In unsaturated coarse disperse materials such as sand, the water on the surface is continous and ‘deep’ enough to be an adequate medium for the migration of surface active substances (SAS). The influence of the tangential force on water migration in unsaturated coarse disperse material is studied by compensating the capillary pressure difference caused by the surface tension gradient. The influence on water migration in unsaturated disperse materials exerted by the additional pressure difference, originating from SAS migration, is comparable to that exerted by capillary pressure difference.
It has long been known to soil science that after water-saturated sand has been allowed to drain freely, a small percentage of fluid (2-3%) is still to be found in the sand. This undrainable water, localized on the surface of particles and at the contact points between particles under a negative capillary pressure, is studied here as a function of its surface tension and the apparent specific surface of sand. The influence of the surface tension of water on the amount of undrainable water in quartz sand suggests that most of the fluid is retained by capillary forces which are presumably localized near the points of contact between particles. However, the influence of the apparent specific surface of sand on the amount of undrainable water suggests that some of the fluid forms a layer c. 0.5 �m thick on the rugose surface of the sand particles.
1. Water evaporation from soil and sand columns is smaller when the surfactant is placed on the surface, and larger when it is located at the bottom. Water evaporation from soil and sand mixed with the surfactant is as high as without the surfactant. 2. The fact that water evaporation from soil and sand depends on the location of the surfactant in the column is accounted for by the dominant role of migration but not by the suppressive action of the surfactant film on water evaporation. 3. Water migration from sites with surfactant towards sites without surfactant is caused by two pressures: the capillary and the additional pressure arising from the spreading of the surfactant. 4. The importance of the additional pressure on water migration is shown by experiments which rule out the existence of a capillary pressure difference.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.