noise and vibration, real or perceived,
often influence some public agencies to
avoid pile driving.
In the author’s experience with designbuild
project delivery, most questions
about which type of pile to use start with
the question, “How can we build things
most easily and meet the schedule?” followed
closely by, “How much will it cost?”
and, “What are the risks?”
There are risks associated with uncertainty
about pile capacity, and these may
vary with confidence and experience
associated with each pile type. Risks may
also include schedule and other risks
associated with hiring specialty subcontractors,
which can be a consideration
when the general contractor can selfperform
some types of foundations under
consideration but not all. Unless there
are other considerations such as ownerspecified
limitations (e.g., see the last bullet
above), all viable foundation types will
Conclusions
The principal lessons that the readers
should take from this discussion are summarized
as follows:
• All types of deep foundations influence
the ground as a part of the process of
installation,
• All the available methods of estimating
pile capacity include empirical correlation
factors that are subject to the
many specific conditions and uncertainties
at the specific locations of load
test from which the empirical correlations
were developed,
• The post-construction conditions of
soil characteristics, in-situ stresses
and influence on the pile to soil bond
strength is quite complicated and not
captured by any simple equation,
• Given all of the above unknowns and
uncertainties, reliability in foundation
design is critically dependent on
a robust testing plan that incorporates
the important aspects of construction
for the specific ground conditions of
the project.
The author hopes that the readers find
this discussion of the many hard to calculate
issues affecting pile behavior to be
interesting and informative rather than
discouraging. As my father once told me
as I was about to leave home for college
almost 50 years ago, “Son, the more you
learn, the more you find out how much
you don’t know.” t
References
• Axelsson, G., 2000, “Long-Term
Set-up of Driven Piles in Sand,”
Doctoral Thesis, Division of Soil and
Rock Mechanics, Dept. of Civil and
Environmental Engineering, Royal
Inst. Of Technology, Sweden, 194p.
• Bottiau, M., 2014, “Installation
Parameters, Pile Performance,
and the Importance of Testing,”
Proceedings, International Conference
on Piling and Deep Foundations, Deep
Foundations Institute and European
Federation of Foundation Contractors,
Stockholm, 39p.
• Brown, D. A., 2002. ”The Effect of
Construction on Axial Capacity of
Drilled Foundations in Piedmont
Soils,” Journal of Geotechnical and
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