Abstract
This paper describes swelling and shear characteristics of a clay in a slip surface during an increase in pore water pressure due to rainfall, snow melting and so on. A saturated clay specimen before failure was subjected to such the increase in pore water pressure under a constant shear stress using triaxial slice shear test apparatus. As the pore water pressure inside the specimen is increased monotonously, effective stress path moves toward a critical state line. Shear strength mobilized on the slip surface decreases along the critical state line, simultaneously. During the increase in pore water pressure, relationships between an increase in void ratio and normalized effective normal stress or shear strength are determined by swelling index, respectively. Safety factor at first-time sliding can be approximately estimated by the changes in void ratio or pore water pressure.
