温度梯度冻土蠕变变形规律和非均质特征

采用K₀DCGF（K₀固结—保持荷载冻结—形成温度梯度—再试验）方法,开展不同温度梯度冻结饱和黏土三轴蠕变试验,研究冻土蠕变变形规律和温度梯度诱导的冻土非均质特征。结果表明：K₀DCGF模式中温度梯度冻结饱和黏土蠕变曲线由瞬时蠕变、衰减蠕变、稳定蠕变和加速蠕变4个阶段组成；温度梯度冻土径向蠕变速率小于轴向蠕变速率；温度梯度冻土最小轴向蠕变速率与蠕变应力之间满足指数函数关系,而长期强度极限与蠕变破坏时间之间则满足对数函数关系；梯度温度冻结过程中的水分场重分布和试验后冻土变形的非均匀分布是K₀DCGF蠕变试验中“温度梯度诱导的冻土非均质性”的重要体现；蠕变试验后温度梯度冻土冷端含水量最高,密实度最大；蠕变试验后温度梯度冻土宏观径向变形/试样高度沿试样高度方向分布随蠕变应力增加由先增加后降低规律逐步演化为持续增加规律,这一现象与冻土初始瞬时蠕变速率密切相关。

Creep deformation and heterogeneous characteristics for frozen soils with thermal gradient

Triaxial creep tests on frozen clay are conducted by using the K₀DCGF (K₀ consolidation, freezing with non-uniform temperature under loading) method under various thermal gradients. The creep deformation and heterogeneous characteristics of the frozen clay with thermal gradient are investigated. The test results indicate that the frozen saturated clay with thermal gradient presents brittle characteristics in creep tests, and the creep curves are composed of transient creep stage, attenuation creep stage and accelerated creep stage. The radial creep rate is smaller than the axial one. The relationship between the minimum axial creep rate and the creep stress can be expressed by the exponential equation, while that between the long-term strength and the creep failure time can be described by the logarithmic equation. The redistribution of the water content before tests and the non-uniform deformation distribution after tests are the specific form of the heterogeneous characteristics caused by the thermal gradient. The water content and the density at the lower temperature end are the largest. The ratio between the radial deformation and the specimen height increases as the specimen height increases, and it decreases as the specimen height increases further under lower creep stress. However, the ratio between the radial deformation and the specimen height presents a continuous increase trend as the specimen height increases under higher creep stress. This phenomenon is related to the initial transient creep rate.