Use of Wavelet Analysis and Filtration on Impulse Response for SASW Measurement in PCC Slab of Pavement Structure

Abstract

A quick and efficient of the spectral analysis of surface wave (SASW) has been developed to non-destructively measure the stiffness of PCC slabs. However, in layered PCC slab with strong stiffness contrast, several wave groups were observed due to the refraction and reflections of stress waves at the layer boundaries. As a result, the phase spectrum affected by these different wave groups is to be complicated. In this study, a time-frequency analysis of wavelet transform was then employed to impulse response analysis to overcome identification problem of the non-stationary wave groups and spectral characteristics of phase spectrum. Time-frequency wavelet spectrogram was utilized to select the interested response spectrum from wave groups. A time-frequency wavelet filtering was then used to remove the interference of unnecessary wave groups or background noise based on simple concept of wavelet filtering. Consequently, the phase spectrum was reconstructed from denoised impulse response by inverse wavelet transform. Results showed that the wavelet analysis of impulse response can be used to improve the phase spectrum and reconstruct better phase velocity dispersion curve. A good agreement was also established between the PCC stiffness from SASW measurements compared to ACI formulation.