Investigation of failure mechanism of embankment under seepage condition and proposal of rational design and inspection method

2019 Fiscal Year Final Research Report

• Project/Area Number: 16H04412
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Geotechnical engineering
• Research Institution: Meijo University
• Principal Investigator: KODAKA Takeshi 名城大学, 理工学部, 教授 (00252271)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 浸透 / 盛土 / 堤防 / 三軸試験 / 細粒土 / 礫質土 / 崩壊 / 一面せん断

Outline of Final Research Achievements

By conducting this research which aims to propose the rational design and inspection of embankment under seepage condition, the following results were obtained. 1. A water absorption softening test was newly developed. It can rationally determine the mechanical constants for inspection and design of soil structures that collapse due to a decrease in effective stress under seepage conditions. 2. Using the newly developed direct shear box test apparatus that can be performed under seepage conditions, it was shown that there is a high correlation between the shear stress-displacement relationship and the fine contents loss-displacement relationship, and it was elucidated that movement and washout of fine grains are activated due to shear deformation. 3. In order to accurately determine the safety factor of slope failure under seepage conditions, a FEM analysis code that is coupling saturated-unsaturated seepage flow analysis and rigid-plastic finite element analysis has been developed.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

盛土構造物は時間とともに安定化するとされているが，降雨や洪水による浸透条件下では著しくせん断強度が低下する細粒土材料が存在し，かつ，それが昨今の豪雨時の盛土被災に結びついていることを明らかとした。これは，本研究で開発，提案した吸水軟化試験による成果であり，浸透時に劣化する地盤材料の力学特性を適正に評価可能としたことによる。また，本研究では，特殊な一面せん断試験によって，浸透条件下での土構造物内の細粒分の移動・流失は，せん断変形に起因して活発化することも明らかにした。これは，盛土からの細粒分の流失現象が，より危険な破壊の兆候であることを学術的に示した初めての研究成果である。