Giant cantilever structure helps build HS2’s River Tame West Viaducts

A specialist cantilever process has been used for the first time in the UK to build the first span of a 472-metre-long single track viaduct in the West Midlands. 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.

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, the 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 initially developed by Campenon Bernard, later becoming part of VINCI Construction. The mast and the swivel crane deployed on the River Tame West Viaducts are designed and manufactured by the company BERD.

A team of 40 people are 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 a total of 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 1,000^th segment out of a total 2,742 segments which are being made for the six segmental viaducts of the Delta Junction.