Quantifying Pile Rebound with Deflection Measuring Systems Best Suited for Florida Soils
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Quantifying Pile Rebound with Deflection Measuring Systems Best Suited for Florida Soils

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  • Creators:
  • Corporate Creators:
    Florida Institute of Technology
  • Corporate Contributors:
    Florida. Department of Transportation
  • Subject/TRT Terms:
  • Resource Type:
    Tech Report
  • Geographical Coverage:
  • Edition:
    Final Report, April 2017 – May 2020
  • Corporate Publisher:
    Florida. Department of Transportation
  • Abstract:
    Certain blends of very fine sands, silts, and clays are producing pile rebound during driving. Two major high rebound items were evaluated during this research: the possibility of using new pile movement techniques during driving to validate or check pile driving analyzer (PDA) deflections and the evaluation of cyclic triaxial test data to determine the effects of damping on rebound. Pile and standard penetration rod movements were monitored with the Inopiles Pile Driving Monitoring (PDM) system and a Florida Tech camera monitoring system (CMS) at six sites throughout Florida. Movements were compared with PDA deflections. Both devices produced deflections with accuracies well below 0.04 inch (1 mm), which compared well to PDA deflections. CMS data recorded at 60 Hz, which currently requires post signal processing, was obtained in all locations, while PDM data were not. Both systems have potential for use as checks on PDA deflections. PDM measurements were most successfully obtained during standard penetration tests (SPT) rod movement evaluations. Both CMS and PDM SPT rod movement evaluations showed time-dependent rod movements when driven through the blends of high rebound fine sands with silts and clays. Using 40 existing cyclic triaxial tests from six sites in Central and Northern Florida, a damping coefficient sensitivity analysis of Florida high rebound soils was completed. Two analytical approaches were used, one based on the change in stress over time and a second based on the viscous energy absorbed per cycle. Over 70% of the damping coefficients obtained from the stress-over-time approach ranges from 0 to 10 s. lb/in2 . These viscous results were not dimensionless and therefore could not be compared to the Case Western Reserve (CASE) 1974 dimensionless published coefficients. From the viscous approach, the results ranged from 0.18 to 0.59, which are similar to the CASE expected values and are also dimensionless. Therefore, the viscous energy approach is shown to be a better option for analysis. Twelve test piles from five sites in Central and Northern Florida were analyzed with the Case Pile Wave Analysis Program (CAPWAP®). The results showed that both Smith’s shaft and toe damping coefficients were acceptable based on the expected range. Smith’s toe coefficient, however, was shown to be more consistent than the Smith shaft damping coefficients. A linear relationship was found between Smith’s shaft and toe damping and rebound, with a stronger shaft versus rebound correlation.
  • Format:
    PDF
  • Funding:
    BD-28-977-07
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