An evaluation method for seepage-induced internal erodibility in levees

Research Project

Project/Area Number	16K18145
Research Category	Grant-in-Aid for Young Scientists (B)
Allocation Type	Multi-year Fund
Research Field	Geotechnical engineering
Research Institution	Tokyo Institute of Technology
Principal Investigator	Horikoshi Kazuki 東京工業大学, 環境・社会理工学院, 助教 (90771965)
Project Period (FY)	2016-04-01 – 2019-03-31
Project Status	Completed (Fiscal Year 2018)
Budget Amount *help	¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000) Fiscal Year 2017: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2016: ¥2,860,000 (Direct Cost: ¥2,200,000、Indirect Cost: ¥660,000)
Keywords	侵食 / 河川堤防 / 浸透流 / 内部侵食 / 侵食速度 / 浸透 / 堤防 / 浸透破壊 / 侵食特性
Outline of Final Research Achievements	In this study, it was investigated the erosion rate of the topsoil along same Japanese River levee, where many traces of piping were observed after the heavy rain, by Hole erosion test. By exploring relationship between the erosion rate and various soil properties, influential soil properties on erodibility were identified. From this study, the following conclusions were obtained. 1) The erosion rate of 18 specimens was judged as Extremely slow, Very slow or Moderately slow and erosion rate of 4 specimens was judged as rapider than moderately slow. 2) Test results obtained by Hole erosion test and engineering properties of soil that the consistency limit, grain size distribution and compaction characteristics affect the erosion rate. This suggests that the clay content is the key parameter for the erosion resistance.
Academic Significance and Societal Importance of the Research Achievements	これまで河川堤防の浸透による侵食の開始に関する知見やその浸透破壊の形態に関する研究は多くなされていたが，その時間スケールに関する定量的な評価に関する研究はわずかであった．本研究は，これまで欧州やオーストラリアのフィルダム材を対象に使用されているHole erosion testを日本の河川堤防材を対象に適用し，その堤防材の侵食速度の評価を示した．また，土の基本的物性値の中で，侵食速度に影響を与える物性を抽出した．その土の基本的物性値から，概算的な侵食速度を算出する評価式を提案した．