A simple non-isothermal-mechanical interface constitutive model and its application on the geotextile and soil interface considering freezing temperature

A non-isothermal constitutive model is proposed to capture the shear response of soil–geotextile interfaces (SGIs) at subzero temperature conditions. The model incorporates temperature-dependent evolution of the void ratio, ice bonding effects, and normal stiffness response within the framework of critical state soil mechanics (CSSM). A total of 12 physically parameters are introduced, most of which can be calibrated using standard laboratory tests. The model is validated against a wide range of experimental data from Constant Normal Stiffness (CNS) direct shear tests conducted at temperatures ranging from 0 °C to −8°C, encompassing four distinct initial normal stresses and four varied stiffness levels. The findings demonstrate that the model accurately captures the key mechanical features of frozen and unfrozen SGIs, including the interfacial strain-hardening or softening behavior, temperature-dependent shear strength with a coefficient of determination greater than 0.88, and volumetric deformation with a coefficient of determination greater than 0.91. It is imperative to note that the proposed model has the capacity to demonstrate the manner in which freezing temperatures exert influence on the critical void ratio. A decline of 10.21% in the critical void ratio was observed as the temperature underwent a drop from positive to −8°C, an effect that conventional interface formulations are incapable of representing. By integrating this mechanism within a unified and physically consistent framework, the model provides a reliable and applicable tool for evaluating soil–geotextile interface performance in geotechnical engineering projects within cold regions.