Engineers working on HS2’s triangular intersection outside Birmingham have completed the construction of four parallel viaduct decks.
Construction of the Coleshill viaducts, which stretch for a combined total of 2.4km, is being delivered by HS2’s main works contractor in the Midlands, Balfour Beatty Vinci (BBV).
The viaducts form a small part of the Delta junction – a major intersection being built to the east of Birmingham for the new high-speed railway.
Like the nearby Spaghetti Junction, the Delta features a series of interconnected viaducts, flyovers and underpasses, taking the high-speed line over motorways, local roads, railways, rivers and floodplains.
The Coleshill East and West viaducts form the southern part of the junction, where the railway splits as it crosses a local road and the floodplain of the River Cole, between the M6 and M42.
Two parallel viaduct spans will carry the four-track mainline running north and south, while two narrower viaducts on either side will carry services to and from the new Birmingham Curzon Street station in the city centre.
‘Precision engineering’
Simon Albarel, section manager at BBV, 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 precast 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.”
The 1,024 concrete segments were manufactured offsite at a purpose-built facility a few miles away at Kingsbury. These were then moved to site before being lifted and secured into position to form the spans of the viaducts.
The central 22m-wide deck consists of two rows of 11m-wide segments, each weighing 60 tonnes, while the two single-track viaducts comprise single rows of smaller, 44-tonne segments. They are supported by 54 reinforced concrete piers, each up to 12m high.
BBV used a cantilever process to install the segments with temporary steel cables supporting each one until the spans were complete. Permanent post-tensioned cables were then installed in the hollow centre of the viaduct to strengthen the structure.
The same process was repeated between each of the piers until all the spans were complete.
Following the installation of the deck segments, the focus is now turning to the finishing works, with the robust kerbs and parapets still to be completed.
