On April 8th, 2024 construction of the new HS2 line has hit another major milestone with the launch of the fourth – and final – machine being used to build the Northolt tunnel, length 13.52 km (8.4-mile), beneath the capital from Victoria Road in Ealing to West Ruislip in Hillingdon. 

The name of the fourth machine was chosen by the local community around Ealing through a public vote. The TBM is named after Lady Anne Byron, 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 the 5.47 km (3.4 miles) last section of the Northolt Tunnel East 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 8 km (5 miles) 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 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 104,61 km (65 miles) worth of twin-bored tunnels needed for the route has now been excavated. 

The TBM EPB Anne - weighs 1,700 t, its length is 170 m and it is 9.11 m in diameter -  she was lowered in parts into the 25m deep crossover box at the end of last year, where she was reconstructed and prepared for launch. 

During the tunnelling the TBM will install concrete rings - made up of seven segments weighing approximately 7t each - with an external diameter of 8.78m, and an internal diameter of 8.10m. 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 t 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 for beneficial reuse across the UK. 

The TBM was manufactured by Herrenknecht in Germany. It is one of 10 machines specially designed for HS2 and the ground through which they will bore. Two remaining TBMs, which will be used to dig the Euston tunnels - the last of HS2’s project -between Old Oak Common and Euston, in central London, 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. 

When complete, HS2 will improve connections between London and the West Midlands, with trains running further north on existing lines. Building a wholly new railway will create quicker and far more reliable journeys, driving economic growth while crucially freeing up space for more local trains on the most congested southern end of the existing West Coast Main Line.

For further information please click here for a video, here and uk/65 for the tunnelbuilder archive. Visit https://www.hs2.org.uk/. 15/24.