HS2 has successfully finished building four parallel viaduct decks on a complex triangular intersection located to the east of Birmingham.

The viaducts are more than 600 metres long and are located near Coleshill in Warwickshire. They form a small part of the massive Delta junction, which consists of a series of interconnected viaducts, flyovers and underpasses. Between them, these will take HS2 over motorways, local roads, railways, rivers and floodplains.

The Coleshill East and West viaducts are the southern part of the junction. In this part of the junction, the railway splits and crosses a local road and the River Cole’s floodplain, between motorways M6 and M42.

Two of the viaduct spans, which are parallel to each other, will carry the four-track mainline running north and south. Two narrower viaducts on either side of these will carry services to and from HS2’s new Birmingham Curzon Street station in the centre of the city. Together, the viaducts stretch for 2.4km.

Their decks are made of 1,024 concrete segments, which were built away from the site at Kingsbury before being moved to the site. The segments were then lifted into position and secured.

The central deck is 22 metres wide, comprising two rows of 11-metre-wide segments, with each weighing sixty tonnes. The two single-track viaducts are comprised of single rows of segments weighing 44 tonnes each, supported by 54 reinforced concrete piers, which are up to twelve metres high.

Balfour Beatty VINCI is building the Coleshill viaducts for HS2. Its engineers used a cantilever system to install the segments, which involved steel cables supporting each one until the spans were finished. They then installed post-tensioned cables in the centre of the viaduct in order to make the structure stronger.

Now that the deck segments have been installed, HS2 will move on to finishing work, including completing kerbs and parapets.

“HS2 will transform journeys between our two largest cities, while freeing up space on the existing West Coast Main Line for more freight and local services.

“The Delta forms a key part of the project and it’s great to see it starting to come together. I’d like to thank everyone involved in the Coleshill viaducts and look forward to seeing more progress in the year ahead, as the focus turns to completing the robust kerbs and parapets.”

Caroline Warrington, HS2 Ltd’s Head of Delivery