Engineers have started assembling two massive tunnelling machines that will excavate the last 4.5 miles of the underground high-speed railway, bringing HS2 trains directly into central London. Each tunnel boring machine (TBM) weighs an astonishing 1,250 tonnes and will be launched from an underground box at Old Oak Common station. The TBMs are expected to take approximately 18 months to reach the railway's final southern terminus at London Euston.
This extension to Euston will not only bring passengers closer to central London but also increase capacity on the new high-speed line, enabling more services to various destinations across the Midlands and the North. The arrival of the line at Euston is anticipated to spur transport-led regeneration in the area, unlocking opportunities for thousands of new homes and jobs.
In line with tradition, the TBMs have been named after notable women in history. One machine is named Karen, in honour of Karen Harrison, the UK's first female train driver who worked at Old Oak Common depot. The other is named Madeleine, after Madeleine Nobbs, the former president of the Women’s Engineering Society.
The unveiling of these TBMs, the final set to be launched for the railway between London and the West Midlands, marks another significant milestone for HS2. This event coincides with the appointment of Mark Wild as the new chief executive of HS2 Ltd. Mr. Wild, the former CEO of Crossrail, will oversee the project's transition from a major construction initiative to an operational railway, with a renewed focus on cost control.
Rail Minister Lord Hendy said:
“I’m delighted to welcome Mark Wild to HS2 and look forward to working with him to successfully deliver Britain’s largest rail project sensibly and efficiently for the benefit of passengers and taxpayers.
“The sheer scale of the progress at Old Oak Common – and the benefits we will realise from taking HS2 to Euston, as confirmed in the Budget - reminds us that this is a once-in-a-generation project. HS2 will not only improve transport links for millions but unlock huge potential for growth, jobs and regeneration right across the country.”
The Mayor of London, Sadiq Khan, said:
“After so much uncertainty, it’s great to finally be working with a Government that recognises the huge importance of this scheme to London and the UK, and understands why terminating HS2 at Euston is so important. It’s exciting that these tunnel boring machines will soon be getting work underway.
“This is another example of the difference that the new Government’s approach is making in London, delivering real benefits that will help to build a fairer and greener London for everyone and deliver the change Britain needs.”
Huw Edwards, Stations Delivery Director, HS2 Ltd, said:
“We welcome the commitment from the government to build HS2 all the way to Euston and preparations to tunnel from Old Oak Common are now well underway.
“A terminus station for HS2 in the heart of the capital will provide a vital gateway for passengers travelling to and from the Midlands and North, and will undoubtedly lead to the transport-led regeneration of Euston – supporting growth in the local economy and creating thousands of new homes and jobs.”
The two 190m-long TBMs were manufactured by world-leading tunnelling experts Herrenknecht AG in Germany and were transported to Old Oak Common in pieces before being reassembled on site. This summer, the HS2 team lifted the machines into the underground station box using a 750-tonne crane. They are now being reassembled at the eastern end of the station, ready to bore to Euston.
The cutterhead of the machine, which has been optimised to cut through London clay, is 8.53m across with the inner diameter of the tunnel set to be 7.55m.
The TBMs are like underground factories, excavating the tunnels using a turning cutterhead, 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 along with teams on the surface supporting them.
HS2’s London tunnels contractor, Skanksa Costain STRABAG (SCS) joint venture, is leading construction of the twin-bored tunnel. In January 2024 the team completed a logistics tunnel from a nearby site at Atlas Road which will provide access for materials, and a route to remove the London Clay being excavated by the machine. It has also built two spray concrete-lined tunnels from which the TBMs will be launched eastwards towards Euston. Boring is expected to begin in 2025.
SCS is already well advanced with construction the Northolt tunnel – a separate structure running west out of Old Oak Common towards West Ruislip, outer London.
James Richardson, Managing Director, SCS JV, said:
“We are delighted that the Government has given the green light to delivering HS2 through to Euston, ensuring the full benefits of the new railway are realised. Over the past two years, we have continued with critical activities to ensure that we can deliver the Euston Tunnel and approaches quickly, and at the lowest possible cost.
“We are also making excellent progress on the tunnelling between West Ruislip and Old Oak Common, with four TBMs in operation, and the works well over 50% complete.”
The machines will complete their journeys underground and the outer can of the machine will be left to form part of the tunnel. The mechanical components of the TBMs will be pulled back through the 4.5 mile tunnel and disassembled.
The approach to Euston will be completed by spray concrete lined tunnels which will then transition into three tunnels, which will enable trains to be fed into and from platforms at Euston station.
Final plans for the future HS2 terminus station at Euston are still under review and HS2 Ltd is continuing to work with the Government and other stakeholders to design an affordable station design that can run HS2 services from London to the Midlands. Further details will be announced by the Government in due course.
Photo credit: HS2
