The designers of the High Speed 2 (HS2) rail link have announced that they’ve figured out how to more than halve the amount of embedded carbon in one of the project’s viaducts.
The innovative ‘double composite’ approach, which involves sandwiching two steel girders between two layers of reinforced concrete to create an extremely strong but lightweight span, was developed by HS2 Ltd’s main works contractor, EKFB (a team made up of Eiffage, Kier, Ferrovial and BAM Nuttall) working with its design partner, ASC (a joint venture between Arcadis Setec and COWI) and specialist architects Moxon, using lessons learnt from the use of double composite structures on the latest French TGV lines.
The 450-metre Wendover Dean Viaduct in Buckinghamshire, one of 50 being built for the first phase of HS2 between London and the West Midlands, will be the first major railway viaduct in the UK to use the new design. The team announced that it has managed to cut the amount of embedded carbon in the viaduct by 7,433 tonnes – the equivalent of 20,500 return flights from London to Edinburgh – by reducing the amount of concrete and steel required for construction.
The viaduct’s slender design will also reduce its silhouette when viewed from across the valley. It will be supported by nine evenly spaced piers, some of which will be up to 14 metres high. In another innovation, the supports will be cast in pieces offsite before being assembled like giant Lego blocks, thereby reducing the amount of work on site and cutting disruption for local residents.
‘By providing a cleaner, greener way to travel, HS2 will help cut the number of cars and lorries on our roads, cut demand for domestic flights, and help the fight against climate change,’ said Ambrose McGuire, HS2 Ltd’s project client director. ‘But we’re also serious about reducing the amount of carbon we use during construction and Wendover Dean is a great example of how we’re using the latest engineering techniques to do just that. Concrete is one of the construction industries’ biggest sources of embedded carbon – and this design will help us cut our carbon footprint while delivering a lighter, stronger and more elegant structure.’
‘This viaduct was inspired by the latest innovative designs in France, but has been enhanced and developed in the context of the Chilterns, said EKFB’s technical director, Janice McKenna. ‘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.’