March/April 2024 - 85

Helical piles are generally installed to a minimum torque
to ensure capacity, and, therefore, the exact depth is not
known prior to installation.
piles to support a prefabricated steel
grillage requires accurate pile location.
The load-bearing clamp allows the pile
to be terminated anywhere along its
length because the clamp can be
connected anywhere along the shaft.
The grillage can is usually a short
section of 12 in (305 mm) square or
round tubing, and the 4.5 in (114 m) pipe
is located inside the tube, allowing ± 3 in
(76 m) of location tolerance in any
direction. The clamp and bearing plates
were designed and tested, without
grout, to the full mechanical rating of
the helical pile - 150,000 lb (68,000 kg)
for the 4.5 in (114 m) diameter pile.
Finally, the can is filled with a nonshrink
grout to provide a fixed endcondition
for the pile.
System Improvements and
Patents
The load bearing clamp and grillage
system has evolved over several years
as improvements have been developed.
The original design used clamps above
and below the can, but the top clamp
was replaced with a threaded spud that
allows preloading the clamp and spud.
The original clamps deformed the pile
by tightening waxed threads to apply
the load, which was labor intensive.
This has been replaced with a tool that
applies load with a hydraulic cylinder.
So, after several iterations, the load
bearing clamp and grillage assembly
system has evolved to provide a robust
solution to supporting structures like a
monopole without any of the usual
challenges of field welding, drilling,
concrete cleanup, or heavy equipment
access roads.
The loadbearing clamp and grillage
system are patented. They system is
being used to support transmission
structures in both Canada and the U.S.
Completed grillage with monopole
DEEP FOUNDATIONS * MAR/APR 2024 * 85
for limited access sites and environmentally
sensitive areas. This technology
has been used with 2.875, 3.50,
4.50 and 5.50 in (73, 89, 114 and 140 mm)
outer diameter pipes and can support
loads up to 280,000 lb (127,000 kg).
In addition to transmission lines,
helical piles have been used in many
applications related to energy production
and transmission. They have
supported infrastructure, associated
structures, and equipment foundations
for the oil and gas, solar, and wind
energy industries, both on land and
offshore. Offering unique benefits for
difficult soil conditions and environmentally
sensitive areas, helical piles
provide engineers with a powerful tool
to address challenging foundation
projects.
Shawn Downey is the senior design engineer
for helical products with the civil and
construction business units at Hubbell
Power Systems and has been working with
the Chance brand helical anchors and piles
for 34 years. He has extensive experience in a
wide variety of soil conditions and has
installed and tested helical piles on five
continents. He holds 10 patents on helical
piles and tooling used to install helical piles.
The original clamps deformed the pile by tightening waxed
threads to apply the load, which was labor intensive.
March/April 2024

Table of Contents for the Digital Edition of March/April 2024
