Innovation: Off-site construction first for HS2 viaduct project


Off-site construction methods are being used to deliver a first-of-its-kind project for HS2. 

Credit: HS2.

Concrete product supplier, Pacadar UK, has been appointed to design and construct 68 giant concrete piers for the Thames Valley Viaduct portion of the high-speed rail project in Buckinghamshire.  

Thames Valley is one of 15 viaducts designed by main works contractor EKFB, a team made up of Eiffage, Kier, Ferrovial Construction and BAM Nuttall. 

The on-site construction partner is FC Civils Solution, and Pacadar is the precast specialist. 

Departing from more traditional viaduct design methods, this will be the first modular viaduct manufactured off site within the wider HS2 development, with Pacadar already beginning to deliver the first precast concrete elements from its factory on the Isle of Grain. 

Design and delivery  

Credit: HS2.

Drawing from off-site construction approaches on similar projects abroad, every major element of the 880m-long Thames Valley Viaduct will be made at the factory before being transported to site and slotted together, which could cut the scheme’s carbon footprint by about a third. 

Another structural solution by the design team involves the construction of two 25m-long 97-tonne hollow beams per span, cutting the amount of carbon-intensive concrete and steel, while improving on-site efficiency. The 68 giant piers that support those beams each weight 42 tonnes. 

Traditionally, viaduct beams are secured together above each of the piers with a concrete diaphragm cast in situ. In this case, however, the larger precast beams can be secured directly to one another, removing the need for the diaphragm, improving durability and reliability, saving time, cutting cost and improving safety by reducing the need for operatives to work at height. 

“This internationally inspired design is the product of best-in-class collaboration between HS2, EKFB and its design partners, Ferrovial Construction and FC Civils Solutions,” said Ignacio Chicharro, EKFB’s project director. “The solution is a lightweight viaduct, set low into the landscape that benefits from the efficiencies associated with off-site prefabrication. 

“Leaning on our on-site construction partner, FC Civils Solutions, to provide the expertise which comes with building a prefabricated structure, the viaduct will be slotted together piece by piece. Seeing the viaduct piers in production is a great milestone in the programme calendar and we’re excited to see the start of assembly on-site very soon.” 

Pacadar UK’s production manager, Fernando Aguilar Pírez, added: Pacadar has brought state-of-the-art construction methods in order to optimise the use of materials, reduction of time and therefore remarkable savings and carbon footprint drop. Also using aesthetic solutions which minimise the visual impact on the environment.” 

Around 200 people, including apprentices and graduate engineers, are employed at the Isle of Grain factory delivering contracts for HS2. 

When operational, the viaduct will be just 3m above the ground, carrying HS2 trains at speeds of up to 360km/h between London, Birmingham and the North.  

Pacadar UK’s factory on the Isle of Grain also produces tunnel wall segments for HS2’s London tunnels. 

Video credit: HS2.

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