2023 Fiscal Year Final Research Report

New developments in fluid and mixed grain size granular mechanics based on Available Porosity theory

Research Project

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Project/Area Number	21K18750
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 22:Civil engineering and related fields
Research Institution	Hiroshima University
Principal Investigator	Uchida Tatsuhiko 広島大学, 先進理工系科学研究科(工), 准教授 (00379900)
Co-Investigator(Kenkyū-buntansha)	橋本涼太京都大学, 工学研究科, 准教授 (60805349) 河原能久広島大学, 先進理工系科学研究科(工), 名誉教授 (70143823) 井上卓也広島大学, 先進理工系科学研究科(工), 准教授 (20647094) 鳩野美佐子広島大学, 先進理工系科学研究科(工), 助教 (40837019)
Project Period (FY)	2021-07-09 – 2024-03-31
Keywords	分級 / 空隙率 / 細粒土砂 / 利用可能空隙率
Outline of Final Research Achievements	By theoretically deriving a continuity equation for a mixed-grain fluvial bed sediment and comparing it with the conventional continuity equation, this study clarified the issues of active layer thickness and bed height in the calculation with the active layer concept and showed that it is important to determine the deposition height for each grain size sediment particle group based on the available porosity (AP). Experiments on the process of sediment sorting with fine sediment entrainment by water flow were conducted and compared with present method for model validation of AP theory. The relationship between particle size distribution and porosity was clarified based on the Coarse Paking and Fine Packing of two particle size groups. It was also shown that differences in porosity due to sediment deposition conditions can be evaluated by the porosity of uniformly sized particles.
Free Research Field	水工学
Academic Significance and Societal Importance of the Research Achievements	河床材料はメートルスケールの大きな石から大きな石の空隙や下流に存在する砂などの細粒分で構成させている．混合粒径の土砂輸送解析は河川の地形変化や土砂輸送解析に必須であるが，広域，長期解析に適する方法は確立されていない．個別の粒子を解析する個別要素法では，交換層の問題が表れないことに着目し，積分可能なオイラー型モデルでも空隙率や交換層の問題を解決することができる利用可能空隙率を提案し，その妥当性と混合粒径土砂輸送解析における有効性を示した．混合粒径粒子群の問題は地盤工学，コンクリート工学，化学工学など多くの分野に関連し，オイラー型モデルでその運動が記述できることを示したことは重要である．