Work on Melbourne’s North East Link has ceased as TBMs encountered a deep sinkhole late last week.
Engineers are now investigating how the sinkhole relates to digging works on the $26 billion Victorian project.
Twin tunnel boring machines (TBMs) were working on the twin 6.5 km tunnels near Lower Plenty Road between Watsonia and Bulleen when crews discovered the sinkhole late Thursday night.
One TBM has stopped operating temporarily after engineers moved it past the sinkhole to a safe zone, according to state transport minister Gabrielle Williams who spoke to 7NEWS.
“[The other TBM] will be continuing to operate to lay concrete rings under the sinkhole to secure that ground,” Ms Williams explained. “It will then also cease [operating] temporarily.”
The minister revealed the sinkhole was around 18 metres deep and about one metre in diameter. No one on site was injured and workers have been kept off-site while engineers investigate the sinkhole.
Ms Williams said there was no risk to the community or any nearby property and that the site is safe. The Canberra Times reported that the sinkhole was in the area of an old army barracks.
Sinkholes are not common in Australia but usually occur in three main situations: limestone or gypsum in the ground where water may be trapped in chasms under a thin surface layer; when rock under the surface is granular and can be carried away by underground water currents; or from intense rain or flooding or long-term leakage from sewers or stormwater pipes.
Image: Aerial view of works on the North East Link last Friday. Source: Jason South, The Age.
About the author
Desi Corbett
Desi is the Editor of Concrete in Australia and at the helm of our magazine for 8 years. She was behind the Institute's weekly news bulletins from 2016-2021 and is now writing our focused news items. Desi has been an engineering news and features journalist/editor across all disciplines since 2013 - part of a 30-year career writing for a wide range of industries.