Capillary rise method for the measurement of the contact angle of soils

Liu, Zhen; Yu, Xiong; Wan, Lin

doi:10.1007/s11440-014-0352-x

Cited by 31 publications

(18 citation statements)

References 51 publications

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“…For spherical particles, wet samples of glass beads may show low contact angle values (ď 10 0 ) [30,32], while the contact angle between steel balls and water is around 50 0 [34]. As far as real sandy soils are concerned, contact angle values reaching 50 0 and more have been reported in [2,20]. Adding to complexity, the contact angle is also dependent on the hydraulic loading path; its value showing a hysteresis between extreme limits that correspond to receding or advancing contact lines.…”

Section: Introductionmentioning

confidence: 99%

Contact angle mechanical influence in wet granular soils

Duriez

Wan

2016

Acta Geotech.

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We investigate the macroscopic mechanical influence of the local liquid-solid contact angle that governs the fluid distribution in granular soils under unsaturated conditions. To this end, a Discrete Element Method (DEM) based implementation that accommodates for any contact angle is proposed and applied to an idealized granular material in the pendular regime. The DEM model includes resultant capillary forces as well as a comprehensive description of the capillary bridges (volume, surface, orientation tensor) by solving the Laplace-Young equation in a general case, instead of using any unnecessary phenomenological relation. Macroscale mechanical simulations for different constant contact angle values reveal that granular assemblies are less sensitive to unsaturated conditions for higher contact angles, which is in line with the contact angle influence at the microscopic capillary bridge

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Section: Introductionmentioning

confidence: 99%

Contact angle mechanical influence in wet granular soils

Duriez

Wan

2016

Acta Geotech.

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“…We referred to already published experimental results to examine whether these differences are general, or specific to the current experimental setup. As we were not aware of any capillary rise in capillary tubes having a CA(t), we referred to a comparable method that has been commonly used for measuring CA for wettable and water‐repellent soils: the capillary rise method (CRM) (Alghunaim et al, 2016; Bachmann et al, 2003; Liu et al, 2016). In the CRM, the tested soil is packed uniformly in a tube, the bottom of which touches or is immersed in the tested fluid.…”

Section: Discussionmentioning

confidence: 99%

Effects of Time‐Dependent Contact Angle on Wettability of Subcritically Water‐Repellent Soils

Wang

Wallach

2020

Water Resources Research

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Recent studies have indicated that under certain conditions, most soils are water repellent to some degree, which impacts agricultural fields, pastures, forests, grasslands, and turf areas. Soil water repellency originates from amphiphilic molecules that reorient during contact with water. However, models to describe the flow in soils affected by time-dependent contact angle (CA(t)) are still lacking. The current study aims to close this gap. The measured CA(t) for an oleic acid-coated glass surface and a uniform capillary tube indicated that the initial CA was substantially higher for the latter. However, the rate of CA decrease was similar for both cases in spite of the fact that the contact area between the water and the tube wall continuously increases by the capillary rise. This indicates that the amphiphilic molecules reorientation at the vicinity of the contact line rather than at the wetted tube area controls the CA dynamics. A mathematical model for flow in a uniform and sinusoidal capillary tube with CA(t) < 90°that includes model for the reorientation of the amphiphilic molecules was introduced. The model for uniform case was successfully verified by comparison with measured capillary rise in a coated uniform tube. The simulations indicated that nonuniform pore geometry amplifies the effect of CA(t) on the capillary rise dynamics. The stepwise meniscus propagation in the sinusoidal capillary tubes is driven by the time for the meniscus to reach the converging section of the tube. The retardation in capillary rise increases with tube waviness.

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“…The CA is typically measured with the sessile drop method (i.e., by fixing solid particles on a glass slide, placing a liquid droplet on top, and measuring the CA optically in upright projection images) (Bachmann et al., 2000). Alternative approaches are to derive the CA indirectly from flow behavior, in terms of water drop penetration time (Wallis & Horne, 1992) or capillary rise dynamics (Letey et al., 1962; Liu et al., 2016), or from measured forces, when dipping and pulling a treated surface into and from a liquid, respectively (Letey et al., 1962). Each method has certain advantages and limitations in terms of accuracy and robustness and may cover different aspects of soil water repellency (e.g., dynamic vs. equilibrium CAs).…”

Section: Introductionmentioning

confidence: 99%

In situ measurement of 3D contact angle in sand based on X‐ray computed tomography

Schlüter

Blaser

Benard

et al. 2022

Vadose Zone Journal

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Soil water repellency is traditionally expressed as contact angle (CA) and measured destructively on exposed surfaces or derived from flow behavior or measured forces.These approaches cannot map local heterogeneities in CA, which typically exist in intact soil. Here, we explore the potential and limitations of in situ measurements of three-dimensional CAs with simplified benchmark tests and in intact sand. The method is based on a protocol for the freely available OpenFOAM software and applied to segmented X-ray computed tomography (X-ray CT) data. This study scrutinizes its suitability under typical vadose zone conditions, as it was originally developed for rock studies in petroleum engineering. The assets of the method are that it allows for accurate measurement of locally varying, equilibrium contact angles and that they can be linked to pore scale features that cause them. This is demonstrated with rehydrated mucilage structures in sand and the associated change in local CAs, where they touch sand grains. In general, the image acquisition time of polychromatic X-ray CT (minutes) precludes the assessments of dynamic CAs that may equilibrate within seconds. Another limitation is that acute CAs are overestimated due to the voxel discretization of interfaces and contact lines in combination with image smoothing. The divergence arises around 60˚and is most severe in the limit of vanishing water repellency. In summary, the method enables the mapping of local heterogeneities of equilibrium CAs, though the absolute values should be critically assessed.

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Capillary rise method for the measurement of the contact angle of soils

Cited by 31 publications

References 51 publications

Contact angle mechanical influence in wet granular soils

Contact angle mechanical influence in wet granular soils

Effects of Time‐Dependent Contact Angle on Wettability of Subcritically Water‐Repellent Soils

In situ measurement of 3D contact angle in sand based on X‐ray computed tomography

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