Tunnel Boring Machines Ordered For Metro Tunnel

22 March 2018

Four giant tunnel boring machines (TBMs) will start arriving early next year to build the $11 billion Metro Tunnel that will transform Melbourne’s transport network.

Minister for Public Transport, Jacinta Allan visited the Metro Tunnel’s Arden worksite today to announce the order has been placed for the mammoth machines that will burrow the project’s twin 9km tunnels.

Each TBM will be 100 metres long, weighing up to 1,000 tonnes and a diameter of 7.2 metres. They will operate like moving factories as they travel beneath the city’s surface, with giant cutting heads burrowing through soil and rock before its transported via pipes to the surface.

The custom-built machines include offices, kitchens and bathrooms to support crews of up to 14 people during a round the clock operation. They will progressively install watertight concrete lining as they move under the surface at around 10 metres a day building the new tunnels.

The heaviest single component of each TBM is the cutterhead, which weighs in at 175 tonnes and can tunnel through rock six times harder than concrete. The deepest tunnelling point will be under Swanston Street, at the northern edge of the CBD near the new State Library Station. Here the TBMs will excavate around 40 metres below the surface.

The four TBMs will install a total of 55,000 individual concrete segments that are needed to create the two tunnels. Upon their arrival, two machines will be transported to Arden and two to Domain, where they will be assembled, lowered into a shaft 20 metres underground and launched into the earth.

Each TBM will head away from the city on the first leg of their journey before being retrieved in Kensington and South Yarra. They will then be retrieved, dismantled and trucked back to their starting points to be relaunched towards the city, with tunnelling expected to be complete by 2021.

Significant work has already been undertaken at both launch sites to prepare the areas for tunnelling work, including the installation of temporary construction power substations to power the TBMs from both locations.

The Metro Tunnel will create a new end-to-end rail line from Sunbury to Cranbourne/Pakenham and five new underground stations, allowing more frequent, reliable trains to run between the city and suburbs each day.

Quotes attributable to Minister for Public Transport Jacinta Allan

“These machines will operate like giant underground factories as they burrow around 40 metres beneath Melbourne to build the Metro Tunnel.”

“They will dig through a variety of ground conditions to link one side of the city to the other and its completion will represent a significant engineering feat.”

“The Metro Tunnel will provide more trains, more often across Melbourne, meaning less time waiting on platforms or stuck on a train, and more time with your family.”

Reviewed 19 August 2020

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