In a major milestone for METRONET’s Forrestfield-Airport Link project in Perth, TBM Grace has broken through the Bayswater dive structure, marking the end of her 8km journey.
Grace is the first of the project’s two Herrenknecht Variable Density TBMs to break through with TBM Sandy expected to finish in May.
In late July 2017, TBM Grace set off from Forrestfield to Bayswater, building one of two 7m diameter, 8km long tunnels that will house the $1.86bn project’s rail lines.
Half of the 54,000 locally fabricated concrete segments were installed during Grace’s journey, with her route taking her under Perth Airport and the Swan River and through diverse ground conditions. On the way she passed through Airport Central and Redcliffe Station boxes.
TBM Grace will now be dismantled and craned out of the drive structure in preparation for the arrival of TBM Sandy.
Trains are set to run on the new rail line in the second half of 2021, providing a 20-minute rail link between the eastern foothills, Perth Airport and the Perth central business district.
In April 2016 the $1.176bn single-package, lump sum design, construct and maintenance contract was awarded to Salini Impregilo – NRW Joint Venture.
The project has not been without its challenges with TBMs Grace and Sandy having been stopped in February and March 2018 respectively, due to ‘ground disturbance issues’. Later in September 2018, TBM works were stopped following the creation of a sinkhole above the twin tunnels, and then again work was stopped to assess issues with the screw conveyors.
Comments attributed to Transport Minister Rita Saffioti:
“This is a proud moment for WA workers, who have just finished the longest rail tunnel ever attempted in WA history.
“We started tunnelling on the Forrestfield-Airport Link project in late July 2017 and we now eagerly anticipate the safe arrival of TBM Sandy in coming months to mark the completion of tunnelling.
“The precision engineering it has taken for this machine to tunnel eight kilometres, through varying and sometimes challenging soil types, to break through in exactly the right spot is truly remarkable.