Tanjong Katong Road sinkhole did not happen overnight: Experts | Singapore Breaking News & Latest Updates

Tanjong Katong Road sinkhole did not happen overnight: Experts — Find out what’s new onST website and app. Workers involve in recovery work at the site of the sinkhole at 5.30am along Tajong Katong Road South on Jul...

Find out what’s new onST website and app.

Workers involve in recovery work at the site of the sinkhole at 5.30am along Tajong Katong Road South on July 27.

ST PHOTO: GIN TAY

Lee Nian Tjoe

Summary

AI generated

PublishedJul 27, 2025, 08:10 PM

UpdatedJul 27, 2025, 08:14 PM

SINGAPORE -The large sinkhole in Tanjong Katong Road South seemed to appear suddenly on the evening of July 26,swallowing a car and its unsuspecting driveras two lanes of the road collapsed into a large pit.

swallowing a car and its unsuspecting driver

But it was unlikely that the erosion of the soil beneath the road happened overnight, instead the collapse could have been the result of changes under the ground that happened much earlier, experts told The Straits Times.

“Sinkholes cannot form suddenly. They need time for the surrounding soil to wash away, causing the cavity to get larger and larger,” saidAssociate Professor Wu Wei, a geotechnical engineering expert at the Nanyang Technological University.

Prof Wu said the rate of ground settlement accelerates before it collapses. Before that happens, cracks might appear on the road surface before it caves in, but these might not always be identifiable to the naked eye, he added.

Mr David Ng, a professional engineer who is also the chairman of the civil and structural technical committee at the Institution of Engineers Singapore,said in some cases, it may be possible to spot the road being uneven, see crack lines on the road surfaces or water bubbling from the road surface.

Referring to the images of the road before it collapsed, Mr Ng said the freshly laid tarmac may be signsthat repairs might have been made recently to fix surface cracks or uneven ground because of soil settlement, although it may also because of other unrelated works.

While Mr Ng saidit was too early to know for sure what caused the collapse,he saidthe erosion could have been caused by a leaking old pipe underground or soil movement triggered by excavation works happening next to the road.

In the case of leaking pipes, if it happensto beprolonged,it would create a void “large enough for the surface above to cave in”, he said.

Meanwhile, excavation works can wash away materials supporting water pipes underground, he added.

Left suspended without support underground, the water pipe may burst, leading to water gushing out and flushing away the materials under the surface, causing the road to cave.

“This is happening underground, so we may not be aware of it,” said Mr Ng, who is also the executive director of One Smart, an engineering company that works on geotechnical and infrastructure works, including sewerage projects with PUB.

The sinkhole was located beside a worksite by national water agency PUB, where work was underway on a sewerage project.

Residents had earlier told reporters that there was a burst water pipe at the same area the night before the sinkhole appeared.

But Mr Ng pointed out that in sewerage projects, precautions against cave-ins are taken from the design phase of the project in order to minimise disturbance to the surroundings, ground movements and changes in ground pressure.

Instruments like settlement markers, which are nails driven into the ground or concrete blocks in the vicinity of the works, are also used to monitor ground movements, he said.

Prof Wu saidmore frequentuse of ground penetration radar couldpossibly have detected the cavitybelow the road before it collapsed.

Such equipment is typically used by engineers to examine thegroundcondition below the surface, including location of cabling and other infrastructure, he said.

But Prof Wu also pointed out that there are limitations to such technology, including that they can only “look” 3m to 5m under the surface, and is less accurate when water is present.

He pointed out that key to preventing incidents like this is taking more frequent ground measurements and closer monitoring efforts.

“In this case, someone observed a burst water pipe one day before. If monitoring is strengthened, at least early warning can be given,” he said.

This is not the first time a road has collapsed here. In November 2022,a PUB project caused a slip roadleading from Holland Road and Commonwealth Road into Farrer Road to be closed for a week because tunnelling works caused a cave-in. There were no injuries reported.

a PUB project caused a slip road

In the latest incident, the car driver, a woman, was rescued by workers and sent to the hospital by the Singapore Civil Defence Force.

The lifting of the car at the site of the sinkhole along Tanjong Katong South road at 2.05pm on July 27.

ST PHOTO: GIN TAY

Lee Nian Tjoeis senior transport correspondent at The Straits Times, where he also oversees the Motoring section.