Frozen-ground-fem: A practical and open Python 3 package for thermo-hydro-mechanical coupled modelling of soils in cold regions

In cold regions, where soils are subjected to recurrent freeze–thaw cycles, frost heave and thaw-induced settlement are among the leading causes of ground deformation and infrastructure failure. This paper presents frozen-ground-fem , an open-source Python 3 package for modelling thermo-hydro-mechanical (THM) processes in frozen and thawing soils. The package enables one-dimensional large-strain finite element simulations that capture complex soil behaviours under freeze–thaw cycles, including temperature-dependent hydraulic conductivity, evolving void ratios, residual stresses, and settlement due to thaw consolidation. Designed with modularity and transparency in mind, frozen-ground-fem organizes code around reusable object-oriented classes for materials, elements, meshes, and boundary conditions. It supports thermal, consolidation, and coupled THM simulations using adaptive implicit time integration with iterative correction. The repository includes examples, unit tests, and detailed documentation following NumPy and PEP-8 conventions. Through benchmark scripts and interface design, this package provides a reproducible and extensible platform for researchers and engineers to simulate freeze-thaw soil deformation and assess the resilience of cold-region infrastructure under changing climatic conditions.