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Metro Tunnel

Tunnelling depths and staging

Tunnelling stages

North Melbourne to Kensington

In mid-2019, two tunnel boring machines (TBMs) were assembled at the Arden Station site and launched separately to tunnel towards the western tunnel entrance at Kensington.

In February 2020, the first TBM, Joan, arrived in Kensington and the second TBM, Meg, arrived in March.

The TBMS were transported back to site of Arden Station to be reassembled in early 2020 before being relaunched towards Parkville.

Kensington breakthrough

In February 2020, the first TBM arrived in Kensington. Joan broke through at the shaft at Childers Street, where the second TBM, Meg, later arrived in March.

Before the TBM’s cutterhead 'broke through' into the retrieval shaft, the shaft was filled with water to balance groundwater levels while the TBM constructed the final section of tunnel. The water was then drained and the TBM retrieved. Water was then pumped back to the water treatment plant at Arden Station site via the TBM.

The TBM cutterhead and front shield sections were cleaned and disassembled using high pressure cleaners and hand tools before being removed from the retrieval shaft and loaded onto trucks using a crane.

The rear (gantry) sections of the TBMs travelled back to Arden Station through the constructed tunnel, and the rest of the oversized pieces were transported back at night by truck.

North Melbourne to CBD

In mid-May, TBM Joan launched from the Arden Station site to tunnel towards Parkville. Joan broke through at the Parkville Station site in late August.

Meg began her journey towards Parkville in June 2020 and is following several weeks behind Joan.

The two TBMs will travel through the Parkville Station site and continue tunnelling towards the CBD later this year.

Parkville breakthrough

TBM Joan arrived in Parkville in August 2020, breaking through into the western end of the station box on Grattan Street. TBM Meg will also be arriving in the coming weeks.

At Parkville, the TBM cutterheads slowly break through the walls of the station box via a ‘soft eye’. The ‘soft eye’ contains fibreglass reinforcement instead of steel, minimising the impacts of noise and vibration as the TBM breaks through.

The TBMs will then be transferred on steel rails with hydraulic ramps through the station box under Grattan Street from the Royal Parade end to the Leicester Street end. This process will take around three weeks after which the TBMs will be cleaned and recommissioned.

Two launch frames will be set up at the eastern end of the station box to assist the TBMs in breaking through the ‘soft eye’ at this end to begin tunnelling towards the CBD.

Arden to Parkville alignment map

Parkville to CBD tunnel depth

Domain precinct to South Yarra

At the future Anzac Station in the Domain Precinct, TBMs Millie and Alice  were assembled in the station box and launched separately to tunnel towards the new tunnel entrance at South Yarra. Millie was launched in April 2020, with Alice following in May.

The TBMs will arrive at South Yarra and will be transported back to site in Domain.

Domain precinct to CBD

The TBMs will be reassembled in the station box and will start their journey towards the CBD, and under the Yarra River.

Tunnel Boring Machine timeline


  • August 2020 - Joan breakthrough at Parkville
  • June 2020 - Meg relaunched towards Parkville
  • May 2020 - Joan relaunched towards Parkville
  • May 2020 - Alice launched towards South Yarra
  • April 2020 - Millie launched towards South Yarra
  • March 2020 - Meg breakthrough at Kensington
  • February 2020 - Joan breakthrough at Kensington


  • October 2019 - Meg launched towards Kensington
  • September 2019 - Joan launched towards Kensington

More information