A study on instability mechanism of granular materials by visualizing effective stress transmission in micro scale

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K14830
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: National Institute of Maritime, Port and Aviation Technology
• Principal Investigator: KONDO Akihiko 国立研究開発法人海上・港湾・航空技術研究所, 港湾空港技術研究所, 主任研究官 (80755893)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: 粒状体 / 可視化 / 応力発光 / 有効応力

Outline of Final Research Achievements

This study aims to elucidate ground instability from the dynamics of the load transmitting inter-particle structure by visualizing the load transmission of microscopic effective stress. In this study, mechanoluminescent-coated particles that emit light in response to mechanical stimulation and transparent particles based on the refractive index matching method were prepared. Pile model penetration tests were conducted in destabilized specimen by controlling effective stress conditions using upward seepage flow. The observed luminescence behavior corresponds to a decrease in penetration resistance with effective stress levels, which showing a stress field process from a microscopic load transmission to macroscopic deformation behavior.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

地盤災害のメカニズム解明において，地盤内の応力状態を知ることは変形や破壊発生前の情報として重要である．特に，有効応力は，地震時の液状化や堤防の浸透破壊に代表される地盤の不安定化を記述する上で欠かせない概念である．しかし，従来の有効応力の計測では，連続体近似した全応力の算定値と間隙水圧計による水圧の計測値の差という要素レベルでの間接的な推定値しか得られず，ミクロな土粒子レベルの有効応力状態は観測できなかった．そのため，本研究では，応力発光現象と屈折率整合法を用いて，有効応力をミクロな粒子単位の作用力から可視化することで，マクロな変形・破壊に至る過程を検討できることを示した．