HS2 engineers have completed the 320-metre Westbury viaduct, which will carry the high-speed railway across the River Great Ouse floodplain near Brackley.
Built low in the landscape to the east of the town, Westbury is the longest viaduct in the Brackley area. It is one of 15 viaducts being delivered by HS2’s central-section main works contractor, EKFB, a joint venture between Eiffage, Kier, Ferrovial Construction and BAM Nuttall.
Double composite design
The viaduct uses a double composite design, a method inspired by recent structures on France’s TGV network. The arrangement places reinforced concrete above and below the steel beam, forming a more efficient box beam rather than relying on a conventional concrete span or a steel beam supporting a concrete deck.
The steel beams weigh 2,695 tonnes in total. They were assembled at the northern abutment before being slid into position between March and October 2024. Low-friction pads with a non-stick coating were used to reduce movement resistance between the deck and temporary steel bearings on the concrete piers.
Once the beams were installed, a travelling formwork system was used to cast the deck in 42-metre sections. Prefabricated parapets were then lifted into place along the edges of the viaduct.
HS2 Ltd senior project manager Paul Cooper said: “It’s been amazing to watch Westbury viaduct come together over the last few years and I’d like to thank everyone involved in getting this incredible structure over the finishing line.
“This section of the railway is now really starting to come together, and with the viaduct complete, our focus will turn to completing the earthworks and other nearby structures.”
Landscaping to follow
With construction finished, the hardstanding installed to support heavy equipment will be removed and landscaping will be completed around the viaduct.
Work is also progressing on nearby HS2 structures, including the Turweston green bridge, completed in April, and the realignment of the A43, completed in July. HS2 is building more than 500 bridging structures across the project, ranging from small road bridges to the Colne Valley Viaduct.
EKFB project sub-agent Arman Yarali said the viaduct demonstrated the “innovation, technical expertise and collaboration” involved in its construction. He added that the double composite design had produced a lighter, more efficient structure using less concrete.
Westbury is the first of five viaducts designed and built using this approach to be completed, according to EKFB. The contractor said Eiffage Metal led the manufacture and installation of the beams, while Infrasolutions Ltd carried out specialist deck finishing works.