Tunnel boring machine Fact Sheet
What is a TBM? A tunnel boring machine TBM , is a machine used to excavate tunnels through a variety of soil and rock strata. It can be designed to bore through almost anything from hard rock to sand. It uses a rotating cutting head to excavate circular tunnels.
Who is making our TBM? Herrenknecht, a German-based company is manufacturing her. Herrenknecht also made Jeffie, which was used by City Rail Link last year to excavate a stormwater main.
Need more information?
Why does she need a name?
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Naming the TBM prior to beginning work is traditionally done for good luck for the project ahead.
The Link Alliance will design, construct and deliver the CRL’s twin rail tunnels, two new underground stations and a new Mt Eden station building. The Link Alliance includes seven companies with a wealth of experience in delivering large-scale infrastructure projects in New Zealand and overseas.
Why is she a “she”? Naming a TBM with a female name dates to the 1500s when miners and anyone working with explosives such as armourers and military engineers looked to Saint Barbara for protection. Saint Barbara is the patron saint of miners and artillery-people, in fact any profession dealing with fire. This includes her protection to tunnellers because of the use of explosives.
The companies in the Link Alliance are: Vinci Construction Grands Projet S.A.S, Soletanche Bachy International NZ, Downer New Zealand Ltd, Tonkin & Taylor, AECOM New Zealand Ltd, WSP, City Rail Link Ltd.
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What will happen to the spoil? The spoil will be removed from the tunnel by conveyor belt to the Link Alliance’s Mt Eden site and from there it will be sorted and moved off-site.
How big is she?
130 metres long 10 metres longer than an entire rugby field . Her diameter is 7.15 metres.
How much does she weigh? Approximately 800 tonnes for the front cutter head or shield, and almost the same for the supporting gantries.
1600 tonnes.
When will SHE arrive in Auckland?
She will arrive by ship in parts in September 2020 and be taken to Mt Eden Station to be assembled.
What will she do on the City Rail Link project?
She will dig two separate tunnels from Mt Eden Station to Aotea Station via Karangahape Station. As well as excavate spoil underground, she will be designed to install concrete segments that will line the excavated tunnel as she moves forward.
How far can she travel each day? 32 metres.
When will she start tunnelling? February 2021.
How long is each drive?
1.6 kilometres.
How long will each drive take?
Nine months.
When will she start digging the second tunnel?
January 2022.
Why use a TBM?
TBMs excavate tunnels quicker, there is less disturbance to the ground they are digging, and there is less impact on buildings, transport links and utilities both at ground or below ground level. These advantages also contribute to a reduction in the overall cost of tunnel construction e.g. excavation, the removal of spoil, and the lining of the tunnel walls with concrete segments.
How much earth can she excavate daily? Up to 2600 tonnes of spoil can be excavated each day – just over 100 truckloads a day.
Will she run 24/7? Yes, although there may be some breaks for maintenance.
What will happen to the TBM when her work is complete? When all tunnelling is completed she will be dismantled and returned to Herrenknecht. The TBM or parts of it will then be reused on another project.