Progress for key Wendover viaduct

Work on the 345m long Small Dean viaduct that will span the A413 south of Wendover, Buckinghamshire took place over the Easter weekend to enable critical preparatory work for a new viaduct that will span the railway and A413. 

The four-day closure allowed HS2’s engineers to work safely on two of the huge viaduct piers that will support the Small Dean viaduct, south of Wendover. This included building the 49m-deep piled foundations for the pier just 5m east of the railway and lifting a 42-tonne ‘Y’ shaped pre-cast segment onto the pier west of the railway. 

Designed to be seen from close-up, the viaduct is one of only two places in the Chilterns where the HS2 route will be above ground level, with the underside of the viaduct just 6m above the road, supported by six huge piers. 

Set low into the landscape, the 345m long viaduct’s enormous girders will be made from weathering steel, which naturally ages to a characteristically dark russet finish to echo the natural tones of the surrounding landscape. In a nod to the great railway bridges of the Victorian age, the side of the girders will feature prominent deck stiffeners which help to manage the structural forces while allowing for a more structurally efficient beam. It is being assembled to one side, ready to be slid out over the completed piers early next year. 

Small Dean is one of 50 major viaducts on the HS2 project, which is designed to improve connections between London, Birmingham and the North while freeing up space for more local trains on the most congested southern end of the existing West Coast Main Line into London Euston. 

The work is being delivered by HS2 Ltd’s main works contractor, EKFB - a team made up of Eiffage, Kier, Ferrovial Construction and BAM Nuttall - working with their design partner, ASC (a joint venture between Arcadis Setec and COWI). They worked closely with a team from Network Rail to plan and deliver the weekend closure. As well as the construction of the viaduct, HS2 will also realign Small Dean Lane and the A413 under the viaduct, with landscaping in the form of a series of subtle terraces to manage the change in height and interplay between road, paths, railway and viaduct. 

A shared foot and cycle path will also be delivered alongside the main road as it passes under the viaduct between the A413 London Road roundabout and the houses near Rocky Lane. This will eventually form part of the Misbourne Greenway project designed to link Wendover with Great Missenden.