A new inversion scheme to derive soil-water characteristic curve in an unsaturated dyke

Abstract

The soil-water characteristic curve (SWCC) is crucial in order to characterize the hydraulic and mechanical properties of unsaturated soils. To overcome the problem of error/uncertainties in laboratory estimates due to sample disturbances and to incorporate spatial heterogeneities, in-situ SWCC inversion using geophysical measurements appears to be a worthwhile, albeit challenging, goal. For SWCC inversion for a dyke under rainfall or rising water level or for a dyke containing low-permeable soils, accounting for the non-hydrostatic condition is crucial. Furthermore, the geometry of a dyke is important in determining the internal stress state. In this research, we model the shear modulus in an unsaturated dyke including the effect of the dyke geometry. This is achieved by solving the static deformation problem using FEM. Our newly developed inversion scheme assumes availability of integrated geophysical measurements to obtain saturation, bulk density and shear-wave velocity. We illustrate numerically the significance of the estimation of confining stress distribution using FEM for modelling the shear modulus and for SWCC inversion. Our inversion scheme can correctly handle the non-hydrostatic condition. This can have a large impact on diverse applications related to stability of earth-retaining structures as well as in problems involving dynamic transportation of fluids.