By lyndamyer
Arriving to the Little Missenden ventilation shaft, the two TBMs that excavated HS2’s longest tunnels have completed over than 75% of the 16km drive beneath the Chilterns.
The spent time by Florence and Cecilia TBMs, which are 2,000 tons and manufactured by Herrenknecht, for digging the twin tunnels between the M25 and South Heath in Buckinghamshire for the high-speed railway is was two years
Additionally, excavation of five shafts, that are due to provide ventilation and emergency access near Chalfont St Peter, Chalfont St Giles, Amersham and the 35m-deep Little Missenden with an intervention shaft at Chesham Road, was completed by engineers along with boring and lining the tunnels, which are 90m below ground at the deepest point.
The news comes just weeks after Buckinghamshire Council granted planning consent for the North Portal, meaning all major design elements now have consent.
According to HS2 Ltd’s project client, David Emms: “The huge progress that Florence and Cecilia have made would not have been possible without a huge team in support – manufacturing the tunnel segments, excavating the vent shafts and I’d like to thank everyone involved.”
Also, a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick are the responsible of operating two TBMs.
“Both TBMs reaching our fourth shaft at Little Missenden is a great achievement for not only the tunneling team and the team involved in excavating and preparing the shaft, but also the supporting teams on the surface at the South Portal, manufacturing the concrete segments required to line the tunnel and processing the spoil from the tunnels,” said Align project director Daniel Altier.
He added: “In particular I would like to pay credit to Align Shafts team, working with our supply chain partners and Keltbray, who have been working over the last few months to ensure the shaft is ready for the arrival of Florence and Cecilia.”
The amount of excavated material, which are mostly chalk and flint, during the construction of the tunnels will be around 2.7 million m3 and they are slated to be used for landscaping. Following commissioning of TBMs in summer 2021, more than 2 million m3 have been dug.
Although HS2 has five TBMs in the ground now, a further five due to be launched over the coming years. Involving major tunnels on the approach to London and Birmingham, together they are going to create 103km of tunnel between London and the West Midlands.
