A multiphase model developed for mesoscopic heat and mass transfer in thawing frozen soil based on lattice Boltzmann method

Abstract

Subgrade engineering in cold region collapsed and settled under the influence of global warming, this was mainly due to the thawing frozen soil. The heat and mass transfers in thawing frozen soils are generally described with continuity equations on the macroscopic scale. However, the processes of ice melting and water migration in soil were rarely described on the mesoscopic scale. In this study, a multiphase pseudo-potential model with enthalpy-based module was developed based on lattice Boltzmann method to predict the distributions of temperature and water content in the thawing process of frozen soil. The force source terms in pseudo-potential model were given as adhesive force, cohesive force, temperature drive force and bulk force to describe the interaction between multiple components in thawing process, and the enthalpy-based module was employed to realize the process of phase transition in soil. The complex initial conditions of thawing process were measured and then set in simulation for the first time. The results showed that as compared with the measured soil temperatures and water contents at different top soil temperature (5 °C and 10 °C) and times (0, 12, and 36 h), the relative errors of model were 0.01 % ∼ 0.72 % and 0.10 % ∼ 19.31 % for the soil temperatures and water contents, respectively. Further, the developed pseudo-potential model can also be used to detail the mesoscopic heat and mass transfers in thawing soils.