VIDEO: HS2 Completes Record-Breaking 4,500-Tonne Viaduct Deck Slide in Just Four Days
HS2 has achieved a remarkable engineering feat by completing the heaviest and longest single-stage viaduct deck slide on the project to date. The four-day operation, which concluded yesterday, involved sliding a massive 4,500-tonne deck across a road and railway line near Wendover in Buckinghamshire.
The Small Dean viaduct, stretching 345 meters, is one of 50 major viaducts on the HS2 project. Once completed, this new high-speed railway will enhance travel between the UK’s two largest cities and alleviate congestion on the southern end of the existing West Coast Main Line.
The viaduct’s concrete and steel deck was fully assembled before the slide, with most precast concrete deck slabs installed in advance. This approach increased the slide's weight but will save time in later project stages. The A413 was reopened nine hours ahead of schedule, showcasing the efficiency of the operation.
Special pads covered in PTFE, a Teflon-like material, minimised friction between the deck and temporary steel bearings on the piers. A cable system enabled the deck to slide forward at speeds of up to 10 meters per hour.
HS2 Ltd Project Manager, Jason Bicknell, praised the achievement: “Small Dean is the longest continuous deck slide on the project and an amazing engineering achievement. This success is due to the extensive preparatory work over the past few years. We set a target to install the deck in summer 2025, and it’s great that we came in ahead of schedule.”
The team spent four years preparing the site, including diverting utilities, realigning the road, building abutments, and constructing six piers to support the viaduct. With the deck now in position, engineers will begin the meticulous task of lowering it by 60cm onto the permanent bearings, a process that will take two months.
The viaduct, one of only two places in the Chilterns where the HS2 route will be above ground, features a deck made from weathering steel, which ages to a dark russet finish, blending with the natural landscape. The innovative ‘double composite’ structure, with reinforced concrete layers on top and bottom, creates a more efficient span and reduces embedded carbon.
The viaduct is being delivered by HS2 Ltd’s main works contractor, EKFB, a team comprising Eiffage, Kier, Ferrovial Construction, and BAM Nuttall, working with design partner ASC (a joint venture between Arcadis Setec and COWI). They collaborated closely with Network Rail to plan and execute work near the railway.
This milestone underscores HS2’s commitment to engineering excellence and sustainable construction, setting new benchmarks in infrastructure development.