Locating and Quantifying Necking in Piles Through Numerical Simulation of PIT

Defects of concrete piles can occur at any point during the construction of piles. Most common types of pile integrity issues are; presence of voids, inconsistency in concrete mix, entrapped groundwater or slurry, and geometric dislocation. These defects can be categorized based on the place in the construction sequence at which the defect occurs. This research introduces several numerical models of defected piles with various scenarios in order to identify, locate, and quantify the necking occurring in these piles. The finite element software (ADINA) is used to simulate the studied models. The soil domain is modeled as an axisymmetric space around the concrete pile. Five diameters of piles (40, 60, 80, 100 and 120 cm) are studied. Necking is modeled at three different locations along the pile namely; upper, middle, and bottom third. Four ratios between the necking diameter and pile diameter are also studied. The dynamic force used in this research is that simulating the pile integrity test (PIT) case, with 2.5 N impact load applied at the pile head, half wave of sinusoidal pattern, and 0.5 kilo hertz frequency. The time domain of the dynamic force analysis is equal to 0.0175 sec, and applied in 450 steps.