According to National Geographic, sinkholes occur when water dissolves the surface rock. The surface rock is often limestone, and rainwater accumulates in cracks that gradually dissolve and wash away this layer. The cracks eventually expand until the ground above becomes unstable and collapses. Sinkholes can be as shallow as 1 meter or as deep as 50 meters.
Sharron Ng, a member of the Institution of Engineers Singapore (IES), stated that in urban areas, sinkholes can also be caused by human activities. “Activities such as excessive groundwater pumping during underground construction, broken pipes, or sewers can cause water to leak, leading to soil erosion on the surface and the formation of large voids that are prone to collapse,” said Sharron Ng.
A new sinkhole has appeared in Malaysia. (Photo: AP).
Warning Signs
Sinkholes often appear very suddenly, however, IES member David Ng pointed out that sometimes we can observe signs of ground subsidence before a sinkhole appears. This occurs when the ground is covered by a temporary hard surface while the area beneath is hollow.
The Honorary President of IES, Chong Kee Sen, added a few more signs: unusual shifts and cracks in the road.
Mitigating the Risk of Sinkholes
Mapping geological features helps identify areas prone to sinkholes. Today, there are also new technologies such as ground-penetrating radar, low-frequency passive electromagnetic fields, and acoustic vibrations.
After discovering a sinkhole, the surrounding area can be excavated and filled with soil. Additionally, it is advisable to inject grout and install steel frames both inside and around the sinkhole to provide support. Next, fill the sinkhole with a mixture of liquids to stabilize the structure and prevent water from seeping in.
