Modeling Field Infiltration into Unsaturated Clay

Abstract

This paper describes the results of a numerical simulation of the observed field behavior of infiltration into an unsaturated clay. In particular, the autumnal recharge of 1984 is considered. A numerical solution of Richards's pressure‐based formulation is presented. A weighted residual finite element approach is adopted to achieve spatial discretization of the moisture flow domain. A fully implicit backward difference time‐stepping algorithm is employed to accommodate the transient nature of the problem. The application of the algorithm to the simulation of the problem at hand is described. The initial moisture content distribution is established from field‐measured data. Boundary conditions are determined from an interpretation of meteorological data. Material parameter identification based on experimental work on undisturbed clay samples is detailed. Comparisons of numerical results with field values collected by British Gas are given. Good correlation is obtained. The numerical simulation is capable of representing the observed field behavior, over the depth of summer moisture deficit penetration.