Physical and Chemical Properties of Volcanic Ejecta Produced by the Eruption of Mt. Kirishima Shinmoe-dake, Japan -A Case Study After the Explosive Eruption on March 25, 2018-

The purpose of this study was to clarify the physical and chemical properties of volcanic ejecta that fell after the explosive eruption on March 25, 2018 at Shinmoe-dake. In order to investigate the infiltration capacity, which is one of the physical properties of volcanic ejecta, plots were set up on the outer forest plain, the forest plain, and the forest talus, and a cylindrical frame test was conducted with reference to the method of Takeshita (2011). In addition, soil samples were collected at the three locations where the cylindrical frame test was conducted. The final infiltration capacity of 38-92 mm / h appeared lower in the forest talus than in the forest plain. It is considered that this is due to the small particle size distribution of 0.1 mm or more, regardless of the particle size of the silt / clay particle size classification. When the chemical properties of the collected volcanic ejecta were examined, Ca and SO4 were contained at high values. Since these compounds become the source of gypsum that reduces infiltration capacity when they react with water, it has become clear that they have the potential to contribute to the generation of debris-flow as a chemical property.