Lesson Learned from Dynamic Load Testing in Challenging Conditions-PPT Presentation

PPT Presentation

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The presentation shares four lessons from dynamic load testing (DLT), addressing common misconceptions in data interpretation.

1. <strong>Signal proportionality:</strong> The force–velocity proportionality (FVP) factor does not need to be close to 1.00. Values such as 0.64 or 1.15 can be valid when the signal behavior and interpretation support them. Reviewers should not require an FVP of 1.00 or change replay factors when the other parameters are correct.

2. <strong>Damping:</strong> Different damping factors serve different purposes and should not be confused. Lumped CASE damping depends not only on soil, but also on pile and hammer characteristics. Common ranges are useful for typical piles, but are not universal: short piles may have JC values above 1.0, while very long piles may have values below 0.4.

3. <strong>Pile damage at pinnacle limestone:</strong> A pile can crack or break from localized side tension caused by bending, even when the calculated average tensile stress (TSX) is well below its limit. Because TSX averages stress across the pile section, it may not reveal high tension on one side; measuring that stress would require strain gauges at the affected location. Cracking can slow wave transmission and delay the toe response.

4. <strong>Pile rebound:</strong> Total rebound is not a reliable measure of soil rebound because it includes elastic shortening of the pile. To assess actual soil rebound, subtract the pile’s elastic shortening from the measured displacement.

Overall, sound DLT interpretation requires understanding what each measurement represents and avoiding rigid rules that do not account for pile, hammer, soil, and loading conditions.

Keywords

dynamic load testing

DLT interpretation

force-velocity proportionality

damping factors

CASE damping

pile damage

pinnacle limestone

tensile stress

pile rebound

soil rebound