Geopier® System For various mid-level structures up to 20 stories, we use Geopier® technology to construct stable, dense pillars that can support spread footings with bearing pressures up to 8,000 pounds per square foot. Also known as the Rammed Aggregate Pier® system, it offers reliable settlement control, fast installation and lower cost than traditional foundation-support methods. The Geopier system has become the standard for soil reinforcement requirements, and GeoStructures is the exclusive licensee for this technology in New York, New Jersey, Pennsylvania, Delaware, Maryland, Washington, D.C., Virginia and North Carolina.
The construction process is remarkably simple and fast:
- Drill a cavity to depths ranging from 7 to 30 feet deep and 24-36 inches in diameter.
- Place a 12-inch layer of open-graded aggregate at the bottom of the cavity.
- Compact the aggregate using a patented tamper that delivers a high-energy impact ramming action. The ramming action compacts the aggregate and prestresses the surrounding soil. Successive lifts of well-graded aggregate are then rammed in place.
The high-energy compaction process produces significant lateral pre-straining and pre-stressing of the adjacent matrix soils, which increases the lateral stress in the adjacent soils. The improved soils essentially “grab and hold” the Geopier element and, thus, improve the strength and stiffness of the combined pier-soil system.
With support provided to foundation loads greater than 3,000 kips, Geopier elements significantly increases the allowable bearing pressure and typically limit foundation settlement to one inch or less.
Geopier technology was originally developed for the support of shallow foundations as an alternative to costly, massive over-excavation and recompaction. Over the past decade, Rammed Aggregate Pier elements have most often been used as a replacement for costly deep foundations (driven piles and drilled piers), and in the following applications:
MSE Wall and Embankment Slope Stabilization
Geopier elements increase bearing capacity and global stability because they provide friction angles from 49 degrees to 52 degrees, thus increasing the composite stiffness of the soft foundation soils. When constructed using open-graded stone, the elements act as vertical drains, increase the rate of settlement, and eliminate the need for staged construction.
Case study: Greenbelt Station in Greenbelt, Md.
Slope Stabilization and Landslide Repairs
With friction angles from 49 degrees to 52 degrees, Rammed Aggregate Pier elements can be installed along unstable or marginally stable slopes to intersect failure planes and provide additional shear reinforcement. This increases the safety factor for slope stability.
Case study: Baltimore-Washington Parkway
Floor Slab Support
When conventional slab-on-grade solutions will not work, Rammed Aggregate Pier elements provide an economical solution to the support of conventional, light to heavily loaded floor slabs. Depending on the design pressures of the slab, the subsurface conditions, and Geopier element spacing, floor slab steel reinforcing is minimized. The structural performance of the slab is often analyzed using Finite Element Analysis techniques to achieve designed performance.
Rammed Aggregate Pier elements have supported some of the heaviest loads. Storage tanks, such as those used by municipalities, petrochemical facilities, and industrial and agricultural facilities, use our system to not only reduce total settlement magnitudes, but also to provide a reinforced composite zone that reduces the potential for damaging differential settlement. This improves safety factors against edge instability around the tank perimeter.
Soil liquefaction can have devastating effects on buildings in seismically active regions. The Rammed Aggregate Pier system can counter this problem by: 1) providing a stiff, non-liquefiable inclusion in the liquefiable soils, 2) reducing the magnitude of shear stresses in the matrix soil between the piers to levels sufficiently loaded to preclude liquefaction triggering, and 3) providing drainage elements for rapid drainage of excess pore water pressures that develop during seismic shaking.
Lateral loads induced by seismic and wind forces often result in uplift forces at building shear walls. Rammed Aggregate Pier elements with uplift anchors provide allowable uplift resistance up to 75 kips per anchor. The uplift anchor assembly extends from the bottom of the pier to the ground surface where it is structurally connected to the shallow foundation. This uplift resistance eliminates the need for deep foundations or oversizing of shallow foundations.
Case study: U.S. Army's Logistics University at Fort Lee, Va.
The Geopier System has become|
the standard for soil reinforcement.
Contact Our Specialist Ed O'Malley,