Tunnel Boring Machines
Tunnel Boring Machines (TBMs) are large machines that excavate below the ground surface, while simultaneously installing concrete lining units to build a tunnel. Two TBMs have been specifically designed for the Forrestfield-Airport Link by German company Herrenknecht, the world’s leading supplier of TBMs.
There are various types of TBMs to cater for different ground conditions and project requirements. For this project, the TBMs are Mixshield, which use the latest dual-mode technology capable of adapting to variable ground conditions (such as sand, rock and clay) as the machine progresses.
Key components for our TBMs were manufactured in various places around the world before an in-depth nine-month assembly and testing program was conducted in China. Once testing was finished, they are disassembled and shipped to Henderson Port. The TBMs were then transported to site and lowered into the dive structure at Forrestfield, where they began their two-year journey towards Bayswater. During this 8km journey, the TBMs will excavate under Perth Airport and the Swan River reaching up to 26m depth below the surface.
To find out more about how these machines operate, view the TBM fact sheet.
Frequently Asked Questions - Tunnelling restarts
Operation of the two tunnel boring machines for the Forrestfield-Airport Link was ceased temporarily in mid-February and late-March, 2018 respectively. The temporary suspension was to allow for the processes associated with the tunnelling to be independently reviewed and validated.
As the review has been completed, TBM Grace was restarted on April 17, 2018. TBM Sandy was restarted on April 24, in order to maintain a safe distance behind TBM Grace.