Geopiers are stiff rock columns that are drilled deep into the earth’s surface to a hard, non-yielding depth. The columns provide support to a building’s foundation and reinforce the soil when the existing ground is unstable, wet, or unsuitable for building construction.
Each geopier column is strategically placed directly below a footing. The shaft is filled with 2 to 4-inches of crushed rock that is then rammed into the bottom of the shaft with a hydraulic hammer. Once compacted, layers of well-crushed rock are rammed to the top of the geopier shaft. The ramming of the rock creates a very stiff, dense rock pier that expands the drilled shaft and reinforces the soil.
Geopiers are often a more economical choice than significant soil remediation on sites that need amendment and can result in 20-50% cost savings over the alternative. They are fast and efficient to install and can be eco-friendly when recycled concrete and other materials are used.
Stahl is using a series of 503 geopiers, which are 20-inches in diameter and will range in 14-feet to 21-feet in depth, for the construction of the new Fairfield Inn and Suites and Cambria Hotel and Suites in Downtown Minneapolis. Three to five geopiers will be placed under each stem wall footing and column footing.