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

268comparison was assessed in terms of match quality as shown in Table 7.7. The application ofthe proposed shaft dynamic soil parameters, while keeping the toe dynamic soil parameterscloser to the values suggested by Smith (1962) during the CAPWAP analysis, has improvedthe match quality by 19%. This study further validates the proposed method in quantifyingthe dynamic soil parameters.7.8. Summary and ConclusionsAlthough dynamic analysis methods have been used in estimating axial pileresistances, the accuracy of these methods is highly dependent upon the proper input ofsuitable dynamic soil parameters. Unfortunately, these parameters have not beensuccessfully quantified in terms of any measured soil properties, due to a large degree ofscatter in the collected parameters resulting from the current default CAPWAP matchingprocedure, where constant parameters are assumed along the entire pile shaft. In addition,due to the indeterminate nature of the CAPWAP analysis, the dynamic soil parameterscannot be uniquely quantified. As a result, a possible range of damping factors and quakevalues are recommended in CAPWAP by Pile Dynamic, Inc. (2000). In fact, manyresearchers have urged the use of improved or better represented dynamic soil parameters inthe analysis. To improve the CAPWAP analysis, a new matching procedure, with variationin shaft dynamic soil parameters based on empirical equations, was developed.The results show that the dynamic soil parameters are not constant along the piledepth, but they vary with different types and properties of soils. For cohesive soils at theEOD condition, the correlation studies revealed a direct relationship between the shaftdamping factor and the SPT N-value and an inverse relationship between the shaft quakevalue and the SPT N-value. Empirical equations were established to quantify these shaftdynamic soil parameters in terms of SPT N-value. Furthermore, correlation studies usingCPT measured soil properties concluded that the shaft damping factor was influenced bydifferent soil types. On the other hand, no relationship was observed between the shaft quakevalue and the CPT measured soil properties. It is believed that the similar process for SPT topile driving, both subjected to a continuous impulsive hammer force, explains the better