By Lynda Myer
Considering that TBMs Florence and Cecilia have arrived the Chesham Road intervention shaft on the 16km twin-bore tunnel beneath the Chilterns, tunneling on HS2’s longest tunnel is on track to be completed in the future year.
Being commissioned in a site near the M25 motorway in summer 2021, the 2,000-tonne, 170m-long Herrenknecht machines have dug almost 2.8 million m3 of chalk and flint.
In addition to excavating and lining the tunnels, completig the excavation of four other shafts that are due to provide ventilation and emergency access near Chalfont St Peter, Chalfont St Giles, Amersham and Little Missenden, is up to engineers from Align, which is a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick. In order to creating the internal structures and the headhouses on the surface, currently work is undergoing and the Chesham Road shaft is slated to be used only for emergency access.
According to HS2 Ltd head of delivery Mark Clapp: “Chiltern tunnel was making good progress, with 90% of tunnel excavation complete. That’s an incredible engineering achievement and I look forward to the breakthrough next year.”
Also Align’s underground construction director, Didier Jacques, said: “With our first TBM Florence having reached our fifth shaft at Chesham Road and our second TBM Cecilia due to reach the shaft shortly, this a great achievement for not only the tunnelling team, but also the supporting teams on the surface at the South Portal, manufacturing the concrete segments required to line the tunnels and processing the spoil from the tunnels.”
The whole plan of HS2’s tunneling process will be 103km, whereas five TBMs already are in the ground, three ready to go and another two due to be delivered next year. Moreover, alongside with Florence and Cecilia, at the moment two TBMs are boring the London tunnels with two more slated to be commission soon. One TBM is excavating the Bromford tunnel in Birmingham, with another ready to go.
The scheduled date for delivering two TBMs that are going to excavate the Euston tunnels is coming year, while in August it was announced they will be stored under Old Oak Common Station until the government gives the go-ahead for the Euston Tunnel.
At the time, HS2 told PA Media that while HS2 passenger services were not due to begin for at least six years, the two TBMs needed to be lowered into place next year to allow for additional train tracks to be built over the top, with the Great Western main line to be widened as part of the Old Oak Common development.
