Water retention of repellent and subcritical repellent soils: New insights from model and experimental investigations

[1] This study sheds light on the limitations of using [(cos ) 1 =2 ] to scale sorptivity by contact angle while reaffirming its scaling by geometrical Miller scaling factor ( 1 =2 ). The sorptivity for uniform and nonuniform (wavy) capillary tubes was determined by a mathematical model that includes the effect of inertia and dynamic contact angle. Given that real porous media are preferably represented by a bundle of nonuniform rather than uniform capillary tubes, the relationship between sorptivity and contact angle was examined for different combinations of contact angles and capillary tube degrees of waviness. A general relationship of S ¼ f [cos )] (with 1 = 2 ) was found. The deviation of from 1 = 2 (associated with uniform capillary tubes) increased with contact angle and capillary waviness increase. Zero sorptivity was obtained even for wettable capillaries, < 90 , a phenomenon that has been generally associated with hydrophobic capillaries ( ! 90 ). Contact angle and nonuniform pore structure had a synergistic effect on sorptivity. Capillary nonuniformity per se diminished sorptivity but its synergy with contact angle markedly magnified this reduction. Thus, following the sorptivity impact on finger width, it is rational to assume that larger-than-zero contact angles are involved in the formation of narrow fingers with an abrupt change between the inner wet and surrounding dry areas.

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“…, as was also noted by Ban et al [1987], Marmur [1989], Shirtcliffe et al [2006], and Czachor et al [2010].…”

supporting

confidence: 78%

An extension of Miller scaling to scale sorptivity by contact angle

Wallach

Wang

2013

Water Resour. Res.

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“…Notably, hydrophilic and water-repellent retention curves were similar in the low (<AEV) and high (greater than residual) suction ranges. Similar results were found by [16] and [18]; lower gravimetric water contents were found for hydrophobised granular soils than for the same soils in a hydrophilic condition for a given suction. Possible desaturation mechanisms for a hydrophilic and water repellent granular soil are shown schematically in Figure 3.…”

Section: Macroscopic Levelsupporting

confidence: 85%

“…It is reasonable, then, that this effect might be heightened in water repellent soils, so that suction may enter a negative domain (e.g. as suggested by [15] and [16] for different liquid bridge or meniscus configurations). The concept of negative 'suctions', however, requires further investigation to be validated.…”

Section: Microscopic Levelmentioning

confidence: 99%

Water repellent soils: the case for unsaturated soil mechanics

2016

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Abstract. Water repellent (or "hydrophobic" or "non-wetting") soils have been studied by soil scientists for well over a century. These soils are typified by poor water infiltration, which leads to increased soil erosion and poor crop growth. However, the importance of water repellence on determining soil properties is now becoming recognised by geotechnical engineers. Water repellent soils may, for example, offer novel solutions for the design of cover systems overlying municipal or mine waste storage facilities. However, investigations into factors affecting their mechanical properties have only recently been initiated. This purpose of this paper is to introduce geotechnical engineers to the concept of water repellent soils and to discuss how their properties can be evaluated under an unsaturated soils framework. Scenarios in which water repellent properties might be relevant in geotechnical applications are presented and methods to quantify these properties in the laboratory and in the field examined.

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“…However, in available modeling software applications for plot or profile scale SWR is not accounted for as a separate parameter, but may be preferably expressed during the procedure of soil hydraulic properties (SHP) estimation. Several studies highlight that the influence of SWR on SHP is evident in the hysteresis effect (Bauters et al, 1998;Czachor et al, 2010). Generally, the hysteresis is highly related to SWR, and the SWR effect is primarily detectable on the wetting curve (Hardie et al, 2013;Stoffregen and Wessolek, 2014).…”

Section: Introductionmentioning

confidence: 99%

Inverse estimation of soil hydraulic properties and water repellency following artificially induced drought stress

Filipović

Weninger

Filipović

et al. 2018

Journal of Hydrology and Hydromechanics

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Abstract:Global climate change is projected to continue and result in prolonged and more intense droughts, which can increase soil water repellency (SWR). To be able to estimate the consequences of SWR on vadose zone hydrology, it is important to determine soil hydraulic properties (SHP). Sequential modeling using HYDRUS (2D/3D) was performed on an experimental field site with artificially imposed drought scenarios (moderately M and severely S stressed) and a control plot. First, inverse modeling was performed for SHP estimation based on water and ethanol infiltration experimental data, followed by model validation on one selected irrigation event. Finally, hillslope modeling was performed to assess water balance for 2014. Results suggest that prolonged dry periods can increase soil water repellency. Inverse modeling was successfully performed for infiltrating liquids, water and ethanol, with R 2 and model efficiency (E) values both > 0.9. SHP derived from the ethanol measurements showed large differences in van Genuchten-Mualem (VGM) parameters for the M and S plots compared to water infiltration experiments. SWR resulted in large saturated hydraulic conductivity (K s ) decrease on the M and S scenarios. After validation of SHP on water content measurements during a selected irrigation event, one year simulations (2014) showed that water repellency increases surface runoff in non-structured soils at hillslopes.

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Water retention of repellent and subcritical repellent soils: New insights from model and experimental investigations

Cited by 66 publications

References 29 publications

An extension of Miller scaling to scale sorptivity by contact angle

An extension of Miller scaling to scale sorptivity by contact angle

Water repellent soils: the case for unsaturated soil mechanics

Inverse estimation of soil hydraulic properties and water repellency following artificially induced drought stress

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