HS2 Delta Junction milestone as four Coleshill viaduct decks completed

Construction teams on HS2 have completed four parallel viaduct decks at the new Delta Junction outside Birmingham, marking a significant milestone on one of the most intricate sections of the high-speed railway.

The structures, located near Coleshill in Warwickshire, extend for more than 600 metres and form part of the vast triangular interchange being built to the east of the city. Much like Birmingham’s Spaghetti Junction, the Delta consists of a network of viaducts, flyovers and underpasses designed to carry the high-speed line over motorways, local roads, existing railways, rivers and floodplains.

The Coleshill East and West viaducts make up the southern section of the junction, where the railway divides as it crosses a local road and the floodplain of the River Cole between the M6 and M42. Two of the parallel spans will accommodate the four-track main line running north to south, while two narrower structures on either side will link services to and from Birmingham Curzon Street station.

Delivered by HS2’s Midlands main works contractor, Balfour Beatty VINCI, the viaducts stretch for a combined 2.4 kilometres. Their decks are formed from 1,024 precast concrete segments produced at a dedicated facility in Kingsbury before being transported to site for installation. The central deck, measuring 22 metres in width, is made up of two rows of 11-metre-wide segments, each weighing 60 tonnes. The two single-track viaducts use smaller segments weighing 44 tonnes. In total, the structures are supported by 54 reinforced concrete piers, each reaching heights of up to 12 metres.

Engineers installed the segments using a cantilever method, temporarily securing each piece with steel cables until individual spans were complete. Permanent post-tensioned cables were then threaded through the hollow core of the viaducts to strengthen the structures. This process was repeated span by span until all decks were assembled.

With the main deck construction now finished, work will continue on final elements including kerbs and parapets.

Caroline Warrington, HS2 Ltd’s Head of Delivery, said:

“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.”

Simon Albarel, Section Manager at Balfour Beatty VINCI, said:

“We’re continuing to make great progress on the construction of HS2’s Delta Junction – one of the most complex sections of the entire route. Our latest milestone is the successful installation of 1,024 pre-cast segments along all the Coleshill Viaducts. Completing the deck assembly is another great achievement for the team, demonstrating their precision engineering and hard work over the last two and a half years.”

Image: HS2