AUSTRALIA: ZÜBLIN Ground Engineering has secured a role on Melbourne’s SRL East to provide ground-freezing expertise and equipment for nearly 30 cross passages in the 26 km twin-tunnel project.

Aerial view of Suburban Rail Loop East construction works in Box Hill Gardens, Melbourne
Aerial view of the Suburban Rail Loop East staging area in Box Hill Gardens, Melbourne. Illustrative photo. Photo: Philip Mallis, CC BY-SA 2.0.

The STRABAG announcement says the specialist scope was awarded by Suburban Connect, the CPB, Ghella and Acciona consortium, to STRABAG Australia. ZÜBLIN Ground Engineering will contribute the ground-freezing expertise and specialist equipment, while Georgiou Group will support STRABAG Australia with local infrastructure experience.

How ground freezing will be used?

Victoria’s Big Build explains that the method uses pipes drilled deep underground and chilled brine — salt and water — to stabilise the ground around the cross-passage works. The technique is intended to make excavation safer where ground improvement is required.

For the Tunnels South design, the project authority said carrying out most of this ground improvement from underground means large machinery is largely not required at street level. It estimated a 90% reduction in disruption to residents and local road traffic and said the approach would prevent disruption for nearly 100 homes and businesses.

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Why the cross passages matter?

Cross passages are small connections between the two main rail tunnels. Official SRL East guidance says they are positioned at regular intervals and provide a route for passengers and emergency-service personnel to move from one tunnel to the other during an emergency.

The passages also carry railway systems and mechanical, electrical and plumbing equipment, as well as drainage at points along the line. That gives the structures both a safety function and an infrastructure-services role within the tunnel system.

SRL East is the first section of Melbourne’s planned 90 km Suburban Rail Loop. The section will run underground between Cheltenham and Box Hill through 26 km of twin tunnels. Construction has been underway since 2022, and passenger service is expected in 2035.

The contract is ZÜBLIN Ground Engineering and STRABAG Australia’s first secured project together in Australia, with the specialist scope centred on ground freezing for nearly 30 cross passages.

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