Despite the widespread use of Ultrasonic Pulse Velocity (UPV) to estimate the dynamic properties of materials, the accuracy of its results for concrete and rock cylinders, even though it does not depend on cylinder slenderness, is directly affected by the a priori assumption of a specific value of the Poisson's ratio ( ), which can lead to errors of up to 50% in the calculation of the dynamic modulus of elasticity (E_d). In contrast, the Impact Echo (IE) method allows the calculation of E_d without the need-to-know Poisson’s ratio, with an error of approximately 2%, but its results are affected not only by the slenderness ratio (L/D) but also by the inertia effect and the mass of the sensor. In this study, both UPV and IE—longitudinal and torsional—tests were carried out on cylindrical steel and aluminium specimens for six different slenderness values and L/D values ranging from 1-5. The experimental results fully confirm the authors’ proposed shape correction factor (SCF). A numerical analysis of short cylinders is conducted to examine how the mass of the accelerometer used on the IE affects the results. Specifically, aluminium and steel specimens with six different slenderness values were simulated via the finite element method (FEM) via experimental evaluation. Inertia and mass interactions significantly affect the results. Two new correction factors were proposed for steel and aluminium cylinders to address this issue, and three different combinations of NDTs were tested to find that the dynamic properties are very sensitive to these parameters. Poisson’s ratio has been accurately calculated for steel and aluminium cylinders and can be calculated for concrete and rock cores by applying the proposed correction factors.

Non-destructive in-situ tests, such as the plate bearing (plate load) test, are widely used to estimate the equivalent deformation modulus (e.g., E_v2) of existing road embankments. However, the depth of influence sampled by such a test is governed by the loading plate diameter, so a single test yields only an average, diameter-dependent modulus rather than the actual variation of stiffness with depth. This study investigates whether systematically varying the plate diameter, and inverting the resulting settlement–diameter (dispersion) curves, can recover the full depth-dependent stiffness profile, E(z). Synthetic settlement–diameter curves were generated using a Boussinesq-based forward model for four families of reference stiffness profiles, representing normal (stiffness increasing with depth) and reverse (stiffness decreasing with depth) linear and exponential trends, combined with six Poisson’s ratios and five profile slopes/exponents (30 cases per profile family, 120 cases in total). Two inversion strategies were applied to back-calculate E(z) from each dispersion curve: a classical Occam-type, smoothness-constrained (Tikhonov-regularized) nonlinear inversion, and a direct, closed-form Simplified Inversion Method (SIM) based on differencing the apparent-modulus-versus-diameter curve. Results were benchmarked against the known reference profiles. Once calibrated so that its governing parameters depend only on Poisson’s ratio and the shape of the measured dispersion curve, SIM could be applied blindly, without prior knowledge of the true profile, and recovered E(z) with markedly lower error than Occam’s inversion (WAD = 2.2–4.7% and RMSPE = 2.6–5.8%, versus 7.4–19.1% and 9.4–28.3%, respectively, across the four profile families). For the Poisson’s ratio most typical of earth materials, ν = 0.3, the calibration further collapses to a universal parameter set (I = 0.66; c = 1.3 for stiffness increasing with depth, c = 2.5 for stiffness decreasing with depth), which attains WAD ≤ 4.2% across all four families with no calibration equation at all. Notably, Occam’s inversion reproduced the settlement–diameter curve itself with good accuracy in most cases, yet this close data fit did not guarantee an accurate stiffness profile—a direct manifestation of the intrinsic non-uniqueness of the settlement-based inverse problem. These findings support the use of a Poisson ratio-calibrated direct inversion method as a practical, robust alternative to generic regularized inversion for recovering stiffness profiles from multi-diameter plate loading data.

Non-destructive in situ tests, such as the plate bearing (plate load) test, are widely used to estimate the equivalent deformation modulus (e.g., $E_{v2}$) of existing road embankments. However, the depth of influence sampled by such a test is governed by the loading plate diameter, so a single test yields only an average, diameter-dependent modulus rather than the actual variation in stiffness with depth. This study investigates whether systematically varying the plate diameter and inverting the resulting settlement–diameter (dispersion) curves can recover the full depth-dependent stiffness profile, $E\left(z\right)$. Synthetic settlement–diameter curves were generated using a Boussinesq-based forward model for four families of reference stiffness profiles, representing normal (stiffness increasing with depth) and reverse (stiffness decreasing with depth) linear and exponential trends, combined with six Poisson’s ratios and five profile slopes/exponents (30 cases per profile family, 120 cases in total). Two inversion strategies were applied to back-calculate $E\left(z\right)$ from each dispersion curve: a classical Occam-type, smoothness-constrained (Tikhonov-regularized) nonlinear inversion, and a direct, closed-form simplified inversion method (SIM) based on differencing the apparent-modulus-versus-diameter curve. The results were benchmarked against the known reference profiles. Once calibrated so that its governing parameters depend only on Poisson’s ratio and the shape of the measured dispersion curve, SIM could be applied blindly—without knowledge of the reference profile or a starting model, requiring only an assumed Poisson’s ratio and the established calibration—and recovered $E\left(z\right)$ with markedly lower error than Occam’s inversion (WAD = 2.2–4.7% and RMSPE = 2.6–5.8%, versus 7.4–19.1% and 9.4–28.3%, respectively, across the four profile families). For the Poisson’s ratio most typical of earth materials, $\nu =0.3$, the calibration further collapses to a single parameter set common to all four families investigated ($I=0.66$; $c=1.3$ for stiffness increasing with depth, $c=2.5$ for stiffness decreasing with depth), which attains WAD ≤ 4.2% across all four families with no calibration equation at all. Notably, Occam’s inversion reproduced the settlement–diameter curve itself with good accuracy in most cases, yet this close data fit did not guarantee an accurate stiffness profile—a direct manifestation of the intrinsic non-uniqueness of the settlement-based inverse problem. These findings are bounded by their evidence base: noise-free data from the same forward operator used in the inversion, smooth profiles, a calibration evaluated on the cases that produced it, and an Occam comparison specific to L-curve-selected regularization. Within these limits, SIM is a promising alternative to regularized inversion; measurement noise, layered profiles and field validation are the next steps.

Surface-wave (MASW) surveys along dam crests systematically overestimate the shear wave velocity (VS) at depth, because all conventional inversion schemes assume a horizontally layered half-space, whereas a dam is a finite-width, tapered waveguide. This paper turns this open problem into a one-step engineering calculation. Three-dimensional finite element simulations of MASW testing on trapezoidal dam sections, covering crest width-to-height ratios (B/H) of 0.1–1.0 and slopes of 1:1, 2:3 and 3:2, quantify the bias—up to ≈17%, increasing with steeper slopes and decreasing B/H, and vanishing as B/H approaches 0.7—and show that it is governed solely by the taper geometry of the cross-section. A single, chart-based depth correction factor, c(B/H, slope), is derived, applicable to the output of any 1D inversion scheme without any site-specific numerical analysis. The correction was tested on three dams of different type, height and construction: at the 40 m high Koris Bridge RCC dam it systematically reduced the deviation of the MASW profiles from uphole measurements in four boreholes; at the 150 m high Mesochora CFRD (B/H = 0.07) the corrected profile agrees with in-situ rockfill stiffness values from the literature; and in a blind test on the published SASW and MASW data of the GamPo ECRD, the chart value c = 1.15 practically coincided with the depth multipliers that minimize the misfit to the downhole measurements (1.09–1.13). The proposed factor thus offers a universal, ready-to-use route to reliable VS–depth distributions for the seismic response analyses of dams.