Derivation of soil water retention curve incorporating electrochemical effects
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RESEARCH PAPER
Derivation of soil water retention curve incorporating electrochemical effects Mehdi Pouragha1
•
Mahdad Eghbalian2 • Richard Wan2 • Tai Wong2,3
Received: 31 January 2020 / Accepted: 3 August 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Water retention of clayey soils with wide particle size distributions involves a combination of capillary and adsorbed layers effects that result into suction–saturation relations spanning over multiple decades of matric suction values. The present study provides a physics-based analysis to reproduce the water retention curve of such soils based solely on particle size distribution and porosity. The distribution of inter-particle pore sizes is inferred through a probabilistic treatment of the particle size distribution, which is then used, together with an assigned pore entry pressure, to estimate the inter-particle water volume at a given suction. The contribution to water content from adsorbed layers is also taken into account by considering the balance of electrochemical forces between water and clay material. The total water content is therefore found by summing up the contribution of inter-particle water, as well as adsorbed layers that form around clay particles and around the individual clay platelets. Comparisons with experimental results on nine different soil samples verify the capability of the model in accurately predicting the wide water retention curves without any prior calibration. Additional to capturing the essential features of the water retention curve with remarkable detail, the analytical model also provides insights into the relative contributions of capillary and adsorbed waters to the overall saturation at different suction regimes. Being based upon easily accessible information such as particle size distribution and void ratio, the model can therefore be considered as a substitute for costly and lengthy laboratory and in situ measurements of water retention curve. Keywords Adsorbed layer Particle size distribution Soil–water characteristics Water retention
1 Introduction
& Mehdi Pouragha [email protected] Mahdad Eghbalian [email protected] Richard Wan [email protected] Tai Wong [email protected] 1
Civil and Environmental Engineering Department, Carleton University, 1125 Colonel By Dr, Ottawa, ON K1S 5B6, Canada
2
Civil Engineering Department, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada
3
Parsons, Calgary, Canada
Clayey soils with a wide particle size distribution are often encountered in geotechnical studies where an accurate knowledge of water retention characteristics is required for a correct quantification of hydro-mechanical responses of soil. A major challenge is to correctly evaluate the water retention behaviour of such soils where both capillary and adsorbed layers effects result into suction–saturation relations that span over multiple decades of matric suction values. Despite recent advances made in
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