GRAIN SIZE AND PORE SIZE DISTRIBUTIONS OF THE SLIP SURFACE SOIL AT NORTH KYUSHU LANDSLIDE DISASTER SITE ON JULY, 2017

Many landslides induced by heavy rainfall have caused. The north Kyushu landslide disaster on July 5-6^th 2017 by heavy rainfall exerted serious damages to many houses, agricultural lands and human life. This disaster was triggered by the heavy down pour of approximately 600 mm/2 days. Many landslides in strong weathered layer were caused along many rivers in this site. The main geology of the site is in the belt of Sangun metamorphic rock and granite. The authors investigated soil properties of the slip surface soil collected by a main scarp of landslide. The grain size analysis carried out by a laser diffraction (MS 3000, Malvern Panalytical Instruments, UK). The pore size distribution analyzed by a mercury porosimetry (PoreMaster 60GT, Quantachrome Instuments, USA). The finer shift of the slip surface soil in the data of grain size was found in comparison to the no-slip surface soil. The coarser peak of pore diameter distribution for the no-slip surface soil was obtained. This difference reflects the shear zone development under vertical stress condition. The authors sincerely acknowledge the support provided by Fukuoka prefecture. the This work was supported by JSPS KAKENHI Grant Number JP 18K14546.