Installation is under way on a viaduct for the HS2 high-speed railway project, the UK’s first major rail viaduct to be entirely manufactured off-site.

Fourteen piers weighting 42t have already been lifted into position by crane, according to the latest video update (June).

The precast method is estimated to have reduced the project’s carbon footprint by around a third while also improving efficiency and site safety.

The viaduct crosses the Thame River plain outside Aylesbury, a town located approximately 65km north-west of London. It consists of 36 spans supported by 68 concrete piers 3m above the ground. Each span is made from two 25m-long hollow beams.

Unlike traditional viaduct beams which are secured together above each pier with a cast in situ concrete diaphragm, the larger Thame Valley precast beams are secured directly to one another without a diaphragm. This approach allows every major element of the structure to be prefabricated, reducing the number of lorries needed to deliver material to site.

The structure was designed by HS2’s main contractor EKFB, a joint venture made up of Eiffage, Kier, Ferrovial Construction and Bam Nuttall, working with their design partner ASC, a joint venture between Arcadis Setec and Cowi, and specialist architects Moxon. Precast concrete specialist Pacadar is manufacturing all components for the viaduct at their factory in Kent, around 64km southeast of London. FC Civil Solutions is the specialist on-site construction partner supporting EKFB in building Thame Valley.

According to production estimates, the manufacturing of Thame Valley Viaduct should finish by the end of this year.

Once complete, the viaduct will carry HS2 trains at speeds of up to 360km/h between London, Birmingham and the North, improving railway connectivity while freeing up space for more freight and local services on the existing network.

You can read more about the prefabricated viaduct solution and its application on the Thame Valley project in Bd&e’s upcoming issue (#112) which will feature a site visit to the Pacadar UK precast facility in Kent.