Dual‐permeability model for flow in shrinking soil with dominant horizontal deformation

Abstract

In this study, a dual‐permeability approach is discussed for modeling preferential flow in shrinking soils by accounting for shrinking effects on macropore and matrix domain hydraulic properties. Conceptually, the soil is treated as a dual‐permeability bulk porous medium consisting of two dynamic interacting pore domains: (1) the fracture (from shrinkage) pore domain and (2) the aggregate (interparticles plus structural) or matrix pore domain. The model assumes that the swell‐shrink dynamics is represented by the inversely proportional volume changes of the fracture and matrix domains, while the overall porosity of the total soil, and hence the layer thickness, remains constant. This assumption can be justified for soils with dominant horizontal soil deformation in the swelling‐shrinkage process (shrinkage geometry factor,rs> 3). The swell‐shrink dynamics was included in a one‐dimensional dual‐permeability model in which water flow in both domains was described with the Richards' equation. Swell‐shrink dynamics was incorporated in the model partly by changing the coupled domain‐specific hydraulic properties according to the shrinkage characteristics of the matrix and partly by allowing the fractional contribution of the two domains to change with the pressure head. As a first step, the hysteresis in the swell‐shrink dynamics was not included. We also assumed that the aggregate behavior and its hydraulic properties depend only on the average aggregate water content and not on its internal real distribution. The model proved, describing successfully effects of shrinkage on the spatial and temporal evolution of water contents measured in a silty loam soil in the field.

Soil–aquifer phenomena affecting groundwater under vertisols: a review

“…Coppola et al (2012) took another step forward in modeling flow and transport in cracking clays by also introducing cracking dynamics (adopting formulation of Chertkov, 2005) into a dualpermeability flow and transport model.…”

Contribution to Numerical Modeling of Water Flow in Variably Saturated, Heterogeneous Porous Media

“…Whereas the dual-permeability model assumes that the porous medium consists of two overlapping pore domains, with water flowing relatively fast in one domain and slow in the other domain. In practice, this approaches assume a porous system which is permanently in the shrinkage state (COPPOLA et al, 2012). The continuum models cannot explain the physical processes at pore scale.…”

Physics of the soil medium organization part 2: pedostructure characterization through measurement and modeling of the soil moisture characteristic curves

“…Still, other studies (Groenevelt and Grant, 2002;Chertkov, 2003) used empirical coefficients and parameters to model the SSC. Few scientists have tried to integrate these shrinkage characteristic points and/or slopes in modeling the water and solute transport through structured soil medium (Armstrong et al, 2000;Larsbo and Jarvis, 2005;Coppola et al, 2012). However, these models still reference their state variables to virtual volume of soil medium (REV).…”

“…Several models were developed to fit the discrete experimental data of the WRC (e.g., El-kadi, 1985;Leij et al, 1997;Groenevelt and Grant, 2004;Fredlund et al, 2011). These WRC models consider the soil as a rigid porous medium whose porosity is represented by equivalent bundle of capillary tubes (Braudeau and Mohtar, 2004;Coppola et al, 2012), their state variables are referenced to a virtual volume, Representative Elementary Volume (REV), which ignores the soil structure (Braudeau and Mohtar, 2009), and their parameters usually have no physical meaning (Chertkov, 2004). However, other researchers (Voronin, 1980;Berezin et al, 1983) followed a thermodynamic-based approach for defining the relationships between the soil water potential and water content by using physiochemical parameters and variables.…”