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Mechanisms of accelerated flow of sediment by rollers of air bubbles in soil

Research Project

Project/Area Number 21K18741
Research Category

Grant-in-Aid for Challenging Research (Exploratory)

Allocation TypeMulti-year Fund
Review Section Medium-sized Section 22:Civil engineering and related fields
Research InstitutionUtsunomiya University

Principal Investigator

UNNO TOSHIYASU  宇都宮大学, 地域デザイン科学部, 准教授 (50570412)

Co-Investigator(Kenkyū-buntansha) 加村 晃良  東北大学, 工学研究科, 准教授 (80761387)
菊本 統  横浜国立大学, 大学院都市イノベーション研究院, 教授 (90508342)
Project Period (FY) 2021-07-09 – 2024-03-31
Project Status Completed (Fiscal Year 2023)
Budget Amount *help
¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000)
Fiscal Year 2023: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
Fiscal Year 2022: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000)
Fiscal Year 2021: ¥1,950,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥450,000)
Keywords不飽和土 / 間隙水 / 間隙空気 / サクション / 繰返し載荷 / 液状化 / 三次元個別要素法 / ベアリング効果 / 気泡 / 要素試験 / 静的載荷 / 繰返しせん断 / 流動化処理土 / 流動化処理 / ベアリング
Outline of Research at the Start

地震や豪雨時に発生する流動性崩壊は,多量の土砂が長距離に移動する現象であるが,流下メカニズムは未だ不明である.申請者らは,これらの現象において土塊中の気泡や土砂の細粒分がベアリング効果(コロ)を発揮することが長距離移動現象の一因となっているのではないか?という仮説を立てた.本研究の目的は,提案する仮説をメカニズムに立脚した実験と理論から検証することである.
本研究では,流動模擬土に対する要素せん断実験(三軸試験,中空ねじり試験)並びに三次元個別要素法による数値実験の2つの実験実施による力学挙動の観察と実験結果に基づく構成則の開発に伴うメカニズムの解明を行い,本研究の仮説を検証する.

Outline of Final Research Achievements

In recent years, ground disasters involving soil turning into mud and flowing during natural calamities like earthquakes and heavy rains have become increasingly frequent. This phenomenon, where large quantities of soil travel over long distances, remains poorly understood. Our study hypothesizes that air bubbles trapped within collapsing soil significantly reduce its strength and stiffness, leading to fluid-like behavior. To confirm this, we conducted mechanical tests and numerical analyses to investigate the impact of pore air on soil's shearing behavior. We created synthetic soil samples by introducing bubbles using special chemical agents. The experiments revealed that soil containing many bubbles in its pores exhibited shear softening behavior, even in conditions not typically associated with softening. These findings highlight the role of pore air in soil's susceptibility to fluidization and offer new insights into ground failure mechanisms during natural disasters.

Academic Significance and Societal Importance of the Research Achievements

自然災害により表層地盤が泥状になり崩壊する流動性崩壊が多発している.この崩壊部は,地下水位より上の比較的浅い不飽和土層である.本研究では,地震動等の外力を受け軟化する不飽和土の力学挙動を室内要素試験,数値解析を用いて検討し,不飽和土の軟弱化メカニズムの把握を試みている.
その結果,従来,間隙空気により高いせん断強度や液状化抵抗を有するとされる不飽和土でも,土中の間隙空気と間隙水の状態によっては十分な強度を発揮しない状態に至ることを明らかにした.この事実は,不飽和土の力学挙動に対し間隙空気と間隙水の状態を精緻に把握する重要性を示す結果であるとともに,不飽和土の耐震検討に対して有益な知見を与える.

Report

(4 results)
  • 2023 Annual Research Report   Final Research Report ( PDF )
  • 2022 Research-status Report
  • 2021 Research-status Report
  • Research Products

    (11 results)

All 2023 2022 2021

All Journal Article (9 results) (of which Int'l Joint Research: 3 results,  Peer Reviewed: 9 results,  Open Access: 2 results) Presentation (2 results)

  • [Journal Article] Mix proportion for cement stabilized soil that satisfies both fluidity and strength conditions2023

    • Author(s)
      海野 寿康, 新舎 博, 吉澤 健太
    • Journal Title

      Japanese Geotechnical Journal

      Volume: 18 Issue: 4 Pages: 421-430

    • DOI

      10.3208/jgs.18.421

    • ISSN
      1880-6341
    • Year and Date
      2023-12-01
    • Related Report
      2023 Annual Research Report
    • Peer Reviewed / Open Access
  • [Journal Article] NUMERICAL SIMULATION OF UNSATURATED CYCLIC SHEAR TEST CONSIDERING ENCLOSED AIR IN VOID WATER2023

