Analyses of water diversion along inclined covers with capillary barrier effects

Various types of cover systems can be used to control water infiltration into waste disposal sites. One promising option is to combine different types of soil to create a layered cover with capillary barrier effects (CCBE). A CCBE basically involves the placement of a relatively fine-grained soil, which acts as a water-retention layer, over a coarser capillary break material. On slopes, a CCBE promotes lateral water diversion. Inclined CCBEs, however, are relatively complex, as their behaviour is influenced by numerous factors. In this paper, the authors present the key results obtained from a numerical investigation into the response of steeply inclined CCBEs. The study evaluates the behaviour of covers under dry and humid climatic conditions. After a review of the physical processes and background studies, the paper presents simulation results that demonstrate the effect of key factors on the diversion length of covers, including layer thicknesses, material properties, and recharge rates. The results shown here indicate that increasing the thickness of the cover may improve its efficiency, but only up to a certain maximum beyond which the gain becomes minimal. These results should be of help to those involved in the design of inclined CCBEs.