Mechanism ofExamination of slope failure mechanism due to rainfall seepage based on stress condition and sediment structure

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K14546
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 41030:Rural environmental engineering and planning-related
• Research Institution: University of the Ryukyus
• Principal Investigator: Kimura Sho 琉球大学, 農学部, 准教授 (10794498)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: すべり面の強度 / 降雨浸透 / リングせん断 / 斜面崩壊発生機構

Outline of Final Research Achievements

Many cases of slope failures were caused by heavy rainfall (approximately 300-400mm/3h) in the Northern Kyushu area, July 2017. This study investigated the mechanisms of slope failures around the area of metamorphic and granitic rocks based on field investigation and laboratory experiment. The high sand fractions were obtained in the strongly weathered soils in both origins. High coble content was shown in granitic soil. The higher fully softened and residual shear strengths in the tested soils in both origins were obtained by the ring shear test. Although the high permeability in the granitic soil was investigated in laboratory experiment, the permeability reduction was induced by shear. This is that the excess pore water pressure was caused by development of low permeability zone in the slip surface.

Free Research Field

地域環境工学

Academic Significance and Societal Importance of the Research Achievements

本研究によって，農村地域における調査研究対象地の斜面崩壊発生機構の一部が捉えられ，豪雨による斜面内での過剰間隙水圧発生の条件を推察することができた。本成果は，対象の地質・土質を有する場合に斜面崩壊の発生予測と災害発生予測を考慮したハザードマップ開発に貢献することができると考えられる。