2022 Fiscal Year Final Research Report
Clarification of influence of liquid bridge distribution in unsaturated soil on strength/deformation characteristics and establish of a constitutive model
| Project/Area Number |
20K14825
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 22030:Geotechnical engineering-related
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| Research Institution | Kyoto University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | 不飽和土 / 液架橋 / バルク水 / 排気条件 / 排水条件 / X線マイクロCT / 画像解析 |
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| Outline of Final Research Achievements |
The entire unsaturated triaxial specimen (35 mm in diameter and 70 mm in height in its initial state) was observed at high resolution, allowing the three phases of soil particles, water, and air to be distinguished. The results show that there is significant volume expansion and saturation reduction from the center to the top of the specimen, while the geometrical changes in the lower part of the specimen are very small. An image analysis algorithm was developed to classify liquid bridges and bulk water and to identify changes in morphological transition of pore water with soil particle displacement, and was applied to CT images obtained in unsaturated triaxial tests with low initial saturation. The results show that the percentage of change in porewater morphology is higher in the order of 1) liquid bridge disappears, 2) liquid bridge remains, and 3) liquid bridges transition to bulk water, and that a decrease in liquid bridges corresponds to a decrease in deviator stress.
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| Free Research Field |
地盤工学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究の背景には，道路盛土など部分的に水で飽和した不飽和土構造物がなぜ，どのように変形し破壊に至るかを厳密に解釈し，土構造物の強度を適切に評価する方法の確立，ひいては力学的により安定な土構造物の設計・施工を実現するという社会的意義がある．不飽和土の力学的安定性を支配する重要な因子は，小さな土粒子間に表面張力によって架橋構造を成す，さらに小さな体積の間隙水（液架橋）の数や分布の変化であるが，このようなミクロスケール挙動の変化が土のマクロな応答に与える影響は検証された事例は世界的に見ても本研究以外になく，学術的意義は大きい．
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