Final design unveiled for Thame Valley viaduct
Plans to construct it ‘like a giant Lego set’ will cut carbon footprint.
THE 880 metre-long viaduct that will carry HS2 trains across the flood plain of the River Thame, near Aylesbury, will use what HS2 Ltd describes as “pioneering prefabricated construction methods”, which will see the structure “slotted together like a giant Lego set”.
With its underside only three metres above the ground, the viaduct will consist of 36 even spans taking the high speed route over the river and adjacent wetlands. The extension of the piers almost to the parapet edge is designed to enhance its light and narrow appearance.
It is estimated that the prefabrication process will reduce the embedded carbon of the structure by 19,000 tonnes. Its carbon footprint is calculated to be 66% lower than that of the original design.
It was changed to allow all major elements (including the 35 viaduct piers, which will arrive ready to be placed onto their foundations) to be made off-site and, in what has been described as a “major step forward for viaduct design in the UK”, engineers decided on two wide box girder beams per span rather than eight smaller beams in order to simplify and speed-up assembly.
Prefabrication
“Prefabrication and off-site manufacturing offer huge benefits in terms of efficiency and this design will help us deliver a more efficient, durable and elegant structure with less concrete and steel,” explained HS2 Ltd’s head of civil structures Tomas Garcia.
Janice McKenna, technical director for main works contractor EFKB added: “The structurally efficient solution means we minimise the embedded carbon in the viaduct materials and we have also been able to reduce emissions during construction by maximising off-site prefabrication to achieve an efficient build, as well as reducing the number of HGVs on local roads.”
Site preparations have already begun and designers are considering whether a similar approach can be applied to the construction of other smaller viaducts on the route.