HS2 installs 1,024 precast segments to complete Coleshill viaduct decks

HS2 engineers have completed deck assembly for four parallel viaducts at Coleshill, marking a significant milestone in the construction of the Delta Junction to the east of Birmingham.

The Coleshill East and West viaducts stretch for more than 600 metres across the B4114 (Birmingham Road) and the floodplain of the River Cole, between the M6 and M42 motorways. Together, the viaduct structures extend for a combined total of 2.4km and form the southern section of the complex triangular junction that will connect the high-speed mainline with services to and from Birmingham Curzon Street station.

The decks were formed using 1,024 precast concrete segments manufactured at a dedicated facility in Kingsbury. Each segment was transported to site and installed using a balanced cantilever construction method. Temporary steel cables supported each segment until spans were completed, after which permanent post-tensioned tendons were installed within the hollow deck to provide structural continuity and strength.

The central 22m-wide deck consists of two parallel rows of 11m-wide segments weighing approximately 60 tonnes each. The two outer single-track viaducts are constructed from smaller segments weighing around 44 tonnes. The structures are supported by 54 reinforced concrete piers rising up to 12 metres in height.

With deck assembly complete, works are now progressing to finishing elements including kerbs and parapets. The Delta Junction comprises interconnected viaducts, flyovers and underpasses designed to carry the high-speed railway over existing roads, rail infrastructure, rivers and floodplains.

HS2 spans 140 miles between London and Birmingham, with the Delta Junction representing one of the most technically complex sections of the route.