On Friday January 18, workers operating TBM Grace on Perth’s 8km long, 7m diameter twin Forrestfield to Airport Link Tunnels, reported a potential mechanical issue with the machine just short of the tunnel 4km mark. Since then tunnelling experts from Salini Impregilo-NRW JV and TBM manufacturer Herrenknecht have identified and isolated the issue – damage to the screw conveyor – and repair works have started.
According to a statement released from the SI-NRW, “Repairs include replacing a 3m section of the 16m-long screw conveyor and repairing cracks that have a been identified. At this stage, it is estimated repair works will be completed in March. TBM Grace will remain stationary during this time.
“On Monday February 4, the second machine operating on the project, TBM Sandy was stopped as a precaution so that the machine’s screw conveyor could be proactively inspected for similar faults. Inspections have confirmed the presence of cracks. A damage assessment has taken place and the machine will remain stopped while repairs are completed.”
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The project has stressed that the mechanical issues pose no 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.
As of Tuesday February 5, TBM Grace had tunnelled 3944m and installed 2363 rings, and is currently stopped underneath a car park at the corner of Snook and Taplin roads for screw conveyor repairs. TBM Sandy had tunnelled 3839m and installed 2297 rings and has been stopped underneath Woods Road for screw conveyor repairs.
The $1.86bn Forrestfield-Airport Link is jointly funded by the Australian and Western Australian governments and will deliver a new rail service to the eastern suburbs of Perth – with three new stations at Redcliffe, Airport Central and Forrestfield via the 8km long twin tunnels.
In April 2016 the PTA awarded the $1.176bn single-package, lump sum design, construct and maintenance contract to Salini Impregilo – NRW Joint Venture.