Abstract: To study the strength and deformation characteristics of frozen clay under complex stress path, a series of directional shear tests on saturated frozen clay is conducted under different negative temperature conditions by using dynamic hollow cylinder testing apparatus of frozen soils (FHCA-300). Stress-strain curves of the axial and torsional shear components for frozen clay are analyzed under different shear directions. The shear deformation, anisotropy and shear band characteristics are discussed. And the effects of temperature, angle of major principal stress direction, mean principal stress and coefficient of intermediate principal stress in the strength and deformation behaviors of frozen clay are explored. The test results indicate that the value of the mean principal stress p has a significant effect on the stress-strain curves of frozen clay. When p=4.5 MPa, the frozen clay has a major shear strength and this stress value (the mean principal stress) may be the critical value of pressure melting. The anisotropy of frozen clay may be induced by the change of major principal stress direction. Shear strength decreases versus the increase of angle of major principal stress direction. The axial strength decreases with the increase of the coefficient of intermediate principal stress, but the effect of the coefficient on the shear strength is neglect. With the decrease of temperature, the strength of frozen clay increases gradually. Meanwhile, the samples produce brittle failure, and a shear failure surface appears and develops. The shear strength of frozen clay depends mainly on the cementation force between soils and ice particles.

Key words: frozen clay, dynamic hollow cylinder testing system, complex stress path, anisotropy, shear band