Evaluating the In Situ Lateral Stress Coefficient (${\mathit{K}}_0$) of Soils via Paired Shear Wave Velocity Modes

The utilization of shear wave velocities toward the evaluation of the in situ geostatic horizontal stress state in soils is validated, specifically the lateral stress coefficient $K_0$. Field shear wave velocities from paired sets of different directional and polarization modes are compiled from 16 well-documented test sites involving a variety of geomaterials. Focus is particularly placed on shear wave velocities measured by downhole tests ($V_{s\text{VH}}$), crosshole tests ($V_{s\text{HV}}$), and special rotary-type crosshole tests ($V_{s\text{HH}}$). At these sites, field $K_0$ stress states have been quantified using one or more direct assessment techniques, including self-boring pressuremeter, total stress cells, and hydrofracture in field testing, as well as suction measurements, special consolidometers, and/or triaxial arrangements on undisturbed samples in the laboratory. Although the specific delineation of stress-induced versus inherent or fabric anisotropy may be difficult, it is shown that the ratio of horizontally polarized to vertically polarized shear waves (i.e., either $V_{s\text{HH}}\text{/}{V}_{s\text{VH}}$ or $V_{s\text{HH}}\text{/}{V}_{s\text{HV}}$) can be used to provide an approximate assessment of $K_0$ in soils, especially if coupled with the age of the formation.