Significance and evaluation of Poisson's ratio in Rayleigh wave testing

Abstract

Important progress has been made in the past 20 years in the use of surface-wave testing in soil characterization. However, the effect of Poisson's ratio on the construction of the theoretical dispersion relationships, associated with the inversion process, has not received enough attention and remains poorly documented. Five ideal profiles with different degrees of variation of shear-wave velocity with depth and three published case records are considered in this paper to study the effect of Poisson's ratio on Rayleigh wave phase velocities. The effect of the variation of Poisson's ratio on the evaluation of shear-wave velocity profiles (Vs) is also examined. Poisson's ratio is generally assumed in surface-wave testing, and therefore the paper also examines the possibility of evaluating its value using a multi-mode inversion process. The results of surface-wave testing obtained at two experimental sites are then used to illustrate the potential of surface-wave testing to evaluate the Poisson's ratio profile in addition to the Vsprofile. The impact of Poisson's ratio in Rayleigh wave testing is shown to be significantly more important than previously demonstrated. The error resulting from Poisson's ratio does not depend solely on the magnitude of the inaccuracy. A multi-mode inversion process is shown to be a useful tool to determine the Poisson's ratio profile, leading to a more accurate soil characterization.