A micromechanics-based elastoplastic constitutive model for frozen sands based on homogenization theory

A micromechanics-based constitutive model is formulated to describe the nonlinear elastoplastic behaviors of frozen sands. In the model, frozen soils are conceptualized as two-phase materials, in which the first phase is regarded as virgin/undamaged frozen soil specimen including the components of soil particles, ice crystals, and partial water with elastic-brittle behaviors (bonded elements), and the second phase is treated as fully damaged soil sample including soil particles and unfrozen water with elastoplastic behaviors (frictional elements). The interactions between bonded elements and frictional elements are well considered in the representative volume element within the framework of continuum micromechanics and homogenization theory. Moreover, the non-uniform distribution of strain is taken into account and the breakage process is considered due to the structural degradation/loss of ice crystals in the representative volume element. It is found that the ice crystals are gradually breaking up and then melting into unfrozen water with the increase of external loads, so at the moment the bonded elements are considered to transform into frictional elements and then both elements bear the external loads collectively. A novel binary-medium constitutive model is established by the Mori-Tanaka technique and then validated by two groups of laboratory tests about frozen soils and unfrozen sands under conventional triaxial compression conditions. Eventually, the predictions demonstrate that the theoretical calibrations are well in agreement with the available experimental stress-strain responses.