Advancements in active surface wave methods: modeling, testing, and inversion

Non-Destructive Modulus Testing and Performance Evaluation for Asphalt Pavement Reflective Cracking Mitigation Treatments

“…The stiffness profile of the tested pavement site is back calculated by matching the experimental dispersion curve to theoretical counterparts calculated by forward modelling for assumed stiffness profiles (Lin & Ashlock, 2011Lin, Ashlock, & Williams, 2016;Nazarian, 1984;Park, Miller, & Xia, 1998;Ryden, Ulriksen, Park, & Miller, 2002). Surface wave tests in this study were carried out using the multichannel simulation with one receiver (MSOR) test method proposed by Ryden et al (2002) and the MSOR testing system developed by Lin andAshlock (2011, 2015). A 0.34 kg ball-peen hammer with an accelerometer attached as a trigger was used as the moving impact source, and a second accelerometer was fixed at zero offsets on the asphalt surface.…”

“…The frequency range of the dispersion characteristics is from 100 Hz to 5000 Hz, the wavelengths of which cover the depths of interest for the pavements and base layers in the present study. Finally, the genetic-simulated annealing (GSA) algorithm developed by Lin (2014) was employed to back-calculate shear wave velocities, which were used to calculate Young's moduli for assumed densities and Poisson's ratios. Moduli obtained from SWM tests are in the very small strain regime, in contrast to those measured under larger strains and deflections in FWD tests.…”

Improving performance and sustainability of unpaved roads: Stabilization and testing

“…Henry et al (2005) also conducted a field investigation to compare different technologies for mitigation freeze-thaw (Lytton 1989;Wightman et al 2004). Compared to the FWD test, the MASW tests applies a much smaller impact on the ground surface to generate seismic surface waves, and the resulting surface motion is measured using an array of geophones or accelerometers (Lin 2014;Lin and Ashlock 2015;Park et al 1998;Park et al 1999;Xia et al 1999). Employing the phenomenon of dispersion of surface waves in layered elastic media, the layer properties (e.g., thickness and modulus) can be inferred by matching experimental dispersion curves to their theoretical counterparts.…”

“…To address these issues, several improvements were made to the dispersion analysis and inversion procedures for MASW data analysis by Lin (2014). The improvements include a new phase-velocity and intercept-time scanning (PIS) method to improve the resolution and sharpness of experimental dispersion images by minimizing side lobes and aliasing that can be generated by conventional wavefield transformation methods.…”

“…The PIS method first converts the field data from the space-time domain to the space-frequency domain by applying a Fourier transform, then uses the slant-stack method to provide a new series of harmonic curves in the phase slowness-time intercept plane, and finally applies another Fourier transform followed by auto-power spectrum analysis to the new harmonic curves to generate the experimental dispersion image. The key differences between the improved PIS and conventional methods are "(1) the additional dimension of scanning the intercept time, whereas the conventional analysis assumes an intercept time of zero, and (2) the use of auto-power spectrum analysis, which presents the dispersion image amplitude in terms of power to greatly reduce effects of side lobes and aliasing" (Lin 2014). A new hybrid genetic-simulated annealing (GSA) optimization algorithm was also developed to improve the inversion procedure by enhancing global searching efficiency, thus reducing the risk of the search becoming trapped in a local minimum.…”