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

52of a match quality (MQ). The match quality is calculated by summing the absolute values ofthe relative differences between measured (F m ) and computed (F c ) signals at individual pointsin time divided by the maximum pile top signal (F x ) given by Eq. (2.29). Also, due to thedifference between measured and computed hammer blow counts, the match quality ispenalized by a blow count penalty (BCP). The signal matching is improved as the MQ valuereduces closer to zero.∑ ∑ | | (2.29)where,BCP = blow count penalty (BCP = 0 if ∆ set < 1 mm, or BCP = ∆ set ‒ 1 if ∆ set ≥ 1mm), and∆ set= absolute difference between measured and computed pile sets.In order to reduce the analytical time required to achieve a reasonably good signalmatching, default and automated CAPWAP (AC) matching procedure is normally usedduring practices. Referred to Figure 2.11, the AC procedure simultaneously adjusts theresistance at each pile segment shown in Window 2 and dynamic soil parameters listed inWindow 3 until the best MQ value shown in Window 1 is achieved. The summation of theresistances for all pile segments yields the total shaft resistance (R s ) as indicated in Window2. The total end bearing is equal to the summation of all resistances at the Toe, Toe2, andToe3. Toe2 and Toe3 refer to as second and third toe cross sections of a composite pile. Theaddition of the total shaft resistance and end bearing gives the ultimate pile resistance (R ult ),which is considered as the total pile resistance estimated using CAPWAP. The limitationswith AC procedure are described below:1. Unrealistic high resistance near pile top may be generated,2. Unrealistic low resistance near pile bottom may be generated,3. The estimated soil resistance distribution may not represent the actual soil profileand properties,