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Effect of wetting and drying on meniscus structures in hydrophobic sands

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Original languageEnglish
Number of pages5
DOIs
Publication statusPublished - 2020
EventEUROPEAN CONFERENCE ON UNSATURATED SOILS: Unsaturated Horizons - Lisbon, Portugal
Duration: 19 Oct 202021 Oct 2020
Conference number: 4th
https://eunsat2020.tecnico.ulisboa.pt/

Conference

ConferenceEUROPEAN CONFERENCE ON UNSATURATED SOILS
Abbreviated titleE-UNSAT2020
CountryPortugal
CityLisbon
Period19/10/2021/10/20
Internet address

Abstract

Hydrophobic soils can occur either naturally when particles are coated with plant-derived hydropho-bic organic compounds or if exposed to very high temperatures, or artificially if treated with contaminated water or chemicals in the laboratory. Hydrophobic soils can resist water infiltration, are associated with preferential flow and may lead to increased surface runoff and soil erosion. Traditional understanding of unsaturated hy-drophobic soils suggests that convex water menisci, and so positive water pressures, should form between soil particles, due to contact angles > 90◦. However, experimental results do not support this theory. The objective of this work was to study the changes in meniscus structures in hydrophobic sand specimens, as well as the overall response of the sand to wetting and drying cycles. A very uniform, fine silica sand was mixed with Dimethyldichlorosilane to induce water repellence. Successive images captured in an environmental scanning electron microscope are presented, to examine the response of the sand in two distinct drying and wetting cycles. Preliminary results show that the non-spherical nature of the sand particles prevent or hinder the formation of convex liquid bridges, despite the high contact angles. Rather, water droplets appear to expand only through droplet coalescence, which prevents structures from contracting on drying.

Event

EUROPEAN CONFERENCE ON UNSATURATED SOILS: Unsaturated Horizons

19/10/2021/10/20

Lisbon, Portugal

Event: Conference

ID: 173215532