TBM - Key Facts
City Rail Link’s Tunnel Boring Machine (TBM) will excavate two 1.6-kilometre-long tunnels from Mt Eden to central Auckland and connects with the tunnels already built from Britomart Station
The diameter of the cutter head at the front of the machine is 7.15 metres (an adult giraffe is about six metres tall), weighs 910 tonnes (that’s roughly the combined weight of nine blue whales, the largest animal ever known to have existed) , and the total length is 130 metres (a rugby field is up to 120 metres long)
The TBM was built by the German tunnel machine company, Herrenknecht, in China for the Link Alliance – the group of New Zealand and international companies responsible for the main CRL contract for City Rail Link Ltd
The TBM’s likely cost is NZ$13.5 million
Following mining tradition, the TBM has been named after an inspirational woman - the Māori rights champion Whina Cooper
After successfully completing factory assessment tests, the TBM was shipped in sections to New Zealand
It is being reassembled at CRL’s Mt Eden construction site and undergoing further tests.
The Link Alliance will start tunnelling in April 2021
The TBM has three jobs underground: excavating the tunnels, removing dirt and rocks to the surface, and installing precast concrete panels that will line the tunnel walls
It will take about nine months to excavate each tunnel
At peak operation, the TBM can travel 32 metres a day
The TBM will work 24/7, operated by a crew of 12 underground
After its first underground drive to the Aotea Station in central Auckland, the TBM will be returned to Mt Eden in sections and reassembled again to excavate the second tunnel
Up to 1,500 tonnes of spoil can be excavated each day. Spoil will be transferred from the TBM by conveyor belt to the Mt Eden site and then transferred to disused quarries
Excavation of the second tunnel is planned to start in March 2022
While the TBM is underground, people above it will feel little to no impacts. This is because it is an Earth Pressure Balanced TBM – it controls and balances the pressure of the earth it excavates which stabilises the tunnel face and reduces any possibility of settlement occurring.
Documentary about TBMs
