for maximum versatility with proven
performance in a variety of problematic
soil conditions for support of foundations,
slabs and other structures.”
Project challenges
In the planning and design stages, this
project involved multiple challenges
related to poor soil conditions coupled
with the surrounding structures and
ongoing construction.
“Developers had only recently
completed neighboring office/residential
construction and workers were actively
working on a large six-story parking garage
located immediately adjacent to the 6 Stack
Street Pavilion project,” said Fitzpatrick.
“Traditional pile driving would be
potentially harmful to the new structures
due to vibrations. Further, the potential
for loss of soil confinement around the
foundations – due to the large planned
10 Stack Street excavation – required
the piling be designed for a portion of
unbraced lengths.”
Due to these conditions. DIPs were a
logical choice for this project, largely since
they are a modular, low-vibration driven
pile system.
The system utilizes a medium-sized
excavator and percussion (demolitiontype)
hammer to install the piles, making
it well suited for constrained urban sites or
interior renovation work where overhead
clearances are 18 feet or higher.
“While the system has been used costeffectively
on wide open sites, the vast
majority of our customer’s projects include
building additions, interior retrofit work
or tight, urban development sites,” said
Fitzpatrick. “The system is versatile and can
be installed to develop capacities ranging
from 25 to more than 100 tons in either
end-bearing on a competent bearing layer
(i.e., rock or very dense ground) or by using
an oversized pile shoe and continuously
pumping grout during driving to create
an efficient grout-to-ground bond zone
for frictional capacity. Projects primarily
include industrial and manufacturing
additions and improvements, warehouse
retrofits, commercial and residential
buildings and additions and the occasional
bridge support and municipal application.”
Soil conditions
The soil conditions for this project
consisted of heterogeneous urban fill with
obstructions extending to depths of about
18 feet, followed by a 4-foot thick peat and
organic layer. Marine and glaciomarine
sand and clay then extended to depths
of approximately 38 feet at which point
medium dense to very dense glacial till
was encountered.
For this project, geotechnical engineers
Haley & Aldrich, Inc. considered a number
of different foundation options including
ground improvement (rigid inclusions),
traditional drilled micropiles, proprietary
displacement micropiles as well as DIPs.
Due to the close proximity of a
future building excavation and concern
for potential reduction of soil support,
ground improvement was eliminated.
Drilled micropiles were feasible but were
eliminated due to the associated costs
and schedule. The specified friction pile
system was approved for displacement
micropiles and DIPs. DIPs were selected
over all the specified options based on cost
and schedule.
“The piles were designed by DuroTerra
as grouted friction piles to penetrate the
fill, organics and marine/glaciomarine
soils to terminate in the glacial till,” said
Robert Tonning, P.E., president of Phoenix
Foundation Company, Inc., which was
the pile installer on this project. “A Series
118/9.0 Ductile Iron Pile (118 mm outer
diameter and 9 mm wall thickness) was
used to deliver a 40-ton (compression)
capacity for design. Each of the piles was
installed by first placing a 220 mm oversized
grouting drive shoe at the tip of the first
five-meter-long pile section. The pile was
then advanced using an Atlas Copco MB
1700 percussion hammer mounted on a
Kobelco SK230SR excavator. Sand cement
grout was mixed onsite with a mobile mixer
from InTerra Innovation, Inc. and pumped
by Independent Concrete Pumping.”
During the pile driving, grout was
pumped through the grouting drive shank,
down the interior of the pile and out the
grout ports in the drive shoe to immediately
deliver grout to fill the annular space
around the pile created by driving the
oversized shoe. During driving, the rate
of advancement and grout quantity was
closely monitored.
“Essentially, the project started with the
installation of a test pile and four tension
reaction piles,” said Tonning. “The reaction
piles were installed in the same fashion as
the test pile but included the installation of
a high strength threadbar into the center
of the wet grout after installation. The
PROJECT SPOTLIGHT
Ductile iron pile installation with iconic
Hood Dairy chimney backdrop
Cut and capped ductile iron piles ready
for foundation construction
Medium-sized excavator installing
the ductile iron piles
92 | ISSUE 6 2020 www.piledrivers.org