Multi-field coupled model for solid-phase degradable soils and its numerical implementation using finite volume method

The internal interaction of solid-phase degradable soils is extremely complex, and analysis of its hydraulic- mechanical-thermal-chemical multi-field coupled behaviors is of great significance for analyzing the related engineering problems. Based on the basic theory of porous media, a multi-field coupled model is developed by incorporating the mass, momentum and energy conservation of the degradable soils characterized by a solid-liquid-gas three-phase system. The coupled model considers the degradation phase transition, liquid-gas migration, skeleton deformation and heat transfer. By selecting the liquid phase pressure, gas phase pressure, mass fraction of gas components, liquid solute concentration, temperature, skeleton displacement and porosity as the basically unknown variables, the finite volume method is used to numerically discretize the governing equations for the established coupled model, and sequentially the solving method is adopted to iteratively solve the coupled model. In addition, the corresponding numerical solver is developed. The simulations of sand column drainage tests, solute migration and heat transfer in porous media, and degradable municipal solid waste experiments are conducted to verify the correctness of the coupled model and the numerical solver. The model and program will help to enhance the understanding of the derivation of the governing equations, the determination of constitutive relations and the numerical implementation for the multi-field coupled model for the degradable soil. It also provides a basis for the development of multi-field coupled model of related degradable soils.