Liquid‒Gas Seepage Constitutive Models for Skeleton-Degradable Soils

This chapter elucidates the properties of liquid‒gas flows and develops a dual-porosity flow constitutive model for skeleton-degradable soils. The degradation of the soil skeleton significantly alters soil pore characteristics such as porosity, pore size, and tortuosity, affecting liquid and gas seepage properties. Considering MSW as an example, this chapter discusses its intrinsic permeability, water retention curve, and relative permeability. The effects of compression, degradation, and anisotropy on the flow characteristics of MSW are examined. To account for the heterogeneity of porous media such as MSW, a dual-porosity flow model is developed for developing new water retention curve and to analyze two-phase flow. Finally, the evolution of pore water and pore gas pressures in HFWC and LFWC MSW landfills is analyzed and compared, revealing faster saturation increments and higher pore gas pressures in HFWC landfills compared to those in LFWC MSW landfills. This comprehensive summary offers valuable insights into the dynamic behaviors of liquid and gas flows in skeleton-degradable soils.