Permeation Grouting

Permeation grouting is typically defined as the injection of a low-viscosity grout (sodium silicate, microfine cement, acrylate or polyurethane) into the pores of the soil without displacing or changing the soil structure to impart strength and/or reduce permeability. The characteristics of the ground are modified with the hardening or gelling of the grout.

Permeation grouting may serve two purposes: to provide increased soil strength and cohesion and to decrease the permeability of the soil (water tightening). Permeation grouting is most often accomplished with sodium silicate, acrylate and polyurethane grouts Sodium silicates are the most widely used due to their safety, availability, ease of use, and environmental compatibility and are commonly applied for soil strengthening purposes. Acrylates exhibit extremely low viscosity and may be used in soils with lower hydraulic conductivities than can be penetrated by sodium silicate grouts.

Grout Injection

Permeation grouting is typically accomplished by Tube à Manchette (TAM) or “sleeve port” pipes installed in vertically, angled, or horizontally drilled holes and sealed in place with a brittle sheathing grout. TAM pipes have regularly spaced groupings of drilled holes covered with tightly fitting rubber sleeves that act as grout check valves. Initial high grouting pressures lift the sleeves and break the sheathing grout at port locations, allowing controlled grout placement as well as repeated injection at any port. A double packer isolates the injection of grout at a distinct port location. In low headroom situations, grout needles that can be installed without a drill rig may be used in lieu of TAM pipes.

Applications

  • To increase the strength of foundation soils for settlement control
  • Utility and footing support
  • Earth support

Advantages & Limitations

  • Low impact technique that can be applied with little risk of movement to surrounding structures
  • TAM pipes allow for precise grout placement
  • Minimal spoil is created
  • Can be accomplished within building interiors and low headroom situations
  • Can be applied in wet ground where conventional pit methods would require significant dewatering effort
  • The technique is only effective within a limited soil range

See Ventnor City Hall and Port St. Lucie Courthouse project descriptions.