Sinkholes can appear suddenly, often with dramatic and serious consequences.
While the ground may seem to unexpectedly collapse, the reality is that sinkholes generally develop over a period of time until the ground above simply loses support and gives way, leaving a gaping hole.
Sinkholes have appeared around the world in all manner of locations - beaches and oceans, residential gardens, motorways, even shopping centre car parks.
While sinkholes are rare, there are a few common natural and man-made causes that can lead to the formation of a sinkhole, including construction or excavation, leaking pipes, reclaimed landfill sites, or historical mining and tunnelling activity. These are usually exacerbated by flowing water, which impacts the stability or compaction of the surrounding layers of earth, creating voids that ultimately lead to sinkholes.
Groundwater is often a major element in sinkhole formation. When water creates natural currents underground, the ground below the surface layer may slowly erode or wash away, causing voids to form.
Over time, the underground void grows, causing the surface layer of the ground to gradually become thinner and span further, eventually caving in.
Sinkholes are most likely found in areas with high levels of groundwater, where the rock below the ground is made up of soluble limestone.
Heavy rainfall, floods, or leaking or burst drainage pipes can also trigger sinkholes, as they cause excess water to travel through the ground, causing cavities.
Fortunately there are a number of warning signs that, when acted on quickly, can prevent sinkhole formation.
Recognising these signs and acting quickly may help to avoid significant damage to homes, public buildings, infrastructure and roads, while also minimising the risk to human safety.
Potential warning signs include changes in the ground such the formation of cracks, unexplained depressions or dips, the rapid appearances of holes or tilted or fallen trees and fence posts.
If signs of underground voids or sinkholes appear, it is best to consult a geotechnical engineer or ground engineering expert.
Professional insight can help determine the level of damage and the subsequent likelihood of a sinkhole forming.
Understanding the scope of the issue can help determine the best course of action - one that solves the problem with minimal disruption to homes, businesses and the public.
- Alan Reid is ACT sales and business development manager at Mainmark Ground Engineering.
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