A non-linear constitutive model for describing the mechanical behaviour of frozen ground and permafrost

The mechanical behaviour of frozen ground and permafrost is changing under the increasing variation of environmental and anthropogenic boundary conditions. This phenomenon affects many civil structures and infrastructures built in Polar and Alpine areas. Mathematical formulations able to capture the mechanical behaviour of frozen ground and permafrost with adherence to reality and a limited employment of technical resources and time appear crucial for the engineering design and retrofit of these structures. To address this challenge, this study presents a relatively simple elasto-plastic constitutive model for capturing the non-linear mechanical behaviour of frozen silt. The model is based on associated flow rules. It employs an elliptical yield surface and a parabolic yield surface for describing the volumetric mechanisms that characterise the modelled material, together with a parabolic yield surface for describing the deviatoric mechanism. Comparisons with experimental triaxial test results available in the literature highlight the suitability of the model to capture the non-linear mechanical response of frozen silt subjected to both low and high confining pressures. This result, together with the doable implicit consideration in the model of the effects induced by environmental boundary conditions such as temperature on the mechanical behaviour of the material, makes this tool attractive for simplified yet thorough analyses of frozen ground and permafrost-related problems.