Enhanced permafrost creep model– user manual and documentation

The mechanical behavior of frozen soils is one of the challenging topics in the field of geotechnical engineering. The behavior of frozen soils is strongly affected by the amount of ice, while on the other hand, the amount of ice depends on the temperature and the applied mechanical stresses. The influence of ice content and temperature on the mechanical behavior and the coupling effects on the reverse direction can be mentioned as the main difference between the behavior of frozen and unfrozen soils. In the light of this difference, an elastoplastic constitutive model for describing the stress-strain behavior of saturated frozen soils is proposed. By dividing the total stress into fluid pressure and solid phase stress, in addition to consideration of the cryogenic suction, the model is formulated within the framework of two-stress state variables. The proposed model is able to represent many of fundamental features of the behavior of frozen soils such as ice segregation phenomenon and strength weakening due to pressure melting. In unfrozen state the model becomes a conventional critical state model. On the other hand, considering the highly rate dependent behavior of ice, highly rate sensitive behavior of frozen soil is expected. Thus, creep deformation of frozen soils, specifically in permafrost, is of great importance. So, the above mentioned elastic-plastic model is developed to an elastic-viscoplastic model to be able to simulate the rate effect and its consequent creep deformation. Typical predictions of the model for simulating the characteristic trends of the frozen soil behavior is described qualitatively. Model predictions are also compared with the available test results and reasonable agreement is achieved.