Damping Coefficient Sensitivity Analysis of High Rebound Soils in Florida
The dynamic response of soils is related to a damping factor, which represents the energy absorbed by the soil as the pile moves. Certain blends of fine sands, silts and clays are producing pile rebound during driving. For that reason, the objective of this thesis is to conduct a damping coefficient sensitivity analysis of high rebound soils in Florida. Forty cyclic triaxial tests from six sites in Central and Northern Florida were analyzed to evaluate damping. Two 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 . The results cannot be compared to Case’s published data because it is not dimensionless. 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 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, showed 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.