VIDEO | HS2 engineers claim UK first
Led by Balfour Beatty VINCI, the high-speed rail project’s delivery team has slid into place a 4,600-tonne viaduct across the M6 without the need to close the motorway.
The 17 hour-long operation was the culmination of a three-stage process to assemble and install the 315m east deck of the M6 South viaduct, which will carry trains heading to Birmingham and further north.
The structural design has been carried out by BBV’s design joint venture, made up of Mott MacDonald and SYSTRA, plus WW+P Architects.
While the previous slide had required a weekend closure of the main carriageway, the team worked with National Highways to develop the ‘fully restrained’ process which allowed them to safely slide the final section above moving traffic.
It is thought to be the first time this technique has been used on a UK motorway, although the project did involve closures to support the project.
The M6 was closed overnight between Junctions 4 and 5 on Thursday 11 December, to shift the viaduct slightly forward by 12m – done to ensure that both ends of the beam were fully supported on concrete piers during the weekend’s slide.
The viaduct was then pushed the rest of the way across the busy motorway on Saturday at a speed of 13 metres per hour. The M42 slip road was closed during the weekend.
Construction of the M6 South viaduct is now at the halfway point. Over the next year, the same process will be repeated, with a parallel west deck slid into position alongside the first one to carry trains heading south.
Caroline Warrington, HS2 Ltd’s head of delivery, said: “Along the HS2 route we are pioneering new approaches to engineering and construction in order to deliver more efficiently and with less impact on our neighbours.
“We believe this fully restrained slide was a first for the country, but most importantly it means we’ve been able to cut in half the number of times we’ve had to close the motorway. I’d like to thank everyone who worked so hard to make the operation a success.”
Russell Luckhurst, the BBV engineer leading the delivery of the works, said: “We’re all feeling a huge sense of pride after sliding a 4,600-tonne viaduct into its final position this weekend. The third and final slide of the East deck viaduct was delivered over a live motorway for the first time in the UK, making this achievement even more special.”
Each viaduct is formed of a hollow double-box structure made of weathering steel. The steel boasts a natural protective layer of oxidisation which gives it a ‘rusty’ appearance and reduces maintenance by eliminating the need for regular repainting.
Four pairs of concrete piers support the viaducts with the tallest one measuring 9.9m tall. A 4.5m parapet will be installed on the side facing Chelmsley Wood to reduce noise and disturbance from passing trains.
The viaduct was launched with 82 precast slabs already installed on top of the steel structure. This will further reduce the number of road closures in the future, to complete the viaduct deck works.
