Evaluating the In Situ Lateral Stress Coefficient (K0) of Soils via Paired Shear Wave Velocity Modes: Fid-Bau Portal

Evaluating the In Situ Lateral Stress Coefficient (K0) of Soils via Paired Shear Wave Velocity Modes

Ku, Taeseo / Mayne, Paul W.

Abstract

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 ( $V_{s VH}$ ), crosshole tests ( $V_{s HV}$ ), and special rotary-type crosshole tests ( $V_{s HH}$ ). 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 $V_{s HH} / V_{s VH}$ or $V_{s HH} / V_{s HV}$ ) can be used to provide an approximate assessment of $K_{0}$ in soils, especially if coupled with the age of the formation.