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HS2 | 700t bridge building machine begins construction of record-breaking viaduct

Work has begun on HS2’s first and longest viaduct, the Colne Valley Viaduct, with the powering up of the 700t bridge building machine.

At 3.4km, the Colne Valley Viaduct will be the longest railway bridge in the UK. It will cross a series of lakes and waterways between Hillingdon and the M25. The viaduct construction is being led by Align JV – made up of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick.

The machine, known as a ‘launching girder’, has been shipped in pieces from Hong Kong, having been used on a number of projects there and in Singapore. It has been put together by engineers on site over the last few months and is the only of its kind operating in the UK.

The 18m-high, 18m-wide and 160m-long machine will sit on top of the bridge piers and lift the giant concrete deck segments that form the viaduct’s arches into position. Once a section is complete, the machine’s hydraulic rams push it forward and into position to build the next stage.

There will be a total of 1,000 concrete segments needed for the viaduct’s deck. They are in a variety of shapes to allow for the viaduct’s gentle curves, and each weigh up to 140t – around the size of a double-decker bus. They are being manufactured in a 105,000m3 purpose-built temporary factory close to the viaduct’s north abutment. The segments are manufactured at a rate of 12 per week and those already completed have been waiting in storage until the launching girder was powered up.

Assembly of the viaduct is expected to complete in 2024.

The viaduct will have 56 piers of around 370t, which each are currently being constructed along the Colne Valley. The machine will then follow along the pre-constructed piers, installing the deck segments. The machine places one segment on each side of the central pier, using a cantilever approach to balance the structure, with the two half-arches on either side of the pier being constructed simultaneously. Steel tensioning cables are then threaded through the segments to strengthen the structure.

The machine has been named Dominique in memory of Bouygues engineer Dominique Droniou who played a leading role in its design and development.

HS2 Ltd chief executive Mark Thurston said: “I’m absolutely delighted that we have started work to assemble the giant deck segments that will form the Colne Valley Viaduct. It is yet another big milestone for HS2 Ltd, as we work to deliver the UK’s new high speed railway. Once complete, this record-breaking structure will form a key part of the HS2 railway – helping to deliver better connections across the UK, free up rail capacity on the train network, and offer passengers a zero carbon travel option.

“I’d like to thank all those involved in getting us to this exciting stage and look forward to seeing the whole viaduct come together over the coming years.”

Align project director Daniel Altier said: “The start of the erection of the deck segments marks the latest important milestone for Align, relating to the construction of the Colne Valley Viaduct.

“There has been a lot of hard work involved to get us to this point, and the achievements so far are a great example of what collaboration and excellent teamwork can deliver. I would specifically like to acknowledge the contribution from our supply chain partners - VSL, Kilnbridge, KVJV, VolkerStevin, Tarmac, Sendin and Vaughan Plant Haulage.”

HS2 minister Andrew Stephenson said: “Today, HS2 began construction on what’s set to be Britain’s longest railway viaduct, a landmark moment for HS2 and a feat of British engineering, taking the HS2 line from London, and into Hertfordshire and Buckinghamshire.

“Infrastructure is the backbone of HS2 and this viaduct will be integral to delivering faster journeys and an increased capacity rail network.”

HS2 has also released a video explaining how the machine will build the bridge:

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