Melbourne Metro Tunnel Project – Numerical Analysis Of Anisotropic Rock Mass For State Library Station

Ben Coombes, Roger Storry and David Sainsbury

The Metro Tunnel Project is delivering twin nine-kilometre rail tunnels in Melbourne, Australia. In addition to the tunnels, five new underground stations are being constructed. Two of the new stations – State Library and Town Hall – are complex cavern and adit excavations located in Melbourne’s City Centre which will directly connect to the existing City Loop Stations.

The State Library station, located predominantly underneath Swanston Street and a busy tram route, was surrounded by a mixture of modern, educational and heritage developments requiring the excavation sequence and primary support to be designed to ensure minimal surface impacts.

To simulate the anisotropic rock mass response to the excavation of the State Library Station, FLAC3D numerical analysis was undertaken. The analysis adopted the ubiquitous joint constitutive model approach and was used to assess the performance of the primary lining design and to determine the impacts the predicted ground displacements may have on the surrounding structures.