Determination of embedment depth of timber poles and piles using wavelet transform

This paper presents an investigation on the wave propagation in timber poles with Wavelet Transform (WT) analysis for identification of the condition and underground depth of embedded timber poles in service. Most of non-destructive testing (NDT) applications for timber poles using wave-based methods consider only single wave mode and no dispersion. However, for wave propagations in timber poles (damaged/undamaged), such simplification may not be correct, especially for broad band excitation using impulse impact. To investigate the problem, a 5m timber pole was investigated numerically and experimentally. A dispersion curve is generated from the numerical results to provide guidance on the velocity and wave mode selection. Continuous wavelet transform (CWT) is applied on the same signal to verify the presence of modes and to process data from experimental testing. The results are presented in both time domain and time-frequency domain for comparison. The results of the investigation showed that, wavelet transform analysis can be a reliable signal processing tool for NDT in terms of condition and embedment length determination.