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Sydney Metro, Australia - TBM Technology Optimisation

Extensive performance testing meets dedicated on-site technical support


John Holland / Cpb Contractor


TBM Technology

The Project 

Sydney Metro City & Southwest is a 31 km rapid transit project in Sydney, New South Wales, Australia. The project will deliver 15.5-kilometre twin rail tunnels extending Sydney Metro Northwest line at Chatswood under the Sydney Harbour to Sydenham. 

Four Double Shield Tunnel Boring Machines have been driving through the Hawkesbury sandstone and shale sections North and South of Sydney Harbour. More than 97% of the tunnelling work has now been excavated with the section under the Sydney Harbour remaining. 

TBM Wendy excavated 6.15 kilometres from Chatswood to the edge of the Sydney Harbour. TBM Nancy excavated 8.16 kilometres from the launch site at Marrickville.  TBM Mum Shirl commenced excavation at Marrickville in 2018 carving out 691,000 tons of rock.  

TBM Mabel tunnelled 6.14 kilometres from Chatswood to the Sydney Metro Station sites at Crows Nest and North Sydney before being retrieved at a temporary construction site at Blues Point. TBM Kathleen is continuing its journey deep under the Sydney Harbour. 

The Challenge 

Double Shield TBMs combine the functional principles of Gripper and Single Shield TBMs in one machine. In stable geologies, combining these methods permits the installation of concrete lining segments parallel to the tunnelling, resulting in very high advancement rates.  

To reach the rate of advance, a fast regripping must be applied, which means a high-performance tail seal grease pumping system and tail sealant grease are needed to fill the chamber during three to five minutes regripping. 

Quick Facts

  • Extensive performance testing to meet client’s requirements
  • Dedicated on-site technical support 
  • 1039 tons of TamSeal TG11 supplied continuously

The Solution 

During the start-up phase of the project, Normet undertook comprehensive testing on the TamSeal TG11 at the Normet Wetherill Park laboratory facility in close partnership with the JV team.  

Further testing was performed on the TBM. This enabled Normet to understand the full requirement and enhance the TamSeal TG11’s performance to meet the client’s product specification for pumpability, water pressure resistance, and adhesion properties.  


Project Outcome

Normet Australia supplied close to 1039 tons of TamSeal TG11 through their dedicated Tail Grease production plant in Sydney, with initial deliveries from Normet UK facility. This ensured uninterrupted supply throughout the duration of the project. 

To complement the product supply, Normet provided dedicated on-site technical support, working alongside the JV to monitor product performance to ensure the required TG pumping time for the tunnel construction was maintained. 

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