Melbourne Metro Tunnel Shafts

Photo credit: Metro Tunnel

The multi-billion Metro Tunnel will create a new rail line with high-capacity trains and five new underground stations in Melbourne, Victoria by 2025. The Tunnel and Stations package is being delivered under an availability based Public Private Partnership by Bouygues Construction Australia as part of Cross Yarra Partnership, together with Lendlease Melbourne Metro, John Holland and Capella Capital. The 9km long twin tunnels are constructed by TBMs up to 40 metres beneath the city’s surface.

Rendel has been engaged to perform an independent check of the steel reinforcement ratio one on the Franklin East Shaft, a multi-storey underground structure to be constructed within an already excavated temporary shaft through the bottom-up method. The study consists of benchmarking the steel ratio resulting from the certified design against the steel ratio commonly found on similar projects, developing a calculation model to determine an optimised steel ratio and preparing detailed steel reinforcement drawings for a typical slab and a typical peripheric wall.

Rendel has also been engaged to investigate the possibility of optimising the construction sequence for the shaft at La Trobe Street. This shaft is constructed using the top-down method with the use of temporary plunge columns to support the structures. The optimisation of the plunge columns removal sequence will reduce the construction programme. Rendel’s scope includes the preparation of structural models, testing of various scenarios and definition of amendments to be implemented in the design to allow the selected alternative plunge columns removal sequence to occur.

Both shafts are part of the State Library/CBD North Station.