Table 5. Summary of the impact of... | Emerald Publishing

Table 5.

Summary of the impact of heterogeneity in the model configuration

Concept	Parameter	Remark
Hydraulic	Intrinsic permeability	Intrinsic permeability is a function of porosity (Equation 5). Porosity is not constant; it varies throughout the hydration stages. Specific sections of the sample experienced increases or decreases in porosity due to swelling and compression during the saturation process.
	Porosity-dependent WRC	A porosity-dependent WRC was utilised for intact clay, where there was no significant increase in gas permeability. Air entry pressure (⁠ $P_{0}$ ⁠) (Equation 2) and shape parameter (⁠ $ψ)$ (Equation 3) are porosity dependent.
	Strain-dependent WRC	Air entry pressure depends on strain level (Equation 4) and characteristics of the apertures (Equation 9). It is used for the sections (Figure 3) where there is a significant increase in permeability because of the development of dilatant gas flow pathways.
Mechanic	Swelling pressure	Variability in dry density leads to different levels of swelling pressure. Varying compaction levels result in distinct magnitudes of swelling pressures (Equation 23). The magnitude of gas breakthrough (BT) pressure is associated with the magnitude of the swelling pressure.
Gas	Kozenys law	Gas matrix permeability (intrinsic) as well as water matrix permeability depend on porosity (Equation 5).
	Cubic law	In the cubic law (Equation 9), gas permeability depends on strain level and characteristics of the aperture itself. Two sets of k_Cubic have been proposed.
	Gas diffusion	Diffusive fluxes are controlled by porosity following Equation 13. In zones with higher porosity, diffusion will be more pronounced until gas breakthrough occurs.

Concept	Parameter	Remark
Hydraulic	Intrinsic permeability	Intrinsic permeability is a function of porosity (Equation 5). Porosity is not constant; it varies throughout the hydration stages. Specific sections of the sample experienced increases or decreases in porosity due to swelling and compression during the saturation process.
	Porosity-dependent WRC	A porosity-dependent WRC was utilised for intact clay, where there was no significant increase in gas permeability. Air entry pressure ( $P_{0}$ ) (Equation 2) and shape parameter ( $ψ)$ (Equation 3) are porosity dependent.
	Strain-dependent WRC	Air entry pressure depends on strain level (Equation 4) and characteristics of the apertures (Equation 9). It is used for the sections (Figure 3) where there is a significant increase in permeability because of the development of dilatant gas flow pathways.
Mechanic	Swelling pressure	Variability in dry density leads to different levels of swelling pressure. Varying compaction levels result in distinct magnitudes of swelling pressures (Equation 23). The magnitude of gas breakthrough (BT) pressure is associated with the magnitude of the swelling pressure.
Gas	Kozenys law	Gas matrix permeability (intrinsic) as well as water matrix permeability depend on porosity (Equation 5).
	Cubic law	In the cubic law (Equation 9), gas permeability depends on strain level and characteristics of the aperture itself. Two sets of k_Cubic have been proposed.
	Gas diffusion	Diffusive fluxes are controlled by porosity following Equation 13. In zones with higher porosity, diffusion will be more pronounced until gas breakthrough occurs.