Gallery: HS2 completes Coleshill viaduct decks at Delta junction

Engineers from the Balfour Beatty Vinci (BBV) joint venture have completed the installation of four parallel viaduct decks at HS2’s Delta junction outside Birmingham.

The structures form part of the high-speed rail route as it approaches Birmingham from the south, carrying the high-speed line over floodplains, local roads and existing infrastructure near Coleshill in Warwickshire.

The Coleshill East and West viaducts stretch for more than 600 metres and sit within the triangular Delta junction, a complex intersection east of Birmingham designed to split the railway towards the city centre and the north.

BBV, as HS2’s main works contractor for the Midlands, is delivering the package under a design-and-build contract.

The Delta junction comprises interconnected viaducts, flyovers and underpasses.

It takes the railway over motorways, railways, rivers and floodplains between the M6 and M42 corridors.

The Coleshill viaducts form the southern section of the junction, where the four-track railway diverges as it crosses a local road and the floodplain of the River Cole.

A pair of parallel spans will carry the four-track main line running north-south. Two narrower single-track viaducts on either side will provide services to and from Birmingham Curzon Street station.

In total, the viaduct decks extend 2.4km and comprise 1,024 precast concrete segments manufactured offsite by BBV at a purpose-built facility in Kingsbury. The segments were transported to site and lifted into position to form the spans.

The central 22-metre-wide deck consists of two rows of 11-metre-wide segments, each weighing 60 tonnes.

Each single-track viaduct was formed from single rows of 44-tonne segments. The decks are supported by 54 reinforced concrete piers, each up to 12 metres high.

BBV installed the segments using a balanced cantilever method. Temporary steel cables supported each segment until the spans were completed.

Permanent post-tensioned cables were then threaded through the hollow core of the deck to strengthen the structure.

The process was repeated between each pier until all spans were in place.

Simon Albarel, section manager at BBV, said the installation of 1,024 precast segments marked a milestone on one of the most complex parts of the route.

With the deck assembly complete, work is now focused on finishing elements including kerbs and parapets before the structures are prepared for track installation, said Caroline Warrington, head of delivery at HS2 Ltd.