Continuous Wavelet Transform Method Applied to Sonic Echo Measurements of Unknown Bridge Foundations

Foundation reuse for bridge replacement projects is an attractive and economical option in many cases but also presents significant challenges. One of these challenges is the need to characterize the length and condition of existing bridge foundation elements. Geophysical and non-destructive evaluation measurements play a critical role in this aspect of bridge foundation reuse. The focus of this paper is on the use of the continuous wavelet transform (CWT) approach for interpreting sonic echo (SE) measurements. Measurements were performed on concrete piles from a 50-year old bridge that is being replaced. The SE data were collected and interpreted using conventional time domain arrival picks and the CWT method, using both amplitude and phase information. After testing, the piles were exhumed and ground truth measurements of length, condition, and seismic velocity were performed. The results from the CWT yielded consistent results with conventional methods. In some cases, the CWT allowed for interpretation that could not be made using conventional methods.