Evaluation of a general model for multimodal unsaturated soil hydraulic properties

Many soils and other porous media exhibit dual- or multi-porosity type features. In a previous study (Seki et al., 2022) we presented multimodal water retention and closed-form hydraulic conductivity equations for such media. The objective of this study is to show that the proposed equations are pra...

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Bibliographic Details
Published in:arXiv.org 2023-01
Main Authors: Seki, Katsutoshi, Toride, Nobuo, Martinus Th van Genuchten
Format: Article
Language:English
Subjects:
Evaluation
Hydraulic properties
Hydraulics
Mathematical models
Optimization
Parameter sensitivity
Porous media
Pressure head
Retention
Soil porosity
Soil properties
Tortuosity
Unsaturated soils
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Summary:Many soils and other porous media exhibit dual- or multi-porosity type features. In a previous study (Seki et al., 2022) we presented multimodal water retention and closed-form hydraulic conductivity equations for such media. The objective of this study is to show that the proposed equations are practically useful. Specifically, dual-BC (Brooks and Corey)-CH (common head) (DBC), dual-VG (van Genuchten)-CH (DVC), and KO (Kosugi)\(_1\)BC\(_2\)-CH (KBC) models were evaluated for a broad range of soil types. The three models showed good agreement with measured water retention and hydraulic conductivity data over a wide range of pressure heads. Results were obtained by first optimizing water retention parameters and then optimizing the saturated hydraulic conductivity (K_s) and two parameters (p, q) or (p, r) in the general hydraulic conductivity equation. Although conventionally the tortuosity factor p is optimized and (q, r) fixed, sensitivity analyses showed that optimization of two parameters (p+r, qr) is required for the multimodal models. For 20 soils from the UNSODA database, the average \(R^2\) for log (hydraulic conductivity) was highest (0.985) for the KBC model with r=1 and optimization of (Ks, p, q). This result was almost equivalent (0.973) to the DVC model with q=1 and optimization of (Ks, p, r); both were higher than \(R^2\) for the widely used Peters model (0.956) when optimizing (Ks, p, a, \(\omega\)). The proposed equations are useful for practical applications while mathematically being simple and consistent.
ISSN:2331-8422
DOI:10.48550/arxiv.2212.02965