Eiffage, Kier, Ferrovial and BAM to cut HS2 viaduct carbon by 50% with new design

The Eiffage, Kier, Ferrovial and BAM Nuttall joint venture is on track to more than halve the amount of embedded carbon on one of the HS2 viaducts it is building thanks to a new ‘double composite’ design.

The contractors, working with design partner ASC (a joint venture between Arcadis Setec and COWI) and specialist architect Moxon, will build the Wendover Dean Viaduct in Buckinhamshire using two steel girders sandwiched between two layers of reinforced concrete to create a strong but lightweight span, which they claim will significantly reduce embedded carbon in the structure.

The 450m viaduct was recently given approval by Buckinghamshire Council under Schedule 17 of the HS2 Act and it will be the first major railway viaduct in the UK to use the double composite approach.

The structure applies lessons from the use of double composite designs on the latest French TGV lines, with nine evenly spaced piers supporting the deck of the viaduct. The amount of embedded carbon will be reduced by 7,433, according to calculations by EKFB and its designers.

The piers – some of which will be up to 14 metres high – will be cast in pieces offsite before being assembled on site. The beams will be made from weathering steel. Total steel weight is around 1,400 tonnes and the structure will be topped with a concrete deck which will carry the track and built-in noise barriers.

A mix of trees and shrubs commonly found across the Chiltern chalk hills will be used for new woodland planting around the viaduct, including oak, beech, hazel and wild cherry.

EKFB’s technical director Janice McKenna, said: “This viaduct was inspired by the innovative design in France, but has been enhanced and developed in the context of the Chilterns. Our design solutions are always created with people and legacy in mind and I am really proud of the carbon savings that the Wendover Dean Viaduct represents.”