FEATURE
By Farid Moradi and Hamed Layssi, FPrimeC Solutions Inc.,
and Ignacio Zulaga, geotecnia.ONLINE
Evaluating the load bearing capacity of existing and
newly constructed deep foundations and piles has
been of interest to engineers and piling contractors
for years. Various testing solutions have been developed
over the decades to determine the static load bearing capacity
as well as dynamic load testing of piles (ASTM D4945, 2017).
However, the main emphasis of these tests is on the global
response of the piles. Since this group of tests are generally
expensive and difficult to deploy, their application is limited
to critical elements.
Certain defects in pile materials, quality of workmanship
and errors in pile construction can negatively impact the
load bearing capacity of these elements. Therefore, quality
control of pile elements is key during the design and construction
processes.
Traditional methods for evaluating pile integrity involve
massive excavation of surrounding soil and extraction of
continuous core samples. This practice is extremely difficult
for testing existing structures. In the case of new construction,
such intrusive methods could increase the cost of the quality
control and impact the construction timeline.
Non-destructive test (NDT) solutions for evaluating the
quality of piles were developed in the 1960s. Electronic
developments significantly helped non-destructive pile
integrity tests become widely and globally available to the
geotechnical engineering market. Modern electronic and
computer techniques allow the processing of signals that
facilitate the subsequent presentation and interpretation
of the results. These NDT solutions have helped engineers
gain additional knowledge about the quality and integrity
of existing and new foundations. NDT solutions help reveal
potential defects that might have happened during pile
construction (in the case of cast-in-place piles) or transportation
and installation (in the case of precast piles).
Among NDT solutions for piles, the pile integrity method
(ASTM D5882, 2016) is certainly the one with the highest
economic return. The test is easy to perform and requires
minimal preparation. However, interpretation of test results
require engineering knowledge, information about the soil
profile and an understanding about soil-pile interaction.
The test method is less accurate for piles of large diameters
or when dealing with very large length to diameter aspect
ratios (>30).
Crosshole Sonic Logging (CSL) (ASTM D6760, 2016) has
been developed to address some of these challenges. CSL
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