With a quartet of TBMs and over 20 construction sites all making significant progress, we are on course to deliver the high-speed line into central London, creating economic growth and opportunities at every step of the way,” he said.

Following the government’s Network North announcement in October last year, alternative funding arrangements for the delivery of Euston station are being considered. However, work is continuing with the preparations and design of the railway between Old Oak Common and Euston.