HYDROSTATICS AND HYDRODYNAMICS IN SWELLING SOILS

The generalization to swelling soils of the mathematical theory of water movement in unsaturated soils involves the following extensions to the classic analysis: (1) recognition that Darcy's law applies relative to the soil particles, (2) inclusion of the void ratio function in the characterization of the soil, and (3) reconsideration of hydrostatics in swelling media. For swelling soils the total potential includes an additional component, the overburden potential Ω. Evaluation of Ω leads to the condition for equilibrium in the vertical, which is a first order linear differential equation with singular coefficients. Three types of equilibrium profile follow: hydric profiles with moisture gradient d∂/dz < 0, pycnotatic profiles with d∂/dz = 0, and xeric profiles with d∂/dz > 0. Other phenomena in swelling soils treated include steady vertical flows and unsteady horizontal and vertical flows. Classic concepts of ground‐water hydrology, tacitly based on the behavior of nonswelling media, fail completely for swelling soils. The approach also provides a theory of consolidation which includes the influences of (1) soil particle movement, (2) unsaturation, and (3) self‐weight. Copyright 1969 by the American Geophysical Union.