GP3® System

25+ ftinstallation depth
3-8 ksftypical bearing capacity
  • Ideal for non-caving soils
  • Rapid installation (schedule savings)
  • 20-50% savings versus deep foundations and over-excavation
  • Minimal spoils and haul-off costs 

The Geopier GP3® pier system is the primary “drill and fill” solution.  This system is ideal for non-caving soils that stay open during drilling.  GP3 piers are constructed using a track-mounted auger to drill out unsuitable soils and a patented track-mounted tamper to construct the Rammed Aggregate Pier (RAP) elements.  The end result is a dense column of aggregate surrounded by stiffened matrix soils that provide excellent settlement control and allow for higher bearing capacities.   The GP3 system is one of Geopier’s oldest systems, with several thousand successful projects in the ground.

Soil Type
  • Non-caving soils such as clays, silts, and sands with high fines content
  • Caving soils with the use of temporary casing
  • Organic soils using cemented treated aggregate (CTA)

The Geopier GP3® installation process consists of drilling out unsuitable soils to a desired design depth and then constructing a dense column of aggregate using a patented tamper.  The pier is constructed in 2-foot-thick lifts using well-graded aggregate, open-graded aggregate, or sand.  The installation process imparts significant lateral pressures into the adjacent matrix soil, which creates excellent coupling and stiffens the soil.  

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Design Considerations

  • Cement-treated aggregate can be used for sites with organic soils, heavy loads, or adjacent structures that are settlement sensitive
  • Foundations and slabs can be constructed as conventional spread footings and slabs-on-grade
  • Geopier® systems can be used for uplift and lateral resistance

Construction Considerations

  • Eliminates the need for casing
  • Generates no spoils, eliminating haul-off costs
  • Often results in 20% to 50% cost savings compared to traditional alternatives (removal and replacement and deep foundations) 
  • Rapid installation process means shorter construction schedules