Sinkhole Pretreatment Grouting

Sinkhole Pretreatment Grouting programs include the injection of Compaction Grout. Compaction Grouting  is the injection of low slump mortar grout under pressure. In karst geologic conditions throughout Florida and the Southeast the Compaction Grout is injected to fill voids and stabilize soil erosion paths found in the soil profile.

Compaction Grout is injected within a treatment zone through steel pipes that are drilled to the limestone formation.  Injection begins at the limestone formation and continues upward in intervals of 1 to 3 feet. At each interval, grout is typically injected until a buildup of pumping pressure, or a predetermined quantity is injected.

The injection zone and injection criteria vary per project. In some sinkhole pre-treatment programs, a combination of Compaction Grouting is used to treat deep erosion and other ground improvement techniques like Vibro-Replacement is used to improve shallower soils to provide bearing capacity and settlement control for a new structure.


  • Used on sites that have been determined to have a high risk of sinkhole development. Risk is determined by a soil investigation or a history of sinkhole activity.
  • Certain critical facilities like hospitals, essential industry, highways, etc. may implement a pretreatment program to significantly reduce their risk of future sinkhole activity.

Construction Advantages

  • Allows for the development of sites that would otherwise be typically ignored
  • Stabilization of a site includes improved performance for all site structures including utilities, streets, walkways, etc.
  • Economical solution in comparison to deep foundation systems
  • Expedient process
  • Very little site disturbance

What to expect

  • A Compaction Grouting program is typically monitored and controlled by the geotechnical engineer of record
  • Minor amounts of drilling spoils and wasted grout must be disposed of
  • In the Tampa Bay Area Earth Tech will provide its own ready-mix grout which can accelerate the project schedule
  • Drivable site access is required for ready-mix trucks delivering the grout
  • On larger projects, an on-site Compaction Grout batch plant may be used