An elastic-viscoplastic model for saturated frozen soils

Abstract

From the material science point of view, saturated frozen soil is a natural particulate composite, composed of solid grains, ice and unfrozen water. The mechanical behaviour of such a material is strongly affected by the amount of ice. The amount of ice depends on the temperature and the applied mechanical stresses. The influence of ice content and temperature on the mechanical behaviour and the coupling effects on the reverse direction can be mentioned as the main difference between frozen and unfrozen soils. On the other hand, considering the highly rate-dependent behaviour of ice, rate-sensitive behaviour of frozen soils is expected. This rate dependency is also affected by the amount of ice existed in the composite. In the light of these differences, an elastic-viscoplastic constitutive model for describing the mechanical behaviour 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 rate-dependent behaviour is considered using the so-called over-stress method. In unfrozen state, the model becomes a conventional elastic-viscoplastic critical state model. Model predictions are compared with the available test results and reasonable agreement is achieved.