Conveying the HS2 High Speed Railway over the Thame Valley on the western edge of Aylesbury, the Thame Valley Viaduct has been conceived as a minimalist elevated causeway passing over the River Thame floodplain - minimising impact on farmland and the adjoining riparian meadow landscape. Set low into the landscape with a simple and consistent profile, the underside of the viaduct will be just 3m above the ground, with 36 25m-long spans crossing the river and surrounding wetlands.
The 35 concrete piers that support the viaduct will be entirely made off site before being placed on their foundations. Traditionally, viaduct beams are secured together above each of the piers with a concrete diaphragm which is cast in situ. However the larger pre-cast beams that will be used at Thame Valley can secured directly to one another, removing the need for the diaphragm. This improves durability and reliability, saves time, cuts cost and improves safety by reducing the need for people to work at height.
In addition, the design utilises two wide ‘box girder’ beams per span instead of eight smaller beams - to simplify and speed up assembly. The new lighter-weight structure is expected to save 19,000t of embedded carbon in comparison to the previous design. As well as cutting embedded carbon in terms of materials, this approach also requires less lorries to deliver material to site, cuts waste and will reduce disruption for the community during construction.
“(HS2 Independent Design Panel) considers the proposals (for Thame Valley Viaduct) to be elegant, refined and responsive to a challenging landscape setting. The way the architectural approach has progressed to address visual,functional and construction challenges is excellent”
(HS2 Independent Design Panel Report on the Schedule 17 stage designs for Thame Valley Viaduct 18/01/22)