Accuracy of parameter identification using the dispersion of surface waves and the role of data quality for inhomogeneous concrete

To perform these studies, cuboidal models of inhomogeneous concrete composed of two layers of different classes of concrete are prepared. During experiments, surface wave signals are acquired within a frequency range of 35 kHz-160 kHz using a non-contact ultrasonic automated scanner, which enables quick and precise signal recording, avoiding concrete surface modification through the use of the coupling agent. Experimental dispersion curves are obtained using the Slant-Stack transformation. The synthetic data are obtained from the solution of the Thomson-Haskell model. The inversions are performed using the in-house software CLOUD and tested and validated on the multilayer model samples. The criteria for the optimum wavelength intervals of the dispersion curves are proposed: the lower wavelength limit λL ≤ d, and the upper wavelength limit λU ≥ 3.5d, where d is the thickness of the top layer. The consequences of narrowing the intervals are thoroughly studied, and upper and lower limits are determined both for experimental and synthetic data. It is shown that the efficiency of inversion depends on both wavelength limits and accuracy of the data.