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Hydraulic properties for unsaturated water flow in aggregated volcanic ash soils
http://hdl.handle.net/10076/13878
http://hdl.handle.net/10076/138784209f5a7-2770-4ffd-949b-41726997b3c8
| 名前 / ファイル | ライセンス | アクション |
|---|---|---|
2013DB004.pdf (1.9 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||||
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| 公開日 | 2014-05-01 | |||||||
| タイトル | ||||||||
| タイトル | Hydraulic properties for unsaturated water flow in aggregated volcanic ash soils | |||||||
| 言語 | en | |||||||
| 言語 | ||||||||
| 言語 | eng | |||||||
| 資源タイプ | ||||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_db06 | |||||||
| 資源タイプ | doctoral thesis | |||||||
| アクセス権 | ||||||||
| アクセス権 | open access | |||||||
| アクセス権URI | http://purl.org/coar/access_right/c_abf2 | |||||||
| 著者 |
RUDIYANTO
× RUDIYANTO
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| 抄録 | ||||||||
| 内容記述タイプ | Abstract | |||||||
| 内容記述 | Numerical analysis of soil water flow is frequently used to assess water management in agriculture. Hydraulic properties (i.e., water retention, θ(h) and unsaturated hydraulic conductivity, K(h) or K(θ)) are required for that analysis. Among soil physical properties, the unsaturated hydraulic conductivity is the most difficult to measure. This thesis mainly describes determination of a wide range of unsaturated hydraulic conductivity of Andisols based on the evaporation method. Subsequently, a hysteretic model for hydraulic properties of Andisols was proposed. Furthermore, roles of aggregate structure of Andisols were also numerically evaluated for water management in the root zone layer. Chapter 2 reviews the uniqueness of Andisols because of a well-developed and stable aggregate structure made up of noncrystaline minerals (e.g., allophane, imogolite, ferrihydrite). Several hydraulic functions for aggregated soils were also presented. This chapter also provides the procedure of the inverse method mainly focusing on the evaporation method for determining hydraulic properties. A hysteretic model based on Kool and Parker (1987) derived from the scaling methods was also reviewed. In Chapter 3, parameters of the bimodal van Genuchten (VG) hydraulic functions for two aggregated Andisols were inversely determined using the evaporation method. Initial estimates of the water retention parameters were determined from separate retention measurements, which facilitated rapid convergence of the parameter optimization process regardless of the number of optimized parameters. When the bimodal water retention parameters were fixed according to the independently measured retention data from near saturation to very low pressure heads down to -105 cm, it was possible to estimate the unsaturated conductivity, K(h), by optimizing only two conductivity parameters (Ks, ℓ). Since the flat region of the bimodal retention curve at intermediate pressures is difficult to measure precisely, however, we still recommend optimizing all bimodal VG parameters to yield the best overall results. Including water retention data at very low pressure heads in the dry range extended the applicable range of the model predictions, at least down to pressure heads of approximately -104 cm. This confirms that collecting water retention data over a wide range of pressure heads will viii give very useful prior information to the parameter estimation process for not only Andisols but also other soils. Chapter 4 proposes a hysteretic model of hydraulic properties for dual porosity soils based on the bimodal van Genuchten (VG) model and the Kool and Parker (K&P) hysteresis model. Hysteresis is considered only in the first pore domain, affecting mainly higher water contents, while a nonhysteretic behaviour is assumed in the second pore domain, affecting mainly lower water contents. The main drying and wetting curves are described with the same set of parameters, except for the α1 parameter, which is different for the drying curve, α1d, and for the wetting curve, α1w. The scanning hysteresis loops in the first subregion are also described using the K&P model. The hysteretic water retention model agrees reasonably well with drying and wetting retention curves and scanning loops observed for Andisols. Although the corresponding unsaturated hydraulic conductivity, evaluated using the Mualem pore-size distribution model, as a function of the water content, K(θ), is nonhysteretic for higher water contents, unrealistic hysteresis occurs in K(θ) for lower water contents. In order to obtain an ‘almost’ nonhysteretic K(θ) function for the entire range of water contents, an additional constraint on the value of the α1 parameter for K(θ) is imposed, and a single value α1k is used for both drying and wetting curves. Chapter 5 reports roles of aggregate structure for Andisols in the root zone layer through numerical water flow evaluation. Similar to sandy loam soil, Kumamoto Andisol exhibits large infiltration and drainage rate from root zone because of large Ks which is resulted in from interaggregate pores. Kumamoto Andisol shows greater water and air storage, the potential and actual plant available water (PAW) than those in sandy loam and clay soils. For water storage and the potential and actual PAW, Kumamoto Andisol is similar to clay soil; however, for air storage, Kumamoto Andisol has similarity to sandy loam soil. Intraaggregate pores are responsible on water storage and the potential and actual PAW. Contrary, interaggregate pores are responsible on soil aeration. Aggregated structure that developed in Kumamoto Andisol accounts combination of sandy loam and clay soils properties. |
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| 言語 | en | |||||||
| 内容記述 | ||||||||
| 内容記述タイプ | Other | |||||||
| 内容記述 | 本文 / Department of Sustainable Resource Sciences Graduate School of Bioresources Mie University | |||||||
| 内容記述 | ||||||||
| 内容記述タイプ | Other | |||||||
| 内容記述 | 124p | |||||||
| 書誌情報 |
発行日 2013-01-01 |
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| フォーマット | ||||||||
| 内容記述タイプ | Other | |||||||
| 内容記述 | application/pdf | |||||||
| 著者版フラグ | ||||||||
| 出版タイプ | VoR | |||||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||||
| 出版者 | ||||||||
| 出版者 | 三重大学 | |||||||
| 学位名 | ||||||||
| 学位名 | 博士（学術） | |||||||
| 学位授与機関 | ||||||||
| 学位授与機関識別子Scheme | kakenhi | |||||||
| 学位授与機関識別子 | 14101 | |||||||
| 学位授与機関名 | 三重大学 | |||||||
| 学位授与年月日 | ||||||||
| 学位授与年月日 | 2013-12-18 | |||||||
| 学位授与番号 | ||||||||
| 学位授与番号 | 乙学術第965号 | |||||||
| 資源タイプ（三重大） | ||||||||
| 値 | Doctoral Dissertation / 博士論文 | |||||||
