• Weather events in regions with rain and floods have caused an extreme amount of sinkhole issues.
• When initiating a sinkhole repair, the objective is to prevent further movement of loose material and remove the triggering mechanism that causes the sinkhole.
• Repair methods are varied depending on the economics and location of the sinkhole.
• Many sinkhole remediation options can be costly and time-intensive – requiring the use of heavy machinery, a wide range of repair materials, and much manpower.
Causes of Sinkholes
Sinkholes can result from the collapse of the roof of a cave (called cover collapse) but typically it is the piping of unconsolidated material from one location to another that causes most sinkhole events. This means that underground soil particles erode and wash through channels in the subsoil down through the Karst drains (Karst: a geologic formation shaped by the dissolution of a layer or layers of soluble bedrock, usually carbonate rock such as limestone or dolomite). Water is generally the primary triggering mechanism for sinkholes. Below is an infographic to common origins of sinkhole formation.
Traditional Sinkhole Repair Methods
Repair methods are varied, and the method used depends largely on economics and the location of the sinkhole. The method and materials needed to fill in a small sinkhole in a backyard or in a rural area can be quite different from those needed to repair a sinkhole in the middle of a street or under an occupied home or business in a highly urbanized area. Repair tools and material vary greatly as well. The two primary goals of sinkhole repair are:
During repair, the sinkhole’s triggering mechanism must be addressed in order to minimize additional soil settlement or sinking. As water is generally the primary triggering mechanism, it is necessary to identify and remove to the extent the possible source of the water that may have caused the sinkhole. It is better to construct the plug (drain stopper) directly at the location of the bedrock drain. This allows the plug to be in direct contact with the bedrock, providing a better seal.
Sinkholes in which no bedrock is encountered, and where the soil cover is thick, require careful geologic analysis followed by various costly repair methods, ranging from pressure grouting (also called permeation grouting) in the subsurface, to driven piles having concrete caps and gravel-mat backfilling.
Inverted Filter Approach
Challenges with Traditional Repair Methods
There are many challenges associated with sinkholes and the traditional methods that are used to repair them:
- Heavy machinery is often required to repair sinkholes. This equipment can require a lot of manpower to get it to the site and to operate it.
- A wide variety of materials and mixes are typically needed for a repair,including concrete, soil, grout, synthetic filter fabrics, and various sizes and mixtures of crushed stone.
- Injection holes for the repair materials are large and very invasive.
- High pressure is required to pump the heavy grout to the location of the repair.
- There is no expansion strength in the repair materials used, so over lift occurs to compensate for any shrinkage that may occur.
- More water is introduced when using a cementitious grout – adding more weight (approx 135 lbs per cubic foot) to already distressed soils.
The Best Solution: URETEK’s Deep Injection© Process
The URETEK Deep Injection© Process is one of the best ways to repair a shallow sinkhole. Because severe structural damage can result from shallow sinkholes, immediate and conclusive sinkhole repair is critical.
URETEK Deep Injection is a combination of chemical, compaction and permeation groutingthat will not cause environmental damage, stabilizes the soil at perimeter of the throat, can fill and plug the throat, and can cap the soil pipes, filling the voids and micro-fissures within the soil at the injection site. The unique URETEK geo-polymer is the key factor in the repair.
While traditional chemical grouting fills the soil cavities and pores with a waterproof material, it does not have expansion characteristics of the URETEK process.
The URETEK Deep Injection© Processgives long-term stability to the area affected by the shallow sinkhole and is the best solution for shallow sinkholes and sinkholes that occur close to the surface where compaction grouting is not an option. The URETEK Deep Injection© Process is the safest and most accurate method of filling sinkhole voids and densifying loose soils that exist within 15 feet of the surface.