Evaluation of pile defects using complex continuous wavelet transform analysis

In recent years, the technique of wavelet transform has been applied widely in signal processing in different fields, including non-destructive testing of pile foundations. However, it was used mostly in signal filtering and the analysis of time-frequency diagram. This paper successfully utilized complex continuous wavelet transform to determine pile length and locations of defects on pile foundations by analyzing the time-frequency-phase angle diagram in different frequency band. Six piles with different types of defects were installed and tested to verify the proposed approach in this study. The results shows that complex continuous wavelet transform not only is able to provide high resolution results in different frequency bands, which is similar to that of continuous wavelet transform, but also simplifies the identification of the reflection of defects using 3D phase spectrogram. The location of defects can then be easily determined using phase diagram under the corresponding specific frequency.