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

43been carried by many researchers for the estimation of these dynamic soil parameters, theaccuracy and reliability of the pile resistance prediction are yet to be achieved. Table 2.4 andTable 2.5 summarize the suggested values of soil quakes and Smith damping factors from tenreferences. Additional references on recommended Smith’s soil parameters can be referredto Soares et al. (1984) for all soil types and Swann & Abbs (1984) for calcareous soils.Robert Liang and Sheng (1993) concluded that the size of the penetrating shaft exertssignificant influence on the soil quake and Smith damping factor, and they gave therelationship between the penetrating velocity (v p ) and acceleration ( ̇ ) and the Smithdamping factor. It can be concluded from Table 2.4 and Table 2.5 that the soil quakes anddamping factors are not only dependent on soil types, but the quakes also depend on piledimension while the damping factors also depend on both pile dimension and pile penetrationrate.2.4.3. CAPWAP modelSimilar to Smith’s model, CAPWAP model is divided into pile and soil models.CAPWAP uses the PDA data to quantify the two of the three unknowns, which are the pileforce and velocity. The remaining unknown is the pile boundary conditions, which aredefined by the soil resistance distribution, soil quake and soil damping factors of the soilmodel (Hannigan et al. 1998). By adjusting the boundary conditions, CAPWAP calculatesan equilibrium pile head force, which is comparable to the PDA measured force. Severaliteration adjustments are made to the soil model until the best matching signal between thecalculated and measured force is obtained. The schematic of a CAPWAP model is shown inFigure 2.8. Goble and Rausche (1980) described that the pile is modeled with a series ofmasses and springs, and the soil resistances are modeled alongside and at toe of the pile withelasto-plastic springs and linear dashpots. CAPWAP model is similar to Smith’s exceptCAPWAP model does not include the driving systems and the pile section above the PDAgauges.