A short section of the road, which runs from Banbury to Daventry, was closed for 11 days to allow the carriageway to be safely realigned over the top of the first section of the tunnel.
Set to stretch for 2.5km, the shallow ‘green tunnel’ is being built inside a cutting, with the earth landscaped on top and designed to blend into the countryside
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This new section of the A361 joins the Chipping Warden Relief Road, which was completed by HS2 in 2022.
The reopening of the road means that HS2’s contractors can now continue work on the tunnel.
Assembled from precast concrete segments, the tunnel is in an ‘M’ shape, with separate halves for northbound and southbound trains.
The precast approach was chosen because it promised quick assembly, with much of the work completed offsite.
Significant productivity challenges
According to HS2 Ltd, the initial construction schedule proved overly optimistic, with the team facing significant productivity challenges during the first two years on site.
In response, the HS2 team worked closely with its main works contractor EKFB – a joint venture comprising Eiffage, Kier, Ferrovial Construction and Bam Nuttall – to identify and implement a series of improvements to the construction process.
As a result, the rate of installation has doubled from an average of two segments a day in 2022/23 to 5.5 per day this year, with 2.1km worth of segments now installed.
Hugo Rebelo, HS2 Ltd’s senior project manager, 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.”
