Abstract To study long-term strength characteristics under complex stress states, a series of hollow cylinder creep tests were conducted on frozen clay under different stress levels at a temperature of −6 °C. Experimental results showed that the creep characteristics of frozen clay were significantly affected by the mean principal stress and the intermediate principal stress coefficient. Most generalized shear creep curves of frozen clay presented typical non-attenuation creep under axial load and torque. A long-term strength criterion for frozen soil, exhibiting the strength characteristics of multiple stress components under complex stress states, was obtained based on activation energy theory. In addition, a modified elliptical function and a generalized nonlinear strength theory (GNST) were introduced to describe the evolution of the strength envelope with time. Finally, a new strength criterion for frozen clay in three-dimensional principal stress space, considering the effect of time, was established by combining the modified elliptical equation and the GNST shape function. The proposed strength criterion has great significance for predicting the strength characteristics of frozen clay under complex stress states.

中文翻译：

---

复杂应力状态下冻结粘土的长期强度准则

摘要 为研究复杂应力状态下的长期强度特性，在-6 °C温度下，对不同应力水平的冷冻粘土进行了一系列空心圆柱蠕变试验。实验结果表明，平均主应力和中间主应力系数显着影响冻结粘土的蠕变特性。冻结粘土的大多数广义剪切蠕变曲线在轴向载荷和扭矩下呈现出典型的非衰减蠕变。基于活化能理论，得到了在复杂应力状态下表现出多应力分量强度特征的冻土长期强度准则。此外，引入了改进的椭圆函数和广义非线性强度理论 (GNST) 来描述强度包络随时间的演变。最后，结合修正椭圆方程和GNST形函数，建立了考虑时间影响的三维主应力空间冻结黏土强度新准则。提出的强度准则对于预测复杂应力状态下冻结粘土的强度特性具有重要意义。