The Colne Valley viaduct, which spans 3.4 km (2.1 miles), is being built by Align JV for HS2 Ltd to carry the new London-Birmingham railway line.
The structure carries HS2 at a height of 10 metres across the Colne Valley near the M25 motorway and the village of Denham.
It takes the record of the country鈥檚 longest rail bridge from the 3.3km Tay Bridge, built in 1887 to link Fife and Dundee.
The Colne Valley viaduct鈥檚 construction is being managed by the main works contractor Align JV 鈥� a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick. It is one of 500 bridging structures on the HS2 project.
Building work on the viaduct鈥檚 deck began in May 2022. Over the 28 months since then, the launching girder has lowered into place 1,000 deck segments.
Edging forward from north to south and supported on the viaduct鈥檚 56 piers, the 160 metre long launcher used a balanced-cantilever method to lower deck segments into place to form half an arch either side of a pier before moving to the next pier to complete the arch span by repeating the process.聽聽聽
The 1,000 pre-cast segments were made on-site at a purpose-built factory. Each of the segments is uniquely shaped to enable the structure to curve.
HS2 Ltd senior project manager Billy Ahluwalia said: 鈥淟owering the Colne Valley viaduct鈥檚 final deck segment into place today marks the culmination of more than 10 years of planning, design and construction. I pay tribute to the dedicated team that has delivered a bridge that is both the longest on HS2 and has become the United Kingdom鈥檚 longest railway bridge 鈥� taking a record that had stood for nearly 140 years. That is a historic achievement of which we can all be immensely proud.鈥�
Align project director Lo茂c Menard said: 鈥淭he Align team, along with our supply chain partners VSL who operated the launching girder, have worked very hard to get us to where we are today, ahead of plan. Working together and as a truly integrated team that includes HS2, Align, our design partners, our supply chain colleagues and the local community, we have built the Colne Valley Viaduct which will be the iconic feature of HS2.鈥�
The milestone comes a week after the completion of HS2's first major viaduct, at Highfurlong Brook in Northamptonshire. [See previous report here.]
Work is also progressing on the Delta Junction viaducts in the West Midlands and the elevated approaches to Curzon Street station.
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