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

68The second output option is the driveability analysis. This analysis calculates thestatic soil resistance, pile stresses, blow count, hammer performance, and soil distribution asa function of a pile penetration depth. The third output option is the Inspector’s Chart, whichcalculates and plots the hammer strokes as a function of hammer blow counts at a desiredpile resistance. It provides a flexible driving criterion to the field inspector to adjust thehammer stroke in order to satisfy the field requirements.2.6. Reliability of Dynamic Analysis MethodsThe reliability of dynamic analysis methods have been studied by many researchers,especially Pile Dynamic Inc., in the past 30 years. The dynamic analysis methods describedhere are PDA, CAPWAP and WEAP. All the reliability studies were correlated with staticload test results based the Davisson’s criterion. Paikowsky (2004) concluded that Davisson’scriterion was the best failure resistance interpretation method for driven piles with diametersof 610 mm (2 ft) or less. The following simple guidelines described by Likins & Rausche(2004) and Hannigan & Webster (1987) are required to obtain reliable correlations betweenthe dynamic and the static load test results.1. A sufficient time is allowed before performing re-strike tests after EOD, so that thechanges in soil resistance are stabilized.2. Ideally, dynamic tests and static load tests should be carried out in a closer timeperiod after EOD. Hannigan and Webster (1987) suggested that the best correlationbetween static load test and CAPWAP results can be achieved by limiting the time ofdynamic re-strike testing to 24 to 48 hours prior to the static load test.3. The test piles must experience sufficient displacement during dynamic testing inorder to mobilize the full dynamic resistance. In fact, Pile Driving ContractorsAssociation (PDCA) specification 102-07 (2007) suggested that the hammer used forre-striking shall be warmed up in order to achieve the required energy to mobilize thetest piles. The maximum penetration required during re-strike shall be 75 mm (3-in)or the maximum total number of hammer blows required shall be 20, whicheveroccurs first. Hannigan and Webster (1987) believed that an order of 36 blows/m (11