UK’s longest railway bridge Colne Valley Viaduct completes foundations

UK’s longest railway bridge Colne Valley Viaduct completes foundations

The 2.1 mile (3.4 km) Colne Valley Viaduct will be 100m longer than Dundee’s Tay Bridge, which currently holds the title

The last of 292 concrete piles that will form the foundation for Britain’s longest railway bridge has been installed at HS2’s Colne Valley Viaduct site.

The viaduct is being built by Align JV, HS2 Ltd’s main contractor – a team of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick, working with his contractor KVJV – who have spent almost two years piling it.

KVJV is a team consisting of the Keller Group and VSL International.

Environmental aspects were part of the project from the beginning

HS2 worked closely with Affinity Water and the Environment Agency to monitor water quality and agree on working methods.

These were overseen by a team of specialized engineers during construction to protect the natural environment.

An extensive test piling program was completed prior to work beginning, during which engineers lowered 12 piles in two locations, with geological and structural data from these tests incorporated into the design of the Colne Valley Viaduct.

This resulted in a 10-15% reduction in pile depth and associated time and cost savings.

The largest spans are reserved where the viaduct crosses the lakes, and narrower spans for the approaches. This design was chosen to allow views across the landscape, minimize the viaduct’s footprint on the lakes and help complement the natural surroundings.

When completed, the 3.4km bridge will carry the new high-speed line across a series of lakes and waterways near Hillingdon on the north-west outskirts of London.

The external construction was used for faster project execution

The construction of the foundations, the 56 huge piers and the deck atop them took place in parallel – with separate teams working from north to south. Erection of the decks began last year, with more than 500 meters of the Colne Valley Viaduct structure now complete.

To drive the 66 piles into the lake bed, the team first had to construct over a kilometer of temporary jetties, with cofferdams to hold back the water around each foundation.

The walkways are also used to transport material and equipment during construction of the piers and viaduct deck to keep vehicles off local roads.

On each group of piles – some of which reach as deep as 60m into the ground – a concrete pile cap will support the pier, which in turn will support the weight of the bridge structure above. Instead of hammering the piles into the ground, holes were drilled before being backfilled to make the piles.

The Colne Valley Viaduct’s main deck is being built in 1,000 separate segments at a temporary factory nearby, and assembled using a bridge-building machine that lifts each piece into position before it shifts itself to the next pier.

The Colne Valley Viaduct foundations were delivered with minimal environmental impact

HS2 Ltd project customer David Emms said:

“The completion of the piles for the Colne Valley Viaduct is a huge achievement for our entire team and marks the end of almost two years of hard work. With pier construction and deck assembly also in full swing, the viaduct is quickly becoming one of the most impressive and iconic parts of the project.”

Derek van Rensburg, Align’s Surface Operations Director, said:

“Completing the piles is a tremendous accomplishment for both Align and the team at KVJV who work across the lakes and waterways throughout the Colne Valley. We were able to complete the pile driving without any significant impact on the environment, a great result for the whole team.”

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