interpretation of macroscopic response of partially saturated soil by clarifying microscopic characteristics of pore fluids
| Project/Area Number |
19K23534
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Multi-year Fund |
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| Review Section |
0303:Civil engineering, social systems engineering, safety engineering, disaster prevention engineering, and related fields
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2019-08-30 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
Fiscal Year 2020: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2019: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
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| Keywords | 不飽和土 / 間隙水 / 間隙空気 / X線CT / 画像解析 / 排水条件 / 排気条件 / 軸差応力 / 液架橋 / 不飽和砂 / 三軸圧縮試験 / 間隙流体 / 連続性 / 不均質性 / 巨視的応答 |
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| Outline of Research at the Start |
土粒子の隙間（間隙）に水と空気が混在する不飽和土はサクションによって高い強度・剛性を示す反面，明瞭なせん断帯を伴い脆性的に破壊する．このようなマクロな力学特性を解明するには，土粒子・水・空気の三相ミクロスケール挙動を解明することが重要である．そこで本研究では，排気条件，排水条件，初期相対密度等を変えた不飽和土の三軸圧縮試験を実施し，X線マイクロCTと画像分析技術を用いて，三相ミクロ構造変化を解明する．本研究では特に，間隙流体（水と空気）の存在形態，体積，空間分布の変化に着目し，それらが不飽和土のマクロな強度・変形特性へ与える影響を解明する．
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| Outline of Final Research Achievements |
The effect of the three-phase microstructure on the macroscopic response of an unsaturated soil consisting of soil particles, water and air was investigated using X-ray CT and image analysis.
The results showed that the number of liquid bridges between soil particles decreased during shear deformation of partially saturated soil. In the undrained condition for water where the suction decreases during deformation, the number of liquid bridges decreases more than in the drained condition for water, where the suction remains constant, resulting in a decrease in the axial differential stress.
The results also suggest that the behavior is more brittle in the undrained condition for air compared to the case where the air pressure is kept at atmospheric pressure. On the other hand, the validity of the behavior under undrained condition for air remains to be examined.
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| Academic Significance and Societal Importance of the Research Achievements |
これまで不飽和土の変形・破壊メカニズムを，軸差応力の大小や供試体の変形モードといったマクロな視点から検討する研究はあったものの，そのようなマクロな応答を司るミクロな挙動の解明に着目し，異なるスケールの挙動のリンクさせる研究は世界的に見ても例がなく，学術的な意義は大きい．
道路や斜面などの不飽和土構造物の設計，施工においては，不飽和土の強度や剛性を事前に評価することが重要である．本研究の研究成果は，不飽和土の強度・変形特性が土の含水状態や変形条件によって異なるメカニズムを解釈し，実際にどういった実験条件を設定し強度評価すればよいかの参考となる点で，社会的意義は大きいといえる．
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Report
(3 results)
Research Products
(10 results)
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[Journal Article] Morphological transitions for pore water and pore air during drying and wetting processes in partially saturated sand2020
Author(s)
Kido, R., Higo, Y., Takamura, F., Morishita, R., Khaddour, G. and Salager, S.
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Journal Title
Acta Geotechnica
Volume: -
DOI
NAID
Related Report
Peer Reviewed / Open Access / Int'l Joint Research
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