Simulation of the wicking effect in a two-layer soil liner system

A series of simulation runs were made using the computer model VSAFT2 (Yeh & Srivastava 1990) to estimate the "wicking" potential of five low-permeability liner materials including excel, celite slurry, kiln dust, rock creek clay and celite waste. The unsaturated hydraulic properties for these materials were assumed to be represented by the van Genuchten model (1978). The hypothetical liner system simulated consisted of 0.305 m (1 foot) of low permeability material underlain by a medium sand. The purpose of this modelling effort was to quantify the effects of liner thickness and leakage rate on the lateral spreading of the wetting front, and to determine the effectiveness of the diffusivity function in predicting the migration of the wetting front. Results indicate, as expected, that the liner material with the lowest permeability retards vertical movement the most; however, the horizontal wicking effect is also limited. Additional multi-layer liner systems will be simulated in the next phase of the project to improve liner wicking performance.