By Lynda Myer
As the fourth, and final, TBM for HS2’s Northolt Tunnel beneath London, TBM Anne has been launched and is due to excavate 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. Stretching from Victoria Road in Ealing to West Ruislip in Hillingdon, the Northolt Tunnel is 13.5km long.
The construction process of the other 8km of twin-bored tunnels has been commenced since 2022, whereas TBMs Sushila and Caroline both over halfway through their journey between West Ruislip, on the outskirts of London, and Greenpark Way. The scheduled date for completing drive of all four TBMs is 2025.
With 170m length and 1,700 tonnes weight TBM Anne is an EPBM manufactured by Herrenknecht and has a 9.11m diameter cutterhead, thata was lowered in parts into the 25m-deep crossover box at the end of last year.
Each of the rings will be made up of seven segments and they will be installed with an external diameter of 8.78m, an internal diameter of 8.10m, while each segment weighs almost 7 tonnes. The responsibility of manufacturing the concrete tunnel ring segments is up to Hartlepool and 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.
In order to commissioning at the Victoria Road Crossover Box, excavating the caterpillar-shaped box, HS2’s London tunnels contractor, Skanska Costain Strabag (SCS) joint venture, has delivered an extensive program of work for the TBM and eventually the trains are going to cross tracks on their way in and out of Old Oak Common station.
For the HS2 project, TBM Anne is the eighth TBM to be started up until now, while around half of the 105km worth of twin-bored tunnels has now been excavated for this project up to date.
Using a conveyor the London clay dug by TBM Anne will be taken away from the Victoria Road Crossover Box site and it eliminates 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.
Also the total number of machines which are building the HS2 tunnels is 10.Following that the government gives approval, two remaining TBMs, which are slated to eventually be used to dig the final tunnel between Old Oak Common and Euston, in central London, will be launched and they 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.
According to SCS JV managing director James Richardson: “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.”
Once that the government’s Network North announcement was published in October 2023, 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.
