HS2’s innovative Wendover Dean Viaduct enters a critical new stage of construction as engineers begin the job that will see almost half a kilometre of bridge deck slid into position over the next year, high above the Misbourne Valley in Buckinghamshire.

The 450m-long viaduct will be the first major railway bridge in the UK to be built with a ‘double composite’ approach, which uses significantly less carbon-intensive concrete and steel than a more traditional design – and has allowed HS2 to halve the amount of embedded carbon in the structure.

It is one of 50 major viaducts on the HS2 project – which is designed to improve connections between London, Birmingham and the North while freeing up space on the most congested southern end of the existing West Coast Main Line.

Instead of using solid pre-stressed concrete beams to form the spans between the viaduct piers, the ‘double composite’ structure uses two steel beams sandwiched between two layers of reinforced concrete to create a lightweight and super strong hollow span. 

Due to the length of the viaduct, the deck is being assembled in three stages, ranging from 90m to 180m sections, with each one pushed out from the north abutment before the next section is attached behind it. This painstaking process means that the weight of the deck will increase with each push, up from an initial 590 tonnes this week to 3700 tonnes by the end of the year.

James Collings, EKFB’s senior engineer, said:

“The project team has reached a fundamental milestone in the build of this industry-leading viaduct. We’re progressing well with the first-of-three steel launches being conducted this year and already looking forward to seeing this viaduct come to life. Along with our supply chain partners, Eiffage Metal, we’re proud to be delivering this viaduct safely and to programme.”