The video shows a timelapse of the viaduct being slid into position, the heaviest and longest single-stage viaduct in HS2 so far
The Small Dean viaduct weighs 4,500 tonnes over 345m and was slid across a road and railway line into position.
The viaduct is located near Wendover in Buckinghamshire, crossing over the A413 and the railway to Aylesbury.
The Small Dean viaduct is one of 50 in HS2
The deck of the viaduct, made of concrete and steel, was fully assembled beforehand, along with the majority of the precast concrete slabs. While this increased the weight before the slide commenced, it did also save time later in the project.
The Small Dean viaduct has been the heaviest and longest slide of a signal-stage viaduct deck of the whole HS2 project so far.
The operation was completed so quickly that the A413 was re-opened at 8:30pm on Friday, a full nine hours ahead of schedule.
Pads made of PTFE were used in the slide to reduce friction between the assembled deck and the temporary steel bearings on top of each of the piers, and a cable system was used to slide the deck forward as fast as 10 metres per hour.
HS2 Ltd project manager, Jason Bicknell, said: “Small Dean is the longest continuous deck slide on the project and an amazing engineering achievement. But it would not have been possible without the huge amount of preparatory work put in over the last few years and I’d like to thank everyone involved. Two years ago, we set a target to install the deck in summer 2025 and it’s great that we came in ahead of schedule.”
The site was prepared for years
The HS2 team in the region had spent the last four years preparing the site for the Small Dean viaduct slide, including diverting utilities, realigning the road, building abutments, and building six piers to support the viaduct, alongside actually constructing the viaduct deck.
Now that the deck is in place, work will commence to lower it by 60cm onto its permanent bearings to support the viaduct’s weight. Over two months, the viaduct will be lowered by 20cm at a time until fully settled.
This viaduct also marks one of only two areas in the Chilterns where HS2 is above ground level.
The deck is made from weathering steel to match the surrounding natural landscape, and along with the Wendover Dean viaduct, the Small Dean viaduct is made of ‘double composite’ structures, including layers of reinforced concrete on the top and bottom to make a box-like span and cutting the amount of embedded carbon.
EKFB, one of the main HS2 contractors is delivering the viaduct. Martin Gamble, EKFB’s senior project manager, said: “The team at Small Dean Viaduct has worked tirelessly over a number of years to prepare for this momentous event. Through careful planning and by implementing time-saving measures, we’ve accelerated the bridge and support construction, bringing the launch date forward.
“The complexity of the interfaces with the road and railway have provided a real challenge which, with the assistance of Network Rail and Buckinghamshire Council, we have risen to and overcome while keeping disruption to the surrounding area to a minimum.”
The post [VIDEO] HS2 Small Dean viaduct slid into position in just four days appeared first on Planning, Building & Construction Today.