Giant Bridge Slide Completed
30 March 2010
Two years of planning came to fruition at the weekend, as the
Costain team on the Wolvercote viaduct project carried out one of
the largest bridge slides ever completed in the UK.
Over the course of 19 hours, eight huge hydraulic rams pushed a
5,000-tonne, 250-metre-long bridge deck 16 metres horizontally from
where it had been constructed on temporary piers alongside the A34
near Oxford, to become the new southbound carriageway of the
The new structure replaces its 1960s predecessor that had
suffered badly from water penetration. The Costain-built
replacement has been designed to have a 120-year lifespan.
"It was a long weekend, but a fantastic achievement," says Project
Manager, Darren Dobson.
Proceedings began with the closure of the southbound carriageway
to traffic at 7pm on Saturday. The expansion joints and components
attaching the deck to its temporary piers were removed and the
entire deck lifted 20mm for the sideways slide.
"We slid it 16 metres to its new, online position and set it
back down on its new crossheads. It was a perfect fit" says
The expansion joints were reconnected, the bearings fixed and
the road was reopened to traffic at 3.15pm on Sunday. This was two
hours later than planned, due to the general complexity of the job
plus individual problems such as re-siting some of the hydraulic
rams and the failure of a power pack near the end of the
Despite the overrun, "We only received two complaints and those
were massively outweighed by the congratulations from all
quarters," says Dobson. "I think everyone understands what we've
achieved in terms of construction techniques."
The temporary piers atop which the southbound deck was built
will now be demolished, the ground landscaped and the project
completed by June - three months ahead of schedule.
• The only known larger slide in the UK occurred in 1996
when a 5,500-tonne, 400-metre deck was moved. However, that
procedure took an entire 48 hours and involved a smaller distance