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

254Although these recommendations have been implemented in current dynamic analysismethods in Wave Equation Analysis Program (WEAP), results obtained from McVay andKuo (1999) and the recently completed field tests conducted in Iowa using CAPWAP (seeFigure 7.3 and Figure 7.4) revealed: (1) the dynamic soil parameters are not constant value assuggested by Hannigan et al. (1998); (2) they have no unique correlation with the SPT N-value as assumed in the current default CAPWAP matching procedure; and (3) the dynamicsoil parameters did not vary distinctly as the soil type varies from cohesive soil tocohesionless soil to limestone.Malkawi and Ayasrah (2000) performed a series of dynamic load tests on a steel,smooth closed ended, pipe pile. With 900 mm length, 61 mm diameter, and 5 mm thickness,this slender pile was comparable to the common pipe piles used in practice. The test pile wasdriven into a fine to medium, poorly graded sand (SP) compacted to three different relativedensities of 35, 50, and 70%. Based on the matching of time-displacement signals, theyconcluded that damping factors (J) were found to be inversely proportional to pile installationdepth, sand relative density, and static sand resistance. These conclusions obtained this testpile are yet to be validated from real pile tests.Liang (2000) conducted a statistical analysis on the dynamic soil parameters using adatabase of 611 driven piles collected by Paikowsky et al. (1994). The dynamic soilparameters were estimated via the default CAPWAP signal matching procedure, summarizedin Table 7.2, with consideration to soil type (sand and clay) and time of dynamic pile testing(EOD and BOR). These statistical analysis results revealed that the quake values variedminimally with the soil type and time of dynamic testing. The damping factors were foundto be influenced more by the time of dynamic testing than by the soil type. Furthermore, therelative high standard of deviation indicated a large scatter in estimating each dynamic soilparameter that could lower the accuracy of pile resistance computations using CAPWAP.Although a larger database was used in these statistical analyses, a unique correlation fordynamic soil parameters quantification cannot be established in terms of soil type and/or timeof dynamic testing.