RamArch – Tunnel Central, Liverpool

PROJECT: Tunnel Central, Liverpool
OWNER: Network Rail
DESIGNER: Donaldson Associates / Innovative Support Systems
CONTRACTOR: AMCO
PURPOSE: Stabilisation of a brick-lined railway tunnel lining crown arch
RAMARCH TYPE: Plain steel 8mm RAMARCH mesh, manufactured to BS standard
RAMARCH FINISH: Galvanised.
DATE: 2016/17

The Central Tunnel is on the HSX1 Line in Liverpool and is 339m long. It was originally constructed to carry rail traffic into the Liverpool Central Ground Station. During the modifications to the Mersey Rail Underground System in the 1970’s the ground level station was closed and demolished. The section of Central Tunnel closest to the station was altered to allow connection to the new Central Underground Station. This resulted in a tunnel 20m high and this section is now known as the High Level Neck.
The tunnel has extensive sandstone sidewalls with the original brickwork haunch and crown springing from the sidewalls. The refurbishment work involves the strengthening of the brick arch by an internal steel reinforced sprayed concrete lining.
Due to the height of the crown and the tight configuration of the connecting tunnels the only safe way to reach the brick arch is to install a scaffold supporting a crash deck, which is designed to take the weight of a concrete spraying robot.

The RAMARCH system was selected as the preferred method of installing the required steel reinforcement as it featured an easily handleable, light-weight, safe method of working that could be rapidly installed, whilst it provided excellent steel encapsulation in the sprayed concrete lining that was applied closely following the RAMARCH erection.
The RAMARCH panels were provided with an arch expansion system that enabled the individual arches to be simply sprung from horizontal steel lintels mounted on either side of the existing brick arch footings and expanded to provide an accurate fit to the brick arch profile.