Analyses of behavior of stress–strain of frozen Lanzhou loess subjected to K0 consolidation

To determine the behavior of stress–strain of frozen soil in the deep alluvium, the axial loading or radial unloading triaxial shear tests were performed at temperature of −2, −5, −7 and −10 °C under the initial confining pressure of 1–5 MPa after specimens of Lanzhou loess experienced K0 consolidation. Results indicate that both the axial loading and the radial unloading stress–strain curves can be divided into three stages: the elastic stage, the strain-hardening stage, and the yield stage (or the flow stage). The failure strength was increasing with increase of initial confining pressure and decrease of temperature. For the radial unloading triaxial test, there is no displacement at a lower negative temperature and somehow a higher initial confining pressure, even if the confining pressure is removed to zero. The ultimate deviator stress and the initial tangent modulus can be obtained from the stress–strain equation established by tested frozen soil. It is found that the initial tangent modulus determined by the axial loading tests increased linearly with an increase of the initial confining pressure but was not pronounced to temperature. Differentially, the ultimate deviator stress was linearly increasing with increase of the initial confining pressure and decreasing with increase of the temperature. The unloading triaxial test shows that the initial tangent modulus was close to a constant at a state of lower negative temperature and higher initial confining pressure, without a relation to the initial confining pressure. The ultimate deviator stress was linearly increasing with increase of the initial confining pressure, while the temperature plays a less obvious role at a condition of lower initial confining pressure. In contrast, the effect of temperature was gradually pronounced with increase of the initial confining pressure.