Crucial work begins on manufactured HS2 viaduct located near Aylesbury

The next phase of work on the major HS2 viaduct located near to Aylesbury has begun.

HS2 has begun assembling the UK’s first major railway viaduct to be entirely manufactured off-site.

Work is happening away from the Bucks location for in a bid to improve safety and efficiency.

Called, Thame Valley Viaduct, on completion the structure will be 88m long. It is being manufactured in a factory before being slotted together on site like a giant Lego set.

Estimations from HS2 state that this move will cut carbon emissions connected to the construction of the viaduct by roughly a third.

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.

Overall, 68 giant concrete piers – each weighing 42 tonnes - are being cast at PACADAR UK’s factory on the Isle of Grain, in Kent, before being transported to site by road.

So far, 14 have been lifted into position on top of their foundations over the last four weeks.

When completed the viaduct will be 3m above the ground, with 36 even spans crossing the river and surrounding wetlands.

Applying lessons from the construction of recent high-speed rail projects in Spain, the design team opted for two 25m long hollow beams per span.

Tomas Garcia, HS2 Ltd’s Head of Civil Structures said: “Thame Valley may not be HS2’s biggest viaduct, but it does represent a major step forward in terms of its structural design. The post-tensioned double-beam approach used here has enabled the whole viaduct to be manufactured off-site - dramatically improving efficiency, safety and quality while delivering outstanding performance and durability.

"It’s great to see the first piers in place as our construction partners begin to assemble this ground-breaking viaduct.”

HS2 Ltd’s main works contractor, EKFB designed the viaduct.

A spokesman for HS2 added: “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 – and allowing every major element of the structure to be pre-fabricated.”

Network Rail has announced further HS2 work to be completed in Aylesbury over the summer. Chiltern Railway services between Princes Risborough and Aylesbury will be halted while engineers make changes to enable HS2 trains to pass under the existing track.

Tiago Palas, FC Civils Solutions head of operations, said of the viaduct project: “The construction team is thrilled with progress made so far. In a short amount of time, we have successfully installed fourteen pre-fabricated piers as well as pressing ahead with the other stages of works, on-and-off site, such as pile cap construction and the production of the precast beams ready for installation in autumn.

“Slotting the piers into place takes precision, collaboration and the expertise of the team, however, it’s a relatively quick process - an efficiency enabled by its innovative design and construction methodology.”