Construction of the HS2 tunnels under London has hit another major milestone with the launch of the fourth – and final – machine being used to build the giant Northolt Tunnel beneath the capital.
Cutterhead of TBM Anne from the Victoria Road Crossover Box (c) HS2
The 8.4-mile tunnel will run from Victoria Road in Ealing to West Ruislip in Hillingdon – carrying trains in and out of London – and is being constructed by four huge tunnel boring machines (TBMs).
In keeping with tunnelling tradition, the fourth machine is named after a prominent woman – Lady Anne Byron. The local community around Ealing chose the name through a public vote.
Lady Anne Byron was an educational reformer and philanthropist who lived between 1792 and 1860. She established the Ealing Grove School in 1834 – England’s first co-operative school, which provided education for the working classes, in an era when it was mainly for the wealthy.
TBM Anne will bore 3.4 miles from Victoria Road in Ealing, near HS2’s Old Oak Common station, to Greenpark Way in Greenford, alongside TBM Emily which launched last month in February.
The other 5 miles of twin-bored tunnels have 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.
HS2 London tunnels map (c) HS2
The quartet of TBMs are all set to complete their journeys in 2025, when they will be extracted from the ground through giant shafts at Greenpark Way.
HS2’s London tunnels contractor, Skanska Costain STRABAG 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.
‘Anne’ is the eighth TBM that has been launched to date across the HS2 project between London and the West Midlands to build the mined tunnels for the trains. In all, almost half of the 65 miles worth of twin-bored tunnels needed for the route has now been excavated.
The TBM is one of 10 machines specially designed for HS2 and the ground through which they will bore. TBM Anne was lowered in parts into the 25m deep crossover box at the end of last year, where she was reconstructed and prepared for launch.
Malcolm Codling, HS2 Railway’s Project Client Director for the London Tunnels, said: “HS2 has reached peak tunnelling activity as we focus on delivering the HS2 route between London and Birmingham. The launch of Anne is the culmination of many years of work for the London Tunnels team and a further triumph in British engineering.”
For the Northolt Tunnel East, the tunnel drive being completed by TBM Anne, 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 brought down to the capital by train, after STRABAG reopened a freight line at the Hartlepool Dock.
The London Clay excavated by the 1,700 tonne TBM will be taken away from the Victoria Road Crossover Box site via a conveyor system, 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 to be reused in landscaping at sites in Cambridgeshire, Kent and Rugby.
The two final TBMs will construct the Euston Tunnels, taking HS2 trains into central London. 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. Following the government’s Network North announcement in October, 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.
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