Generalized Soil Water Retention Equation for Adsorption and Capillarity
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 142, Issue 10
Abstract
A new soil water retention curve (SWRC) equation, generalized from previous models and the latest understanding of soil-water interaction, explicitly accounts for capillary and adsorptive processes. Under the assumption of local thermodynamic energy equilibrium, soil water is one of two types (capillary and adsorptive), and occurs in three retention regimes in the order from high to low matric potential: Capillary, adsorbed film, and tightly adsorbed soil water. A new equation for adsorptive water as a function of matric potential is introduced. The transition between adsorption and capillary regimes is smoothly described with a cavitation probability function imposed on a commonly used SWRC model. Three parameters (adsorption capacity, adsorption strength, and mean cavitation suction) are defined, replacing the commonly used parameters of residual moisture content, pore structure, and residual suction. The soil water retention data for 21 soils, representing a variety of soil compositions, are used to assess the proposed SWRC equation in comparison with other SWRC models. The proposed SWRC equation is shown to be a statistical improvement over other models in both the high and full suction range. The calculated adsorption capacities of these soils accord well with an existing adsorption-capillary based SWRC model and experimental evidence.
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Acknowledgments
This research was funded by a grant from the National Science Foundation (NSF CMMI 1233063).
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 142 • Issue 10 • October 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Aug 7, 2015
Accepted: Feb 25, 2016
Published online: Jun 7, 2016
Published in print: Oct 1, 2016
Discussion open until: Nov 7, 2016
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