HS2 unveils Euston-bound TBMs
HS2 has revealed two massive tunnel boring machines (TBMs), Karen and Madeleine, ready to carve the final 7.2km of the high-speed railway from Old Oak Common to Euston. Weighing 1,250 tonnes each, the machines are set to begin tunnelling in 2025, marking a significant step forward for the UK’s largest rail infrastructure project.
The twin-bored tunnels will be constructed by HS2’s London tunnels contractor, the Skanska Costain STRABAG joint venture. The machines will excavate London clay, creating tunnels with an inner diameter of 7.55m. Once complete, the tunnels will increase passenger capacity to central London and unlock potential regeneration in the Euston area.
The tunnel boring machines (TBMs) operate like underground factories. They excavate tunnels with a turning cutterhead, line them with pre-cast concrete segments, grout the segments into place, and then move forward at an average speed of 16m per day. Teams work around the clock underground, supported by surface teams managing logistics and materials.
Rail minister Lord Hendy said, “The progress at Old Oak Common and the extension to Euston highlights HS2’s once-in-a-generation impact, improving transport links and supporting jobs and growth across the country.”
Named after pioneering women
In keeping with tradition, the TBMs have been named after pioneering women in rail and engineering. Karen honours Karen Harrison, the UK’s first female train driver, who worked at Old Oak Common depot in the 1970s. Her sister, Marie Harrison, said, “Karen would have been delighted to have this TBM named after her. It reflects her strength and perseverance.”
Madeleine is named after Madeleine Nobbs, a building services engineer and former president of the Women’s Engineering Society. Helen Close, heritage manager at the society, said, “This is a wonderful recognition of Madeleine’s contributions to engineering and her advocacy for women in the profession.”
Major progress
The 190-metre-long TBMs were manufactured in Germany and transported in parts to Old Oak Common. SCS is also advancing construction on the Northolt tunnel to West Ruislip, with more than 50% of tunnelling completed.
The final approach to Euston will feature spray concrete-lined tunnels transitioning into three smaller tunnels, enabling trains to connect to platforms. HS2 is working with the government to finalise the design of Euston’s terminus station, with further announcements expected soon.
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