Internal Erosion in a Foundation Soil under a Sand Levee and its Manifestation on the Levee Surface

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K18907
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Research Field: Civil engineering and related fields
• Research Institution: Ehime University
• Principal Investigator: Mitsu Okamura 愛媛大学, 理工学研究科(工学系), 教授 (50251624)
• Co-Investigator(Kenkyū-buntansha): 二宮 崇 愛媛大学, 理工学研究科(工学系), 教授 (20444094)
• Project Period (FY): 2017-06-30 – 2019-03-31
• Keywords: 河川堤防 / 洪水 / 浸透 / パイピング / DEM

Outline of Final Research Achievements

River levees occasionally fail during flooding because of the mechanics of internal erosion or piping within or below the levees. Current inspection methods cannot detect the pipes until it manifests itself at the exterior sur-face. There is a strong need for non-destructive techniques that can identify internal damage. In this study it was found that specific deformation pattern appears on the surface of levees just above pipes. A method was established for estimating the size and location of the pipes based on the characteristic shape of the de-formed slope. The method was applied to levees, where significant sand boils occurred at the levee toe during recent flooding events. In addition, a number of mini-ram soundings were conducted at small intervals to identify the pipe locations in a more direct manner. It was confirmed that the penetration tests were effective in detecting the pipe locations. The detected locations compared well with those estimated from the surface topography.

Free Research Field

土木工学

Academic Significance and Societal Importance of the Research Achievements

近年，激甚な豪雨による高水が頻繁に発生して河川堤防が破堤しており，その防止が重要な課題となっている。今後は降雨や高水の繰り返し作用により，堤体土が徐々に吸い出され劣化が進行し，パイピングによる破堤の増加が危惧されている。しかし既往の調査法やセンサーの設置でパイピング破壊の進行を検知することはほぼ不可能である。
本研究は，近年の技術開発によって取得することが可能となった高密度・高精度のリアルタイム堤体表面形状情報を利用し，新たなアプローチによる堤体の健全度評価及び高水中のリアルタイムでの損傷進行度評価法の構築の基礎を築いたものである。