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

266(a) and (b) for J s and q s , respectively. It is expected that the soil near the surface wouldexperience a larger number of repetitive cycles of disturbance from the pile installation thanthe soils near the mid-depth and pile toe. Figure 7.22 (a) shows the dot-dashed best fit linerepresenting the correlation analysis between J s and SPT N-value of soil layers within 3 mbelow the ground surface has the least R 2 of 0.35. However, soil layers at mid depth, thatexperienced relatively lesser amount of disturbance, produced a slightly better correlationwith a larger R 2 of 0.37. As expected, soil layers within 3 m from the pile toe, thatexperienced the least amount of disturbance, generated the best correlation study with thehighest R 2 of 0.66. Besides comparing and contrasting the correlation results on J s value,similar evaluations were achieved based on the q s value as shown in Figure 7.22 (b). Similarobservations were noticed from which soil layers within 3 m below the surface had thepoorest correlation with R 2 of only 0.05; the best correlation with R 2 of 0.82 occurred at soillayers near pile toe, and correlation for soil layers at mid-depth with R 2 of 0.72 fell inbetween. These observations conclude that the effect of pile installation action on theaccuracy of the dynamic soil parameters quantification. Nevertheless, it is impracticable toperform the SPT during different stages of pile installation. Hence, it is assumed that theuncertainty associated with the variation in SPT N-values at different stages of a pileinstallation was indirectly accounted for during the aforementioned correlation analysisperformed based on an average dynamic soil parameter corresponding to the same SPT N-value.7.6. Quantification of Toe Dynamic Soil ParametersTable 7.6 summarizes the measured soil properties near the pile toe, estimated piletoe resistance, toe damping factor (J T ), and toe quake value (q T ) determined during theproposed CAPWAP matching process for the EOD condition. A poor relationship wasobserved between measured soil properties, such as SPT N-value, q s , and f s values, and thetoe dynamic soil parameters. For instance, although the low plasticity clay (CL) at the piletoes of ISU4 and ISU5 had the same SPT N-value and shared similar q c and f s values, therewas a relative large difference in the J T and q T values. This observation became apparentwhen these dynamic soil parameters for cohesive soils (i.e., for all test piles except ISU9)