Helical Piles Overview
Helical piles, also called screwpiles, are hollow tubular piles that have a screw or helix design. They are commonly used as ground anchors for building deep foundations. The screw design is fabricated by welding helical steel plates (called blades or flights) to the pile shaft, with positioning and plate thickness determined by load requirements, ground conditions, and expected design life.
Helical piling systems are installed by applying torque via a hydraulic drill motor to the pre-fabricated helical pile, winding it into the ground. Depths can range from ten to sixty feet deep. Helical piles can be installed with small, portable equipment, such as a skid steer or mini-excavator. To ensure a strong deep foundation, the topmost helix plate is embedded at least five plate diameters below the surface of the ground. Brackets are often attached to the tops of the piles to attach to structures. Unlike an auger where soil is displaced, the installation results in minimal soil disturbance.
Originally used for building lighthouse foundations, helical piling systems are now used in many structure types, especially where fast installation is required or the construction site is close to existing structures. Screwpiles are cost-efficient and have a smaller environmental impact, since they displace less soil than traditional boring techniques. They are useful in sites with high water tables, and are easy to remove when a foundation is no longer needed. Helical piles can be used immediately after installation, not requiring concrete to cure.
The plates creating the helical shape must be far enough apart from one another that each can function as independent load-bearing elements. The plate distance also ensures that a given helix is not impacted by the loads of the helixes above or below it.
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