Helical piers are a deep foundation system used to repair existing structures that have settled. They are also used in new construction where support from greater depths is required due to the structure being built on unstable soils. Because helical piers screw into the ground, they typically require less excavation than other types of piers and can be installed in areas with limited access.
A helical pier is constructed of a steel central shaft with one or more bent plates (helixes) along the pile. The pile sizes differ by various shafts and combination of shafts of high-strength solid steel bar from 1-1⁄2” to 2-1⁄2” thick to tubular with diameters from 2-7/8′′ to 12′′ with various steel thicknesses. The piles are advanced into the soil by screwing them in with hydraulic gear motors. They are bolted and connected in shaft lengths from 3 to 20 feet to extend the depth of the pile. Capacity can be measured during installation, and there is a direct relationship between torque (force required to cause rotation) and capacity. The stiffer the soil, the more drive force by way of torque is required, measuring the end-bearing capacity of the soil and the pile. Loads are transferred from the foundation to the pier shaft to end-bearing strata.