Engineers delivering the HS2 high-speed railway have completed construction of the Westbury Viaduct, a major new structure that will carry trains across the floodplain of the River Great Ouse near Brackley.
Stretching 320 metres across the landscape east of the Northamptonshire town, the viaduct represents a significant milestone for the project and showcases a pioneering construction method more commonly associated with France's high-speed rail network.
The structure has been built using an innovative 'double composite' design, a technique inspired by viaducts on the French TGV network. The approach reduces the amount of carbon-intensive materials required by combining steel beams with reinforced concrete layers above and below, creating a highly efficient box-beam arrangement.
Unlike traditional viaduct construction, which typically relies on either concrete spans or steel beams supporting a concrete deck, the double composite technique delivers greater structural efficiency while reducing material usage.
A key element of the project involved the installation of the viaduct's steelwork. The 2,695-tonne steel beam assembly was constructed on the north abutment before being carefully slid into position between March and October 2024.
During the complex operation, engineers utilised specially designed non-stick pads, similar in principle to the coating found on frying pans, to minimise friction as the deck was pushed across temporary bearings positioned on top of the concrete piers.
Following the successful launch of the steel structure, construction teams used a travelling formwork system to cast the concrete deck in 42-metre sections. The formwork was progressively advanced after each pour, enabling the next section to be completed before the installation of prefabricated parapets along the viaduct edges.
HS2’s 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."
Westbury Viaduct is the largest of several structures being built around Brackley and forms part of the central section of HS2 being delivered by EKFB, a joint venture comprising Eiffage, Kier, Ferrovial Construction and BAM Nuttall.
With major construction activities now complete, the temporary hardstanding installed beneath the viaduct to support heavy construction equipment will be removed, allowing final landscaping works to progress.
The project also sits alongside several other recently completed milestones in the area. The nearby Turweston Green Bridge was completed in April, while the realigned A43 opened in July, helping reshape local infrastructure ahead of the arrival of the new railway.
Across the wider route, significant progress continues on HS2's major viaduct programme, including structures spanning the M42 and M6 near Birmingham, as well as the viaducts that will carry trains into the new Curzon Street Station.
In total, HS2 is constructing more than 500 bridges and viaducts along the route, ranging from local road crossings to the landmark Colne Valley Viaduct, the longest railway bridge in the UK.
Once operational, HS2 is expected to improve connectivity between London and Birmingham while creating additional capacity on the existing West Coast Main Line for regional passenger services and freight traffic.
Image credit: HS2
