Flow of Water in Rigid and Non-Rigid, Saturated and Unsaturated Soils

Abstract

Flow of water in soils is studied intensely in soil physics and hydrology. The continuum theory of mixtures can be used as a framework for outlining the theory. The well-established theory for flow of water in rigid soils is reviewed briefly, with emphasis on the description and main implications of the non-linear theory proposed by Richards in 1931. For non-rigid soils, it is convenient to formulate the theory in terms of material coordinates of the solid phase. For one-dimensional, vertical flow, it is shown that, compared to the theory for rigid soils, the effect of the weight of the soil may be to reverse the sign of the gravitational force in the Richards equation. Progress with multi-dimensional deformation processes is outlined, including the complications arising from cracking. Finally, available analytical and numerical solutions of one-dimensional, equilibrium and flow problems for water in non-rigid soils are reviewed.