The first designs have been released of the longest of three ‘green tunnels’ that will be built for HS2 across Buckinghamshire and Northamptonshire.
Greatworth Tunnel in Northamptonshire will be 1.5 miles long and similar in design to tunnels planned for Wendover and Chipping Warden.
The tunnels are intended to blend the new line into the landscape and reduce disruption for local residents. Greatworth Tunnel will be built in a factory in Derbyshire and then shipped to site, where it will be assembled over the railway line as it passes the village of the same name. The tunnel will then be covered with earth and landscaped into the surrounding countryside.
This method is similar to those used on the construction of French high-speed lines, developed by HS2’s main works contractor EKFB (Eiffage, Kier, Ferrovial Construction and BAM Nuttall).
The tunnel will feature an ‘m’-shaped double arch with two separate halves for southbound and northbound trains. Five concrete precast segments will be slotted together (one central pier, two side walls and two roof slabs) to create the arch shape. In total, 5,400 segments will be needed at Greatworth and will be steel reinforced.
Using this lighter-weight modular approach is expected to more than halve the amount of carbon embedded in the structure, since concrete and steel are some of the largest sources of emissions in the construction industry.