Bracket/ Helical Piles
Bracket and helical piles are structural underpinning elements installed to support and/or stabilize existing foundations. The basic components are similar: the pile shaft itself and an angled bracket that connects the pile to the footing to be supported and transfers the structural load to a competent bearing stratum. However, the construction of the pile element and method of installation differ.
Bracket piles are typically used in conjunction with earth retention work to support and/or stabilize existing foundations adjacent to a proposed excavation. Underpinning contractors use helical piles for foundation settlement control.
Bracket piles are installed to design depth in pre-drilled holes alongside the exposed wall or column footings. A bracket is mounted to the underside of the footing and attached perpendicular to the new pile. The load is transferred from the structure to the pile through the bracket.
A helical, or screw, pile consists of one or more helix-shaped plates, also referred to as flights, attached to a shaft. The pile is hydraulically screwed in the ground until the required resistance is reached to achieve pile capacity, and attached by means of a bracket to the adjacent distressed footing. Helical piles generally develop their load-carrying capacity through end-bearing on the flights.
- Settlement Control
- Support of temporary or permanent structures
Advantages & Limitations
- Can be installed in limited headroom, tight access areas
- Vibration-free installation
- Can be post-tensioned or pre-stressed to mitigate displacement
- Capacity is typically limited by the connection to the structure