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Abstract The loading and unloading triaxial tests were carried out on the deep frozen clay at four temperature gradients using the method of freezing before K0 consolidation，and attenuation law for deviatoric stress as well as deviatoric stress increasing rates in the process of loading and unloading was investigated. The results show that the increasing rate of deviatoric stress at different temperature gradients is similar to that in the homogeneous temperature fields，which can be fitted by modified Duncan-Chang hyperbolic model. However，the influence of temperature gradients on the deviatoric stress is larger than that of the temperature. The most obvious regularity observed in the initial stage of loading and unloading process is that both increasing rates of deviatoric stress and attenuation degree are weakened by the temperature gradients. The attenuation law for deviatoric stress under the same axial deformation can be described by the attenuation factor A；and the relationship between A and temperature gradients agrees well with that of the generalized hyperbolic model. The unloading process enhances the attenuation trend of deviatoric stress increasing rates for deep frozen clay at the initial stage both in loading and unloading processes；and the influence of unloading process on the attenuation rates along with the amplitude of the deviatoric stress is obviously larger than that of the loading process as the temperature gradients increase. The strength of deep frozen clay would be overestimated if the effects of non-homogeneous temperature fields and unloading path for the frozen walls are neglected.
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Received: 31 December 2008
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