Western Australia’s Public Transport Authority (PTA) has said that the ground conditions that halted both tunnel boring machines (TBM) on the Forrestfield-Airport Link have been resolved.
The PTA has said in a statement: “The matter has been comprehensively investigated and changes made to reduce the risk of further disturbances.”
The organisation also said that the ground conditions in and around Perth are challenging for tunnelling and that some element of uncertainty and adaptation of the TBMs to the ground conditions was expected.
The PTA said that the TBMs would operate at a different pressure while passing through the non-cohesive granular Ascot Formation in which the ground disturbances were experienced in and the project team would laso adjust the quality of slurry and bentonite to minimise losses. The TBMs will also avoid weekend stoppages while passing under Perth Airport infrastructure to further minimise risk.
The PTA said that it expects the second TBM to restart in a few weeks once the first TBM has made more progress.
The authority said that the delays to tunnelling would not result in delay to the planned opening of the new metro in 2020.