Every major element of the viaduct will be manufactured by Pacadar UK at its factory on the Isle of Grain in Kent.
Thame Valley is one of 15 viaducts designed by client HS2 Ltd’s main works contractor, EKFB - a team made up of Eiffage, Kier, Ferrovial Construction and BAM Nuttall - working with on-site construction partner FC Civils Solutions and precast specialist, Pacadar UK.
The first of the 68 piers has now been produced for the high-speed rail project’s first entirely offsite-manufactured modular viaduct.
HS2 said that that project represents a major step forward for viaduct design in the UK. The 880m-long viaduct’s carbon footprint is being cut by about a third thanks to the decision to make every major element in the factory before slotting them together on site. This includes all of the 68 concrete piers that will support the viaduct.
Above: completed pier components
Lessons are being applied from the construction of recent high-speed rail projects in Spain. The design team opted for a simple structural solution with two 25m-long hollow beams per span, which cuts the amount of carbon-intensive concrete and steel, while simplifying work on site.
These 97t beams – and the 42t piers that support them – are being manufactured at the factory on the Isle of Grain, which also produces tunnel wall segments for HS2’s London tunnels. The workforce has doubled to 200 people, including apprentices and graduate engineers from nearby universities.
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. It’s great to see the start of work at Pacadar UK and I look forward to seeing assembly begin on site, later this year.”
The viaduct will cross flood plain of the River Thame, just outside Aylesbury in Buckinghamshire. It will carry HS2 trains at speeds of up to 360km/h between London, Birmingham and the north. The underside of the viaduct will be just 3m above the ground, with thirty-six even spans crossing the river and surrounding wetlands.
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 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.”
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.”