HS2 has released stunning new time-lapse footage showing engineers carefully pushing a 3,700-tonne viaduct deck nearly half a mile uphill into position near the town of Wendover in Buckinghamshire.
The deck of the 450-metre-long Wendover Dean Viaduct was assembled in three stages, each 90 to 180 metres long, with each stage being pushed out from the northern abutment before the next section was fitted behind it.
This painstaking eight-month process meant that the weight of the deck increased with each push, from an initial 590 tonnes when work began in January to 3,700 tonnes when it reached the south abutment on Saturday.
It is one of 50 major viaducts on the HS2 project, which aims to improve connections between London, Birmingham and the North, while creating space at the busiest southern end of the existing West Coast Main Line.
During the landslide, special pads coated with Teflon – a material normally found on the surface of non-stick frying pans – were used to minimise friction between the deck and temporary steel bearings on top of each of the concrete pillars.
To maintain control, the deck – which weighs as much as 264 double-decker buses – was pushed slightly uphill, with the end point approximately 1.8 meters higher than the starting point.
With the steel structure now in position, engineers can begin the challenging task of lowering the deck 60 cm onto the permanent bearings that will support the entire weight of the structure.
During the two-month operation, the steel structure above each pillar will be carefully lowered by 20 centimeters, pillar by pillar, until the entire 450-meter-long deck is in its final position.
Nicola Henderson-Reid, Head of Delivery at HS2 Ltd, said: “The last eight months have been incredible and I would like to thank everyone who has got us to where we are today. It has been fascinating to watch the deck slowly being lowered into position and we are now looking forward to the next phase of the project – lowering the deck into its final position and completing the complex concrete works that will support the new railway.”
Once the deck is in its final position, concreting of the track can begin, using specially designed movable formwork. This phase, which will proceed slowly from north to south, is expected to take around a year. The parapets will then be installed along the edge of the viaduct.
The Wendover Dean Viaduct is the first major railway bridge in the UK to be built using ‘double composite’ construction, using significantly less carbon-intensive concrete and steel than more traditional construction.
Rather than using massive prestressed concrete beams to form the bridge spans between the viaduct piers, the hollow ‘double composite’ structure uses two steel beams between two layers of reinforced concrete to create a more efficient, super-strong bridge span. A similar approach is also used at Small Dean, Westbury, Lower Thorpe and Turweston, all of which are at an earlier stage of construction.
All five viaducts will be built by HS2 Ltd’s main contractor, EKFB – a team comprising Eiffage, Kier, Ferrovial Construction and BAM Nuttall. The fabrication and installation of the girders will be managed by specialists at Eiffage Metal.
Photo credit: HS2
