On 01 February HS2 Ltd confirmed that Florence and Cecilia, the two giant TBMs driving the HS2 high speed rail project’s longest tunnels, have passed the halfway point of the 16 km (10 mile) long Chiltern tunnels.
The two identical 2,000 t machines - designed specifically for the mix of chalk and flints under the Chilterns - have spent the last 18 months excavating the twin tunnels for north and southbound trains between the M25 and South Heath in Buckinghamshire. The tunnels will help protect the environment while improving connections between London, Birmingham and the North.
More than 1.3 million cubic metres of chalk and flint has been excavated and then mixed with water to form a slurry, before being pumped back to the surface of an ambitious chalk grassland restoration project at the south portal of the tunnel.
This significant progress would not have been possible without the supporting teams on the surface at the South Portal, who supply the 8.5 t fibre-reinforced concrete 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. More than 56,000 segments - made on site in a dedicated temporary pre-cast factory - have been installed.
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.
The teams has 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.
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.
HS2’s main works contractor, Align – a joint venture formed of three international infrastructure companies: Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick is responsible for the Chiltern tunnel and nearby Colne Valley Viaduct.
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.
