Abstract
Accurate modeling and prediction of the variation of the hydraulic conductivity of unsaturated soils at a very low degree of saturation has important implications in various engineering problems. Physical processes underlying the hydraulic behavior of unsaturated soils (retention behavior and variation of hydraulic conductivity) are first explained, and then a consistent set of new definitions for key transition hydraulic states is proposed. This lays the foundation for the presentation of a new predictive hydraulic conductivity model, accurate for the full range of degree of saturation and applicable to relatively coarse-grained soils (i.e., gravels, sands, and silts). The hydraulic conductivity is divided into two components—a bulk water component and a liquid film component—each of which varies with the degree of saturation or suction. The model is then validated against experimental data. Finally, the new hydraulic conductivity model is applied to the numerical study of the hydraulic behavior of capillary barrier systems (CBSs). The new model is able to predict the behavior of CBSs better than conventional models, and the numerical modeling highlights the role of liquid film flow, which is often neglected.
Highlights
The hydraulic properties of unsaturated soils are described by the soil water retention curve (SWRC), namely the relationship between degree of liquid saturation Sl and suction s, and the soil hydraulic conductivity curve (SHCC), namely the relationship between hydraulic conductivity k and either degree of saturation or suction.Many hydraulic constitutive models describing mathematically the SWRC and the SHCC have been proposed.Conventionally, water retention models are empirical and their parameter values for a given soil are typically calibrated with experimental data
The results of the numerical analyses of the infiltration process in a capillary barrier systems (CBSs) are presented here in order to highlight the influence of the SHCC models used for the coarser layer and the influence of the liquid film conductivity, which is commonly neglected. In this set of analyses, the fitted value of Slr of the coarser layer in the VG model is close to 0 and the VG and modified van Genuchten (modVG) models lead to very similar SWRCs
The hydraulic conductivity is split into two components: the bulk water component and the liquid film component
Summary
The hydraulic properties of unsaturated soils are described by the soil water retention curve (SWRC), namely the relationship between degree of liquid saturation Sl and suction s, and the soil hydraulic conductivity curve (SHCC), namely the relationship between hydraulic conductivity k and either degree of saturation or suction.Many hydraulic constitutive models describing mathematically the SWRC and the SHCC have been proposed.Conventionally, water retention models are empirical and their parameter values for a given soil are typically calibrated with experimental data. The hydraulic properties of unsaturated soils are described by the soil water retention curve (SWRC), namely the relationship between degree of liquid saturation Sl and suction s, and the soil hydraulic conductivity curve (SHCC), namely the relationship between hydraulic conductivity k and either degree of saturation or suction. Many hydraulic constitutive models describing mathematically the SWRC and the SHCC have been proposed. Water retention models are empirical and their parameter values for a given soil are typically calibrated with experimental data. Models for the SHCC generally rely on information from. Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G128LT, UK. Engineering, University of Glasgow, Rankine Building, Oakfield Avenue, Glasgow G128LT, UK. *Corresponding author.
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