Effect to Temperature and Trapped Air on Matric Suction

Chahal, R. S.

doi:10.1097/00010694-196510000-00006

Cited by 40 publications

(21 citation statements)

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“…The process of air trapping in soils is very complicated as a result of the chaotic nature of the microscopic migration of water through the pore spaces. Such flow induces hysteresis in the hydraulic properties of soils [Youngs and Peck, 1964], affecting the hydraulic conductivity, water retention curve [Chahal, 1965;Faybishenko, 1983;Hopmans and Dane, 1986;Kaluarachchi and Parker, 1987;Stonestrom and Rubin, 1989], and specific yield. Several factors may create air-filled domains that are surrounded by water-filled regions in the soils in both the vadose and groundwater zones.…”

Section: Basic Characteristics Of Entrapped Airmentioning

confidence: 99%

Hydraulic Behavior of Quasi‐Saturated Soils in the Presence of Entrapped Air: Laboratory Experiments

Faybishenko¹

1995

Water Resources Research

191

206

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Entrapped air in soils beneath the water table is one of the key factors controlling the hydraulic behavior under conditions of ponded infiltration, in perched waters, and in unconfined aquifers. The term quasi-saturated soils defines the soils with entrapped air, and the term quasi-saturated hydraulic conductivity defines the relationship between the hydraulic conductivity and entrapped air content. This paper focuses on an investigation of how entrapped air, along with other factors, affects the three-stage temporal behavior of the quasi-saturated hydraulic conductivity of soils. During the first stage the quasi-saturated hydraulic conductivity of soils decreases by as much as 5-8 times, presumably because mobile entrapped air blocks the largest pores. During the second stage, as the mobile entrapped air is discharged from the core, the quasi-saturated hydraulic conductivity of the soils slowly increases. When the mobile air is removed, the remaining immobile entrapped air is discharged as a dissolved phase, and the. quasisaturated hydraulic conductivity increases rapidly by about 1-2 orders of magnitude, essentially reaching the value of the saturated hydraulic conductivity. During the third stage the hydraulic conductivity is decreased to minimum values. The effects of sealing at the soil surface and microbiological activities are assumed to be major factors in the final decrease of the hydraulic conductivity. This three-stage temporal behavior of percolation in loam soils is repeatable. A new power law and an exponential relationship are proposed to describe the quasi-saturated hydraulic conductivity of loams as a function of the entrapped air content. in developing (1) a theory of two-phase flow [Morel-Seytoux, 1973], (2) methods for field investigations and monitoring [Stephens et al., 1984], (3) methods for managing groundwater systems for many practical applications, such as irrigation and drainage systems [Powers, 1934; Aver3:anov, 1950; Luthin, 1957], injection of water in the vadose zone [Stephens and Neuman, 1982a; Stephens et al., 1984], secondary water recovery [Moridis and Reddell, 1991a, b], remediation of waste site soils using air barriers [Wilson and Clarke, 1994], artificial recharge of groundwater [Todd, 1980], and (4) designing waste Copyright 1995 by the American Geophysical Union. Paper number 95WR01654. 0043-1397/95/95WR-01654505.00 water treatment plants using filtration and aeration [Sekoulov, 1982; Amirtharajah, 1993]. Air from the atmosphere can migrate down to depths of several meters [Massmann and Farrier, 1992] or as much as 100 m [Montazer et al., 1988] as the atmospheric pressure fluctuates. In the case of soil contamination by volatile organic compounds (VOC), air in the vadose zon e can become mixed with VOC [Cho et al., 1993]. If part of this air has been immobilized as entrapped gas, it can be a long-term source of VOC in the soils. The VOC contained in this immobile air phase is not easily removed during air extraction. Consequently, the effectiveness of remediation activit...

