Both pressure grouting and compaction grouting involve injecting cementitious grout to stabilize areas or fill voids underground .

Pressure grouting uses a fluid, low-viscosity grout that can permeate through pores in permeable soils. The curing grout binds particles together.

Compaction grouting utilizes a thick, mortar-like grout injected at high pressures to laterally displace and compact soil without penetrating it.

This densifies the ground and increases shear strength. Other grouting methods like chemical or jet grouting have different applications again.

We’ll compare key differences between pressure and compaction grouting processes, properties like the grout itself, equipment required, site conditions suited for the technique, costs, and overall strengths and limitations.

pressure grouting vs compaction grouting examples
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Pressure Grouting vs Compaction Grouting

While both techniques inject cement grouts, key differences include:

  1. Compaction grouting uses a thick, mortar-like grout, while pressure grouting employs a thin, fluid grout that flows easily.
  2. Compaction grouting displaces and compact soil through grout injection at high pressures. Pressure grouting permeates voids and pores within soil at lower pressures.
  3. The stiff grout bulbs formed in compaction grouting compress soil outwards. Pressure grouting binds soil by curing within pores.
  4. Compaction grouting is better suited for tight soils like silts and clays. Pressure grouting requires permeability to distribute the grout.
  5. The specialized equipment for compaction grouting can pressure-inject grout at over 1000 psi. Standard pressure grouting equipment suffices at less than 150 psi.
  6. While compaction grouting provides excellent strength in all soil types, pressure grouting is mostly limited to sands and gravels for permeation.
  7. Compaction grouting costs start around $30 per linear foot with higher equipment requirements. Pressure grouting costs about $20 per linear foot.
  8. Applications best fit for compaction grouting include liquefaction mitigation, structural lifting, and sinkhole stabilization.
  9. Pressure grouting works for improving shallow foundations, creating seepage barriers, and filling voids behind retaining walls.
  10. Both methods improve ground conditions, but suit different soil types and purposes.

The list covers the critical comparative differences between the two grouting mechanisms in terms of materials, application suitability, capabilities, equipment and costs.

Is Compaction Grouting Better Than Pressure Grouting?

Compaction grouting allows targeted soil improvement even in tight, granular soils. The stiff grout’s compressive action provides consistent stability.

Pressure grouting’s permeation is less reliable in variable or clayey soils. However, permeation may suit some larger, shallow treatment zones.

compaction grouting
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Pressure Grouting vs Compaction Grouting Cost

Compaction grouting costs start around $30 per linear foot, including labor and materials. Pressure grouting costs about $20 per linear foot but works best in highly permeable soils. Compaction grouting carries equipment costs from higher pumping pressures and flow control.

Equipment Used in Pressure Grouting vs Compaction Grouting

Pressure grouting equipment uses standard pumps and hoses given low 150 psi injection pressures.

Compaction grouting utilizes specialized positive displacement pumps and stiff supply lines that withstand over 1000 psi pressures. Compaction equipment does cost more to install and needs extensive quality control

Pressure Grouting Applications vs Compaction Grouting Applications

Pressure grouting applications like stabilizing foundations, constructing subsurface barriers, or filling abandoned utilities rely on the grout mixture’s ability to travel readily through permeable ground.

Pressure grouting applications include:

  • Permeation of dam and levee foundations
  • Filling voids behind tunnels or underground structures
  • Reducing service line settlements
  • Shallow foundation stabilization

Compaction grouting handles sites needing more robust soil improvement against seismic loads or soil liquefaction. The localized compaction also reduces settlements across fill layers and collapsible/loose deposits

Compaction grouting suits:

  • Liquefaction mitigation
  • Settlement reduction under existing buildings
  • Sinkhole stabilization
  • Machine tunnel pre-support
  • Load transfer for controlled structure lifting

When to Use Pressure Grouting or Compaction Grouting

Pressure grouting works best in free-draining gravels, sands, or other pervious soils needing broad permeation.

Compaction grouting provides robust, deep strength improvements in both pervious and lower permeability soils across a site.

Soil Types Suitable For Pressure Grouting vs Compaction Grouting

Pressure grouting effectively permeates well-graded sands & gravels. In permeable soils needing shallow permeation strength, pressure grouting delivers the most competitive value.

Compaction grouting strengthens all soil types. The displacement mechanism densifies even silty clays and uniform sands. Permeation becomes inefficient in those tight soils.


What is the difference between compaction grouting and pressure grouting?

The key difference is that compaction grouting injects low mobility grouts to displace and compact surrounding soil to densify it, while pressure grouting injects higher mobility grouts into soil voids and fractures to fill them.
Compaction grouting aims to strengthen the soil itself, while pressure grouting seals fissures/cracks.

When would compaction grouting be used over pressure grouting?

Compaction grouting would be used when the objective is to densify and strengthen loose or collapsible native soils.
It is effective for soil stabilization beneath foundations, slabs, and tanks.
Pressure grouting would be used when the goal is to fill voids in rock or soils, especially to prevent water migration.

What type of grout mix is used for compaction grouting vs pressure grouting?

Compaction grouting utilizes thick, low slump mixes with less than 1 inch of flow to displace and compact soils locally.
Pressure grouting uses thinner, more fluid mixes that can penetrate small fractures and voids without cracking the surrounding ground.
Grout mixes are customized to site soil conditions and project requirements.


Both pressure grouting and compaction grouting strengthen ground using cementitious grouts.

While pressure grouting suffices for broad subsidence control, compaction grouting offers superior precision in fortifying discrete zones.

Its deep injection depths and confined shape prevent adjacent structure or environmental impacts.

Consider existing soil conditions, available space, project loads and budget when choosing between these two versatile grouting methods.

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