Impact® System

40+ ftinstallation depth
3-8 ksftypical bearing capacity
  • Ideal for caving soils
  • Rapid installation (schedule savings)
  • 20-50% savings versus deep foundations and over-excavation
  • No spoils and haul-off costs

The Geopier Impact® system is our solution to soils that simply won’t stay open during drilling.  Impact piers are a displacement type system that uses a steel pipe mandrel outfitted with a patented compaction chamber to penetrate through caving soils and construct piers from the bottom up.  This installation method allows for the construction of high-quality Rammed Aggregate Piers (RAPs) below the groundwater table without having to worry about contamination and/or fouling of the aggregate.  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.

Soil Type

•    Caving sands below the groundwater table and soft squeezing clays and silts

•    Organic soils after the addition of grout to the aggregate

•    Liquefiable soils



Geopier Impact® piers are installed by advancing a displacement mandrel through unsuitable soils to a desired design depth. Once at depth, the mandrel is withdrawn several feet to allow open-graded aggregate to flow into the annular space.  The mandrel is then redriven to create a densified 2-foot-thick lift of aggregate.  These steps are repeated up to the ground surface to create a dense column of aggregate surrounded by stiffened matrix soils.

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Design Considerations

  • Grout can be added to Impact® system piers to address sites with organics, heavy loads, or adjacent structures
  • Great for mitigating liquefaction-induced settlements
  • Foundations and slabs can be constructed as conventional spread footings and slabs-on-grade
  • Geopier Impact® 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