Sinkholes are defects or depressions in the ground’s surface which can be caused by natural or artificial processes. The major causes of sinkhole formation include:

Sinkholes will cause the loss of integrity of a ground surface and can have dire effects on overlying building and construction installations.

This article will detail ways to identify sinkholes, outline the various types and discuss the best sinkhole remediation techniques.

How to Identify a Sinkhole

When most people think of sinkholes, they imagine the type from movies that unexpectedly opens and swallows a car. In most cases, sinkholes appear gradually and give plenty of warning before their advanced onset.

There are ways to assess and predict the risk of a sinkhole occurrence. The key danger signs to watch out for are listed below.

For building structures:

Within the property environment:

  • Formation of gullies, small ponds following rainfall
  • Re-emergence/exposure of previously buried structures e.g. tree roots, building foundations
  • Poor growth/death of vegetation over the ground surface due to the erosion of nutrient-rich topsoil

3 Different Types of Sinkholes

Depending on the mechanism of formation, three major types of sinkholes are recognized. These are the solution, cover-subsidence, and cover-collapse sinkholes.

Solution Sinkholes

These sinkholes form in areas where water has dissolved limestone underneath the topsoil. With the onset of limestone dissolution, natural crevices in underground rock formations widen. The topsoil is then pulled by gravity into these defects, creating depressions in the ground surface where rainwater may collect, forming ponds.

This type of sinkhole is unlikely in the Greater Houston because of the soil content.

Cover-subsidence Sinkholes

Poorly compacted topsoil with loose aggregation (especially sand soils) is at particular risk of this type of sinkhole formation. These soil particles track downwards into defects in the underlying bedrock formations leaving large defects on the ground surface.

Cover-collapse Sinkholes

These are also termed “dropouts” as the ground surface collapses, creating large breaches in the surface continuity. Although cover-collapse sinkholes appear dramatically, the process leading to their occurrence is more gradual.

When the thinned topsoil roof is no longer able to sustain its weight, a collapse occurs creating a large sinkhole. A sinkhole like a cover-collapse in Greater Houston is likely the effect of major leaks in underground infrastructure.

These are rare, and the URETEK team does not provide solutions for this type of sinkhole.

The kind of sinkholes we frequently see appear gradually and are typically caused by water leaks. It could be water from:

  • An under-slab plumbing leak
  • Water leaking from municipal storm/sewer lines and manholes
  • Water from a lake/ocean that pulls soil into the lake/ocean because of a leak in the bulkhead

Can Sinkholes Be Repaired?

Depending on the extent of damage, various sinkhole repair methods can be utilized. While a small-sized sinkhole can simply be packed with dirt and covered with a soil layer, an extensive surface defect will require more specialized sinkhole remediation methods.

2 Common Sinkhole Repair Methods

sinkhole remediation methods

Understanding how to repair sinkholes may depend on the type of sinkhole. The URETEK solution is generally to seal and fill the void.

  • For leaks from under a concrete slab, we would locate and repair plumbing leak, then inject our expanding polymer to fill voids and stabilize soil.
  • For a leaking municipal storm/sewer, we would inject our polymer to seal the leaking area and fill the void space created by the leak.
  • For a leaking bulkhead, we would inject where the leak is allowing the polymer to fill the leaking joint and inject to fill the void space.

The most popularly employed techniques to achieve these repairs are listed below:

  • Grouting
  • Underpinning/Piling

1. Grouting

Grouting involves the use of concrete or other chemical substances to fill subsurface defects. If expertly done, these solutions for sinkholes will seal off breaks in the continuity of the underlying bedrocks and restore stability to the affected areas.

Compaction Grouting

Cement grout is used to fill the sinkhole defect. A significant drawback to this method is the fact that cement-based grout may be required in excessively large amounts as defect size may be underestimated.

Chemical Grouting

Chemical grouting uses a stable expansive material to achieve sinkhole repair. An effective example of chemical grouting is void-filling foam. This unique polymer is pumped into targeted sinkhole cavities to eliminate dangerous voids. Polyurethane foam is particularly advantageous while filling voids under concrete slabs due to its expanding properties. It spreads into hard to reach cracks and crevices, resulting in a stable, more permanent grout layer.

Contact the foundation soil stabilization contractors at URETEK Gulf Coast today for help.

2. Underpinning/Piling

The use of underpins to support a building structure’s foundation is an effective way of tackling sinkhole under a house. These pins which are driven beneath the ground surface to the point of refusal to achieve stability and prevent further settling of overlying structures.

This is the concept behind pressed pilings foundation repair, where concrete cylinders are used to stabilize your subsiding foundation at its perimeter. The pressed piling system used by URETEK Gulf Coast reaches a deeper soil base that isn’t as vulnerable to poor and inconsistent environmental conditions like sinkholes.

Who Fixes Sinkholes?

URETEK Gulf Coast provides the best foundation repair solutions for both residential and commercial buildings. Our unique sinkhole repair techniques will ensure that you get the most effective void elimination solutions.

If you’re in Houston and you’d like to learn more about our highly effective residential or commercial foundation repair, please contact us online today for a free estimate!