VERIFY
FOUNDATION
CAPACITY &
INTEGRITY
Real-time Dynamic
Load Testing
Dynamic load testing (DLT) is a
quick, efficient method to provide
verification of pile capacity and
integrity by applying impact force
on the pile top while monitoring
the pile response using a Pile
Driving Analyzer (PDA). Combined
with static tests, the DLT addresses
site variability and allows a more
economical design. The PDA
monitors pile stresses to help avoid
installation damage and provides
real-time feedback on capacity.
FUGRO LOADTEST
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info@loadtest.com
www.loadtest.com
This innovative methodology has been
incorporated into the Federal Highway
Administration (FHWA)’s design
manual but is not widely used.
allowable limits. However, due to substantial
setup within the Cooper Marl after 14
days, a large hammer is required for the
restrike test. Due to these performance
issues, contractors often face the problem
of supplying two different hammers just to
perform PDA testing on one pile. Based on
WEAP results and multiple conversations
with the contractor, Insight Group was able
to economize by having a single Vulcan 510
air hammer to be used for both initial drive
and re-strikes.
Owing to extreme test pile lengths, the
size of the leads was not long enough to set
the hammer on top of pile. Thus pre-augering
was an essential aid to the pile installation.
However, the rock used to surcharge
would often collapse into the hole, creating
difficulties setting the hammer. Hence, it
became imperative not only to reduce the
pile lengths in order to save cost but also
to improve constructability and schedule.
The root problem was the consolidation
of the underlying soft soils, which can
induce drag forces on the piles. This is what
caused the design to require such excessively
long piles in which the extra embedment
into the Cooper Marl Formation
was used to overcome these theoretical
forces. An emerging geotechnical concept
is the Neutral Plane design methodology.
This innovative methodology has been
incorporated into the Federal Highway
Administration (FHWA)’s design manual
but is not widely used. By treating
downdrag force as a settlement consideration
in the geotechnical service limit
state and as a structural consideration in
the pile structural limit state, the method
results in decreased applied loading
and can relieve the foundation element of
artificially high resistance requirements.
Research has shown that this design methodology
more closely reflects the observed
soil-pile interaction.
PROJECT SPOTLIGHT
The delivery of a 130-foot-long pile to the project site
A Parker Marine driving hammer
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