HS2 4,500t Viaduct Deck Slide Completed in 4 days - Timelapse Video – Heavy Lift News
4 Feb 2025

HS2 4,500t Viaduct Deck Slide Completed in 4 days – Timelapse Video

In a 4 day operation, from Thursday until Sunday,2nd February, a massive 4,500t deck was carefully slid across a road and railway line near Wendover, Buckinghamshire. The deck, part of the Small Dean viaduct, stretches 345m and is one of 50 major viaducts being built as part of the HS2 project.

Once completed, the new high-speed railway will significantly shorten travel times between the UK’s two largest cities and ease congestion on the southern end of the already-busy West Coast Main Line.

 

The site in the last week of January before the slide

 

Before the slide began, the viaduct’s concrete and steel deck was assembled in full, with most of the precast concrete slabs already in place. While this added weight to the operation, it will help save time later in the project. This operation marked the heaviest and longest single-stage viaduct deck slide on the HS2 project to date.

The whole operation was therefore the heaviest and longest slide of a signal-stage viaduct deck on the HS2 project so far. The A413 was reopened at around 8.30pm on Friday, nine hours ahead of schedule.

 

The nose of the Small Dean viaduct deck over the A413 during the launch 31 Jan 2025

 

During the slide, special pads covered in PTFE – a Teflon-like material usually found on the surface of a non-stick frying pan – were used to minimise friction between the deck and the temporary steel bearings on top of each of the piers. A cable system was used to slide the deck forward at speeds of up to 10 metres per hour.

Before the slide could begin, the team spent four years preparing the site, diverting utilities, realigning the road, building the abutments and six piers that support the viaduct and assembling the deck.

 

Small Dean viaduct during the deck slide Feb 2025

 

With the deck now in position, engineers can begin the challenging job of lowering it by 60cm onto the permanent bearings which will support the full weight of the viaduct. The two-month long operation will see it carefully lowered by 20cm at a time, pier-by pier, until the whole deck settles into its final position.

 

Small Dean Viaduct deck in position above the railway Feb 2025

 

The viaduct is one of only two places in the Chilterns where the HS2 route will be above ground level, with the underside of the viaduct just 6m above the road, supported by the huge Y-shaped piers.

 

The A413 open to traffic after the Small Dean viaduct deck slide Feb 2025

 

The viaduct is being delivered by HS2 Ltd’s main works contractor, EKFB – a team made up of Eiffage, Kier, Ferrovial Construction and BAM Nuttall – working with their design partner, ASC (a joint venture between Arcadis Setec and COWI). They worked closely with a team from Network Rail to plan and deliver work close to the railway.

 

CGI image showing Small Dean Viaduct A413 looking north

 

The last few months has also seen significant progress at HS2’s other major viaducts, including the key structures that will form the Delta Junction in North Warwickshire and the viaducts taking the railway into Birmingham Curzon Street.

In total, HS2 is building hundreds of bridges – ranging from small road bridges to the record-breaking Colne Valley Viaduct which became the longest railway bridge in the UK when deck installation was finished last year.

 

Featured Title photograph

Aerial view of Small Dean viaduct deck in final position across road and railway line in Wendover

 

 

Video

 

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