Construction of an 880-metre long viaduct that will carry HS2 across the Thame Valley near Aylesbury in Buckinghamshire has now passed the halfway point.

When complete, the viaduct with 36 even spans crossing the river and surrounding floodplain will merge into the landscape, as it has a simple and consistent profile that is just 3 metres above the ground.

44 of the viaduct’s 72 customised pre-cast beams are now in position, 66 of the 70 piers installed, and work is well underway on the deck to support the railway.

The beams, 42-tonne concrete piers, parapets, and concrete planks that form the track deck were all cast by Pacadar UK at its factory on the Isle of Grain.

Instead of using the traditional approach of multiple narrow beams for each span, a simpler solution has been adopted with just two larger hollow 20 or 25-metre U-shaped beams for each span.

The design was inspired by viaducts on the Spanish high-speed rail network.

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Traditional construction methods secure the beams above each pier with a concrete ‘diaphragm’ cast in situ.

In the Thame Valley viaduct, the beams are secured directly to each other, which removes the need for the diaphragm or concrete to be poured on site.

This process results in a much-reduced carbon footprint by using less carbon-intensive concrete and steel in the structure.

HS2’s main works contractor EKFB comprising Eiffage, Kier, Ferrovial Construction, and BAM Nuttall, was responsible for the design, with construction being carried out by FC Civils Solutions.

A similar approach to the methods used for construction of the Thame Valley Viaduct is being used for the nearby Edgcote Viaduct in Northamptonshire.

Thame Valley is one of the longest – and from an engineering perspective, one of the most interesting – structures on the project and it’s been great to see so much progress over the last six months.  

The post-tensioned double-beam approach used here has enabled more of the viaduct to be manufactured off-site – dramatically improving efficiency, safety and quality while delivering outstanding performance and durability.

Ben Sebastian-Green, HS2 Ltd Senior Project Manager

We’re at a crucial and exciting stage with the construction of this innovative viaduct, with beams, piers, post tensioning and pre-cast slabs under construction. This incredible progress is a testament to the hard work and drive of our expert teams. We’re all very excited to see this structure being delivered safely and to programme.

Emma Bolado-Arroyo, EKFB’Project Manager