    • Author(s)
      MATSUMARU Takaki、UNNO Toshiyasu
    • Journal Title

      Japanese Journal of JSCE

      Volume: 79 Issue: 15 Pages: n/a

    • DOI

      10.2208/jscejj.22-15039

    • ISSN
      2436-6021
    • Related Report
      2023 Annual Research Report 2022 Research-status Report
    • Peer Reviewed
  • [Journal Article] Role of particle rotation in sheared granular media2023

    • Author(s)
      Ali Usman、Kikumoto Mamoru、Cui Ying、Ciantia Matteo、Previtali Marco
    • Journal Title

      Acta Geotechnica

      Volume: - Issue: 9 Pages: 1-16

    • DOI

      10.1007/s11440-023-01860-1

    • Related Report
      2023 Annual Research Report
    • Peer Reviewed / Open Access / Int'l Joint Research
  • [Journal Article] Experimental micro-macromechanics: particle shape effect on the biaxial shear response of particulate systems2023

    • Author(s)
      Ali Usman、Kikumoto Mamoru、Ciantia Matteo、Previtali Marco、Cui Ying
    • Journal Title

      Geotechnique

      Volume: - Issue: 13 Pages: 1-13

    • DOI

      10.1680/jgeot.22.00364

    • Related Report
      2023 Annual Research Report
    • Peer Reviewed
  • [Journal Article] A study on mix proportion that satisfies both fluidity and strength of Kanto Loam cement stabilized soil2022

    • Author(s)
      UNNO Toshiyasu、SHINSHA Hiroshi、YOSHIZAWA Kenta
    • Journal Title

      Japanese Geotechnical Journal

      Volume: 17 Issue: 4 Pages: 511-521

    • DOI

      10.3208/jgs.17.511

    • ISSN
      1880-6341
    • Year and Date
      2022-12-01
    • Related Report
      2022 Research-status Report
    • Peer Reviewed
  • [Journal Article] Mix proportion and strength characteristics of cement stabilized soil with adjusted fluidity2022

    • Author(s)
      UNNO Tomoyasu、SHINSHA Hiroshi、YOSHIZAWA Kenta
    • Journal Title

      Japanese Geotechnical Journal

      Volume: 17 Issue: 3 Pages: 255-265

    • DOI

      10.3208/jgs.17.255

    • ISSN
      1880-6341
    • Year and Date
      2022-09-01
    • Related Report
      2022 Research-status Report
    • Peer Reviewed
  • [Journal Article] Mechanism of wetting-induced deformation and failure of unsaturated soils2022

    • Author(s)
      Komolvilas, V., Kikumoto, M. and Kyokawa, H.
    • Journal Title

      International Journal for Numerical and Analytical Methods in Geomechanics

      Volume: 46(6) Issue: 6 Pages: 1064-1092

    • DOI

      10.1002/nag.3336

    • Related Report
      2021 Research-status Report
    • Peer Reviewed / Int'l Joint Research
  • [Journal Article] NUMERICAL SIMULATION OF UNSATURATED LIQUEFACTION TEST USING VOLCANIC SOILS DAMAGED IN THE 2018 HOKKAIDO IBURI EASTERN EARTHQUAKE2021

    • Author(s)
      MATSUMARU Takaki、UNNO Toshiyasu、MIDORIKAWA Yusuke
    • Journal Title

      Journal of Japan Society of Civil Engineers, Ser. A1 (Structural Engineering & Earthquake Engineering (SE/EE))

      Volume: 77 Issue: 4 Pages: I_533-I_543

    • DOI

      10.2208/jscejseee.77.4_I_533

    • NAID

      130008067186

    • ISSN
      2185-4653
    • Related Report
      2021 Research-status Report
    • Peer Reviewed
  • [Journal Article] Wetting-induced deformation of soils triggering landslides in Pakistan2021

    • Author(s)
      Riaz, S., Kikumoto, M., Basharat, M. and Putra, A. D.
    • Journal Title

      Geotechnical and Geological Engineering

      Volume: 39 Issue: 8 Pages: 5633-5649

    • DOI

      10.1007/s10706-021-01851-7

    • NAID

      120007176791

    • Related Report
      2021 Research-status Report
    • Peer Reviewed / Int'l Joint Research
  • [Presentation] 繰返し載荷を伴うセメント改良砂のせん断波速度と液状化の相関性2022

    • Author(s)
      伊藤恭祐、佐藤颯,吉直卓也、海野寿康
    • Organizer
      第15回地盤改良シンポジウム,日本材料学会
    • Related Report
      2022 Research-status Report
  • [Presentation] 建設発生土を原料とした流動化処理土の強度特性2021

    • Author(s)
      吉澤健太, 新舎博, 海野寿康
    • Organizer
      第14回環境地盤工学シンポジウム
    • Related Report
      2021 Research-status Report

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Published: 2021-07-13   Modified: 2025-01-30  

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