Concrete saves the day at sinkhole

Contractors have poured concrete into a sinkhole to prevent the collapse of a two-storey building close to Sydney Airport and Botany Bay over the weekend.

Early Friday morning a sinkhole close to 20 metres-wide was discovered in Rockdale, above construction of the M6 motorway tunnel, causing the building to sag visibly in the middle (pictured).

Stage one of the project involves north- and south-bound 4km-long tunnels from the M5 at Arncliffe to Kogarah, a tunnel portal at Brighton-Le-Sands, and stub tunnels for the future southern stage of the M6 extension.

Around 5am on Friday, workers underground saw material falling from the roof of the tunnel work site and 20 people were evacuated. No-one was in the building at the time when the sinkhole appeared.

NSW Premier Chris Minns revealed that structural engineers are assessing whether the sinkhole was related to the construction of the M6 project.

“I know that the builders of the road regarded that part as one of the most tricky because it’s the closest to the surface at only 16 metres, whereas a lot of the rest of the project would be up to 60 metres underground,” he said.

Laser monitoring equipment has been set up and drones are being used to detect any further movement of the area and engineers are trying to determine how to shore up the building to stop it collapsing.

It is thought there have been issues with water tables and ground conditions in the underground site and workers will not be returning until it is declared safe.

Image source: FRNSW

About the author

Desi Corbett

Desi is our weekly news journalist and the editor of Concrete in Australia magazine for 10 years. She has been heavily involved in all forms of engineering since 2013; part of a 30-year writing career across a range of subjects and media.