Rigid inclusions and aggregate piers are ground improvement techniques and columns that create solid foundations in soft soils. Let’s look at how these ground improvement techniques work and what types of foundation construction projects each one works best with.
Rigid inclusions are unreinforced concrete columns installed in soft soils to support a structure with shallow foundations. They’re not directly connected to the structure they support, so they are considered ground improvement elements. When we install these inclusions, we put the concrete or grouted columns in place first, then add a layer of granular material called a load transfer platform on top of each column. This platform balances the load between the columns and the surrounding soil. Rigid inclusions often work best in very soft soil profiles such as organic soil, soft clay, or loose sands.
Aggregate piers are columns of compacted stone. We install them in groups into soft soil profiles that require densification and reinforcement to support the building loads. We often use aggregate piers for ground improvement projects on sites that have soft clay, silt, or man-made fill soils. When we install these piers, we install compacted stone into a cavity created in the soil, and force the compacted rock into the surrounding soil. These piers provide the ground modifications needed to support a variety of structures, including agricultural facilities, manufacturing facilities, and multi-story commercial or government buildings.
If large structures are constructed with shallow foundations on soft, natural soils, there could be total and differential settlements well beyond the allowable limits, resulting in performance issues. Ground improvement can be installed to increase allowable bearing pressure in the densified soils, resulting in smaller footing sizes, and decreasing the expected settlements to ensure the structure’s long term performance.
Rigid Inclusions reinforce soft, compressible soils, but they differ from most rigid inclusions in their installation process. We install them by drilling them into the ground with reverse flight displacement augers. The augers are hollow, so we fill them with concrete or grout to create RIs. They’re also drilled on a uniform grid to ensure even load distribution. However, they do have a load transfer platform on top of their installations, like other rigid inclusions.
Aggregate piers also have specialized types. Vibratory stone columns (VSCs) are types of aggregate piers that we install with high-frequency vibratory probes called vibroflots. We install them without any drilling, so they leave few to no spoils (construction waste) behind after their installation is complete.
We use these types of rigid inclusions and aggregate piers in our ground improvement projects where necessary. We understand when these solutions can be utilized, and when other techniques need to be utilized.
Rigid inclusions and aggregate piers offer many benefits, including the fact that they’re cost effective. They improve the ground under your foundation while keeping your project on time and within budget. Each inclusion or pier type also stabilizes the subgrade and the soil beneath it, ensuring your project has stable ground to build on. Overall, these techniques provide civil engineering solutions that make your project a cost-effective reality.
If your project needs ground improvement services and solutions, get in touch with CNC Foundations today. We can integrate our solutions with your existing plans to create a solid foundation that supports your structure, no matter how large it is. Our geotechnical engineers offer the inclusions or piers you need based on the soil in the ground on your site. We can assess your site’s soil profile and determine whether you need rigid inclusions or aggregate piers. We’re ready to use our ground improvement services to ensure your building’s foundation can support your structure safely.