Rainfall-induced landslides in the southeastern part of the Republic of Korea

Some of the natural slopes in the southeastern part of the Republic of Korea, which encompasses an area of about 3324 km(2): have suffered rapid failures resulting from heavy rainfalls during the rainy season from June: to September, thus not only killing residents but also causing economic loss. Approximately 100 landslides have occurred since 1973 in the area; most of them are classified into mud and debris flows. Four typic:al cases, Moonhyondong, Janglimdong, Myongchonri, and Songdaeri are discussed in the paper, including physical and engineering properties. Based on the results of both field and laboratory investigation on the above mentioned cases, it was found out that all the slope failures had occurred in the areas composed of the colluvial soils, which were classified into CL, ML, and GC according to the Unified Soil Classification System, and having a slope angle greater than 8.5 degrees.