Hs2 | Delta Junction Construction Progresses With Completion Of First 472M Viaduct

The construction of High Speed 2 (HS2) has seen the completion of the River Tame West Viaduct, North Warwickshire – the first to be finished in the Delta Junction complex.

This 472m single-track structure marks the first instance in the UK of a giant cantilever technique being employed for such a project.

A team of 40 construction workers from Balfour Beatty Vinci JV (BBV), the contractor responsible for the Midlands section of HS2, utilised this innovative method to gradually move concrete segments into place, span by span. This approach not only enhances construction efficiency but also provides flexibility in the building process.

The construction of the viaduct’s piers commenced in 2023, followed by the beginning of the concrete deck construction in early 2024. To date, 190 pre-cast concrete segments have been installed using the cantilever technique. Ultimately, the River Tame West Viaduct will form part of a larger structure comprising three railway tracks, including the ongoing construction of a double-track viaduct adjacent to the completed single-track segment.

The two River Tame West Viaducts traverse the River Tame and will connect with the Curdworth Box, allowing high-speed trains to cross over the existing Birmingham to Derby railway.

Construction of the 20 supporting piers started in 2023 and the first spans of the three-track configuration were completed in spring 2024. This initial phase involved placing the segments onto two 42m truss beams, moving them into place with a skidding trolley, and securing them by post-tensioning techniques.

Following this, the giant cantilever structure was built, using a 22m high mast, including temporary post-tensioning cable stays and a 14m-high swivel crane.

This crane facilitates the precise positioning of concrete segments into place one at a time until it reaches the 45m 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 the spans are complete.

This method traces its origins to Campenon Bernard, which later became a part of Vinci Construction. It is new to the UK, is set to facilitate the construction of nine out of the 13 viaducts at Delta Junction, which together will stretch over 6,500m.

Delta Junction plays a crucial role in the HS2 line and rail network, connecting London, Birmingham, and northern regions of the UK. The junction consists of 13 viaducts and over 10km of track designed to navigate rivers, existing rail lines, local roads, and motorways. In addition to the River Tame West Viaduct, the project includes the construction of the  single-track River Tame East Viaduct and two Water Orton Viaducts.

Pre-cast segments are being produced at a dedicated factory situated in nearby Lea Marston and a total of 2,742 concrete segments will be necessary to complete all nine viaducts, with final installations projected to be concluded by late 2026.

Last year, NCE spoke in-depth with HS2 Ltd, BBV and National Highways about how standards are being challenged in the construction of the Delta Junction viaducts.

HS2 Ltd lead senior project manager for Delta Junction Sam Hinkley said: “The completion of the River Tame West single-track viaduct is a big milestone for the Delta Junction team. In this very complex construction area, we’re building a network of 13 viaducts to carry new high-speed trains over motorways, existing rail lines, rivers and floodplains.

“Nearly 10,000 people in the West Midlands are delivering this world-class engineering, which will lay the foundations for Britain’s future rail network.”

BBC pre-case segmental viaducts project manager Nicolas Gallone said: “This is the first time in the UK we’ve used this innovative technique to build segmental viaducts. It’s an efficient and flexible process using cable stays from the cantilever structure to keep the viaduct in place, while a mast and swivel crane are used to place each segment in place.

“It’s a great achievement for the whole team and work now continues using this technique on the other eight pre-cast segmental viaducts in the Delta Junction.”

Like what you've read? To receive New Civil Engineer's daily and weekly newsletters click here.