Caverns completed on Sydney Metro’s Martin Place

22 October 2020

Twin mammoth caverns on Sydney’s Martin Place station have been completed six months ahead of schedule and after two years of excavation. It is the first time in 50 years that train tunnels are being built under the central business district.

Located 28m below street level, the caverns – both 220m long and 14m wide – lie beneath Castlereagh and Elizabeth streets. Martin Place station will be an interchange that will connect the Sydney Metro City and South West line – a 30km extension (Chatswood to Bankstown) and currently under construction – with the completed Stage 1 (North West metro from Chatswood to Rouse Hill. Nine tunnels have also been constructed to provide pedestrian access to commuters and to connect with the existing Sydney Trains network at Martin Place.

Excavation was undertaken by two TBMs and roadheaders and has involved the removal of around 126,000t of sandstone. Recent months have seen a workforce of more than 600 people help complete the work. The caverns will now be fitted out with electronics, signalling systems and track work for the driverless metro trains. With testing expected to begin in 2023, the station is scheduled to open in 2024, and will see up to 200 trains rushing through at peak travel times.

Martin Place station forms part of Stage 2 (Sydney Metro City and South West) which is being driven by five Herrenknecht TBMs. It will feature 15.5km-long twin-tube tunnels which will run beneath Sydney Harbour. Here, a mixshield TBM will bore in high water pressures 35m below the sea bed in sandstone, clay and sediments and be able to switch between EPB and slurry mode. The other four TBMs driving the routes north and south of the harbour are double-shield machines.

Sydney Metro is Australia's first metro line and biggest public transportation project. When it opens fully in 2024, it will be 66km-long and have 31 stations.