Historic breakthrough for HS2’s longest tunnel

Historic breakthrough for HS2’s longest tunnel
© HS2

Giant tunnelling machine - called 'Florence' - completes 16km journey under the Chilterns in 2 years and 9 months.

The massive 2,000-tonne tunnel boring machine (TBM), named 'Florence', is one of 10 machines that will bore the 51.5km tunnel on the new rail link between London Euston and Birmingham.

"This groundbreaking moment for HS2 demonstrates the significant progress being made on the country's biggest infrastructure project, with Florence paving the way for faster, greener journeys between London and Birmingham, while supporting hundreds of jobs and apprenticeships along the way," said Rail Minister Huw Merriman.

The twin-bore Chiltern Tunnel, which runs from the South Portal near the M25 to South Heath in Buckinghamshire, has been built using two identical TBMs. Parallel tunnels will carry northbound and southbound trains with a second TBM, named 'Cecilia', due to break through in the coming weeks.

Designed specifically for the geology beneath the Chilterns, each TBM is an underground factory - excavating the tunnel, lining it with 56,000 precast concrete segments and grouting them in place as it advances at an average speed of 16m per day.

"When complete, HS2 will dramatically improve journeys between our two biggest cities and also free up space on the existing main line for more local trains," said Jon Thompson, Executive Chairman of HS2.

Each TBM is operated by a crew of around 17 people working in shifts to keep the machines running 24 hours a day, seven days a week. They are supported by more than 100 people on the surface who manage the logistics and keep the tunnelling operation running smoothly.

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