State-dependent anisotrophy: Comparison of quasi-analytical solutions with stochastic results for steady gravity drainage

Water Resources Research
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Abstract

Anisotropy in large-scale unsaturated hydraulic conductivity of layered soils changes with the moisture state. Here, state-dependent anisotropy is computed under conditions of large-scale gravity drainage. Soils represented by Gardner's exponential function are perfectly stratified, periodic, and inclined. Analytical integration of Darcy’s law across each layer results in a system of nonlinear equations that is solved iteratively for capillary suction at layer interfaces and for the Darcy flux normal to layering. Computed fluxes and suction profiles are used to determine both upscaled hydraulic conductivity in the principal directions and the corresponding “state-dependent” anisotropy ratio as functions of the mean suction. Three groups of layered soils are analyzed and compared with independent predictions from the stochastic results of Yeh et al. (1985b). The small-perturbation approach predicts appropriate behaviors for anisotropy under nonarid conditions. However, the stochastic results are limited to moderate values of mean suction; this limitation is linked to a Taylor series approximation in terms of a group of statistical and geometric parameters. Two alternative forms of the Taylor series provide upper and lower bounds for the state-dependent anisotropy of relatively dry soils.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title State-dependent anisotrophy: Comparison of quasi-analytical solutions with stochastic results for steady gravity drainage
Series title Water Resources Research
DOI 10.1029/95WR00790
Volume 31
Issue 9
Year Published 1995
Language English
Publisher American Geophysical Union
Contributing office(s) Toxic Substances Hydrology Program
Description 11 p.
First page 2201
Last page 2211