Developing continuum‐scale models for water flow in frozen soil

Abstract

A widely accepted continuum‐scale model capable of accounting for pore‐scale processes reasonably remains elusive in the study of water flow through frozen soil, particularly within geo‐environmental science and geotechnical engineering applications. The development of such models for frozen soil lags significantly behind that for unfrozen soil, a disparity primarily attributable to inherent complexities in geometrical configuration and multiple driving forces. In this Technical Review, we first discuss historical phenomenological models for water flow in frozen soil. Subsequently, to address these complexities, feasible approaches for constructing a water flow model within a representative elementary volume of frozen porous media are analyzed through two distinct theoretical frameworks: micromechanics (to resolve geometrical heterogeneity) and thermodynamics (to account for multiple driving forces). Recognizing the limitations in these approaches, we adopt an Eyring‐form function to describe water flow. Within this statistically informed model, two key state variables, namely the energy of activation and effective temperature, which incorporate information about both driving forces and microstructure associated to internal geometrical measures, can be determined via nonequilibrium thermodynamic analysis of subsystems involving physical processes with widely separated scales. Finally, these modeling paradigms are compared, highlighting their respective theoretical bases (or restrictions) and characteristic features.