Abstract
Abstract. Most landslides in Korea are classified as shallow landslides with an average depth of less than 2 m. These shallow landslides are associated with the advance of a wetting front in the unsaturated soil due to rainfall infiltration, which results in an increase in water content and a reduction in the matric suction in the soil. Therefore, this study presents a modified equation of infinite slope stability analysis based on the concept of the saturation depth ratio to analyze the slope stability change associated with the rainfall on a slope. A rainfall infiltration test in unsaturated soil was performed using a column to develop an understanding of the effect of the saturation depth ratio following rainfall infiltration. The results indicated that the rainfall infiltration velocity due to the increase in rainfall in the soil layer was faster when the rainfall intensity increased. In addition, the rainfall infiltration velocity tends to decrease with increases in the unit weight of soil. The proposed model was applied to assess its feasibility and to develop a regional landslide susceptibility map using a geographic information system (GIS). For that purpose, spatial databases for input parameters were constructed and landslide locations were obtained. In order to validate the proposed approach, the results of the proposed approach were compared with the landslide inventory using a ROC (receiver operating characteristics) graph. In addition, the results of the proposed approach were compared with the previous approach used: a steady-state hydrological model. Consequently, the approach proposed in this study displayed satisfactory performance in classifying landslide susceptibility and showed better performance than the steady-state approach.
Highlights
Landslides in Korea, which are primarily caused by intense rainfall during the summer, are typically shallow landslides due to their shallow ( ≤ 2 m) failure planes
The true–positive rate (TPR) is the ratio of the number of true positive (TP) to the total number of positives, and the false–positive rate (FPR) is the ratio of the number of false positive (FP) to the total number of negatives. These two metrics were used to plot the receiver operating characteristics (ROC) graph, which is a two-dimensional graph in which the TPR is plotted on the y-axis and the FPR is plotted on the x axis
Since landslides in Korea are typically shallow landslides, which are related to rainfall infiltration, we have proposed a modified equation of infinite slope analysis by applying the concept of the saturation depth ratio to analyze the slope stability as a function of rainfall falling on a slope
Summary
Landslides in Korea, which are primarily caused by intense rainfall during the summer, are typically shallow landslides due to their shallow ( ≤ 2 m) failure planes. In the case of shallow landslides, these perched zones are typically caused by increases in volumetric water content and porewater pressure due to water infiltration from the surface This infiltration induces saturation of the soil at a certain depth and time. This study presents a landslide prediction method based on the wetting front, infiltration velocity and saturation depth ratio rather than a complex relationship between rainfall intensity and physical factors. Because the proposed method involves the relatively simple measurement of the wetting front, landslides can be predicted relatively based on the changes in the slope factor of safety with time as a function of the rainfall infiltration
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