Validating the Generality of a Closed-Form Equation for Soil Water Isotherm
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 147, Issue 12
Abstract
Total soil water potential is conventionally defined as the sum of matric potential and osmotic potential , i.e., , when gravitational potential is ignored. Soil water isotherm (SWI) is the constitutive relationship between and soil water content , i.e., , where is called soil water retention curve (SWRC) or soil water characteristic curve. SWI and SWRC are arguably the two most important soil constitutive relationships because they govern virtually all phenomena in soil such as flow, stress and deformation, and biological activities. A closed-form SWI, recast from a generalized SWRC equation for adsorption and capillarity, is experimentally validated for its generality in representing SWI. Adsorption isotherms of 49 soils, covering all spectrum of soil types with plasticity index up to 185% and specific surface area up to , are used to validate the SWI equation. It is shown that the SWI equation can nearly perfectly represent the isotherms of these soils with almost all of the coefficients of determination , validating the generality of the SWI equation. Comparative analysis is also conducted by using two existing SWI equations, namely, the Brunauer–Emmett–Teller (BET) equation and the augmented BET (A-BET) equation. It is demonstrated that the SWI equation is superior to the BET and A-BET equations in representing soil–water interactions by adsorption and capillarity, and in the full relative humidity range.
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Data Availability Statement
All data, models, and code generated or used during the study appear in the published article.
Acknowledgments
This research is supported by the US National Science Foundation (NSF CMMI-1902045).
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Received: Mar 28, 2021
Accepted: Jul 22, 2021
Published online: Sep 16, 2021
Published in print: Dec 1, 2021
Discussion open until: Feb 16, 2022
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