A Two-Domain Model for Infiltration into Unsaturated Fine-Textured Soils

In this paper, a one-dimensional model handling the vertical infiltration process within a compacted clay column submitted on its top to a constant hydraulic head is presented. The model is based on the flow mechanism described by Philip (1968) and Jayawickrama (1990). The infiltration is supposed to take place simultaneously in two different porosity-domains. The first is the soil intact matrix and the second represents a net of interconnected channels presenting much higher hydraulic conductivities. The flow in the two domains is described by Richards’ pressure-based formulation and an exchange term reflects the interaction on the basis of Darcy’s law. A time-centered Finite Difference scheme is used to accommodate the transient nature of the problem. No attempt is made here to reproduce the geometry of the two domains, thus no assumption is needed concerning macropore-distribution, only an estimation of macropore hydraulic conductivity is required. Numerical simulation of laboratory infiltration tests yielded good agreement with measured data.