Premium
Anisotropy of Unsaturated Layered Soils: Impact of Layer Composition and Domain Size
Author(s) -
Deng Peng,
Zhu Jianting
Publication year - 2015
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2014.08.0309
Subject(s) - soil water , anisotropy , domain (mathematical analysis) , layer (electronics) , composition (language) , geology , soil science , materials science , mineralogy , environmental science , composite material , physics , optics , mathematics , mathematical analysis , linguistics , philosophy
Soils commonly exhibit hydraulic anisotropy under field conditions due to layering. Previous studies on saturation‐dependent anisotropy were mostly focused on the impact of saturation degree, bulk density, and soil texture. In this study, the impact of layer composition and domain size on the anisotropy of unsaturated soils was investigated. We applied the same capillary pressure at top and bottom of the layered domain to simulate a mean unit hydraulic gradient condition and determined the anisotropy factor by the ratio of fluxes in the directions parallel and perpendicular to the layering. The anisotropy factors were then examined in relation to the layer composition, domain size, and mean capillary pressure for both two‐ and three‐layer formations. In addition, the performance of the conveniently used conceptual anisotropy based on the harmonic and arithmetic mean hydraulic conductivities was also investigated for comparison. The maximum anisotropy is reached when the more permeable layer thickness is <50% in the two‐layer formation. Both two‐layer and three‐layer formations exhibit a nonmonotonic anisotropic behavior in relation to the mean capillary pressure head. In the three‐layer formations, anisotropy always exists because the minimum anisotropy factor is larger than one. In the dry range, the anisotropy of layered formations decreases significantly with increasing domain size. The anisotropy behavior of layered formations that is influenced by layer composition and domain size should be appropriately quantified, as the commonly used approach based on the harmonic and arithmetic mean of hydraulic conductivities may introduce large errors.