Construction of one of HS2’s longest ‘cut and cover’ tunnels has now taken a major step forward with the last of 5,020 reinforced concrete segments lifted into position.
Situated at a site near Chipping Warden in Northamptonshire; the tunnel will stretch for one-and-a-half miles (2.5km) and be covered with a section of earth once completed, earning its nickname as one of HS2’s ‘green tunnels’.
There are five green tunnels on the HS2 project between London and Birmingham, with two others situated at Burton Green, in Warwickshire, and Copthall, on the outskirts of London – both of which are rapidly approaching completion.
Assembled entirely from precast concrete segments; Chipping Warden’s green tunnel takes the form of an ‘M’ shape, with separate halves for northbound and southbound trains, and with the pre-cast wall installation now finished, the team have now turned their full attention to completing the waterproofing and internal floor slab and all other internal works, including the emergency walkways that will run alongside the track.
In order to speed up construction, the tunnel was built in two parts, which were joined together last week when the final segments were lifted into position near the A361.
More than two million cubic metres of material – mainly mudstone – was excavated to form the level base for the tunnel, all of which was stored on site and is now being put back and compressed in order to ensure that the weight is spread equally across the structure.
This material will be landscaped to blend in with the surrounding countryside, with new trees planted and hedgerows restored.
HS2 Ltd’s Senior Project Manager, Sam Arrowsmith said:It’s great to see the final segment slotted into position at Chipping Warden and I’d like to thank everyone who pulled together to find ways to optimise all the stages of construction - from excavation, tunnel construction, and backfilling.
We’ve still got a long way to go, but with the tunnel precast structure complete, we can now focus on finishing the interior works and the earthworks and landscaping that will blend the railway into the surrounding countryside.
Chipping Warden forms one of three tunnels currently being built by HS2’s main works contractor in this area, EKFB – a team made up of Eiffage, Kier, Ferrovial Construction and Bam Nuttall; all of which will use lessons learnt during the process for similar tunnels at Wendover and Greatworth.
