Building work continues on Britain's longest rail bridge

Aerial view of HS2's Colne Valley Viaduct - image copyright HS2 Ltd

HS2 has released new images showing the progress on Britain’s longest railway bridge.

The high seed railway's longest viaduct will span 2.1miles across the Colne Valley on London's north western edge when complete.

It has been engineered to carry trains speeding between HS2's London and Chiltern Hills tunnels at up to 200 miles per hour.

Stretching for more than 3.4km across a series of lakes and waterways between Hillingdon and the M25, the Colne Valley Viaduct will carry the new high-speed line across a series of lakes and waterways. It will be almost a kilometre longer than the Forth Rail Bridge.

The viaduct project is being led by HS2’s main works contractor Align JV – a team made up of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick.

Construction began in early 2021, with a team of ground engineers sinking the first of almost 300 piles that form the foundations for the Colne Valley Viaduct.

In spring 2022, a 700 tonne bridge-building machine was launched on site. Known as a ‘launching girder’, the 160m long bridge-building machine is the only one of its kind in the UK and will be used to lift the giant concrete deck segments that form the viaduct’s arches into position. 

Once each section is complete, the machine will inch itself forward into position to build the next stage.

A total of 1,000 deck segments will be needed, with each one weighing up to 140 tonnes. To allow for the gentle curves of the viaduct as it crosses the valley, all the segments are slightly different shapes and made on site at a purpose-built temporary factory close to the north abutment.

In November 2023 main construction of the bridge officially passed the half-way mark. 

Once construction is complete, the factory and surrounding buildings will be removed and the whole area between the viaduct and the Chiltern tunnel will be transformed into an area of chalk grassland and woodland as part of HS2’s ‘green corridor’ project.

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