ABSTRACT
Heavy rainfall attacked Boso Peninsula, Chiba, Japan in September 1971, and caused slope failures at Omigawa area. In order to examine the cause and initiation of such shallow-depth soil failures due to rainfall, a series of tests are conducted on soil samples recovered from the Omigawa site. Isotropically consolidated and anisotropically consolidated undrained triaxial compression tests are performed. The characteristics of undrained stress paths of the samples, which are anisotropically consolidated to different values of a principal stress ratio Kc (= σ1’/σ3’), are examined in terms of the peak shear stress and the shear stress at steady states. Constant shear drained tests, which duplicate the hydrologic response of soils subject to rainfall, are also performed on anisotropically consolidated samples with different values of Kc. With these sets of experimental data, the influence of the hydrologie response of soils on the initiation of soil failures is addressed, with special reference to drained initiation and undrained mobilization of sloping soil masses.
