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Chapter 2
Helical Foundation Systems
CHAPTER 2
HELICAL FOUNDATION SYSTEMS
2.2 – Summary Description
Helical piles are a factory-manufactured
steel foundation designed to resist axial
compression, axial tension, and/or lateral loads
from residential and commercial structures. The
system consists of a central shaft, one or more
helix-shaped bearing plates, and a bracket that
allows attachment to structures. The helix plates
are commonly referred to as blades or flights
and are welded to the lead section. Extension
shafts, with or without additional helix plates,
are used to extend the pile to competent load
bearing soil and to achieve design depth and
capacity. Brackets are used at the tops of the
piles for attachment to structures, either for new
construction or retrofit applications. Helical piles
are advanced (screwed) into the ground with the
application of torque.
The terms helical piles, screw piles, helical piers,
helical anchors, helix piers, and helix anchors
are often used interchangeably by specifiers.
However, the term “pier” more often refers to a
helical pile loaded in axial compression, while
the term “anchor” more often refers to a helical
pile loaded in axial tension. The term “pile”
traditionally describes a deep foundation that
can resist both tension and compression loads.
Helical tiebacks and helical soil nails are
types of helical anchors differentiated by their
specific design methodology and/or installation
orientation. Helical tiebacks are designed similarly
but differ from vertically-installed helical piles in
that they are typically installed in a horizontal to
45-degree downward from horizontal orientation
to laterally support the tops of earth retaining
structures; e.g., retaining walls, foundation walls,
sheet pile walls, soldier pile walls with wood
lagging, etc. Helix plates are typically limited to
the lead section or the lead and first extension
of the tieback. Multi-helix leads for piles and
tiebacks generally consist of increasing plate
sizes from the tip. Helical soil nails are designed
with same-sized helix plates, typically 6 or 8
inches in diameter, spaced evenly along the
entire length of the nail, including the lead and
extensions. Soil nails are typically installed in a
closely-spaced grid pattern to reinforce the soil
and provide a stable earth mass. Helical tiebacks
and helical soil nails are presented in their own
sections later in this chapter.
New construction helical pile installation
Sheet pile wall stabilization
with helical tiebacks
Helical tieback installation
with hand-held equipment
