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

165were compared using the proposed methods, Figure 4.9 shows the shifting of mean values (μ)towards unity (from 1.53 to 1.04 for CAPWAP and from 1.78 to 1.06 for WEAP-SA) and thereduction of standard of deviations (σ) (from 0.32 to 0.17 for CAPWAP and from 0.39 to0.20 for WEAP-SA). The results clearly show that the proposed pile setup Eq. (4.9) hasadequately and consistently predicted the increase in pile resistances in different cohesivesoil conditions for steel H-piles with different sizes. Similar observations presented in Figure4.10 based on all data records were shown. This statistical assessment validates the proposedpile setup method for steel H-piles.4.5.2. Other pile typesSimilar assessment was performed to evaluate the application of the proposed methodon other pile types installed in cohesive soils. Six well documented cases were used for thispurpose as summarized in Table 4.4, which include the following information: (1) SPT N-values; (2) initial pile resistances at EOD (R EOD ); (3) CAPWAP measured pile resistances atthe beginning of restrikes (BORs) and/or measured pile resistances from SLTs (R m ); and (4)times of restrikes and/or SLTs (t). Pile types comprised of closed-ended pipe piles (CEP)and opened-ended pipe piles (OEP), square precast prestressed concrete piles (PCP) and steelmonotube piles (MP). The pile sizes or diameters ranged from 244 mm to 750 mm.Furthermore, the number of piles, embedded pile lengths, hammer type, and brief soil profiledescriptions were also included in Table 4.4. To differentiate between the small displacementand large displacement piles, a pile area ratio (AR) (i.e., a ratio between pile embeddedsurface area and pile tip area) was calculated for each pile type and compared with aquantitative boundary of 350 suggested by Paikowsky et al. 1994. Since the largestestimated AR is 278 for 273 mm OEP was smaller than 350, all piles were classified as largedisplacement piles.The comparison between pile resistances obtained during restrikes and SLTs (R m ) andinitial pile resistances at EOD (R EOD ) reported in the literatures are plotted in Figure 4.11shows that the R m values are larger than the R EOD values (most data points above the solidequal line) confirming the occurrence of pile setup. Using the reported R EOD value, estimated