Main contractor Balfour Beatty Vinci has adopted French post-tensioning techniques from a Vinci subsidiary to build a series viaducts near Water Orton in north Warwickshire.
The River Tame West Viaducts carry three rail tracks in total, made up of one single track viaduct and one double-track viaduct. These precast segmental viaducts are located at the northern tip of the Delta Junction – the triangular section of the railway that enables trains to run between London, Birmingham and the north.
The two River Tame West Viaducts cross the River Tame near Water Orton and join the Curdworth Box, which will take high speed trains over the existing Birmingham to Derby railway.
Construction of the 20 piers to support the viaducts started in 2023, with the first spans of the three track section completed in spring 2024. This initial phase involved placing the segments onto two 42-metre truss beams, moving them into place with a skidding trolley, and securing them by post-tensioning techniques.
Since then, a giant cantilever structure has been built, using a 22-metre-high mast, including temporary post-tensioning cable stays and a 14-metre-high swivel crane.
The crane lifts and installs one concrete segment into place at a time, eventually completing each 45-metre span length. The permanent post-tensioning tendons are then stressed to allow the removal of the temporary cable stays, leaving the permanent structure securely in place. The same process is repeated between each pier until all of the spans are complete.
The process was originally developed by Campenon Bernard, which Vinci predecessor company SGE acquired in 1988. The mast and the swivel crane deployed on the River Tame West Viaducts are designed and manufactured by Portuguese bridge building specialist Berd.
Vinci director of works Nicolas Gallone said: “We’re using a specialist construction method to build the River Tame West Viaducts – a technique that has never been used in the UK before. It’s a significant moment for Balfour Beatty Vinci, the HS2 project and the construction industry in this country.
“This post-tensioning technology, pioneered by Vinci, is used on other major construction projects around the world. Now, it’s helping us to deliver these complex viaducts and overcome engineering challenges along the way, including existing waterways and utilities.”
A team of 40 people is currently involved in the operation, and a total of 2,500 concrete segments will be moved into place using this specialist technique. All the deck segments are due to be in place by August 2026. The same process will be used to build nine viaducts in the Delta Junction.
The concrete segments are being manufactured at HS2’s bespoke outdoor factory near Lea Marston. The 200-strong team on this site has just celebrated producing the 1,000th segment out of a total 2,742 segments that are being made for Delta Junction.
Sam Hinkley, HS2’s lead senior project manager for Delta Junction, said: “This is a fantastic UK-first for HS2, signifying another proud moment for everyone working on the project. It has only been possible through the collaborative and innovative approach with our designers, civils contractor and wider supply chain, who are delivering this huge feat of engineering.”
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