The $8.3 billion Sydney Metro Northwest project is Australia’s biggest public transport project. It includes twin 15 km tunnels from Bella Vista to Epping – Australia’s longest railway tunnels – and a 4 km elevated sky train. In 2016, the Sydney Metro Northwest completed the tunnelling phase and moved to the second phase of construction; Operations, Trains & Systems (OTS). This phase of construction included the fit out of the tunnels, consisting of approximately 30 km of underground track slab construction.
Designed by Mott MacDonald and being delivered by a John Holland/CPB joint venture, the tunnels incorporate an Australian first macro synthetic fibre reinforced concrete track slab. This design innovation follows similar successful applications of BarChip concrete track slab in Japan, Europe and North America.
Being fitted out using a top down methodology, to ensure the accuracy of the finished rail levels, this track slab sits atop a slip formed concrete invert slab and satisfies the required 100-year design life. Given the nature of the track slab, and the difficulty of constructing this with conventional reinforcement in such tight working conditions, it was decided that a BarChip fibre reinforced concrete would be used for the track slab. This meant that no additional steel (other than that required for electrical purposes) was required for the placement of the concrete track slab in the tunnels.
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