Geotechnical and Geoacoustic Properties of Volcanic Soil in Ulleung Island, East Sea of Korea

The unique material properties of volcanic soils may cause stability problems within the soil. However, few studies have examined the composition and engineering characteristics of volcanic soils below sea level. The objective of this study is to investigate the engineering properties of volcanic soils sampled from Ulleung Island. For the volcanic soils, the index properties, particle geometry, and mineralogy are analyzed in the laboratory. An oedometer cell incorporated with bender elements is used to measure the small-strain stiffness and compressibility of the volcanic soils. To obtain the large strain strength parameter and hydraulic conductivity of the volcanic soils, direct shear tests, and constant head permeability tests are performed. The experimental results show that the basic index properties of volcanic soils sampled from Ulleung Island are very similar to the values of previously published reference data: poorly graded with a median grain size, very low fine fraction, and slightly high specific gravity. In addition, the particle surface texture features and elementary analysis indicates a dark grain color, small pits or holes in the grain, and relatively low SiO₂ and high Fe₂O₃ contents. The friction angle of the volcanic soils depends on the relative density, and the hydraulic conductivity varies according to e³/(1 + e) and D₁₀². The characterization of the electrical properties in Ulleung Island needs to be conducted with caution due to the high Fe₂O₃ content in the volcanic soils.