Design and construction of station caverns – Melbourne Metro Tunnel Project

The Metro Tunnel Project in Melbourne, Australia, involves the construction of 9 kms of twin rail tunnels and five new underground stations, including the State Library and Town Hall in the City Centre. The stations aim to provide spacious areas measuring around 260 m in length, 30 m in width, and 23 m in height. To address ground conditions, load behaviour, and land constraints, the stations are being built as trinocular form caverns, with a sequential excavation of the central (cavern) tunnel followed by the outer (platform) tunnels. Advanced 3D numerical analyses guided the design of the primary support and permanent linings, with temporary steel columns incorporated into permanent linings for efficiency. Close collaboration and an observational design approach facilitated efficient construction methods and work sequencing. The paper presents insights into the successful design, construction, and verification approaches on aspects of the project.