Regulations for the sealing of landfill sites require two independent sealing components. To satisfy this requirement, the combined capillary barrier was developed using impermeable sheeting placed between the capillary layer and the capillary block of the traditional capillary barrier. In this study, a numerical model is introduced based on hydraulic characteristics obtained by means of measurements of samples of capillary barrier materials. To make a comparison possible, samples of a laboratory investigated barrier were measured. Two laboratory experiments with a simple and a combined capillary barrier were repeated using the developed numerical model and good agreement between computed and measured results was found. Subsequently, the model was used for investigating the effect of failure of the artificial sheeting on the capillary barrier's efficiency. The obtained results are presented and discussed.