Ground Improvement

Geopier X1® System

3The Geopier X1® system creates Rammed Aggregate Pier® (RAP) elements using a patent pending vertical ramming process which is a combination of both replacement and displacement methods.

The Geopier X1 system builds replacement/displacement RAP elements to reinforce good to poor soils, allowing for construction flexibility and the ability to build through caving zones that are encountered during drilling operations.

Like the original Geopier systems, the X1 systems drilling operation allows for visible inspection of the hole and the opportunity to address changing ground conditions as they happen. Its performance, flexibility, and cost-effective qualities make it the ideal solution for reinforcing a variety of different soil types.

For a list of Geopier X1 project profiles click here.

Greensville County Power Station – Emporia, VA – Using 24-inch diameter CTA (Cement Treated Aggregate) Piers

Navy Federal Credit Union Building & Garage – Vienna, VA – Installing 36-inch Dia. X1 RAPs

The RAP elements are constructed by applying direct vertical ramming energy to densely compact successive lifts of high quality crushed rock to form high stiffness engineered elements. The vertical ramming action also increases the lateral stress and improves the soils surrounding the cavity, which results in foundation settlement control and greater bearing pressures for design.


  • STRONG AND STIFF – Vertical impact ramming results in high density and high strength RAP elements providing superior support capacity and excellent settlement control.
  • DEPTH – Drilled RAP treatment depths of 40 feet or more.
  • QUALITY – Superior on-site quality control is maintained through full-time quality control personnel to observe, inspect and test the system, including visual spoil observation and full-scale modulus load tests.
  • VERSATILE – Can be used for various soil and groundwater conditions and loading conditions. Sizes from 18 to 36-inch diameter allows for low and high capacity piers.
  • FAST – Rapid installation process means shorter construction schedules.
  • ECONOMICAL – Often results in 20% to 50% savings compared to traditional deep foundation alternatives.

Virginia Tech Rasche Hall, Blacksburg, VA Installing 30-inch Diameter X1 CTA Geopier Elements


RAP solutions are designed to provide total and differential settlement control and increased bearing support to meet project requirements.

  1. The process first involves drilling a cavity. Drill depths normally range from about 5 to 40+ feet, depending on design requirements. Pre-drilling allows you to see the soil between the borings, ensuring that the piers are engineered to reinforce the right soils.
  2. Layers of aggregate are then introduced into the drilled cavity in lifts. A patented chamber compaction head allows lifts of aggregate to flow to the bottom of the hole allowing for fast pier construction.
  3. Compaction is achieved through static downforce and dynamic vertical ramming from the hammer. The process densifies aggregate vertically and the patented compaction head forces aggregate laterally into cavity sidewalls. This results in excellent coupling with surrounding soils and reliable settlement control with superior strength and stiffness.
  4. Following installation, RAP elements support shallow foundations and floor slabs, 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.


The following links provide brief case histories for projects that used the Geopier X1 system:

VA Tech Rasche Hall – Blacksburg, VA


Navy Federal Credit Union Headquarters – Vienna, VA


Geopier X1

Rex Hospital Parking Garage – Raleigh, NC