ABSTRACT
In the southern part of Kyushu Island, Japan, slope failures often occur due to heavy rainfalls in the rainy season (from June to September). Most of these slope failures are classified as the surface slip failure whose depth is commonly less than 1m. The phase change of pore fluid due to temperature and pressure is deeply related to the occurrence of slope failure due to the change in effective stress in unsaturated soil. In this paper the phase change of pore fluid in unsaturated soil with the change of temperature, humidity and pressure in atmosphere is investigated to make clear the mechanism of surface slip. The numerical model is proposed to simulate the seepage behavior in unsaturated soil. Then the numerical experiment is carried out by the proposed numerical model. The results are compared with the data obtained by the field measuring of suction.
