Modelling of Freeze‐Thaw‐Induced Plastic Behaviour in Compacted Soil

ABSTRACT Freeze‐thaw cycles can induce irreversible deformation in compacted soils in cold regions, thereby reducing their durability. This study develops a new elasto‐plastic partially frozen model ( EPPF ‐Model) within the framework of critical state soil mechanics. A Terzaghi‐like effective stress and an ice saturation degree were incorporated in the model to account for the effects of ice content on mechanical properties. Simulation results under triaxial compression at a confining pressure of 50 kPa show that the EPPF ‐Model well demonstrates the typical relationship between strength increase and rising ice content, which reveals the strength enhancement mechanism of ice contribution in compacted soils. A coupled thermo–hydro–mechanical (THM) finite element model was developed within the framework of poromechanics, in which the mechanical behaviour is governed by the EPPF ‐Model. The formulation integrates the balance equations of momentum, water mass, and heat with the physics of in‐pore water phase change. The finite element implementation was validated against a benchmark of a freezing poroelastic soil layer. Simulated results demonstrate that the THM model can reproduce the typical cyclic shrinkage and swelling deformation phases, as well as the gradual increase in net swelling during freeze‐thaw cycle tests. The proposed approach provides a reliable computational tool for predicting the freeze‐thaw behaviour of compacted soil, supporting improved design and maintenance in cold regions.