Construction of the Metro Tunnel Project’s new State Library Station is well underway, with the main cavern now excavated and work starting on the permanent station.
The cavern under the CBD has been excavated using three road headers, each of which excavate around 500 tonnes of rock every day. They are equipped with cutterheads that smash through rock three times harder than concrete.
The road headers have finished more than 12 months’ work under the city, digging 36 metres under Swanston St while also excavating the station length between Franklin and La Trobe streets.
Later this year, the road headers will go back underground to dig out the rail tunnels on each side of the central station cavern.
The first permanent building works for the station are also now underway, with a concrete floor installed that will form part of the future platform.
State Library and Town Hall stations feature “trinocular caverns” – three overlapping tunnels dug by road headers to create an open space for passengers. This design allows the concourse and platforms to be integrated on one level.
State Library Station will be 240 metres long and 30 metres wide, and its 19-metre platforms will be some of the widest underground metro platforms in the world.
The new station will have three entrances, including the underground connection directly into Melbourne Central Station.
At street level, the main entrance will be located near the corner of Swanston and La Trobe streets, providing easy access to RMIT and the State Library of Victoria and northwards to Literature Lane and Stewart St. Another entrance will be located on Franklin St near the corner of Swanston St, between RMIT and the Melbourne City Baths.
To minimise disruption during the construction of the new CBD stations, five access shafts have been built for State Library Station at A’Beckett St and Franklin St east and west, La Trobe St and Little La Trobe St. Three have been built for Town Hall Station at Federation Square, City Square and Flinders Quarter.
Acoustic sheds have also been constructed over access shafts at Federation Square, City Square, A’Beckett St, Franklin St west and east to minimise noise and dust during excavation.
A total of seven road headers will be used in the CBD as part of the project – four for State Library Station and three for Town Hall Station.