Deformation and failure of a slope during drying process after rainfall

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K21061
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 25:Social systems engineering, safety engineering, disaster prevention engineering, and related fields
• Research Institution: Kochi University
• Principal Investigator: Katsuo Sasahara 高知大学, 教育研究部自然科学系理工学部門, 教授 (90391622)
• Project Period (FY): 2020-07-30 – 2023-03-31
• Keywords: 斜面崩壊 / 地すべり / 降雨 / 地下水位 / 変位 / クリープ / 予測

Outline of Final Research Achievements

Measurement of the displacement on the slope could be one of the effective tools to predict failure time of landslides. The displacement on the slope increased up to failure not only with rising groundwater level in most cases but also with constant or lowering groundwater level in the field or on model slope under rainfall, which was against the common understanding in soil mechanics. In this research project, the modelling of time-dependent displacement based on the relationship between the velocity and acceleration derived from the measured displacement was combined to the model of stress-dependent displacement based on the relationship between the groundwater level and the displacement to simulate the increase of the displacement with constant or lowering groundwater level in the slope. The proposed model could simulate the displacement on model slope with not only rising groundwater level but also constant or lowering groundwater level in the slope well.

Free Research Field

土砂災害発生の土質力学的メカニズムと発生予測システムの構築

Academic Significance and Societal Importance of the Research Achievements

降雨による斜面崩壊発生直前には，通常地下水位が上昇しながら斜面の変位が増加し，崩壊に至ることが多い。土質力学的な手法は，通常はこの地下水位上昇に伴う崩壊発生を説明している。しかし実際には，地下水位が一定ないしは低下する条件の下で，斜面の変位が進行し，崩壊に至る事例も多い。これを説明し，再現するモデルを構築することは，斜面崩壊の発生予測のために重要であり，土砂災害や斜面災害の対策，特に警戒避難などのソフト対策に大きく資することとなる。