Using cutting edge technology, railway engineers in Liverpool have been keeping passengers moving whilst they tackle tricky tunnel trouble beneath the city.
Causing zero disruption to passengers above, Network Rail engineers have worked unnoticed on a key section of the Merseyrail network for six months, waterproofing and strengthening the ceiling of High Neck Tunnel between Liverpool Central and Brunswick stations.
The £3.5 million investment will fix leaks and loose brickwork in the 130-year-old tunnel, helping improve reliability for passengers between Southport and Hunts Cross.
Computer-aided design (CAD) helped engineers map a 3D plan of the tunnel interior, capturing every uneven brick and lump of loose stonework meant scaffolding teams could build a massive temporary platform – affectionately dubbed ‘the dance floor’ – so workers could be safe high above the tracks while allowing trains to pass underneath as normal. Working from the ‘dance floor’, engineers will be able to affix a steel ‘ram-arch’ tension system to the tunnel roof. The curved metal trusses are bolted into place using a mechanical guide and tightened like a giant cobweb. The entire frame will then be sprayed with concrete to ensure it stays firm for a further 100 years.
Helen Little, Network Rail works delivery supervisor, said: “In the past some previous repairs to High Neck Tunnel caused major disruption because accessing the tunnel ceiling is so difficult and the railway needed to be closed entirely. Building on similar repairs in 2017 – it was our priority this time to once again make sure we didn’t disrupt present day journeys while we fixed the structure for the future.
“It’s been great to train up to install the ‘ram-arch’ system ourselves and the team now has the skills to take this on to further work within Network Rail and save taxpayers’ money. The CAD also improved efficiency because it’s enabled us to plan the project right down to the last bolt – minimising materials being wasted.”
All the while Merseyrail passengers have been blissfully unaware that above their heads this major engineering project has been underway since March.
Zoe Hands, Merseyrail’s chief operating officer, said: “We are pleased to work with our partners at Network Rail as they utilise cutting edge technology to ensure vital work on our network can be undertaken without impacting on the service we offer to our passengers. We hope to see more works of this nature undertaken in this way going forward, so that we can continue to offer the best possible train service to the people of the Liverpool City Region.”
The final phase of the project when concrete is sprayed into the reinforced metalwork starts this month with the underground upgrades expected to finish by the end of 2022.
It will complete work started in 2017 and will mean the entire length of the 125 metre long tunnel has a reinforced concrete roof needing minimal to no maintenance for decades to come.
Image credit: Network Rail
