Close of work at HS2 Chiltern tunnel vent shafts at Chesham Road and Little Missenden brings to an end a project that began almost five years ago.
The 10-mile twin-bore Chiltern tunnels are now ready to be fitted out with tracks and overhead electrical equipment.
Enabling works for the installation of mechanical, electrical and plumbing equipment will begin later this year (design work is still going on). Rail systems including track and overhead electrical equipment to power the trains will follow once this work is completed.聽
Align JV, a joint venture between Bouygues Travaux Publics, Sir Robert McAlpine and Volker Fitzpatrick, began main construction in May 2021 with the staggered launch of two 2,000-tonne tunnel boring machines (TBMs) from a site next to the M25 near Maple Cross in Hertfordshire.
Five deep ventilation and access shafts were sunk to depths of 78 metres along its route and completed before the TBMs鈥� arrival. Each shaft鈥檚 headhouse is designed by Grimshaw Architects to blend in with the surrounding Chiltern hills landscape.
The machines drove north at an average speed of 16 metres per day before breaking through near Great Missenden, Buckinghamshire, in early 2024. Since then, work has continued to build the porous extensions to its north and south portals, install its internal walkways and fit out 40 cross passages.
HS2 Ltd head of civil engineering for Chiltern tunnel, Mark Clapp, said: 鈥淢ulti-faceted projects of the Chiltern tunnel鈥檚 scale and complexity don鈥檛 often come along; as a civil engineer, you鈥檙e lucky to be involved in anything like it. The team we assembled at HS2 Ltd, and with Align JV 鈥� our main civil works contractor 鈥� and all its subcontractors, to deliver this part of the new high-speed railway was exemplary. I pay tribute to everyone involved. They can all feel certain that their hard work will stand the test of time.鈥�
Align JV project director Adrien Baudard said: 鈥淏eing part of the successful delivery of the Chiltern tunnel has been a source of immense pride for everyone at Align and our partners across the supply chain. Their unwavering commitment, technical skill, and collaborative spirit have been truly impressive. Whether it was advancing safety standards, setting new TBM records, or helping to train future engineers, we鈥檝e had the privilege of learning from and working with some of the top talent in our field.
鈥淲ith the completion of the Chiltern tunnel鈥檚 civil works, the achievements of this integrated project team as well as the sustainable benefits such as carbon reduction and safety innovations will set a standard in tunnelling for generations to come.鈥�
This is the second of HS2鈥檚 five twin-bore tunnels to be structurally complete after the one-mile Long Itchington Wood tunnel in Warwickshire, which was completed last year.
However, while progress is being made to construct the 140-mile line between London and Birmingham, the overall project remain badly behind schedule and over budget . More than a year into the job, HS2 Ltd chief executive Mark Wild is still working on a rescue plan to reset the project to ensure the remainder of the route is delivered as efficiently as possible and for the lowest reasonable cost.
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