Infiltration into Soil with Dynamic Surface Seals

摘要

For the purpose of developing infiltration equation under a dynamically sealling soil surface, Richards' equation of unsaturated flow for a layered system is considered. An analytical approach based on the concept of dynamic wetting front is utilized to form the basis of fundamental solutions of Richards' equation applied to the layered system. Since the interface between the layer and the substrate gives rise to a discontinuity in water content, another dynamic variable representing hydraulic conductance is introduced to facilitate the analysis. Thus, we consider a dynamic seal of thickness h(t) to be on top of the soil column, z ≥ h. Both media are homogeneous and isotropic and the seal is much less conductive than the column and h is of the order of a few millimeters. First, the general solution of unsaturated flow with appropriate boundary conditions are developed, which consists of concentration and flux boundary value cases. The dynamic condition at the interfaces, between the seal and the substrate permits utilization of these solutions to yield infiltration rate under natural rainfall condition. The same set of solutions also are used to examine the role played by the seal parameters. In particular, infiltration process by the concept of hydrodynamic conductance is examined through the solutions of Richards' equation. The dynamics of cumulative infiltration R is studied at the end by the solution of a set of differential equations in terms of R, wetting front *, and the interfacial water content 2_0. An analytical closed for m solution for R is also found for certain cases.