Development of global correlation models between in situ stress-normalized shear wave velocity and soil unit weight for plastic soils

Shear wave velocity (V-s) in geo-materials is strongly dependent on factors such as stress state, void ratio, and soil structure. Stress-dependency and void-ratio dependency can be represented by the equations V-s = alpha(sigma(c)')(beta) and V-s = a(e)(b) (where alpha and a are material constants; exponents beta and b represent the sensitivity of stress and the void dependent effect, respectively; sigma(c)' is effective confining stress; e is void ratio), respectively. To consider the effect of soil disturbance and stress relief in geomaterials, shear wave velocity is often required to be normalized by adopting the site-specific model parameters (beta or b). Based on a special in situ database compiled from 156 well-documented test sites that include various geo-materials, this study presents (i) the apparent relationships of the model parameters alpha and beta for all soil and rock materials as well as a and b for all soil materials, (ii) new global correlations between soil unit weight and two types of stress-normalized shear wave velocities (V-s1 and V-sn), instead of the conventional V-s - soil unit weight relationship for clays, and (iii) the best-fitted multi-regression models between soil unit weight and site-specifically normalized shear wave velocity as well as the plasticity index for plastic soils. Moreover, this study presents the importance of site-specific stress normalization (V-sn) in creating a better correlation model. The proposed relationships offer first-order assessments of soil unit weight within the ranges of available data, which are also approximately guided by a hyperbolic unit weight model with depth.