Improve Your Soil Conditions With Rigid Inclusions

An Ideal Solution for Less Than Ideal Conditions

Rigid Inclusions are one of the solutions we recommend when there is weak soil and we need to increase bearing in the project area.

Rigid Inclusions

Rigid Inclusions (RIs) are used as a ground improvement solution for weak, compressible, or otherwise soft soil. Some commercial projects require high load-bearing capacity, but the soil that the structure will be built upon cannot stand up to the weight of the structure. To remedy this issue, you can use rigid inclusions. Since their development in the 1990s, RIs have become known as a sustainable, cost-effective choice for improving soil stability.

These products are classified as displacement piles in our inventory. CNC Foundations has made considerable efforts to develop and maintain an extensive inventory of the products and tools in our library of services. We do this to shrink our response time, keep costs low, and increase our flexibility in meeting your needs.

Take advantage of everything we have to offer.

Looking for deep foundation solutions as well? We have the support services you need.

How Rigid Inclusions Work

Rigid Inclusions are essentially concrete columns that are installed by drilling into the earth. The actual rigid inclusion installation process, however, is a bit more complicated. A reverse flight displacement auger utilizes high torque capacity and down-thrust to bore holes, known as rigid inclusions or semi-rigid inclusions, into the ground on a grid.

These rigid inclusions are roughly 10 to 18 inches in diameter and about 3 to 10 feet apart. The auger drills these inclusions up to 40 meters (roughly 130 feet) into the ground; it moves past soft soil down to more stable soil or dense sand or silt. As the auger drills, it moves soil laterally, thus avoiding the soil displacement that can be typical of other ground improvement systems.

The auger is hollow, which allows us to fill the inclusions with grout or concrete all the way down to the bottom of the inclusion. Once all of the inclusions are drilled and filled, there is essentially a grid of stone columns reaching far down into the earth.

Because the RIs are drilled on a uniform grid, they offer an optimal distribution of loads between the inclusions and the surrounding soil. Before the foundation is poured, the RIs are covered with a load transfer platform, also known as a granular mattress, to create a smooth, even layer for the foundation.

Rigid Inclusion Benefits and Uses

Ideal Soil Conditions

  • Soft clay
  • Silt
  • Peat
  • Loose sand
  • Gravel
  • Fill
  • Organic soil


  • Heavy loads on commercial or industrial floor slabs
  • Road or rail loading docks
  • Silos and water tanks
  • Residential buildings that typically require driven piles
  • Mechanically stabilized earth (MSE) retaining walls
  • Bridge abutments
  • Embankments

Benefits of Rigid Inclusions

  • Use shallow-build foundations on soil types that are not normally compatible
  • Reduces soil settlements for ground-bearing foundations
  • Vibration-free process, making it ideal for sensitive locations
  • Optimizes the amount of steel and concrete needed
  • Therefore, sustainable
  • Cost-effective
  • Quicker process

Related Case Studies

Let’s Talk