HS2 main works contractor Align JV – Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick – has started excavating one of five giant ventilation and emergency access shafts.
The shafts will provide access to the 10-mile-long tunnels Align JV is digging under the Chiltern Hills.
Once complete, the 78m deep shaft near the village of Chalfont St Peter will be topped with a headhouse inspired by nearby barns and other agricultural buildings to help it fit into the surrounding landscape.
Below ground level, the shaft will reach down to the twin tunnels, with fans and other equipment designed to regulate air quality and temperature, and remove smoke in the event of a fire.
The structure has been designed by Align JV in conjunction with design partners Jacobs and Ingerop-Rendel, and the architect Grimshaw and landscape designers, LDA.
A 120t drilling rig with a specialised cutting head was used to excavate the walls of the shaft, before concrete was poured in to form each of the 16 wall panels. The walls are now complete and the team is excavating the chalk from inside the shaft.
The two tunnel boring machines (TBMs) – named Florence and Cecilia – are expected to reach the shaft next year and complete their 10-mile journey in three years’ time.