The International Information Center for Geotechnical Engineers

Tuesday, 08 January 2019 01:00

Ground collapse due to tunneling work in Perth railway

Ground collapse due to tunneling work in Perth railway Ground collapse due to tunneling work in Perth railway.

A leak in a cross passage between twin-bored tunnels has led to a ground collapse in Perth's Forrestfield Airport railway, Australia.

The leak developed about 200m. north of the Forrestfield station and damaged 16 concrete rings and a large section of the tunnel. The incident led to a sinkhole in the surface of the ground. The tunnels were excavated using TBMs. 

The collapse occurred on 22 of September, 2018. Back then, Forrestfield-Airport Link stated: "Immediate efforts were made to stop the leak, and this continued throughout the night. Despite these efforts, groundwater and silt is still flowing into the cross passage and one of the tunnels. A sinkhole developed immediately above the site, on Dundas Road about 200m north of the Forrestfield Station site. Dundas Road has been closed to traffic while work takes place to fix the leak and repair the road."

The causes of the leak have been under investigation. Construction flaws in the grout block and failure to properly join the tunnel lining and grout may have caused the collapse. "Tunneling through the grout block and/or vibration from excavation of the cross passage may also have contributed. New measures will be put in place for the construction of future cross passages to reduce the risk of a similar event occurring. The construction of the next cross passage is due to start in January," Western Australia transport minister Rita Saffioti said.

Recently, the Public Transport Authority of Western Australia announced that the Forrestfield-Airport Link will be delayed due to the ground collapse. The railway is expected to open in late 2021, a year later than intended, but the budget of the project has not changed.

The tunnel will be repaired either by fixing the issue from inside or by removing the damaged rings and building the tunnel section again. In any case, the design life of the construction should be 120 years. The failure on the top of the ground has been stabilized and 2 traffic lanes are soon to be opened.


Read 527 times Last modified on Tuesday, 08 January 2019 15:54

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