Abstract：In order to determine the behaviour of stress-strain of frozen soil in the deep alluvium，the triaxial unloading shear tests at temperature of －2 ℃，－5 ℃，－7 ℃，－10 ℃ and a confining pressure of 1～5 MPa were performed in cold laboratory after specimen experienced K0 consolidation. The testig results indicate that the radial unloading stress-strain curves can be divided into three different stages，that is，elastic stage，strain-hardening stage and the yield stage or flow stage. There is no displacement at a lower negative temperature and somewhat higher initial confining pressure，even if the confining pressure is removed to zero. The failure strength increases with the initial confining pressure increasing and the temperature decreasing. From the stress-strain equation of tested frozen soil，the ultimate principal stress difference (s1－s3)ult and the initial tangent modulus Ei can be obtained. The initial tangent modulus Ei does not depend on the initial confining pressure and is close to a constant at a state of lower negative temperature and higher initial confining pressure. The ultimate principal stress difference (s1－s3)ult increases linearly with increment of initial confining pressure and the role of temperature is not obvious at lower initial confining pressure. However，with the confining pressure increasing，it becomes pronounced gradually.
