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

258where,( ) = measured or estimated pile force near pile head at time t, N,Z = = pile impedance, N-s/m,( ) = measured or estimated pile velocity near the pile head at time t, m/s, andA = pile cross sectional area, m 2 .As a result of the multiple matching processes up to the final soil segment at a timeinterval of 2L/C, where L is the entire wave traveling distance, a distribution of damping soilparameters was preliminarily determined. This distribution is further refined and adjustedproportionally until a best match is achieved for the complete time period that includes therebounding and unloading conditions as illustrated in Figure 7.6. In CAPWAP analysis, theaccuracy of a matching is evaluated in terms of a match quality (MQ), which is thenormalized, weight sum of the absolute values of the differences between computed andmeasured responses of the specified time interval. The matching of hammer blow count (i.e.,pile set) within the 2L/C during the preliminary estimation of the dynamic soil parameters isnot considered and its error is not added to the MQ value; however, this error is includedduring the final matching for the entire time period.The aforementioned procedure is applicable for both EOD and BOR conditions. Forexample, at the EOD condition, the static soil resistances estimated using Schmertmann’s(1978) method are adjusted to match with the total CAPWAP estimated pile resistance forthe EOD, and the estimated dynamic soil parameters represent the dynamic characteristic ofthe surrounding soil at the EOD condition.7.5. Quantification of Shaft Dynamic Soil ParametersAs part of this research project, ten steel H-piles were driven and load tested in thefield. The pile top responses (strains and accelerations) during driving were recorded usingthe PDA. With adequate in-situ (Standard Penetration Test (SPT) and Cone Penetration Test(CPT)) and laboratory soil characterizations, five test piles embedded in cohesive soil profile,