Hybrid analysis of surface wavefield data from Portland cement and asphalt concrete plates

Impact-echo and multi-channel analysis of surface wave (MASW) methods were combined for a hybrid analysis of multi-channel surface wavefield data sets to iteratively solve for the thickness, elastic modulus, and Poisson's ratio of Portland cement and asphalt concrete plates. The time-frequency method was used to evaluate the plate thickness resonance frequency of the zero group velocity component of the first-order symmetric Lamb wave mode for use in the impact-echo analysis. It was observed that the thickness resonance frequency may not be resolved using focusing or amplifying signal processing techniques when plate/base interface conditions result in weak reflection amplitudes. Hybrid analysis results compared favourably against longitudinal resonant frequency tests of both cast cylinders and drilled cores from Portland cement concrete plates. It was shown that the hybrid analysis technique can be used to provide accurate compression wave velocity estimates used in impact-echo surveys.