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

166average SPT N-value (N a ) calculated using Eq. (4.5), horizontal coefficient of consolidation(C h ) estimated using Eq. (4.7), and pile radius (r p ), a pile resistance was estimated using theproposed pile setup method presented in Eq. (4.9) at the time of restrike or SLT. With theconsideration of pile setup using the proposed method, Figure 4.12 shows that the data pointsrepresented with a linear best fit dashed line shifts towards the solid equal line of measuredand estimated resistances.For comparative purposes, means (μ) and standard deviations (σ) of pile resistanceratios for both EOD condition (R m /R EOD ) and the proposed setup method (R m /R t ) werecalculated based on two pile categories: (1) pile sizes equal to and greater than 600 mm(referred to as large diameter piles); and (2) pile sizes smaller than 600 mm (referred to smalldiameter piles). Based on the μ and σ values summarized in Figure 4.11, large diameter pilesexhibited a greater pile setup than smaller piles, supported by larger μ and σ values of 1.663and 0.591, respectively. The consideration of pile setup using the proposed method not onlyreduces the μ values from 1.663 to 1.184 and from 1.454 to 1.063 for large and smalldiameter piles, respectively, but it also reduces the σ values. When comparing the μ and σvalues given in Figure 4.12, the smaller μ and σ values of 1.063 and 0.274, respectively,reveal that the proposed setup method provides a better pile setup prediction for smallerdiameter piles. When compared with the values computed based on steel H-piles given inFigure 4.10 (μ = 1.024 and σ = 0.153), the results confirm that the proposed setup methodprovides a better setup prediction for low displacement piles (steel H-piles) than largedisplacement piles. This assessment provides a potential for future refinement of the pilesetup method for large displacement piles, providing that detailed soil information and pileresponse measurements as similarly performed on steel H-piles.4.5.3. Mixed soil profileThe application of the proposed Eq. (4.9) to quantifying the increase in pile resistanceof a steel H-pile embedded in a mixed soil profile was evaluated using the field test results ofa recently completed test pile ISU8. It is a HP 250 × 63 steel pile embedded in a layer ofapproximately 6.4 m (21 ft) low plasticity clay (CL) underlying with approximately 5.18 m