Numerical Model of 3-Dimensional Anisotropic Deformation and 1-Dimensional Water Flow in Swelling Soils

Current models of water flow in deforming soils generally involve a transformation from spatial to material coordinates. Existing forms of this coordinate transformation either assume that soil deformation is one-dimensional, or that it is isotropic. In the present article, we propose a new expression of the transformation gradient tensor, that allows different extents of deformation in the vertical and horizontal directions. The resulting generalized water flow equation is calibrated with experimental data obtained for one-dimensional vertical infiltration in a bentonite sample. The hydraulic characteristics obtained from this calibration are then used to analyze, via simulations, the sensitivity of water flow to anisotropy in soil deformation. The results indicate that the extent of the lateral deformation strongly influences not only the height of the soil surface, as expected, but also the distribution of water and the total volume of water in a swelling/shrinking soil undergoing infiltration or drainage. Consequently, this lateral deformation should be taken into account explicitly in modeling efforts or in the determination of the hydraulic characteristics of soils that deform anisotropically.