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interpretation of macroscopic response of partially saturated soil by clarifying microscopic characteristics of pore fluids

Research Project

Project/Area Number 19K23534
Research Category

Grant-in-Aid for Research Activity Start-up

Allocation TypeMulti-year Fund
Review Section 0303:Civil engineering, social systems engineering, safety engineering, disaster prevention engineering, and related fields
Research InstitutionKyoto University

Principal Investigator

Kido Ryunosuke  京都大学, 工学研究科, 助教 (40847365)

Project Period (FY) 2019-08-30 – 2021-03-31
Project Status Completed (Fiscal Year 2020)
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)
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
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.

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.

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.

Report

(3 results)
  • 2020 Annual Research Report   Final Research Report ( PDF )
  • 2019 Research-status Report
  • Research Products

    (10 results)

All 2020 2019

All Journal Article (3 results) (of which Int'l Joint Research: 1 results,  Peer Reviewed: 3 results,  Open Access: 3 results) Presentation (7 results) (of which Int'l Joint Research: 3 results)

  • [Journal Article] Microscopic characteristics of partially saturated dense sand and their link to macroscopic responses under triaxial compression conditions2020

    • Author(s)
      Kido Ryunosuke、Higo Yosuke
    • Journal Title

      Acta Geotechnica

      Volume: 15 Issue: 11 Pages: 3055-3073

    • DOI

      10.1007/s11440-020-01049-w

    • NAID

      120006898161

    • Related Report
      2020 Annual Research Report
    • Peer Reviewed / Open Access
  • [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.
    • Journal Title

      Acta Geotechnica

      Volume: - Issue: 7 Pages: 1745-1761

    • DOI

      10.1007/s11440-020-00939-3

    • NAID

      120006799247

    • Related Report
      2019 Research-status Report
    • Peer Reviewed / Open Access / Int'l Joint Research
  • [Journal Article] Distribution changes of grain contacts and menisci in shear band during triaxial compression test for unsaturated sand2019

    • Author(s)
      Kido Ryunosuke、Higo Yosuke
    • Journal Title

      Japanese Geotechnical Society Special Publication

      Volume: 7 Issue: 2 Pages: 627-635

    • DOI

      10.3208/jgssp.v07.096

    • NAID

      130007694749

    • ISSN
      2188-8027
    • Year and Date
      2019-04-30
    • Related Report
      2019 Research-status Report
    • Peer Reviewed / Open Access
  • [Presentation] 異なる排水条件での三軸圧縮下における不飽和淀川砂の軸差応力と変形の特性2020

    • Author(s)
      木戸隆之祐,肥後陽介
    • Organizer
      第55回地盤工学研究発表会
    • Related Report
      2020 Annual Research Report
  • [Presentation] Microscopic observation of variation in pore volume and local degree of saturation in partially saturated sand under triaxial compression using voronoi tessellation2019

    • Author(s)
      Kido, R, Higo, Y, Fukushima, Y
    • Organizer
      9th Asian Young Geotechnical Engineers Conference (9AYGEC)
    • Related Report
      2019 Research-status Report
    • Int'l Joint Research
  • [Presentation] Investigation of volume distribution for pore water and pore air in partially saturated sand subjected to drying and wetting through morphological image processing2019

    • Author(s)
      Kido, R, Higo, Y, Takamura, F
    • Organizer
      16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering
    • Related Report
      2019 Research-status Report
    • Int'l Joint Research
  • [Presentation] X-ray image processing to investigate variation in water retention state of partially saturated sand during triaxial compression tests2019

    • Author(s)
      Kido, R. and Higo, Y.
    • Organizer
      International Conference on Tomography of Materials and Structures2019
    • Related Report
      2019 Research-status Report
    • Int'l Joint Research
  • [Presentation] 微視的特性と巨視的応答の関係に基づく不飽和砂の三軸圧縮試験条件の分類2019

    • Author(s)
      木戸隆之祐,肥後陽介
    • Organizer
      第74回土木学会年次学術講演会
    • Related Report
      2019 Research-status Report
  • [Presentation] 三軸圧縮下における不飽和砂の軸差応力へ及ぼす微視的特性の影響の解釈2019

    • Author(s)
      木戸隆之祐,肥後陽介,福島 陽
    • Organizer
      第54回地盤工学研究発表会
    • Related Report
      2019 Research-status Report
  • [Presentation] 三軸圧縮条件における低飽和砂のミクロ構造変化とマクロな応答との関係2019

    • Author(s)
      木戸隆之祐,肥後陽介
    • Organizer
      日本材料学会第68期学術講演会
    • Related Report
      2019 Research-status Report

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Published: 2019-09-03   Modified: 2022-01-27  

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