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

252establish relationships between these parameters and soil properties have been accomplished,due to large degree of scatter typically seen for the collected soil parameters as illustrated byMcVay and Kuo (1999) and shown in Figure 7.3. These parameters are currently determinedthrough CAPWAP analyses by matching the PDA measured signals representing force andvelocity measured near pile top with the computed signals, based on a one-dimensional soilpilemodel in Figure 7.1. The large variation among the collected soil parameters shown inFigure 7.3 is attributed to the current approach in performing the CAPWAP analysis with anemphasis in achieving a best signal matching, from which the constant shaft damping factorand the quake value are determined, regardless of the different soil properties alongside of apile. Furthermore, the fact that this best fit solution achieved from the CAPWAP analysis isnot being unique, and that it is influenced by the magnitude of the shaft and toe resistancesthat may be adjusted arbitrarily in striving to achieve the best signal match. Due to theindeterminate nature of the CAPWAP analysis, the dynamic soil parameters cannot beuniquely quantified. Svinkin and Woods (1998) noted one of the limitations of dynamicanalysis methods is the difficulty in quantifying these soil parameters in terms of anystandard geotechnical in-situ or laboratory test results. As a result, based on a databasecollected by Pile Dynamic, Inc. (2000), a possible range of damping factors (0.078 to 1.44s/m for shaft and toe) and quake values (1.02 to 17.96 mm for shaft and 1.02 to 5.36 mm fortoe) are recommended in CAPWAP,.In lieu of the current setback with dynamic soil parameters quantification, empiricalrelationships were developed herein to uniquely estimate them using Standard PenetrationTest (SPT) N-value. These empirical relationships were established through a systematicapproach in performing the signal matching adopted during the CAPWAP analysis, asexplicitly described in Section 7.3. The proposed procedure not only provides a realisticdistribution of dynamic soil parameters in accordance with the soil stratigraphy, but it alsoimproves the quality of the signal matching.Svinkin and Woods (1998) suggested the use of variable soil parameters as a functionof time to simulate the increase in pile resistance due to pile setup.Recognizing the