Network Rail to Strengthen Merseyrail Underground Tunnel

Network Rail is using 21st century technology to fix a Merseyrail underground tunnel in Liverpool without disrupting passenger services.

This 3.5 million GBP investment involves waterproofing and strengthening the ceiling of High Neck Tunnel to fix its leaks and loose Victorian brickwork.

As part of this work, a steel ‘ram-arch’ tension system is being installed to the tunnel roof, which will be sprayed with concrete to strengthen it for the next 100 years.

This will make future journeys between Southport and Hunts Cross more reliable.

Liverpool High Neck Tunnel
From track to the arch peak High Neck Tunnel is 15 metres high

Thanks to the use of computer-aided design (CAD) this complex project is able to be completed without disrupting rail services.

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.”

Specialist LiDAR laser surveys have been used to map the tunnel interior and create a 3D computer model that includes every uneven brick and lump of loose stonework. This enabled the scaffolding teams to build a temporary platform dubbed ‘the dance floor’, so work can take place high above the tracks while trains pass underneath as normal.

Liverpool Tunnel
Track side view during ‘dance floor’ deck installation

The Network Rail Civils Internal Delivery team was specially trained and accredited to use the ‘ram-arch’ system to provide structural support to the tunnel ceiling. This has eradicated the need to employ external contractors for this or similar future projects.

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.”

The underground upgrades are expected to finish by the end of 2022. This will complete work started in 2017 and will mean the entire length of the 125 metre long tunnel will have a reinforced concrete roof.

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