Excavation of Town Hall Station’s first level is now complete, with three roadheaders breaking through into the station’s central cavern 25 metres below Swanston Street.
The roadheaders - named Lily, Sharon and Clara - each weigh 118 tonnes and have been tunnelling around-the-clock after being launched last year.
The breakthrough connects all three future station entrances at City Square, Federation Square and Flinders Quarter, creating the full length of the new 240-metre Town Hall Station.
More than 42,000 cubic metres of soil and rock has already been dug out by the roadheaders - enough to fill 17 Olympic swimming pools.
- The first roadheader tunnelled directly under Swanston Street from City Square, to begin excavation on the main station cavern.
- The second was launched under Federation Square to create the underground passenger connection across Flinders Street to the station site at City Square.
- The third has been working to create the underground passenger connection from Flinders Quarter across to the station site on the other side of Swanston Street.
Excavation will continue, with the roadheaders now set to dig another eight metres down to complete the station cavern. This is expected to be completed later this year.
Next year, following roadheader excavation of the tunnels within the CBD stations, tunnel boring machines will carve out the tunnels between Town Hall Station and State Library Station around 30-40 metres below Swanston Street.