Development of analysis model for backward erosion piping in foundation under levee based on new concept of seepage flow

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K14841
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 22040:Hydroengineering-related
• Research Institution: National Institute for Land and Infrastructure Management (2021-2023); Chuo University (2020)
• Principal Investigator: Kosuke Tabata 国土技術政策総合研究所, 河川研究部, 主任研究官 (90756678)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 堤防 / 基盤浸透 / パイピング破壊 / 浸透流 / 粒度分布 / 空隙率

Outline of Final Research Achievements

A numerical analysis model was constructed that can represent the progression of piping in the basement layer beneath the embankment. Two models were attempted: solid-liquid two-phase flow and multiphase flow. It was difficult to perform stable analysis with the two-phase flow model, but it was confirmed that the multiphase flow model can generally represent the expansion process of the sand boiling area due to differences in interlayer structure and particle size distribution by incorporating elements that are considered important for reproducing the phenomenon, such as changes in permeability coefficient due to increased porosity. However, it was not possible to reproduce the formation of piping with a completely void area. This is presumably due to the inability to fully model the mechanism of skeleton destruction caused by excessive escape of particles, and the resistance law when transitioning from laminar to turbulent flow.

Free Research Field

河川工学

Academic Significance and Societal Importance of the Research Achievements

洪水外力の巨大化が著しい昨今において，最も重要な治水施設である堤防の破壊危険性を
科学的に推定し，堤防強化対策に生かすことのできる技術の確立が強く求められる．基盤漏水に伴う堤防パイピング破壊は，見えないところで徐々に進行する破壊現象であり，危険箇所の推定が困難である．本研究では，パイピング発達機構の理解，堤防破壊の危険性を高める要因推定，有効な対策の検討とその効果検証等に繋げるための1つのアプローチが提示されており社会的意義があると考えられる．また，単純な混相流モデルに，現象再現上重要と考えられる要素を取り込むことでパイピング進行を概ね表現できており，学術的知見も得られている．