HS2, the UK’s new high-speed railway, has completed the construction of its first cut and cover ‘green’ tunnel, at Copthall near West Ruislip on the outskirts of London.
The 880m tunnel forms part of the UK’s future high-speed railway and stands as the first of five such structures planned along the route between London and the West Midlands.
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Constructed by SCS, a civil engineering partnership of Skanska, Costain and Strabag, Copthall tunnel was created using 1.2million cubic metres of material excavated during the assembly of the nearby twin-bore Northolt tunnel.
HS2 stated that this approach eliminated the need for approximately 100,000 heavy goods vehicle journeys, as excavated material that otherwise would have been transported by road was instead reused on site.
The structure, which stretches over half a mile, is both 12m high and up to 16m wide inside, accommodating the forces generated by trains travelling at speeds up to 200mph. It is the only single bore tunnel on the HS2 network and features five natural ventilation shafts extending a maximu of 17m from the top of the tunnel to the newly formed landscape above.
HS2 delivery head James Leeming said: “Finishing civil works on HS2’s first-completed ‘green’ tunnel clearly demonstrates the progress that’s being made to deliver the first new intercity railway north of London in over a century.
“I pay tribute to the dedicated workforce that has worked since early 2021 – and in all weathers – to deliver this remarkable structure, which was a key component of our plan to deal with the muck excavated to build part of HS2’s tunnelled sections.”
Copthall tunnel is located between the twin-bore Northolt tunnel and the Colne Valley viaduct, the latter being the UK’s longest railway bridge, completed last year.
Construction involved moving and rebuilding the busy Harvil Road with a new bridge to permit the high-speed line to pass beneath.
The engineering team used travelling ‘form work’ and ‘false work’ systems, advancing the framework 20m at a time, which allowed for a gentle curve in the tunnel’s structure.
Following the completion of both tunnel structure and the earth covering above, attention will turn to planting trees, plants and shrubs on top of Copthall tunnel over the next two years to blend the site into its surroundings.
The remaining four green tunnels along the HS2 route are progressing, with the Chipping Warden tunnel structure in Northamptonshire having also been finished ahead of backfilling.
The HS2 project as a whole is undergoing an operational reset led by CEO Mark Wild, with the aim of delivering the 140-mile railway cost-effectively.
In May this year, the Department for Transport issued revised delivery timelines and cost estimates, which included plans to align train speeds with those seen in Japan and Europe, potentially saving up to £2.5bn and reducing the construction programme by a year.
Six major milestones have reportedly been reached ahead of schedule over the past year, according to HS2.
