Theoretical basis and numerical simulation of impedance log test for evaluating the integrity of columns and piles

In this paper, the theoretical capabilities of the impedance log method in profiling the geometry of a column or pile along its length are investigated. The main idea of this method is to introduce a transient stress wave into the member and then utilize the reflected signals to obtain the impedance profile. The impedance profile is then used to recover the equivalent cross-sectional area along the length of the pile. To gain an insight into this nondestructive evaluation technique, this research started with a review of its theoretical background. The dynamic behavior of defective columns or piles with weak zones, bulges, and necks of constant or varying cross sections were then simulated with finite element models. The success in recovering the profiles of this kind of rod-like structural members proved that the impedance log method is a tool with high potential for evaluating the integrity of piles.Key words: impedance log method, nondestructive test, stress wave, column, pile.