- Abstract. A series of consolidated undrained triaxial tests have been undertaken on material from the Yamauchi landslide in northern Kyushu. The samples were obtained from two specially drilled boreholes. Both the logging and the geotechnical test results indicate a wide variation which is probably attributable to the differing degree of weathering/ hydrothermal alternation. Two types of stress strain and pore-water pressure responses were observed during the test. Two failure modes were identified–plastic and semiplastic.