The two Water Orton viaducts form part of Delta Junction, HS2’s most complex network of structures in the West Midlands, and at 20-metres high are among the tallest structures on the line.
HS2’s main works contractor for the West Midlands, Balfour Beatty Vinci (BBV) is building the 1,400-metre long north-south structures to connect HS2’s Birmingham Curzon Street Station with Crewe and Manchester.
Delta Junction is a triangular section of the high-speed railway made up of nine precast segmental viaducts, embankments, and other bridging structures, with around 10km of track crossing a network of motorways, roads and rivers.
The Water Orton viaducts – east of the M42 and Lichfield Road – will carry 700 metres of HS2 track over the River Tame and a network of existing transport links, including the Birmingham-Peterborough line, running between Water Orton and Coleshill Parkway stations.
Completion of the first pier represents a sign of progress for BBV.
While elsewhere on HS2 much use is being made of precast concrete segments, these piers are cast in situ with bespoke formwork. The reinforcement cage is assembled in a rebar factory near Coleshill.
The deck segments will be precast, however, produced at HS2’s nearby purpose-built Kingsbury factory near Lea Marston. The outdoor factory is making 2,742 segments for the entire Delta Junction – more than 6km of post-tensioned viaduct. The segments will be trucked to site on dedicated haul roads.
Sam Hinkley, HS2 senior project manager for Delta Junction, said: “This is another key moment for HS2 in the West Midlands as work ramps up on one of the most complex sections of the whole route. The Delta Junction is HS2’s key interchange where the new zero-carbon high speed railway will connect between London, the midlands and the north.
“Minimising disruption to local communities in this area has been a key consideration in our planning, including the use of innovative pre-cast construction techniques, and haul roads to take lorries off local roads.”
Once the piers are constructed, the spans will be built by raising each segment from a temporary suspension tower erected on top of each pier. When each span is complete, the suspension tower will be disassembled and moved along the viaduct to build the next span.
An ‘match-casting’ technique sees each viaduct segment cast against its neighbouring segment in a production line. Each segment is unique, and adjustable by as little as 5mm. Pouring each segment against the previous one ensures the whole arch fits together when assembled on site.
BBV construction director David Waite said: “Witnessing the removal of the shuttering to reveal the first completed pier for Water Orton viaduct was an important occasion for the 1,100 people who make up the Delta workforce.
“With the production line at the Kingsbury pre-cast factory now in full swing, we will start to see the viaduct take shape over the coming months, with the first span due to be completed early next year.”