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

253difficulty in pile setup investigation based solely on limited data available in the literature(see Section 3.3), the relationship between dynamic soil parameters and time has not beenestablished. To enhance the capability of dynamic analysis methods in accounting for pilesetup and to avoid the performance of practically infeasible pile restrikes, two recentlycompleted field results of test piles ISU5 and ISU6, as described in Chapter 3, were selectedto examine the effect of pile setup on the dynamic soil parameters.7.3. BackgroundAlthough dynamic soil damping factor and quake values have been investigated bymany researchers, (e.g. Smith (1962), Coyle et al. (1973), Hannigan et al. (1998), McVay andKuo (1999), Malkawi and Ayasrah (2000), Liang (2000), and Roling (2010)), a generalapproach for accurately quantifying these parameters cannot be established from all therecommendations. Based on the experience gained through working extensively with thisproblem and a limited number of comparisons with static load tests, Smith (1962) suggestedconstant values, as listed in Table 7.1 for practical applications. After approximately adecade later, Coyle et al. (1973) estimated a set of dynamic parameters for three different soiltypes (i.e., clay, sand, and silt) from full-scale pile tests, in which the most accuratecorrelation of the dynamic parameters were achieved. They acknowledged that an extensivedata set was not available at that time for the damping characteristics of soils, and the use ofmore accurate values was recommended if they are available in the future.Based on pile driving experience, Hannigan et al. (1998) observed that the dampingfactors vary with the waiting times after the end of driving (EOD), and that higher valuesmay be appropriated for analyses modeling the restrike conditions. They believed dampingfactors are not a constant for a given soil type and a higher value may be expected for softsoils than hard rock. Due to the lack of dynamic measurements and quantitative analyses,their hypotheses on damping factors have not been validated, and constant values weresuggested as listed in Table 7.1. In addition, shaft quakes were recommended at 2.54 mm forthe most cases, whereas toe quake values were recommended as the value obtained from thepile diameter (D) divided by 120 for very dense and hard soils and 60 for soft soils.