Continuous wavelet transform technique for low-strain integrity testing of deep drilled shafts

Non-destructive evaluation techniques have been adopted to provide pile construction quality control for many years. In particular, low strain pile integrity test methods have been used to check lengths and integrity of newly installed pile. The pile integrity testing signals acquired from the receivers on pile heads are complicated by defects and undesired background noise. The continuous wavelet transform (CWT) method with time-frequency distribution is adopted to enhance the characteristics of the testing signal to raise the identification ability in experimental cases. The in-situ tests of drilled shaft indicate that testing signals could be displayed in the time-frequency domain at the same time and then be explored at every single time by CWT. CWT can enhance the signal and make more information visible. Coupling CWT and Sonic Echo (SE) methods to interpret and identify the pile integrity visually, easily and quickly is proven, even for long drilled shafts.