September/October 2023 - 110

load was challenging and there was
minor change in vertical displacement
with the unloading process.
The data collected during the test
confirmed that the ultimate pile uplift
capacity was on the order of 170 kip
(756 kN). This information will be
valuable in determining the pile's
ability to withstand uplift forces and
ensure its stability under various soil
subgrade and load conditions.
Lateral Load Tests - The depths of
embedment for each foundation were
33 ft (10 m) below ground line.
The overturning moment was
generated by applying a lateral load to
the top of the 40 ft (12 m) long test pole
mounted on top of the FRP foundation.
The test arrangement used a standoff
distance for cable tension load application
that would provide a moment
to axial load ratio that very closely
resembles the ratio typically encountered
in transmission line structures.
The cable tension was applied via
a pulley system driven by a winch
attached to a Caterpillar D6R XL TrackType
Tractor that had a four-part steel
cable arrangement. An approximately
270 ft (82 m) long, 1 in (25 mm) diameter,
19 x 7 rotation-resistant wire rope
connected the four-part pulley system to
the test poles about 6 in (150 mm) below
their top. Applied loads were measured
Load deflection relationship during the determination of the uplift capacity
by a Dillon EDxtreme dynamometer
(load cell) with wireless remote
readouts, located near the connection of
the cable with four-part pulley system
connected to the dozer. Four dial gauges
were used to monitor lateral and vertical
movements at the base plate on top of
the foundations: a set of one vertical dial
and one horizontal dial were each set at
12 and 6 o'clock respectively for each
test, where 12 o'clock refers to the front
side of the foundation pole, in the
direction of the longitudinal pull. Linear
displacement transducers were installed
near the dial gages to provide
digital readout to an automated data
acquisition system. At the 3 o'clock
Full-scale lateral load application to embedded FRP foundation
direction, a plumb bob recorded vertical
movement; at the 9 o'clock direction, the
base angle of rotation was measured
using a level.
Strain gauges mounted at the front
and back of the pile every 2 ft (0.6 m) in
depth from the top to bottom were
installed to determine stress levels in
the wall of the pipe section of the
foundation. Data from the strain gauges
was conditioned and collected at each
load increment using four DAQ and a
laptop computer.
Procedure - Two lateral load tests
were conducted, one with the load
applied in plane with the 12 and
6 o'clock box stiffeners, resulting in a
direction perpendicular to the box
stiffeners at 3 and 9 o'clock. The load
application for the second test was 45
degrees in the diagonal direction of the
stiffeners. The tests were performed
according to procedures developed by
the Electric Power Research Institute to
model lateral loads typically induced
on transmission line structures during
wind, rain, ice and conductor loads.
The test pile was loaded incrementally,
starting from 0-70 kip
(0-310 kN), in 5 kip (22 kN) increments
up to 20 kip (89 kN), and 10 kip (45 kN)
increments thereafter. Each increment
was held for about five minutes. After
reaching 70 kip (310 kN), the pile was
gradually unloaded.
110 * DEEP FOUNDATIONS * SEPT/OCT 2023
September/October 2023

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