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Chapter 2
Helical Foundation Systems
CHAPTER 2
HELICAL FOUNDATION SYSTEMS
force during the press operations are important
to ensure parallel leading and trailing edges and
the required pitch tolerances. The amount of die
press; i.e., the pressed shape and deflection, must
also be adjusted for changing plate thicknesses,
steel grades and anticipated spring back.
ICC-ES AC358 establishes design and testing
criteria for helical piles evaluated in accordance
with the International Building Code. AC358
provides the following criteria for helix plates in
order to be considered as a “conforming system”.
• True helix shaped plates that are normal with
the shaft such that the leading and trailing
edges are within
¼
inch of parallel.
• Helix plate diameters may be between 8 and
14 inches with thicknesses between
3/8
inch
and
½
inch.
• Helix plates and shafts are smooth and absent
of irregularities that extend more than
1/16
inch from the surface excluding connection
hardware and fittings.
• Helix spacing along the shaft shall be between
2.4 to 3.6 times the helix diameter.
• The helix pitch is 3 inches ±
¼
inch.
• All helix plates have the same pitch.
• Helical plates are arranged such that they
theoretically track the same path as the
leading helix.
• For shafts with multiple helices, the smallest
diameter helix shall be mounted to the leading
end of the shaft with progressively larger
diameter helices above.
• Helical foundation shaft advancement equals
or exceeds 85% of helix pitch revolution at
time of final torque measurement.
• Helix plates have generally circular edge
geometry.
Non-conforming systems may also seek an
ICC-ES product evaluation, but must undergo
additional product testing.
Foundation Supportworks’ helical piles feature
platesmanufacturedwithahelixshapeconforming
to the geometry criteria of ICC-ES AC358.
Conversely, plates that are not a helix shape are
often formed to a “duckbill” appearance. These
plates create a great deal of soil disturbance, do
not conform to the helix geometry requirements
of ICC-ES AC358, and their torque to capacity
relationships are not well documented.
The helix plate diameter, thickness and cut are
selected based upon the soil and load conditions
for the project. FSI currently offers:
• Helix plate diameters ranging from 6 inches to
16 inches
• Helix plate thicknesses of
5/16
inch,
3/8
inch, and
½
inch
• Plate steel yield strengths of at least 50 ksi
(Grade 50).
• Standard H-style cut and V-style cut plates
(Figure 2.3.1.c)
. V-style plates are special
order to assist in penetrating dense or rocky
soils. The leading edges of all helix plates are
sharpened (cut) to a 45-degree angle.
Figure 2.3.1.c
Standard H-style and V-style plates