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The PDA is the most widely employed system for Dynamic Load Testing in the
world. It can assess the capacity of multiple drilled shafts, cast-in-place, continuous flight auger or
bored piles in a single day.
PDA tests, or High Strain Dynamic Tests, simply require a drop weight (see examples) to
impact the shaft, and that the top of the foundation be cushioned by a few thin plywood sheets.
The PDA is available in two models, PAK and PAX. Both are self
contained and display results in real time on a color LCD screen. Both are available with 8 channels of
data acquisition, an important feature for testing cast-in-place piles and drilled shafts.
The light and battery operated PAX gives the engineer the
option of being present for the test or avoiding travel to the job site. When the engineer is present
for the test the PAX runs in local mode and displays all test data and results for immediate
interpretation. When only the PAX is on site a field crew sets up the test and the PAX transmits test
data via a broad band internet connection, while an engineer located elsewhere follows the test in real
time.
A testing engineer uses the PAK on site to estimate capacity at
the time of the test. The PAK displays all test data and results for immediate interpretation.
The PDA software calculates its results from velocity and force signals
obtained by accelerometers
and strain transducers attached to the foundation. These sensors may be wireless if a PDA model PAX is used.
CAPWAP® analysis of PDA data is
essential for a Dynamic Load Test. It provides the soil resistance distribution along the foundation and simulates
a static load test. Extensive correlations between CAPWAP-simulated and actual static load tests have proven the
reliability of this method of determining foundation capacity.
Both PDA models conform to
ASTM D4945 and many other codes and specifications. The PDA software suite, consisting of PDA-W,
PDIPLOT and PDICURVES, outputs reports that satisfy ASTM 4945 requirements.
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