S - Kam Ng PhD Dissertation Final.pdf - Digital Repository of CCEE ...

28t m = time when maximum total resistance occurs, s,t* = time corresponding to the maximum velocity, s,J cCEAL= Case damping factor, dimensionless,= pile wave speed, m/s or ft/s,= modulus of elasticity of a pile material, kN/mm 2 or ksi,= cross sectional area of a pile, mm 2 or in 2 , and= pile length below gauges, m or ft.2.3.4.2. Case damping factorReferred to Eq. (2.9), all the variables on the right can be measured or determinedexcept the Case damping factor J c which is a purely empirical value that describes thedynamic soil resistances. Rausche et al. (1985) pointed out that the J c can be calculated bysubstituting the maximum static soil resistance shown in Eq. (2.9) with the ultimate pileresistance determined from a static load test using the Davisson’s criteria. The recommendedJ c values given by Hannigan et al. (1998) are shown in Table 2.1. The original J c values weredetermined by Goble et al. (1975) from 69 static load test data, and they were organizedaccording to five soil types in the region of the pile toe. The data used in the original J ccorrelation were within 20% of the difference between Case method predicted results and thestatic load test results. In addition, a single best J c value was selected from the correlationstudy for each soil type and tabulated under the ―Best Correlation Value‖ in Table 2.1.Subsequently, the J c values were updated by Pile Dynamic, Inc. (1996) with additional staticload test data.Table 2.1: Summary of Case damping factors (after Hannigan et al. 1998)Soil Type at Pile ToeOriginal CaseDamping FactorsBest CorrelationValueUpdated CaseDamping FactorsClean Sand 0.05 to 0.20 0.05 0.10 to 0.15Silty Sand, Sandy Silt 0.15 to 0.30 0.15 0.15 to 0.25Silt 0.20 to 0.45 0.3 0.25 to 0.40Silty Clay, Clayey Silt 0.40 to 0.70 0.55 0.40 to 0.70Clay 0.60 to 1.10 1.10 0.70 or higher