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

158Karlsrud et al. (2005) has incorporated the plasticity index (PI) and overconsolidationratio (OCR) in their setup method based on a database of the Norwegian GeotechnicalInstitute (NGI), which consisted of 36 well documented pile tests on steel pipe piles withouter diameters greater than 200 mm. Fellenius (2008) concluded that the referenceresistance at 100 days (R 100 ) by assuming complete pore water dissipation at this time is nottrue and not feasible in practice. To validate this method on steel H-piles, ISU field testresults were used to extrapolate the R 100 for each test pile by best fitting a logarithmic trendthrough the estimated pile resistances determined using CAse Pile Wave Analysis Program(CAPWAP) from restrikes and the measured pile resistance obtained from static load test andlater reading the R 100 from the trend at the 100 days. The estimated pile resistances and themeasured pile resistance for each test pile were normalized by its respective R 100 to determinethe pile resistance ratio (R t /R 100 ) as plotted in Figure 4.2. Using the estimated R 100 value, theaverage PI value, and the average OCR value for each site, the pile resistances (R t ) atdifferent times within 100 days were estimated using the pile setup equation of Karlsrud et al.(2005) and plotted in Figure 4.2. The poor comparison between the ISU field test results andthe Karlsrud et al. (2005) method suggests that this pile setup method cannot be generallyapplied to different soil and pile conditions.4.4. Pile Setup4.4.1. Pile setup observationsAs discussed in the companion paper (Ng et al. 2011b), steel H-pile is the mostcommon foundation type used to support bridges in the United States based on a recentsurvey of State Departments of Transportation (AbdelSalam et al., 2010). The field testresults on five HP 250 × 63 steel piles embedded in cohesive soils as explicitly described inthe companion paper show a linear relationship between a normalized pile resistance(R t /R EOD ) and a logarithmic normalized time (Log 10 (t/t EOD )) as plotted in Figure 4.3. Toeliminate the pile resistance gain resulting from the additional pile penetrations duringrestrikes, the normalized pile resistance was corrected by multiplying with the normalizedpile embedded pile length (L EOD /L t ). In order to satisfy the logarithmic relationship and to