01 July 1997
(e) The dynamic force must be sufficient to maintain an adequate amplitude to continue
penetration of the soil. This is especially important if the soil is clay. Driving is still possible if the driver is
sufficiently large. A rule of thumb for vibratory drivers is a small driver for piles up to 30 feet, medium driver
for piles up to 50 feet, and a larger driver for piles over 50 feet in length.
b. Pile Driving Analyzer. The PDA is recommended during pile installation or during some part of the
pile installation operation to calibrate wave equation analysis and to evaluate the quality of the driven pile.
calculated by wave equation analysis.
(1) PDA analysis will be performed at the start of any significant project and later during pile
(a) The number of static load tests can be reduced to just one or two when PDA is
performed. More static load tests are required for variable or erratic soils.
(b) The PDA can be expected to provide good estimates of pile capacity in uncemented
(c) The PDA can provide good estimates of pile capacity in silts or clays, but careful analysis
is required because of high damping forces.
(2) The pile is expected to have sufficient capacity if the bearing graph calculated by wave
equation analysis indicates an ultimate bearing capacity of at least twice the design load for the measured
(a) Sample production piles will be tested by PDA to ensure that the pile foundation will have
(b) PDA will be performed if the pile driving record indicates a significant reduction in pile
capacity so that there is doubt that the piles can adequately support the structure.
(3) Results of the PDA and wave equation analysis performed by the PDA technician should
indicate the load-displacement behavior of the pile and provide a value of the pile settlement at the design
(a) The settlement for the design load should usually be less than 0.5 inch.
(b) Calculation of load-displacement behavior with PDA equipment requires calibration with
a static load test.
(4) Observation of the wave forms on the oscilloscope of the PDA equipment by the PDA
technician will be performed to indicate the quality of the pile and to determine if any damage occurred to
the pile as a result of driving.
(a) The PDA data will tell if there is any probable damage to the pile top.
(b) The PDA will show the effect of changes in the helmet, cushions, or stresses induced at
the pile top.
(5) PDA data will permit analysis of hammer performance.