Finite-Element Modeling of Continuous Surface Waves Tests: Numerical Accuracy with respect to Domain Size

Abstract

Near-field effects are inherent in continuous surface wave (CSW) tests. Such effects on the dispersion curves can be studied using the finite-element (FE) method. However, near-field effects may be obscured by boundary effects in a FE model. Although the use of local nonreflecting boundary conditions (NRBCs) may alleviate the problem, these need to be placed sufficiently far away to be effective. Quantitative guidelines on domain size with NRBCs are still lacking. This paper provides specific guidelines to determine the domain size in terms of the wavelength-to-domain size ratio, λ*/l*. With local NRBCs, numerical errors were found to be negligible when the domain size (l*) was extended to twice the longest wavelength (λ*). However, in modeling soft soil deposits in which shear-wave velocity (Vs) is less than 100 m/s, a smaller domain size (e.g., λ*/l*=2) is sufficient.