The first of five cut and cover tunnels along the HS2 route has been completed in west London.
The Copthall ‘green’ tunnel near West Ruislip was created using 1.2 million m3 of material excavated during construction of the line’s nearby twin-bore Northolt tunnel. It is 880m long, 12m high and up to 16m wide internally. Its five natural ventilation shafts reach down a maximum of 17m to the tunnel’s roof from the newly-created landscape above.
The Copthall Tunnel was originally planned as an open cutting but switching to a cut and cover design enabled the Northolt Tunnel material to be kept on site. This removed the need for around 100,000 truck movements to transport the material.
The tunnel, built by Skanska, Costain and Strabag (SCS), is the only single bore tunnel on the high-speed line.
The team used innovative travelling form work and false work systems that moved forward 20m at a time, enabling them to achieve the tunnel’s gentle curve.
The other four green tunnels are also well advanced. Last week HS2 announced that the structure of Chipping Warden tunnel in Northamptonshire had been completed ahead of works to backfill material.
Rail minister Lord Peter Hendy said completion of the Copthall Tunnel was another significant milestone for HS2.
“Making use of innovative design, the tunnel reduces the impact on nearby communities by blending into its surroundings whilst keeping thousands of truck journeys off local roads by using materials close to the site,” he said.
“Our reset of HS2 is driving faster, more efficient construction on-the-ground and supporting thousands of jobs as we work to deliver the project at the lowest reasonable cost.”
HS2’s head of delivery, James Leeming, said finishing civil works on the first ‘green’ tunnel demonstrated the project’s progress.
“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,” he said.
