Coupled flow equations for water, electricity and ionic contaminants through clayey soils under hydraulic, electrical and chemical gradients

The transport of water, electricity and ionic contaminants through a clay stratum, which is a clay-water-electrolyte system out of thermodynamic equilibrium is studied in this paper. An exact description of the transport processes on the phenomenological level by the formalism of non-equilibrium thermodynamics defines the problem clearly and gives a quantitative description of the phenomenological coefficients. The simultaneous flows of water, electricity and contaminants under the influences of hydraulic, electrical and chemical gradients are formulated, and the phenomenological coefficients are related to experimentally measurable parameters in soil mechanics. Special cases of the general coupled flow theory are compared with existing solutions describing related phenomena for consistency. These cases include: the diffusion potential, the advection dispersion equation, the van't Hoff equation, and osmosis and ultra-filtration. These comparisons indicate that the developed theory is general and incorporates all these flow phenomena as special cases.