Provided below is a definition of terms for helical piles.
Batter Angle: Inclination angle from vertical at which helical piles are installed; can be given as percentage, ratio of vertical depth to horizontal run, or angle in degrees.
Bracket: Manufactured steel cap or assembly that attaches to the helical pile butt and is used to transfer loads to new or existing foundation elements; examples include angle bracket, plate bracket, new construction bracket.
Cohesion: Soil shear strength parameter that is constant with respect to confining pressure; basically, the forces within soil that hold it together.
Coupling: Pinned, bolted, or welded connection of two helical piles shafts.
Down Drag: The phenomenon where soft soils surrounding a pile consolidate and produce a downward force on the pile tending to cause additional settlement. Consolidation can be triggered by soil self-weight, periodic changes in groundwater, placement of fill, or other surcharge loads on the ground surface.
Drive Pin: Pin used to connect a helical pile butt to a drive tool on a torque motor; typically, a high strength smooth round pin, although any dowel of appropriate strength can be used.
Drive Tool: Adapter for transferring torque between the torque motor and the helical pile consisting of a hex or other shape Kelly bar socket and a round or square collar sleeve.
End Bearing: Term used to describe a pile that generates most of its capacity from the pile tip such as piles that bear directly on bedrock; essentially all helical piles with single helix are end bearing.
Flange: Pair of often-identical plates that form the main structural components of a wide flange beam, H-pile, or I-joist; flanges are separated and held apart by the web.
Helix: Generally circular steel plate pressed in a spiral shape with uniform pitch. The helix is welded to the shaft and used to install the helical pile in a screwing action into the ground and to transfer the load from the shaft into the surrounding soil or rock material.
Kelly Bar: Short, typically round or hexagonal drive shaft extending from a torque motor, auger drive, or soil/rock drill.
Lateral Load: Force acting on a helical pier in a direction that is transverse (perpendicular) to the central shaft.
Lateral Resistance: Capacity of a helical foundation system or devise to resist lateral loads.
Micropile: Small-diameter (typically 4-inch to 8-inch) drilled pile with central reinforcing steel bar surrounded by cement grout; One of the main distinctions of micropiles compared to other types of drilled piles is the use of smaller drilling equipment, with short mast and segmental drill stem.
Mooring: Underwater anchoring system for securing a boat or ship. Typically consists of a helical anchor, cable or chain, and buoy.
Pile Cap: Reinforced concrete structure of variable thickness and geometry placed over one or a group of helical piles and used to transfer loads to a column, grade, beam, wall or other structure.
Solider Pile: Vertical pile used in earth retention.
Static Load Test: Pile load test wherein load increments are applied to a helical pile at a slow rate to simulate static conditions. The quick test method is considered a type of static load test; loads may be applied with deadweight blocks or by hydraulic ram; the word “static” is used to differentiate this test from cyclic, dynamic, impulse, or statinamic load testing.
Tie-Back: Helical anchor used in earth retention with helical bearing plates located a significant distance past the active zone of retained earth and a central shaft that extends through the active zone to a rigid wall facing; also a term used for grouted anchors, duck-bill anchors, and deadman anchors where the bond zone is outside of the active zone of retained earth.
Underpinning: Method of installing helical piles alongside or underneath an existing structure, connecting the piles to the structure, and transferring support from the existing foundation elements to the helical piles; may be associated with lifting and re-leveling of structures.