Anisotropy factor of saturated and unsaturated soils
Anisotropy factor of saturated and unsaturated soils
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饱和土和非饱和土的各向异性因子
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
Dani Or
中科院分区：
文献类型：
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作者：
S. Assouline;Dani Or
土壤导水率各向异性程度随水饱和度 (Se) 变化的变化可能会对水流和输送过程的可预测性产生不利影响。概念性的“分层蛋糕”模型被扩展以考虑特定土壤类型内堆积密度变化的影响。作为基质势 A(ψ) 函数的各向异性因子对于不同的土壤质地表现出不同的行为。例如，沙子的 A(ψ) 表现出复杂的行为，在 A(ψ) 降至最小值之前具有局部最大值，此时沙子在 ψ = -1.0 bar 附近变为各向同性 (A(ψ) = 1)。实验确定的土壤容重和水力特性之间的关系表明，在整个饱和范围和多种土壤类型中，每种土壤的 A(Se) 和极端水力传导率值 K(Se)max/K(Se)min 之比之间存在很强的相关性。针对堆积密度的四个简单且连续的概率密度函数，研究了各向异性因子对极值 Kmax 和 Kmin 的强烈依赖性。此外，还导出了仅具有 Kmax 和 Kmin 的交替层二元系统的简单解析表达式。 A(Se) 的上限是通过 Kmax 和 Kmin 的权重相等 (w = 0.5) 获得的。实验数据和模型预测对于分配给 Kmax 或 Kmin 的某些权重值一致（∼w = 0.02）。基于 Kmax 和 Kmin 的其他近似提供了各向异性因子的简单估计，该因子可能与导水率统计分布的形状有关。
Variations in the degree of anisotropy in soil hydraulic conductivity with changes in water saturation (Se) may adversely impact predictability of flow and transport processes. The conceptual “layered cake” model was extended to consider effects of bulk density variations within a particular soil type. The anisotropy factor as function of matric potential A(ψ) exhibits different behavior for different soil textures. For example, A(ψ) for sand shows complex behavior with a local maximum just before A(ψ) drops to a minimum where sand becomes isotropic (A(ψ) = 1) near ψ = −1.0 bar. Experimentally determined relationships between soil bulk density and hydraulic properties show existence of strong correlation between A(Se) and the ratio of extreme hydraulic conductivity values K(Se)max/K(Se)min for each soil for the entire saturation range and across several soil types. The strong dependency of anisotropy factor on extreme values Kmax and Kmin was investigated for four simple and continuous probability density functions of bulk density. Additionally, simple analytical expressions for a binary system of alternating layers with Kmax and Kmin only were derived. An upper bound for A(Se) is obtained with equal weight for Kmax and Kmin (w = 0.5). The experimental data and model predictions agreed for certain values of weight assigned to either Kmax or Kmin (∼w = 0.02). Other approximations based on Kmax and Kmin provide simple estimates for anisotropy factor that could be related to shape of statistical distribution of hydraulic conductivity.