Geopier Impact®

The Geopier Impact System is an efficient and cost-effective intermediate foundation solution for the support of settlement-sensitive structures. The Impact System, like the Geopier GP3® System, creates stiff Rammed Aggregate Pier® elements using a patented vertical ramming process.


The Geopier Impact System is extremely effective for loose sands and semi-cohesive soils and when caving soils are expected. It is used as a cost-effective alternative to overexcavation and replacement, deep foundations (piles, caissons). It also puts you right back to spread footings and floor slabs-on-grade, right where you want to be.

The Geopier Impact Construction Process

  1. A specially designed mandrel and tamper foot is driven into the ground using a strong static force augmented by dynamic vertical impact energy. Depths range from about 10 to 50 feet, depending on design requirements. Flow restrictors prevent soil from entering the tamper foot and mandrel during driving. The process eliminates spoils and displaces soils laterally, densifying and reinforcing the existing soils.
  2. After driving to design depth, the hollow mandrel serves as a conduit for aggregate placement. Aggregate is placed inside the mandrel. The mandrel is then lifted approximately two to three feet and then driven back down one to two feet, forming a compacted lift. Compaction is achieved through static down force and dynamic vertical ramming from the hammer. 
  3. The process densifies aggregate vertically and the patented beveled tamper foot forces aggregate laterally into cavity sidewalls. This results in soil improvement, excellent coupling with surrounding soils and reliable settlement control with superior strength and stiffness.
  4. Following installation, the Rammed Aggregate Pier (RAP) elements support shallow foundations, floor slabs and reduce liquefaction potential and improve stability support of embankments, walls and tank pads. The footing stresses are attracted to the stiff RAP elements, resulting in engineered settlement control.

Case History

Logistics Health, La Crosse, WI