A wave-based model for predicting K0 values

The coefficient of earth pressure at rest (K_0) is a basic soil parameter for characterising the initial stress conditions of soils. Direct measurement of K_0 through laboratory or field testing is often challenging, time-consuming and prone to errors due to soil disturbance. A more reliable alternative is to use shear-wave velocity (V_s(ij) ), which is measured at near-zero strain, to determine K_0. Existing wave-based model is largely empirical and lacks a consistent theoretical basis. This study proposed a theoretical model to predict K_0 based on soil fabric and V_s(ij) measurements in different propagation and polarisation directions. The model incorporates the influence of soil fabric—a microstructural representation of morphology, ageing and packing—by using of an anisotropic fabric variable, which are expressed as joint invariants of the fabric and loading direction tensors. The model was validated against existing field and laboratory datasets. The model showed reasonably good performance across a range of soil types and geological histories, including different ages and isotropic over-consolidation ratios (R_0). The model accuracy declines with increasing R_0, when the K_0 measurements are highly sensitive to small strain movements that violate the K_0 condition.