The UK’s HS2 Ltd has confirmed that HS2’s main works contractor, Align – a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick using TBMs ‘Florence’ and ‘Cecilia’ have passed the halfway point on their 16km journey under the Chilterns, the project’s longest tunnels.
The 10.2m diameter Herrenknecht TBMs have spent the last 18 months excavating the twin tunnels between the M25 and South Heath in Buckinghamshire that will help protect the environment while improving connections between London, Birmingham and the North.
The crews have also completed the excavation of five shafts that will provide ventilation and emergency access near Chalfont St Peter, Chalfont St Giles, Amersham, Little Missenden and Chesham Road. They also recently completed the first breakthrough from a cross passageway to the shaft at Chalfont St Peter.
More than 1.3 million cubic metres of chalk and flint has been excavated and will be used as part of a chalk grassland restoration project at the south portal of the tunnel.
Once complete, the Chiltern tunnels will carry high speed trains between London and the North at speeds of up to 200mph (320km/h), helping to improve connections, free up space for more freight and local trains on the existing railway and provide zero carbon journeys for people across the UK.
Didier Jacques, Align’s Underground Construction Director, said: “Florence and Cecilia passing the half-way point on what is a long drive for the TBMs, is a great achievement. I would like to pay credit to TGT, our supply chain partner, whose personnel are manning the TBMs.
This significant progress would not have been possible without the supporting teams on the surface at the South Portal, who supply the thousands of 8.5 tonne segments required to line the tunnels, process the spoil pumped back as slurry through our slurry treatment plant and landscape the chalk produced across the site. Overall, a great team effort.’
Designed specifically for the mix of chalk and flints under the Chilterns, the two identical TBMs are excavating separate 9.1m i.d. tunnels for north and southbound trains.
Each machine has operated on an advance of approx. 15m a day, with more than 56,000 precision-engineered, fibre-reinforced segments installed – with each made on site in a dedicated temporary pre-cast factory.
A crew of 17 people operate each TBM, working in shifts to keep the machines running 24/7. They are supported by over 100 people on the surface, managing the logistics and maintaining the smooth progress of the tunnelling operation.
As well as the Chiltern tunnels, HS2 also recently launched two TBMs to begin the project’s London tunnels and celebrated the first breakthrough with the completion of the first of two tunnels under Long Itchington Wood in Warwickshire.