The methodology, devised collaboratively by Amey Consulting, demolition contractor Graham Construction and other specialist contractors, will enable deconstruction without having to implement a three month road closure on major roads servicing Liverpool city centre and the Birkenhead (Queensway) Tunnel.
The phased dismantling of the two flyovers has also been devised to minimise vibrations to protect antique art and cultural collections, as well as wildlife housed at the Walker Art Gallery, Central Library and World Museum Liverpool – all of which sit next to the south flyover.
Liverpool City Council approved the demolition after the two-lane highways were closed at the end of September 2018 following the discovery of construction flaws.
A Post-Tensioned Special Inspection (PTSI) report completed by Amey Consulting was handed to the city council in February 2019, following more than 140 different types of structural testing. The tests found multiple flaws including that the quality of the concrete and steel was poor, with tendons and ducts corroded and signs of structural distress including cracking over some supports. It concluded the structures could not be strengthened.
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The first phase of the dismantling process will begin in early September 2019, with the taking down of the three footbridges that sit underneath the two flyovers.
Once removed, the focus of the engineering task will swing to the removal of the flyovers – each of which are more than 240m in length. This phase will involve heavy machinery removing individual spans in a pre-determined sequence.
Each span – weighing between 300 and 600 tonnes – will be temporarily supported, before being cut free and moved on to a special transporter to a nearby compound, where it will be lowered to ground level, cut into smaller sections and removed off site to be crushed. A total of 20 spans and supporting piers will be removed over a four-month period.
Mayor of Liverpool Joe Anderson said: "The Churchill Way flyovers are a relic of a cancelled highways plan from half a century ago and given the overwhelming weight of evidence from independent experts about their safety, their removal was the only viable option. We simply have no choice but to take them down as soon as possible.
"This deconstruction is going to be a complex process. It cannot be done overnight and a lot of thought has gone into the methodology to ensure the inconvenience to city centre traffic and surrounding buildings is kept to a minimum – but people need to understand that this is going to cause a huge amount of unavoidable disruption.
"Detailed designs for junction improvements are also a key element in making the area a better experience for everyone, post demolition, and we will be working hard to keep all of our city centre stakeholders and the public informed at every stage of the dismantling and how the new traffic proposals will look."
Steven McKinney, Principal Engineering Manager, Amey Consulting, said: "Our design engineers have worked closely with Liverpool City Council and demolition contractors, Graham Construction, on an innovative engineering solution that aims to minimise disruption and ensure the safety of the public.
"Provisions have also been made to protect local landmarks such as museums and galleries. We believe this represents the best solution for the city and for local communities."
(MH/JG)
