HS2 has announced that it has completed the first 920-tonne deck span on the first precast segmental viaduct being at the Delta Junction.

What HS2 calls a “construction milestone” is on the 472-metre River Tame West viaduct, one of thirteen viaducts that make up the complex Delta Junction network.

A crane lifted the sixteen concrete segments for the first span, placed them one-by-one onto two 42-metre truss beams, which a skidding trolley then moved into place. Engineers used temporary and then permanent post-tensioning techniques to secure the construction.

The span, which weighs 920 tonnes, was then jacked up, and the truss moved onto the abutment and pier next to it, which enables the process to start again on the next span.

Delta Junction is a triangular section of HS2 line, which will enable trains to travel between London and Birmingham, Birmingham and Manchester, and directly between London and Manchester without stopping at Birmingham.

It consists of embankments, cuttings and thirteen viaducts carrying high-speed tracks over motorways, local roads, existing rail lines, rivers and floodplains.

Delta Junction Viaducts are of three types:

• Six precast segmental viaducts (River Tame East and West; Water Orton 1 and 2; Coleshill East and West), with standard spans of 45 metres with decks built off concrete precast segments prefabricated at HS2’s Kingsbury Precast Yard at Lea Marston
• Four composite viaducts (M42/M6 Link Road East and West; River Cole East and West), with standard spans of more than 45 metres with their decks built off weathered steel boxes or beams, with a concrete deck on top
• Three low viaducts (M42 Coleshill North and South; Watton House), with standard spans of 25 metres with their decks built off standard concrete precast beams, with a concrete deck on top.

The River Tame West Viaduct is at the northern tip of the Delta Junction, crossing the River Tame near Water Orton. In this section of the Junction, six tracks of the railway run alongside each other as they join the southern end of the Curdworth Box, which will take high-speed trains over the existing Birmingham-to-Derby railway. Of the six, the River Tame West Viaduct carries three tracks, the River Tame East Viaduct carries one track and the Water Orton Viaducts carry two tracks.

In the southern part of the Junction, the 1,400-metre Water Orton No.1 Viaduct and 1,300-metre Water Orton No.2 Viaduct allow trains to travel along their curve to and from Birmingham Curzon Street station. HS2 completed the first of thirty-two giant piers for these viaducts in August. The other four lines, on the River Tame Viaducts, join on to the HS2 mainline to Interchange Station and on to London.

HS2 began building the viaduct piers earlier this year, and deck construction is now progressing.

The three initial spans are all from the same abutment and next to each other, and HS2 expects to complete them by spring 2024. It will construct further spans using temporary staying masts, swivel cranes, and temporary and permanent post-tensioning techniques.

A total of 153 piers will be built for the Delta Junction’s viaducts, with fifteen completed so far. HS2’s outdoor factory near Lea Marston is making a total of 2,762 viaduct segments, using a ‘match-casting’ technique which precisely casts each segment against the following segment in a production line, ensuring that they fit perfectly when assembled on site.

The triangular layout of the Delta Junction triangle facilitates the three main routes:

• The railway from London curves west on a spur towards Birmingham Curzon Street Station.
• Trains come out of Birmingham on a line heading north to meet the main HS2 line, which then connects to the West Coast Mainline to Manchester.
• The third side of the triangle allows trains to run between London and Manchester without stopping at Birmingham.

HS2’s main works contractor for the West Midlands, Balfour Beatty VINCI (BBV) is delivering the project, constructing 90km of HS2 between Long Itchington in Warwickshire to the centre of Birmingham and on to Staffordshire.

A Mott MacDonald and SYSTRA Design Joint Venture (MMSDJV) is providing all the design requirements for the BBV and HS2 works between London and Birmingham, and is sourcing materials through a local supply chain around the Midlands.

Sam Hinkley, HS2’s Senior Project Manager for the Delta Junction, said: “This is a great moment for the Delta Junction team, as construction gets into full swing on this linchpin section of HS2. Building this triangular network of 13 viaducts is a huge feat of engineering, with a total of 10km of HS2 tracks crossing a network of motorways, local roads, railways and rivers to enable high speed trains to travel between London, Birmingham and the North.”

Nicolas Gallone, Section Manager at Balfour Beatty VINCI said, “It’s an exciting moment to see the River Tame West Viaduct starting to take shape, now we’ve successfully completed the first deck span. It’s the clearest sign yet of the huge progress we’re making on this complex network of viaducts, known as the Delta Junction.

“Construction of this iconic stretch of the route is set to ramp up further over the coming weeks and months, as we continue assembly of more deck spans along this 472-metre-long viaduct, and the adjacent viaducts that run alongside it.”

Ian Johnson, Project Director MMSDJV, said, “This is a fantastic milestone moment for the project team. Seeing the first span in place is the realisation of the collaborative, innovative approach to design that the Mott MacDonald and SYSTRA Design Joint Venture has embraced, which will ultimately help high speed trains to run from Old Oak Common to Birmingham.”