Clarification of the mechanism of residual bearing capacity of a river bridge foundation caused by settlement and incline due to scouring

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04687
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Chuo University
• Principal Investigator: Nishioka Hidetoshi 中央大学, 理工学部, 教授 (50450747)
• Co-Investigator(Kenkyū-buntansha): 山栗 祐樹 金沢大学, 地球社会基盤学系, 研究協力員 (30972062)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 洗掘 / 河川橋梁 / 直接基礎 / 豪雨災害対策 / 再供用可否診断 / 残存支持力

Outline of Final Research Achievements

With the recent intensification of heavy rain and typhoon disasters, there has been an increase in cases where bridges across rivers have become unusable. The cause of this damage is scour, a phenomenon in which sediment flows out around the foundation of a bridge. As the scour phenomenon increases, bridges sink and tilt significantly. To quickly resume the use of bridges after such damage has occurred, it is necessary to clarify the mechanism of residual bearing capacity of foundations damaged by scour. This study systematically conducted loading experiments under conditions that artificially reproduced the scour phenomenon using an aluminum rod model of the ground around the foundation. Then, rigid-plastic finite element analyses were performed to reproduce the model experiments. Thus, the primary mechanism of residual bearing capacity was elucidated.

Free Research Field

地盤工学

Academic Significance and Societal Importance of the Research Achievements

河川橋梁の洗掘現象自体は，以前より広く認識されているが，国内外での既往研究は，「どこまで洗堀されるか」という水理学的なアプローチであった。本研究では，従来は着目されていなかった被災直後の残存支持力について地盤工学な検討を行った。本成果は，端的に言えば，洪水後に橋梁が倒壊していない限り，発生した残留変位および残留傾斜分を桁のジャッキアップ等で補修することで早期に再供用できる可能性が高いことを実験的・解析的に示したものである。この成果は，橋の利用再開可否を早期に判断する技術基準策定に活用できるなど，交通物流網のレジリエンス向上に大きく貢献するものである。