[VIDEO] HS2 Lower Thorpe viaduct slide completed in just three days

Located near Thorpe Mandeville, West Northamptonshire, the viaduct is the last of five to be slid into place by EKFB

The HS2 Lower Thorpe viaduct is a ‘double composite’ structure, 220m in length and weighing 1,300 tonnes.

The slide took place near the village of Northants and lasted just three days, reaching the north abutment on June 20.

Non-stick pads were used

Pads were used on the slide to reduce friction between the steel bearings on top of the five concrete pillars and the deck. The pads were covered in PTFE, a material not dissimilar to Teflon.

The sliding process can be seen in full in the video below:

This technique has been used in several viaduct slides, including the M6 viaduct near Birmingham, earlier this month.

The Lower Thorpe viaduct is the last of five that are slid using this technique by EKFB – a team of HS2 contractors made up of Eiffage, Kier, Ferrovial Construction, and BAM Nuttall.

With the slide finished, work will now begin on lowering the deck onto the permanent bearings, making way for work on the concrete deck and parapets.

Flood defence and carbon reduction

Built to carry the future HS2 trains over Banbury Lane, the viaduct is built to ensure that rain will not be obstructed from running off into the existing watercourses.

The carbon footprint of the design has also been reduced through the use of the ‘double composite’ structure. This means that pre-stressed concrete beams are replaced with steel beams in a hollow structure, with reinforced concrete used on the top and bottom to maintain the strength.

This technique reduces the carbon footprint of these viaducts by 39-59%.

EKFB’s technical director, Janice McKenna, said: “The strategic design approach applied to these double composite structures has been a game-changer in how we’re building these viaducts. The double composite solution can be applied to multiple structures in different locations, and we have five across EKFB’s 50-mile route that are all well into construction.

“The philosophy was to design the viaducts with architectural input to ‘blend’ the structures into their respective landscapes and reduce the visual impact on the environment. We also required a solution that offered specific delivery benefits too, from saving embedded carbon in the materials we use, to enhancing productivity on site and reducing safety risk.”

HS2 Ltd project manager, Sam Arrowsmith, said: “It’s great to see the viaduct deck in position and I’d like the thank everyone who’s helped get us to where we are today. The slide may only have taken three days, but it was the culmination of four years of work – developing the design, completing the groundworks and the piers and assembling the enormous steelwork.”

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