50
Geotechnical News June 2011
GEO-INTEREST
in the Next Article
Up to this point I’ve been looking at the
behaviour of a single particle falling
through water because that, to a large
degree, is what I think liquefaction is
all about. What I want to do in the
next article is to generally conclude
my thoughts on this particular type
of failure. Also at that time I will
suggest: why silts are not as prone
to liquefaction as sands seem to be;
point out the areas of agreement and
conflict between this proposal and the
triaxial testing at Harvard and UBC;
and, discuss the comparative effects
of earthquake shear waves and surface
waves on a saturated soil-structure.
Glossary of Terms
F
D
= (C
D
ρ
v
2
/2) A
F
B
= (12 μ v / D) A = c N
c
A = q
ult
A
F
P
= (ρ v
2
/ 2) A = γ
w
h A
where:
F
D
Drag Force
N
C
D
Coefficient of Drag
-
ρ mass density of water
kg/m
3
v relative velocity
m/s
A equatorial area of sphere m
2
F
B
Bearing component
N
μ viscosity of water
Pa.s
D diameter of sphere
m
c cohesion
Pa
N
c
bearing capacity factor
-
q
ult
ultimate bearing capacity Pa
F
P
Pressure Component
N
γ
w
unit weight of water
N/ m
3
h velocity head
m
W.E. Hodge, Geotechnical Engineer,
P.Eng., M.ASCE,
(250) 307 4357,
Ram Jack Announces Helical Pile
Milestone
Angus W. Stocking, L.S.
Ram Jack Systems Distribution, LLC,
based in Ada, Oklahoma, recently
became the first (and so far, only)
helical pile manufacturer to receive
an International Code Council (ICC)
Evaluation Service Report (ESR-1854)
per the Acceptance Criteria for Helical
Foundation Systems (AC358) adopted
June 5th, 2007.
Now that ESR-1854 has been ap-
proved, engineers and contractors can
choose a helical pile that is compliant
with the International Building Code
and recognized by ICC-ES.
Helical piles were first used in 1836,
and by 1900 had been used to support
hundreds of marine structures (like
lighthouses and ship moorings) in Eu-
rope and the United States. Over the
last 175 years, the applications for he-
lical piles have been virtually endless.
Helical piles are basically a central
shaft with one or more helix-shaped
bearing plates attached. They’re typi-
cally installed with hydraulic torque
drivers that ‘screw’ the pile into the
ground; extension shafts are added un-
til the desired depth and/or torque are
achieved. Integral brackets are then
used to attach the pile to structures.
Because helical piles resist both
compressive and tension loads, can
be installed at any angle, and are ef-
fective in problem soils they’re one of
the most versatile geotechnical tools
available to engineers. Helical piles
are commonly used to support new and
existing residential, commercial and
industrial structures, retaining walls,
pipelines, boardwalks as well as utility
and renewable energy structures. ESR-
1854 applies specifically to the Ram
Jack 2.875” O.D. x 0.217” wall thick-
ness pile. “It’s our most popular prod-
uct, and hundreds of thousands have
been installed in the Americas,” says
Willis, “But of course we’re working
on updating our ESR to include more
of our product line, starting with larger
diameters.”
Before AC358 was adopted by ICC-
ES, there was not a common standard
for helical pile systems in the indus-
try. Most manufacturers only provided
capacities of individual components
and not the capacity of how the sys-
tem worked as a unit. A handful of
manufacturers, including Ram Jack,
had obtained certification under vari-
ous agencies and these manufacturers
were granted ‘legacy’ status after the
ICC was formed in 2000. But this sta-
tus didn’t provide a standard guideline.
In 2005, some helical pile manufactur-
ers began to work with the ICC-ES and
private consultants and that work led to
official acceptance criteria.
ESR-1854 also applies to Ram
Jack’s 2.875” push pile, a move that
surprised some industry observers. “It
makes sense,” says Willis, “Our push
piles have the same shaft and bracket
configuration as the helical pile, minus
the bearing plates, and it’s only those
parts of the push pile that are certified.
They only work in compression but
are ideal for remedial repair of exist-
ing structures.” The ESR extension to
push piles gives engineers even more
versatility when designing appropriate
foundation systems.
Ram Jack has been designing and
making steel piles for more than 40
years, but was primarily a contracting
firm until the 1980s.
Angus W. Stocking, L.S., 207A S. Uni-
versity Drive, Beaver Dam WI 53916,
270.363.0033 cell 920.219.9544 home/
office,
.,
Angus W. Stocking, L.S. is a licensed
land surveyor now writing fulltime on
infrastructure topics.
