Moisture equilibrium in the vertical in swelling soils. II. Applications

Abstract

The paper discusses, with the aid of calculated examples, applications in hydrology and soil mechanics of the analysis developed in Part I. Various classical concepts of groundwater hydrology fail completely for swelling soils. The distributions of saturation and of hydraulic conductivity relative to the water table differ entirely from the conventional picture. Variations in surface topography affect moisture distribution in swelling soils. The theory of this effect is developed for topographies that are not too steep and is illustrated by examples. The equilibrium distributions found would be classically interpreted as disequilibrium states persisting because of small hydraulic conductivity; but, in fact, the moisture differentials are maintained, not by a lack of conductivity, but by a lack of difference in total potential. The variation of specific yield with water table elevation and stratum thickness in swelling soils is basically different from that in non-swelling soils. The analysis of Part I is used to discuss the following topics in soil mechanics: the variation of equilibrium soil levels with water-table depth, and with water depth over the soil; the effect of surface loading on equilibrium moisture profiles and on soil levels. Extension of the analysis to two- and three-dimensional systems is treated briefly.