Liquid Flow in Swelling Soils

Theory of flow of water in media that change volume with water content change owes much to the insights of John Philip. In particular, his development and explanation of a one‐dimensional model in Eulerian space that correctly accounts for the statics and dynamics of the phases in a two‐phase swelling system is a paradigm of the combination of the models of mathematics with clear physical insights. In addition, transformation of the approach from Eulerian to Lagrangian space permits use, for swelling systems, of all the methods of analysis developed in soil physics to describe water flow in nonswelling soils. The approach has been used to describe important practical problems of filtration, sedimentation, centrifugation, and consolidation of colloidal and soil systems in chemical, civil, and mine tailings engineering. Regrettably, material coordinates, rather than the more familiar spatial coordinates, continue to present conceptual difficulties for many engineers and soil scientists, as does the effect of volume change on the potential of the water. Furthermore, the approach has yet to be satisfactorily extended to unsaturated systems and to multidimensional ones. Its use in agriculture thus remains uncertain despite the great importance of water management in swelling and cracking soils. This review discusses some of these issues and specifically identifies the energetics and mechanics of cracking, overburden effects in unsaturated porous materials, and structural effects of the equilibrium ambient solution type and concentration in swelling systems as practically important areas for further study.