Surfactant and water migration in unsaturated sand

1 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). 2 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. 3 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.