HS2 slides an enormous 4,600-tonne viaduct across the M6 without closing motorway in UK first
It is thought to be the first time this technique has been used on a UK motorway.
Engineers working for the HS2 project claimed a UK-first over the weekend when they successfully slid an enormous 4,600-tonne viaduct across the M6 without closing the motorway – significantly reducing disruption to drivers.
The 17 hour-long operation was the culmination of an epic three-stage process to assemble and install the 315-metre East deck of the M6 South viaduct, which will carry high-speed trains heading to Birmingham and further north.
While the previous slide had required a weekend closure of the main carriageway, the team – led by HS2’s main work contractor Balfour Beatty VINCI (BBV) – worked closely with National Highways to develop the ‘fully restrained’ process which allowed them to safely slide the final section above the moving traffic.
To deliver this, they initially closed the M6 overnight between Junctions 4 and 5 on Thursday 11 December to shift the viaduct slightly forward by twelve metres. This was to ensure that both ends of the enormous beam were fully supported on concrete piers during this 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, with only the M42 slip closed during the weekend.
The successful operation means the project to construct the M6 South viaduct has reached 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.
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 characteristic ‘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 in height. A 4.5-metre-high 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.