A study of Triaxial creep test and yield criterion of artificial frozen soil under unloading stress paths

- Strength is one of the main factors influencing the creep of artificial frozen soil at different freezing temperatures.
- The characteristics of the stress-strain curve of frozen soil at low temperature can be described with viscous-elastic-plastic deformation law.
- The creep strength envelope of artificial frozen soil under high confining pressure can be fitted with the modified Zienkiewicz-Pande parabolic strength criterion.

The triaxial shear test method with consolidation, low temperature freezing, and radial unloading was applied to simulate the mechanics process of the unloading process of deep artificial frozen clay during the excavation of a freezing mine shaft. The triaxial unloading creep test on artificial frozen clay showed that the first and second stages of the creep deformation occur only when the deviatoric stress is low and that creep deformation accounts for > 70% of the total deformation. The third stage of creep deformation occurs only when the stress level exceeds a certain critical value, and is characterized by the frozen soil undergoing a large plastic flow, with breaking for 3 to 5 h. The creep strength envelope at low confining pressure is linear, in compliance with the Mohr-Coulomb strength criterion, and the critical stress value in the third stage can be described with the improved Zienkiewicz-Pande parabolic yield criterion.