A 1.5-mile section of the Grand Union Canal, owned by the charity Canal & River Trust, has reopened to the public seven days ahead of schedule after HS2 engineers successfully launched a 130-metre-long steel bridge into position over the canal.
The launch operation, which began on Wednesday 4 March, involved sliding the 1,620-tonne deck across a country road, canal, and towpath near Ufton in Warwickshire.
It took engineers just two days to successfully complete the manoeuvre using the tried and tested ‘skid shoe methodology’. Two giant hydraulic jacks pushed the structure forward at speeds of up to 10 metres per hour, aided by specialist pads coated in a Teflon-like material to minimise friction and ease the slide process.
The weathering steel viaduct, supported by two abutments and two piers on either side of the canal, was then lowered to its final position and secured in place before engineers confirmed the job was complete at 19.00 on Thursday 5 March.
The successful launch follows a two-and-a-half-year programme of work led by engineers working on behalf of HS2’s construction partner, Balfour Beatty VINCI (BBV).
At peak construction, a team of 40 worked on the project. This included the installation of 34 piles at depths of up to 30 metres and two concrete piers cast parallel with the canal to enhance the aesthetic for canal users. The project also involved construction of two abutments, and 37 precast planks, which form the base of the bridge deck.
A new retaining wall was also built to ensure the structural integrity of the canal ahead of works commencing. Constructed with seven-metre-deep sheet piles, the new concrete-capped wall replaces the original ‘wash wall’ and soft bank, which is believed to have been formed around a century ago when the canal was widened.
Vibration levels were carefully monitored throughout the work programme to protect the nearby Grade II listed Longhole Bridge, which carries traffic and pedestrians over the Grand Union Canal between Ufton and Hunningham Hill.
Harry Toase, Balfour Beatty VINCI’s civil engineering lead for the project said: “The team has put in a huge amount of work to prepare for the bridge installation and shown meticulous attention to detail throughout to protect the canal and nearby Grade II listed bridge.
“I’m delighted we’ve been able to complete the works one week ahead of schedule and thank the local community for their patience.”
Longhole viaduct is situated just one kilometre from the north portal of the Long Itchington Wood Tunnel. When trains emerge from the tunnel, they will travel along the Ufton Wood cutting before joining the Welsh Road embankment, which connects to Longhole viaduct.
Vicki Lee, Senior Project Manager at HS2 Ltd commented: “Thanks to the hard work of our engineers and site-based teams, we’ve made good progress in this area over the last 12 months, with completion of the Long Itchington Wood Tunnel and the successful Longhole viaduct slide operation.
“There’s still a vast amount of work to do as we turn our attention to the embankments and cuttings that will link these sections of the railway ahead of track and power being installed.”
HS2 Ltd and BBV have worked closely with the Canal & River Trust to prepare for the viaduct installation. The launch was deliberately timed to take place during the close season, which ended on Friday 13 March, to minimise disruption for boaters on this popular stretch of the UK’s most famous canal.
Image credit: HS2