Major work has been completed on two viaducts being constructed near Brackley in Northamptonshire for the HS2 line between London and Birmingham.

A 2,695-tonne deck for the Westbury viaduct has been successfully slid into position, and construction of abutments at each end of the nearby Turweston viaduct has been completed.

Both viaducts cross the floodplain of the River Great Ouse and are three miles apart.

Built using similar designs, they use an unusual ‘double composite’ approach where a box beam was created with layers of reinforced concrete above and below steel beams.

Westbury viaduct is 320 metres long and was assembled in three stages by pushing one section out from the north abutment before the next section was attached behind it.

It took six months from start to finish until the last section reached the south abutment last week.

To cut friction during the slide, special pads covered in Teflon were placed between the deck and temporary steel bearings on top of each of the concrete piers.

Engineers will now start to lower the deck onto permanent bearings that will support the full weight of the viaduct.

At the nearby Turweston viaduct, now that the two abutments have been constructed, work will begin on assembling the deck girders before they are launched early next year.

Turweston is also the site of a ‘green bridge’ that will provide a path across HS2 for wildlife.

Work on HS2 viaducts is progressing rapidly, with construction being carried out simultaneously on many structures, such as another viaduct in Northamptonshire at Highfurlong Brook.

“It’s been incredible to watch the enormous deck at Westbury come together over the last year and see it so carefully slid into position. I’d like to thank everyone who helped make it happen – and I look forward to seeing similar progress at Turweston in the coming months.
“The innovative double composite structure they share has huge potential to cut carbon in construction by enabling more efficient bridges and I hope that the lessons we have learnt can be successfully applied to other projects across the UK in the future.”

Elizabeth Longinotti, HS2 Ltd’s Senior Project Manager