Thermal Characteristics of Unsaturated Soils

This chapter suggests a hybrid SPH-FDM boundary method for analyzing thermal processes in homogeneous media with discontinuous interfaces. The smoothed particle hydrodynamics (SPH) is employed in the interior computational domain, while the finite difference method (FDM) is utilized for function approximation near the boundary. The combined methodology ensures second-order accuracy across the entire solution domain and effectively handles challenges posed by second-type (i.e., Neumann) and third-type (i.e., Robin) boundary conditions. The SPH-FDM boundary method is particularly suited for solving heat conduction problems of homogeneous media, including scenarios with discontinuous interfaces and phase transition boundaries moving during material solidification. Furthermore, the nonlinear transport equations of heat-moisture-contaminant are developed to investigate the thermally-driven migration of moisture and the transport of heavy metal pollutants. A novel soil–water characteristic curve (i.e., SWCC) incorporating hysteresis is introduced, which is validated through one-dimensional column test results. This chapter explores the dynamic process of moisture movement under thermal cycling conditions and examines the behavior of heavy metal contaminant migration within the medium.