Sinkholes Don T Form Overnight Singapore Experts Say Warning Signs Often Missed Before Tanjong Katong Collapse

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A sinkhole opened along Tanjong Katong Road South at around 5.50pm on July 26, submerging a car in water. One person was taken to hospital. — Picture from Facebook/SG Warehouse Sale & EventsSINGAPORE, July 28 — The sinkhole that appeared along Tanjong Katong Road South on July 26 likely did not form overnight, experts have said, following the collapse of two lanes which swallowed a car.
Although the incident seemed sudden, geotechnical specialists explained that the erosion causing the void beneath the road likely began earlier, according to a report published in 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,” said Associate Professor Wu Wei of Nanyang Technological University.
“This is happening underground, so we may not be aware of it,” said David Ng, executive director of One Smart and chairman of the civil and structural technical committee at the Institution of Engineers Singapore.
Prof Wu said cracks may form on the road before a collapse, but these are not always visible, and ground settlement tends to accelerate before failure.
Ng noted uneven roads, crack lines or water bubbling may signal underground issues, and pointed to images suggesting repairs could have been made recently.
He said erosion could result from a leaking underground pipe or from excavation works disturbing surrounding soil.
A prolonged leak, he said, may create a void “large enough for the surface above to cave in”, especially if pipe supports are washed away.
The sinkhole was beside a sewerage worksite managed by national water agency PUB, and residents reported a burst water pipe the night before.
Ng said sewerage projects include safety measures to minimise ground disturbance, such as the use of settlement markers to monitor movements.
Prof Wu said ground-penetrating radar may have helped detect the cavity, though the technology is limited in depth and accuracy when water is present.
He stressed the importance of more frequent ground monitoring, saying, “If monitoring is strengthened, at least early warning can be given.”
On July 26, a car was swallowed by a sinkhole along Tanjong Katong Road South, prompting road closures and water disruptions.
A day later, it was lifted out using a crane and placed back on the road, Channel News Asia reported. - malaymail

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