On Friday January 18, workers operating TBM Grace reported a potential mechanical issue with the machine. Since then tunnelling experts from SI-NRW and German TBM manufacturer Herrenknecht have been able to identify and isolate the issue – damage to the screw conveyor, which moves excavated material away from the front of the TBM – and repair works have started. 

Repairs include replacing a 3m section of the 16m-long screw conveyor and repairing hairline cracks that have a been identified. At this stage, it is estimated repair works will be completed late-February. TBM Grace will remain stationary during this time.

On Monday February 4, TBM Sandy was stopped as a precaution so that the machine’s screw conveyor could be proactively inspected for similar faults. Early visual inspections have confirmed the presence of hairline cracks. A full damage assessment will now take place and the machine will remain stopped while assessment and repairs are completed.

The mechanical issue does not pose a risk to worker safety, and no ground disturbance issues are expected.

Two new screw conveyors will be manufactured by Herrenknecht and will be installed while the TBMs are at Redcliffe Station later this year.

You can follow the progress of both the TBMs on the Forrestfield website https://www.forrestfieldairportlink.wa.gov.au/tunnelling/tunnel-boring-machines.

Additional links:

https://tunnelbuilder.com/News/Forrestfield-Airport-Link-Update-.aspx

https://tunnelbuilder.com/Archive/Projects.aspx?&projectcode=au%2f34

http://forrestfieldairportlink.wa.gov.au/news-resources/display-article/february-2019-update