Construction of a 14,500-tonne box structure designed to take the UK’s new HS2 line under the A46 Kenilworth Bypass in Warwickshire has taken a major step forward, following the successful installation of 120 beams. The concrete beams, ranging between 13m and 24m in length, were carefully lifted into place using three giant cranes to form an integral part of the structure’s top. A dedicated team of engineers worked round the clock to successfully complete the entire operation ahead of schedule in just 14 days.
Due for completion later this year, the huge box is currently being built on land next to a section of the A46 rather than constructing it beneath the carriageway itself – avoiding the need for up to two years of traffic management measures.
With the beams now in place on top of the box, the finishing touches include completing the deck – the flat surface placed on top of the beams – and installing parapets. In spring, the completed structure will be moved into position under the existing carriageway using an innovative technique.
This will involve a jacking mechanism, designed by specialist civil and structural engineering company Freyssinet, which will push the box across on a guiding raft at a speed of up to 2.5m per hour for a total distance of 64m.
Together with National Highways and its construction partner for the West Midlands, Balfour Beatty VINCI (BBV), HS2 has started preparing for the box push procedure.
A section of the A46 between Festival Island (Coventry) and Thickthorn Island (Kenilworth) will be closed for two weekends next month for the first stage of preparation work – with plans to move the structure into position during a full closure of the A46 Kenilworth Bypass in spring 2025 for up to three weeks.
John McNiffe, Project Director at Balfour Beatty VINCI, said: “The safe and successful installation of 120 giant beams is another great achievement for the Balfour Beatty VINCI team who are delivering this box bridge slide in Warwickshire. This 14-day operation required huge amounts of planning and precision and I’m really proud of the way they’ve responded to this challenge.
“The next stage includes construction of the deck and installation of the bridge parapets before the bridge can be moved into position under the existing carriageway, allowing HS2 trains to pass underneath.”
The structural design has been carried out by Balfour Beatty VINCI’s Design Joint Venture, made up of Mott MacDonald and SYSTRA (MMSDJV).
Tim Akers, Engineering Manager for the Mott MacDonald SYSTRA Design Joint Venture, said: “We’re incredibly proud of the part we’ve played in the development of this structure. Through significant collaboration between HS2, National Highways and Balfour Beatty VINCI, the design has been reviewed and changed from a traditional ‘top down’ approach to an offline construction method with automated rapid and safe installation, reducing the impact to road users significantly.”
Construction of HS2 continues at pace between the West Midlands and London, with the programme now supporting over 31,000 jobs. When complete, HS2 services will run between London and the West Midlands on a dedicated high-speed line before reaching destinations further north via the existing West Coast Main Line.
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