Geotechnical Properties of Landslide Sites in Korea with Differing Geology

The goal of this study is to find out the relationship between geotechnical properties and landslide occurrence in areas with differing geology in Korea. The soil properties were measured in three study areas (Jangheung, Sangju and Pohang) which are underlain by gneiss, granite and sedimentary rock, respectively. Many landslides occurred in these areas during the rainy season. To investigate the factors that influence the landslides, a landslide survey was made, and a series of laboratory soil tests were carried out. The results of soil tests show that the average porosity of the soils originated from the gneiss of Jangheung and the granite of Sangju is greater than that of soils originated from the sedimentary rocks of Pohang. The average coefficient of permeability of the soils originating from the granite of Sangju is higher than that of soils from the gneiss of Jangheung and the sedimentary rocks of Pohang. The average coefficient of permeability of soils obtained from the landslide sites is greater than that of soils obtained from landslide-free sites in the same geology. The average shear strengths of soils obtained from the landslide sites are smaller than those of soils obtained from the landslide-free sites. It is confirmed that soils with low shear strength and high permeability are especially vulnerable to landslide occurrence.