Sydney Metro City & Southwest Tunnel Track Slab

The Sydney Metro City & Southwest project extends Australia’s first fully automated metro railway beneath Sydney Harbour, through the Sydney CBD and southwest to Bankstown. The project included the construction of approximately 31 km of underground railway, incorporating permanent tunnel track slab, power systems, ventilation, drainage and associated rail infrastructure.

BarChip macro synthetic fibre was selected as the primary structural reinforcement for the tunnel track slab, replacing conventional reinforcing steel throughout the underground alignment. This innovative approach simplified construction while significantly reducing embodied carbon, establishing a new benchmark for sustainable metro rail infrastructure.

• Location: Sydney, Australia
• Owner: Sydney Metro
• Contractor: Systems Connect (CPB Contractors & UGL Joint Venture)
• Designer: WSP
• Application: Tunnel Track Slab
• Reinforcement: BarChip48 Macro Synthetic Fibre

Project Highlights

• Approximately 31 km of underground metro railway.
• Around 1,900 tonnes of reinforcing steel replaced.
• Approximately 200 tonnes of BarChip macro synthetic fibres installed.
• More than 3,000 tCO₂e reduction in embodied carbon.
• 44% lower embodied carbon compared with conventional reinforcement.
• Recognised by the Infrastructure Sustainability Council as an Outstanding Achievement.

Engineering Innovation

The permanent tunnel track slab formed a key component of the Sydney Metro City & Southwest project, supporting approximately 45,000 sleepers and 62 km of rail throughout the underground metro alignment. Around 98,000 tonnes of concrete were placed during construction of the permanent track slab.

BarChip macro synthetic fibre helped optimise construction of the tunnel track slab by eliminating the need for complex steel reinforcement installation within the confined tunnel environment. The result was a simpler reinforcement solution that reduced labour, improved construction efficiency and maintained the required structural performance.

Sustainability Outcomes

The Sydney Metro City & Southwest project received a Leading Infrastructure Sustainability (IS) rating, recognising a range of low-carbon material innovations implemented throughout the project. The tunnel track slab contributed significantly to this outcome through the use of BarChip macro synthetic fibre reinforcement and a concrete mix incorporating 50% supplementary cementitious materials (SCMs).

According to the Infrastructure Sustainability Council, replacing approximately 1,900 tonnes of conventional reinforcing steel with around 200 tonnes of BarChip macro synthetic fibre reduced embodied carbon by more than 3,000 tCO₂e. This made the tunnel track slab one of the project’s most significant sustainability achievements, delivering a 44% reduction in embodied carbon compared with conventional steel reinforcement. Full details are available in the Infrastructure Sustainability Council project case study.

Industry Recognition

The Infrastructure Sustainability Council highlighted the tunnel track slab as a major innovation contributing to the project’s Outstanding Achievement Award, while WSP also identified the synthetic fibre reinforced low-carbon concrete solution as a significant contributor to the project’s sustainability outcomes.

Sydney Metro City & Southwest demonstrates how macro synthetic fibre reinforced concrete tunnel track slab can successfully replace conventional steel reinforcement on major underground rail infrastructure. Beyond improving construction efficiency, the project established a new benchmark for low-carbon railway construction, delivering independently verified reductions in embodied carbon while supporting one of Australia’s largest transport infrastructure projects.