Abstract
Abstract. Traditional models employed to predict the soil water retention curve (SWRC) from the particle size distribution (PSD) always underestimate the water content in the dry range of the SWRC. Using the measured physical parameters of 48 soil samples from the UNSODA unsaturated soil hydraulic property database, these errors were proven to originate from an inaccurate estimation of the pore size distribution. A method was therefore proposed to improve the estimation of the water content at high suction heads using a pore model comprising a circle-shaped central pore connected to slit-shaped spaces. In this model, the pore volume fraction of the minimum pore diameter range and the corresponding water content were accordingly increased. The predicted SWRCs using the improved method reasonably approximated the measured SWRCs, which were more accurate than those obtained using the traditional method and the scaling approach in the dry range of the SWRC.
Highlights
The soil water retention curve (SWRC), which represents the relationship between the water pressure and water content, is fundamental to researching water flow and chemical transport in unsaturated media (Pollacco et al, 2017)
The results showed that there is a significant difference between the performance of the improved method and the traditional method (p = 0.001)
The traditional models employed to translate the particle size distribution (PSD) into the SWRC underestimate the water content in the dry range of the SWRC
Summary
The soil water retention curve (SWRC), which represents the relationship between the water pressure and water content, is fundamental to researching water flow and chemical transport in unsaturated media (Pollacco et al, 2017). The first attempt to directly translate a PSD into an SWRC was made by Arya and Paris (1981) (hereafter referred to as the AP model). Based on the principle of the AP model, many researchers have focused on improving the suction head calculations, which are commonly based on the capillary equation; but methods that are used to translate the particle diameter into the pore diameter are different (Haverkamp and Parlange, 1986; Zhuang et al, 2001; Mohammadi and Vanclooster, 2011; Jensen et al, 2015).
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