On its way! CRL tunnel boring machine passes big factory tests

New Zealand’s largest transport infrastructure project is celebrating a significant milestone – Auckland’s City Rail Link (CRL) has formally accepted ownership of its big tunnel boring machine (TBM) after extensive factory tests in China.

Dr Sean Sweeney, chief executive of City Rail Link Ltd, says the successful factory assessment tests and the handover of the TBM to the Link Alliance is a very clear and strong indication that the CRL project can meet critical milestones in a Covid-19 world. The tests were conducted on the fully constructed TBM by the German manufacturer, Herrenknecht, at its factory at Guangzhou in southern China.

Francois Dudouit, project director for CRL’s Link Alliance – the group of New Zealand and international companies building the substantive tunnels and stations contract for City Rail Link Ltd – says the TBM successfully underwent more than 500 tests to make sure everything works as it should. “There is now great excitement that we are ready for the next step – to bring the TBM to Auckland,” he says.

Rigorous checks tested the TBM’s three big jobs underground: excavating the tunnels, transporting tonnes of excavated spoil to the surface, and installing the thousands of concrete panels that will line the tunnels.

Francois Dudouit, project director for CRL’s Link Alliance

“It is a unique, world-class machine – an underground factory, purpose-built to carve its way through Auckland’s sticky soil,” Mr Dudouit says. “Just about everything that moves was tested to make sure it can do the transformational job it’s been designed for.”


The TBM will be used by the Link Alliance to excavate two tunnels side by side between Mt Eden and central Auckland to connect with the cut-and-cover tunnels already constructed from Britomart Station.

The Link Alliance describes the TBM as big by international standards for rail projects. The revolving cutter head at the front of the TBM measures 7.15 m in diameter and weighs 910 tonnes, and at 130 m long the TBM stretches more than the length of a rugby field.

After testing was completed the TBM was dismantled and is now being shipped in pieces to New Zealand – it is due to arrive in October. The arrival has been delayed by the Covid-19 pandemic which forced the closure of the factory in China for several weeks earlier this year.

The TBM will be reassembled at CRL’s Mt Eden site where it will undergo further testing and be officially blessed for safe journeys before it starts the first of its two excavation drives next April. Both tunnels are 1.6 km long and each TBM drive will take about nine months.

Mining tradition will be observed before the start of tunnelling when the TBM is formally named after an inspirational woman. Earlier this year New Zealanders voted for the TBM to be named in honour of the Maori rights champion, Dame Whina Cooper.

Take a look at the Link Alliance’s tunnel boring machine here