How Sinkholes Form

Sinkholes are common throughout Tennessee, north Georgia, and west North Carolina. This is because we have lots of limestone below our soil—in fact, it’s the state rock of Tennessee because there’s so much of it present! Sinkholes appear when water below the surface level eats away at limestone or other soft bedrock. Soon, it becomes too weak to support the sediment layer on top of it, and the ground collapses in on itself, forming the pits we know as sinkholes. There are three major types of sinkholes you’ll need to watch out for.

Sink hole

Solution sinkholes

These sinkholes appear when there’s very little surface soil covering the limestone below. As water eats away at the limestone, a hole begins to form. It may present as small at first, but it will gradually grow larger with time. These holes are usually bowl-shaped and, if left untreated, can collapse suddenly.

Sink hole in road

Cover collapse sinkholes

These are sinkholes that appear in places where there’s lots of soil or sand above the limestone layer. As the limestone deteriorates, the weight of the soil above becomes too heavy for the limestone to support, and it will eventually crack. These sinkholes typically appear quickly as opposed to a more gradual onset.

Sink hole in road

Cover subsidence sinkholes

The last type of sinkhole is similar to a solution sinkhole, but these typically occur in areas where soil has a high clay content as opposed to sand. As the limestone erodes away and cracks, the soil above starts to sink through the limestone layer and fills the void left behind. In these sinkholes, the topsoil has a large depression in it, but that’s because it has moved below the surface of the limestone layer, so there’s still support below the surface.


If a sinkhole is forming in your yard, treating it quickly is the best way to save yourself from further damage down the line. Our Knoxville sinkhole repair and filling experts can help repair sinkhole damage with the following services:

  • Compaction Grouting: Compaction grouting is a process we often use in Knoxville. Sinkhole repair with this process involves using high pressure to inject a cement grout mixture into the subsurface, displacing and compacting the soil to restabilize soil particles. Because the grout takes up space where it’s injected, the remaining soils are pushed together until they’re tightly compacted, creating a supportive surface that you can safely walk or build on.
  • Cap Grouting: Cap grouting uses a process very similar to compaction grouting, but instead of creating a grid pattern, the grout is injected to create one continuous “cap.” This cap layer covers the entirety of the affected rock layer, preventing more soil from sinking into the void.
  • Injection Piers: Similar to foundation repair, we can drill perforated piers beneath the surface of the soil. Once they’ve reached stable bedrock, we inject the grout mixture through a hollow tube running through the pier. As it reaches the perforated holes, it exits and escapes into the soil below to compact and stabilize loose soil.
Concrete mix to repair foundation


For sinkhole remediation services in Tennessee, northern Georgia, and western North Carolina, trust the team at American Foundation & Waterproofing. Contact our Knoxville sinkhole repair and remediation team today for a free evaluation and estimate on your sinkhole repair project.