I’m observing that the forces are of different magnitudes in a PDA test. Should I use the “Replay Factors” to adjust the data?

“Replay factors” should be used only sparingly and very cautiously. For displacement piles, the force differences are likely due to bending in the pile, and the average of diametrically opposite strains should result in an average force that is “proportional” to the velocity. Differences in velocity amplitudes can possibly be caused by not having one of the accelerometers aligned axially with the pile, so care must be taken to properly align the accelerometers parallel to the pile axis. Differences between F and V at the impact peak can be due to diesel hammer pre-compression, soft cushions making a long rise time, reflections of soil resistance along the upper shaft (or a very short pile), or pile non-uniformity. So, in general, you should trust the calibrations and not alter them. Small adjustments are perhaps reasonable (due to the accuracy of calibration), so our general suggestion is to limit the Replay Factors to values between 0.97 and 1.03.

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