Press release - New images showing the green tunnel at Greatworth, Northamptonshire, with similar designs planned for Wendover and Chipping Warden Modular design set to cut embedded carbon in construction by 50% inspired by TGV-style off-site manufacturing techniques.

HS2 has revealed the first images of the longest of three innovative ‘green tunnels’ that will be built across Buckinghamshire and Northamptonshire to help blend the new high-speed rail line into the landscape and reduce disruption for residents.  

The 2.4 km (1.5 mile) long Greatworth tunnel will be built in a factory in Derbyshire before being shipped to site and assembled over the railway line as it passes the village. It will then be covered with earth and landscaped to fit into the surrounding countryside.  

Applying lessons from the construction of the latest French high-speed lines, an ‘off site’ modular approach was developed by HS2’s main works contractor, EKFB - a team made up of Eiffage, Kier, Ferrovial Construction and BAM Nuttall.  

Designed as an ‘m’ shaped double arch, the tunnel will have two separate halves for southbound and northbound trains. Instead of the whole tunnel being cast on site, five different concrete precast segments will be slotted together to achieve the double arch - one central pier, two side walls and two roof slabs. All 5,400 segments installed at Greatworth will be steel reinforced, with the largest weighing up to 43 t.  

Concrete and steel are some of the biggest sources of carbon emissions within the construction industry and by reducing the amount of both materials needed for the tunnel, this lighter-weight modular approach is expected to more than halve the amount of carbon embedded in the structure. It also requires less people and equipment on site, improving safety and reducing disruption for residents.  

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