Shear behavior of ice-frozen soil interface: Experiments and elastoplastic modeling

Ice lenses and their unique patterns formed by the amount and distribution of ice within sediments and rock within various geologic and climate environments, or cryostructures, are ubiquitous in permafrost. The mechanical characteristics and deformation properties of the individual components (i.e., ice lenses, frozen soil) and the interaction between them control the overall behavior of permafrost. Unlike ice lenses and frozen soil, the mechanical behavior of the ice lenses-frozen soil interface is less studied. This article presents the results from a series of cryogenic direct shear tests and an elastoplastic model based on the damage at the ice-frozen soil interface. The tests were conducted under different temperatures (i.e., -3, -2, and -1 & DEG;C), normal stresses (i.e., 50, 100, and 200 kPa), and initial saturations (i.e., 55, 67, 77, 96, and 100%), respectively. The test results show that under the same normal stress and initial saturation, the shear stress curves transit from strain-softening to strain-hardening as the temperature increases. The volumetric deformation initially contracts and then dilates as the shear displacement increases. Further, rheological elements are introduced to explain the various components of the interface's mechanical behavior. An elastoplastic damage constitutive model is established to describe the overall shear behavior of the ice-frozen soil interface during the entire shearing process. The parameters in the model are clearly defined with physical meanings and are easy to determine. Finally, the proposed model is applied to predict the experimental data. Comparison of the model results with experimental data demonstrates that the proposed model can well capture the shear behavior of the ice-frozen soil interface.