Proposal of laboratory test method and consept model on water retention, permeability and evaporation properties of unsaturated soil

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04602
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Kagoshima University
• Principal Investigator: SAKO KAZUNARI 鹿児島大学, 理工学域工学系, 教授 (20388143)
• Co-Investigator(Kenkyū-buntansha): 伊藤 真一 鹿児島大学, 理工学域工学系, 助教 (20825690)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 不飽和土 / 水分特性曲線 / 透水係数 / 蒸発効率

Outline of Final Research Achievements

An unsaturated seepage analysis and slope stability analysis are usually employed to estimate safety factors of slopes during rainfall. Then, the safety factor of slopes after rainfall is also important to cancel a warning on rainfall-induced slope failure. The properties of water retention, hydraulic conductivity and evaporation of unsaturated soils are important parameters to calculate a unsaturated seepage behavior and safety factor of a slope. The new laboratory experiment method for simultaneous measurement of these properties was proposed using HYPROP in this research. The validity of the measurement method was checked and points to be improved were discussed. Moreover, the mathematic model to estimate these properties was proposed based on physical and statistical consideration. The validity of the mathematical model was also inspected.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

降雨時および降雨後の斜面の安定性の定量的評価には，不飽和浸透解析と斜面安定解析を組み合わせた数値解析が用いられる。不飽和浸透特性には，不飽和土の水分特性曲線および飽和・不飽和透水係数が必要であり，また，境界条件として雨量や蒸発量が用いられるが，バルク法による蒸発量推定には，不飽和土の蒸発効率が必要となる。よって，本研究課題の成果により，これら数値解析に必要な不飽和土の土質パラメータに関する土質試験法および推定方法が確立することができれば，降雨時に発せられた警報の解除に役立つ防災情報を定量的な評価結果を基に提供するための技術に役立つことができる。