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It’s in the can! – HS2 tunnelling machine finishes its 5-mile journey

20 Dec 2024
Gathering of people in a tunnel holding a sign saying 'TBM Sushila Completes 5 Mile Journey to Green Park Way' © HS2 Ltd
© HS2 Ltd

The giant Tunnel Boring Machine (TBM), named Sushila, reached the Green Park Way vent shaft in Ealing, breaking through into a reception can filled with foam concrete.

The innovative method has been adopted due to high water pressure in the ground on the site. It allows the TBM to maintain its pressure while sealant can be applied from the tunnel lining to prevent water ingress.

Once the reception can is depressurised, it will be opened, and the TBM will be lifted out.

The 8.4-mile twin-bored Northolt Tunnel is being constructed by a quartet of machines named Sushila, Caroline, Emily, and Anne. They will complete the tunnel that will carry high-speed trains between HS2’s super-hub station at Old Oak Common, west London, and the outskirts of the capital at West Ruislip.

Person walking along a concrete segment lined tunnel at the back of a TBM © HS2 Ltd

Sushila, named after a local school teacher, was the first to start and is the first to complete the journey. All four will finish their journeys at Green Park Way, arriving in a main and satellite shaft.

The Northolt Tunnel is being built by a joint venture formed of the companies Skanska, Costain and STRABAG (SCS). The same JV will also construct the Euston Tunnel eastward from Old Oak Common to the centre of London. The tunnel boring machines are made by world leading tunnelling experts Herrenknecht AG.

  • "To have had the opportunity to witness the progress of the TBM over the last 2 years has been a real honour. I am in awe of the sheer scale and incredible work of the engineers and excited for the day I will be able to take my first HS2 train journey through the tunnel".

    Sushila Hirani
    Local school teacher after whom the TBM was named

Each machine operates like an underground factory, excavating the tunnels, lining them with pre-cast concrete tunnel segments, grouting them into place before moving forward at an average speed of 16 metres per day. Teams work around the clock below ground on the TBMs along with teams on the surface supporting them.  

Launched in October 2022 from West Ruislip, TBM Sushila has excavated over 1.2 million tonnes of earth and installed 4217 tunnel rings. All the earth excavated by the machine has been placed in two areas west of the tunnel, eliminating the need to use public roads for lorry removal. These areas will be turned into wildlife meadows and wooded areas as part of HS2’s Green Corridor.