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

129embedded length before and after each restrike were precisely recorded for each test pile (seeTable 3.3). Furthermore, pile driving resistance in terms of the total number of hammerblows per 300 mm (1 ft) of pile penetration (i.e., hammer blow count) was accuratelyobtained using videos recorded during pile installation restrikes. Figure 3.7 depicts thegathered data for ISU5 as a function of hammer blow count for the pile to penetrate 300 mmdepth, which increased from 30 at the EOD to 72 at the beginning of restrike No. 6 (i.e.,BOR6) over a period of 7.92 days. This substantial rise in hammer blow count withoutsignificantly increasing the pile embedded length is mainly caused by pile setup, ultimatelyincreasing the pile resistance.3.4.6. Dynamic analysis methodsWith the available pile, soil, and hammer information and the recorded hammer blowcount, the total pile resistance of each restrike was estimated using the WEAP SPT N-valuebased method (i.e., SA method specified by Pile Dynamic, Inc. 2005). Two assumptionswere made to complete the WEAP analyses: (1) since the bearing graph (pile resistanceversus hammer blow rate) generated from WEAP is independent of the water table and allrestrikes were conducted within 10 days at most (see Table 3.3), water table at each test siteremained constant at the EOD and at every BOR; and (2) the percentage of shaft resistanceestimated from a driveability analysis was reasonably used for a bearing graph analysis,because our sensitivity studies revealed that the increase in percent shaft resistance from 50%to 99% does not vary the estimated pile resistances by more than 10%.Furthermore, the measured force and velocity records near the pile head from PDAwere used in CAPWAP analysis to calculate the total pile resistance at each event assummarized in Table 3.3. Unlike WEAP where a total shaft resistance is estimated from thedriveability analysis, CAPWAP estimates the resistance distribution along the pile length. Inboth methods, the end bearing components are also estimated. Figure 3.8 presents theCAPWAP estimated pile shaft resistance distributions for ISU5 from EOD to the 6 th restrike(BOR6).