The realignment of the B4525 allows the excavation of the Greatworth tunnel, HS2’s longest cut-and-cover tunnel, to continue at pace
The tunnel will stretch for 2.7km, making this HS2’s longest green tunnel, created using the ‘cut-and-cover’ method, which places soil back on top of the tunnel to blend it into the surrounding countryside.
The first kilometre of the tunnel has already been assembled, and work can now start on the next stage.
The tunnel uses offsite construction techniques
Sections of the tunnel are pre-built in concrete segments, making the tunnel into the shape of an ‘M’ with separate halves for north- and southbound trains.
The construction of this tunnel is taking lessons from similar structures used in the French high-speed train network, but also from the nearby Chipping Warden tunnel, which, while shorter, has used similar construction methods.
The tunnels at Greatworth and Chipping Warden are both installing five or six concrete segments per day.
HS2 Ltd’s project manager, Sam Arrowsmith, said: “I’m really pleased to see the temporary realignment of the B4525 open to drivers. This major milestone means that we can keep local traffic moving while we deliver the next stage of the Greatworth green tunnel.
“Once complete, the tunnel will help protect the rural landscape and reduce disruption for people living nearby. We’ve still got a long way to go, but the lessons from Chipping Warden have helped us significantly increased productivity and I’d like to thank everyone who’s worked so hard to get us to this point.”
The Chipping Warden tunnel was re-aligned earlier this year
The road over the Chipping Warden tunnel was re-aligned in early October, with work being undertaken on the A361 carriageway over the tunnel.
The road was closed for 11 days, disrupting traffic between Banbury to Daventry until it could be connected to the new relief road that was built in 2022.
At the time, HS2 Ltd’s senior project manager, Hugo Rebelo, said: “We’ve had some serious challenges with the Chipping Warden green tunnel, so it’s great to see the A361 permanently diverted and a clear path ahead for the completion of the tunnel.
“The improvements we’ve made to construction processes over the last year have helped us turn a corner – but we still need to keep up the focus on productivity, while delivering the work safely and to the necessary quality.
“I’d also like to thank our neighbours for their patience during the road closure, which was necessary to complete the realignment of the road and our site teams for working so hard to get it reopened on time.”
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