Anisotropic and Noncoaxial Behavior of K0-Consolidated Soft Clays under Stress Paths with Principal Stress Rotation

During embankment construction, the deformation behavior of soil will vary with increasing fill height because the principal stresses applied on soil elements in K0-consolidated subsoil will rotate. In this study, a series of tests is conducted on natural K0-consolidated Wenzhou soft clay in a hollow cylinder apparatus (HCA) to clarify the response of soils during principal stress rotation. Specimens are sheared with different angles of inclination (beta) with respect to the vertical direction in undrained conditions. The stress-strain relationship, pore-water pressure evolution, shear strength, and noncoaxiality are discussed. The test results show that the development of strain components (vertical, radial, circumferential, and shear strains) is clearly distinct during orientational shearing. The coupling action of the axial and shear stresses results in different evolution processes of the excess pore-water pressure in tests with different beta values. Under a critical state, the elliptical and asymmetric effective stress strength envelope conclusively shows a strong undrained strength anisotropy. In addition, the different noncoaxial angles between the major principal strain increment direction and corresponding major principal stress direction at failure is revealed, and the noncoaxial behavior is dependent on the beta value.