HS2 has revealed the first of 68 giant piers that will support the high-speed-rail project’s first entirely offsite manufactured modular viaduct.
HS2 says the move represents a “major step forward” for viaduct design in the UK.
Unlike more traditional viaduct designs, every major piece of the 880-metre-long Thame Valley Viaduct will be made in a factory before being slotted together on site “like a giant Lego set”.
This process cuts carbon emissions by around a third, according to HS2.
The design team opted for a simple structural solution with two 25-metre-long hollow beams per span, which, as similar projects in Spain have shown, cuts the amount of carbon-intensive concrete and steel, while simplifying work on site.
These enormous 97 tonne beams – as well as the 42-tonne piers that support them – are being manufactured at PACADAR UK’s factory on the Isle of Grain.
The MMC factory also produces tunnel-wall segments for HS2’s London tunnels.
Commenting on the start of production, Tomas Garcia, HS2 Ltd’s head of Civil Structures, said: “HS2 will offer zero-carbon journeys from day one, providing a cleaner, greener way to travel and help the fight against climate change.
“But we’re also serious about cutting embedded carbon in construction, reducing cost and programme, and improving safety, performance, and durability.
“Thame Valley is a great example of how our contractors are embracing the latest engineering techniques to do just that.”
Crossing the flood plain of the River Thame, just outside Aylesbury, the viaduct will carry HS2 trains at speeds of up to 360km/h between London, Birmingham, and the north of England.
Set low into the landscape with a simple and consistent profile, the underside of the viaduct will sit just three metres above the ground, with 36 even spans crossing the river and surrounding wetlands.
Traditionally, viaduct beams are secured together above each of the piers with a concrete diaphragm, which is cast in situ.
The larger pre-cast beams that will be used at Thame Valley can be secured directly to one another, removing the need for the diaphragm.
HS2 says this improves durability and reliability, saving time, cutting costs, and improving safety by reducing the need for people to work at height.
Ignacio Chicharro, EKFB’s project director, said: “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.
“The solution is a lightweight viaduct, set low into the landscape that benefits from the efficiencies associated with offsite prefabrication.
“Leaning on our onsite 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.”
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- HS2 tunnelling team celebrate milestone tunnel boring machine breakthrough
Fernando Aguilar Pírez, PACADAR UK’s production manager, said: “We’re delighted to have been awarded the contract to manufacture the precast concrete elements for the Thame Valley Viaduct.
“This solution is based on a modular design which is widely implemented by PACADAR on previous high-speed lines.
“This contract reinforces our commitment to HS2, and we look forward to working on this project together with FC Civils Solutions and EKFB.
“PACADAR has brought state of the art construction method 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.”
Main image: Completed piers for the Thame Valley Viaduct at the Pacadar UK factory May 2023. Credit: HS2
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