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Section: Basic Characteristics Of Entrapped Airmentioning

confidence: 99%

Hydraulic Behavior of Quasi‐Saturated Soils in the Presence of Entrapped Air: Laboratory Experiments

Faybishenko¹

1995

Water Resources Research

191

206

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“…Many experimental results [Gardner, 1955;Chahal, 1965; Haridasan and Jensen, 1972;Constantz, 1983;Constantz, 1991; Nimmo and Miller, 1986] could not be explained on the basis of changes in air-water IFT alone because the temperature effect was larger than that predicted by the temperature dependence of IFT by a factor of 1-5 [Nimmo and Miller, 1986]. The presence of dissolved substances such as fulvic and humic acids may increase the temperature dependence of capillary pressures but not enough to explain the measured changes in capillary pressures [Nimmo and Miller, 1986].…”

Section: Introductionmentioning

confidence: 99%

The effect of temperature on capillary pressure‐saturation relationships for air‐water and perchloroethylene‐water systems

She¹,

Sleep²

1998

Water Resources Research

133

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Abstract. The temperature dependence of capillary pressure-saturation relationships was measured for air-water and perchloroethylene-water systems in silica sand. Changes in capillary pressures, irreducible water phase saturations, and residual nonwetting saturations with temperature were determined. Relationships for temperature dependence of contact angle and interfacial tension were incorporated into the van Genuchten [1980] model and fitted to the data. Capillary pressures at constant degrees of saturation decreased as temperature increased. Hysteresis decreased, irreducible water saturations increased, and residual nonwetting saturations decreased as temperature increased. The magnitude of the change in capillary pressures could not be explained by the temperature dependence of wetting-nonwetting interfacial tensions alone. Derived parameters for the temperature dependence of the contact angle predicted an increase of contact angle of roughly 45o-50 ø for air-water and perchloroethylene systems with a temperature increase from 20 ø to 80øC, while literature studies suggest that contact angles should decrease with increasing temperature. It was concluded that the parametric relationship for temperature effects incorporated into the van Genuchten [1980] model fit the data well, but other effects in addition to changes in interfacial tension and contact angle played a role in the temperature dependence of capillary pressure-saturation relationships.

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“…The content of this document is not copyrighted. Chahal (1964Chahal ( , 1965, reported that neither entrappedThe capillary pressure () in unsaturated porous media is known …”

mentioning

confidence: 99%

Temperature Dependence of Water Retention Curves for Wettable and Water‐Repellent Soils

Bachmann

Horton

Grant

et al. 2002

Soil Science Soc of Amer J

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The capillary pressure (ψ) in unsaturated porous media is known to be a function of temperature (T). Temperature affects the surface tension (σ) of the pore water, but possibly also the angle of contact (γ). Because information on the temperature dependence of γ in porous media is rare, we conducted experiments with three wettable soils and their hydrophobic counterparts. The objectives were (i) to determine the temperature dependence of the water retention curve (WRC) for wettable and water-repellent soils, (ii) to assess temperature effects on the apparent contact angle γ A derived from those WRCs, and (iii) to evaluate two models (Philip-de Vries and Grant-Salehzadeh) that describe temperature effects on ψ. Columns packed with natural or hydrophobized soil materials were first water saturated, then drained at 5, 20, and 38°C, and rewetted again to saturation. Capillary pressure and water content, θ, at five depths in the columns were measured continuously. The observations were used to determine the change in γ A with T, as well as a parameter β 0 that describes the change in ψ with T It was found that the Philip-de Vries model did not adequately describe the observed relation between ψ and T A mean value for β 0 of −457 K was measured, whereas the Philip-de Vries model predicts a value of −766 K. Our results seem to confirm the GrantSalezahdeh model that predicts a temperature effect on γ A For the sand and the silt we studied, we found a decrease in γ A between 1.0 to 8.5°, when the temperature was increased from 5 to 38°C. Both β 0 and γ A were only weak functions of θ. Furthermore, it seemed that for the humic soil under study, surfactants, i.e., the dissolution of soil organic matter, may compound the contact angle effect of the soil solids. RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. Chahal (1964Chahal ( , 1965, reported that neither entrappedThe capillary pressure () in unsaturated porous media is known

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Effect to Temperature and Trapped Air on Matric Suction

Cited by 40 publications

References 0 publications

Hydraulic Behavior of Quasi‐Saturated Soils in the Presence of Entrapped Air: Laboratory Experiments

Hydraulic Behavior of Quasi‐Saturated Soils in the Presence of Entrapped Air: Laboratory Experiments

The effect of temperature on capillary pressure‐saturation relationships for air‐water and perchloroethylene‐water systems

Temperature Dependence of Water Retention Curves for Wettable and Water‐Repellent Soils

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