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

2657.5.4. EOD condition for cohesionless soilsCorrelation studies between dynamic soil parameters and SPT N-value were alsoperformed for cohesionless soils, referred to as silty sand (SM), well-graded sand (SW), andpoorly graded sand (SP) in accordance with Unified Soil Classification System (USCS). Asshown in Table 7.4, limited data points were available for the cohesionless soil layers, whichpresented between 4.02 and 6.34 m depth of ISU6 and below 4.05 m depth of ISU9. Basedon these data points, Figure 7.20 shows an inverse relationship between damping factor andSPT N-value, which contradicts the relationship generated using Eq. (7.4) as recommendedby Liang (2000). Figure 7.20 shows that the damping factor for cohesionless soils can bebest estimated using Eq. (7.14). Furthermore, Figure 7.21 also shows an inverse relationshipbetween the quake value and the SPT N-value, which can be best represented with Eq.(7.15).( ⁄ ) ( ) (7.14)( ) ( ) (7.15)In addition, the 95% confidence intervals of the predicted equations are included. Bothfigures show the variation of dynamic soil parameters with SPT N-value, as opposed to theconstant values recommended by Smith (1962) and Hannigan et al. (1998) given in Table7.1. Nevertheless, the quantification of these dynamic soil parameters for cohesionless soilscan be improved with continuously populated data points in the future.7.5.5. Effect of pile installationIt is important to investigate the effect of pile installation on the aforementionedcorrelation studies of the dynamic soil parameters for the EOD condition in terms of the SPTN-value measured in a nearly virgin stage of disturbance before the pile installation.Dynamic soil parameters (J s and q s ) were selected from Table 7.4 at three designatedlocations: (1) within 3 m below ground surface; (2) at mid-depth between 6 and 9 m belowground surface; and (3) within 3 m from pile toe, and were plotted separately in Figure 7.22