Video | HS2 tunnelling machines reach first ventilation shaft
CM Staff
https://www.youtube.com/watch?v=HW3unjOLJSo
Two 2,000t tunnelling machines digging the HS2 tunnel under the Chilterns have completed the first stage of works, reaching the ventilation shaft at Chalfont St Peter.
The machines, named Florence and Cecilia, have now dug 3.6 miles since they launched at the southern end of the tunnels last summer.
The 78m-deep shaft at Chalfont St Peter is the first of five that will provide ventilation and emergency access. The twin tunnels will run for 10 miles – the longest stretch on the HS2 project.
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The TBMs are 170m long and dig the tunnels at the same time as lining them with concrete wall segments and grouting them in place. The work runs at a rate of around 30m per day.
More than 20,000 concrete segments, each weighing around 8.5t, have been installed so far. Factories at the south portal of the tunnel just inside the M25 are manufacturing the panels.
Align – a joint venture formed of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick – is operating the machines.
A crew of 17 people on board each machine keep them running, working in shifts and supported by more than 100 people on the surface.
Align project director, Daniel Altier, said: “Florence and Cecilia reaching our first shaft at Chalfont St Peter is a great achievement for not only the tunnelling team, but also construction team involved in excavating and preparing the shaft. In particular I would like to pay credit to KVJV and Keltbray, our supply chain partners, who have been working tirelessly over the last few months to ensure the shaft is ready for the arrival of Florence and Cecilia.”
The January/February 2026 issue of Construction Management magazine is now available to read in digital format.
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