Development and Geographical Evaluation of Slope Failure Risk Index Due to Changes of Soil Moisture

The development of for sediment disaster prediction system for the community requires observational method for slope failure and mapping of slope failure risk index by using GIS. In this study, first, we prepared a field for experimental studies on slope failure. Second, a slope stability analysis is performed for surface slides, considering changes in cohesion associated with soil moisture, to derive the slope safety factor and probability of failure with changes in moisture content by volume. In addition, this study method is discussed to represent slope failure risk index due to changes in soil moisture on topographic maps. The occurrence of a small slope failure was captured on June 4, 2021, from 2:00 a.m. to 3:00 a.m. The stability analysis of the experimental slope field showed slope failure probability of more than 60% at the slope failure time. Slope failure probabilities were greater than 70% when the moisture content by volume was greater than approximately 35%. Slope failure probabilities were greater than 70% when the moisture content by volume was greater than approximately 35%. In the analysis of the area around National Institute of Technology, Tokuyama College, the analysis results were mapped by using GIS. At 25% moisture content by volume, the safety factor became less than 1.5, and the slope failure probability began to increase significantly. Slope failure probability was rapidly increased when the safety factor approached 1.