What Types of Ground are Most Susceptible to Sinkholes?

Let’s delve into the geotechnical aspects that make some ground more prone to sinkholes than others.

One of the most common landscapes for sinkhole formation is in regions with limestone or karst terrain. Limestone forms as a sedimentary rock primarily composed of calcium carbonate.

Rainwater with naturally dissolved carbon dioxide forms a weak carbonic acid. Over time, this dissolves and erodes the limestone, creating underground cavities and networks of interconnected voids. Eventually, the ground above can no longer hold its weight. A sinkhole forms when the ground collapses into the underground spaces.

Gypsum is another type of sedimentary rock, rich in calcium sulphate. Like limestone, it is susceptible to dissolution by water.

Areas with extensive deposits of gypsum and other evaporite minerals are also prone to formation. Water slowly dissolves the minerals, leaving behind hollow spaces. Again, when the ground can no longer bear the load above it, sinkholes can form.

Finally, loose sediments like sand and clay may not be solid rock, but they can still play a role in sinkhole formation. In regions with a lot of unconsolidated sediment, water can easily percolate through the ground and create voids.

These voids make the ground weaker and less able to support weight. Experts often call these “cover-collapse” sinkholes.

However, they can also form in many different geological settings. Human activities like mining and construction can affect formation of this geohazard. They create voids underground that may collapse above.

Moreover, a collapse often happens after heavy rain. The soil that forms the roof of the sinkhole gets heavier and weaker with more moisture. Eventually, it cannot hold up the void and collapses under its own weight.

Studying and understanding the geotechnical properties of different types of ground is crucial for predicting and mitigating the risks to infrastructure associated with sinkholes. Geotechnical engineers work alongside infrastructure stakeholders to recommend appropriate remediation techniques to minimise the potential for sinkhole related problems.