不同温度梯度冻结深部黏土偏应力演变规律研究

 采用先冻结后K0固结(FC)的传统冻土试验方法进行4种不同温度梯度冻结深部黏土的加、卸荷三轴试验，研究不同温度梯度冻结深部黏土在加、卸荷过程中的偏应力增长速率及偏应力的衰减规律。结果表明：不同温度梯度冻结深部黏土加、卸荷过程中偏应力增长速率与均匀温度下的试验结果基本相同，均可用变换的Duncan- Chang双曲线模型进行拟合，但温度梯度对冻结深部黏土偏应力增长速率衰减影响程度远大于温度；温度梯度减弱冻结黏土偏应力增长速率，同时抑制其衰减程度，这种弱化效应在加、卸荷初期最为显著；相同轴向变形对应的偏应力随温度梯度增长而衰减的规律可以通过衰减因子A加以描述，A与温度梯度的之间的关系符合广义双曲线模型；卸荷过程明显增加了加、卸荷初期冻结黏土偏应力增长速率的衰减，且随温度梯度增长，卸荷过程对冻结深部黏土偏应力衰减幅度和衰减速率影响均大于加荷过程；不考虑冻结壁(冻土墙)冻土温度的非均匀性以及卸荷路径的影响将高估冻土强度。

RESEARCH ON DEVIATORIC STRESS VARIATION LAWS FOR DEEP FROZEN CLAY AT DIFFERENT TEMPERATURE GRADIENTS

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.