Is there a sinkhole in your own neighborhood?

(The content is compiled from difference sources referenced at the bottom of article).

Is there a sinkhole in your own neighborhood? If so, you’re definitely concerned and probably wondering if your property will be impacted, and what you can do about it.

While a sinkhole is forming underground, the land above usually stays intact for a while. Then, the space below ground just becomes too?large to support the surface weight. A sudden, dramatic collapse ensues. How can a property owner know if there is a sinkhole forming — and what steps can they take to protect themselves, their neighborhood, home and belongings? ?First, it’s good to know the common signs of a sinkhole.

The common signs of sinkholes

• Cracks in interior joint areas, windows or doors
• Cracks in your exterior block or stucco
• Windows and doors become harder to close properly
• Depressions in your yard or the street or other yards near you
• Deep cracks and separation of paved concrete walks and drives
• Circular patches of wilting plants
• Sediment in your water
• Neighbors have had or confirmed possible sinkhole activity
• Observation of an actual cavity beginning to open
• A round circular depression?in the earth.
• Localized subsidence or depression?anywhere on the property. In other words, an area that has dropped down relative to the surrounding land.
• A circular lake, as this can be indicative of a sinkhole that has opened up and been filled with water.
• A foundation settling—if part of the structure starts dropping down and cracking, this could be a sign of a sinkhole forming under a house or building.
• Cracking on roads or pavement.
• A sudden drop of well levels?on a site, as this could be indicative of a sinkhole opening up and changing the water table beneath the site with no surface expression.
• A small opening in the ground?that rainwater seems to disappear into.

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How sinkholes form

One way that sinkholes form is when water in the atmosphere reacts with carbon dioxide and forms a weak carbonic acid. As the slightly acidic rainwater moves through fissures in the limestone, it begins to dissolve and widens the fissures—which eventually creates air or water filled pockets. When those pockets become expansive, they’re called “caves” or “voids.” This is a common natural phenomenon in limestone or dolomite known as?karstification—but it can be dangerous, expensive, and life-threatening when the ceiling of a void weakens and caves in. This is known as a “sinkhole.”?

At large developments and building sites, knowing whether or not you’re sitting on a?karst?area—an area with a high density of fractures, solution channels, and caves formed in limestone and thus, possible sinkholes—is critical and can greatly impact safety and also the value of the land.

The City of Kuala Lumpur

The city of Kuala Lumpur's name in Malay means "muddy estuary"; the city lies in hilly country astride the confluence of the Kelang and Gombak rivers. Before it became a city,?Kuala Lumpur?was a modest mining settlement in Malaysia, notably tin mining, characterized by its colonial history, burgeoning population, and the thriving tin mining industry that laid the groundwork for its future development as a multicultural urban center.

By the end of the 19th century Malaya was the largest tin producer in the world, suppling over half of the world’s tin.

Poorly mapped and recorded historic mine workings in coal, salt, potash, tin and copper often leave voids in the ground. These voids may eventually come to the surface over time as the roof progressively collapses. These collapses can be gradual, or can happen suddenly, with surface depressions appearing overnight without warning. Such rapid events are often associated with changes in groundwater or during excessive rainfall events.

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About sinkholes again…

Not all sinkholes provide surface expressions before opening up—but many do. And it pays to be aware of the most common indicators that your property may be situated right above a sinkhole!

If you know that you are building in an area with karst terrain that is sinkhole-prone—for example, if you’re in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, or Pennsylvania… and Kuala Lumpur—there is a far greater likelihood that you may have to deal with this issue in the future. Thus, it is wise to take a look around your property and the area in general for one of the seven signs of sinkholes listed above.

Sinkhole Inspection: How To Test For Sinkholes

Locating sinkholes and subsidence without digging, probing, or drilling can be accomplished using non-destructive field surveys.

The two main methods for detecting sinkholes are aerial photography and geophysical procedures. Using ground penetrating radar (GPR) can conduct sinkhole investigations without disturbing your property.

Various geophysical investigation techniques can be applied in Karst terrains including?ground penetrating radar, electrical conductivity,?electrical resistivity,?magnetic field, very low frequency measurement (ELF),?gravity field recording?and?seismic velocity measurements.

If you identify signs of a sinkhole at your site, you’ll have to test the area to see what kind of karst area or sinkhole you’re dealing with. To do so, you can set up several electrical resistivity survey lines over the site, image the target area, and look for high resistivity areas. These areas could indicate an air-filled void that hasn’t yet caved in but will likely continue to subside.

In filling in the sinkhole, the following should be considered:

• A full ground assessment undertaken by a chartered geotechnical engineer or engineering geologist prior to filling.
• Determination of the size and scale of the sinkhole to enable the right solution to be designed for backfilling and the impact on the ground (e.g. groundwater).
• Different solutions depending on whether the sinkhole is formed naturally or from a man-made influences (e.g. mining).
• Properties of the backfill material needed to provide strength and/or flow to fill cavities.
• Presence of local infrastructure and monitoring of the solution during and after backfill.
• The backfill solution does not result in temporary bridging of the sinkhole that could be reactivated.
• Typical backfill materials can be granular material or bulk grouts or even foam grouts, but this is very dependent on the local conditions found at the site of the sinkhole.
• In rural locations many sinkholes are backfilled with refuse and could be a source of ground contamination.

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References:

https://www.agiusa.com/7-common-signs-of-sinkholes-how-to-test-for-them

https://geomodel.com/locating-underground-sinkholes/#:~:text=Locating%20sinkholes%20with%20GPR,sinkholes%20below%20the%20earth's%20surface.

Advice for Local Authorities on what action to take when a sinkhole appears (publishing.service.gov.uk)

The History Of Kuala Lumpur (waynehighlands.com)

The great Tin Rush in 19th century Malaya – Malaysia 1786 – 1957 (home.blog)

Kuala Lumpur Facts | Britannica