The effectiveness of two capillary barriers on a 10% slope

Abstract

Capillary barriers, consisting of fine-over-coarse soil layers, are being considered as an alternative cover component for waste-disposal facilities, especially in dry climates. Infiltrating water is removed from the fine layer by evaporation or transpiration, or percolation into the coarse layer (failure). If the fine-coarse interface is sloped, water in the fine layer can also drain laterally under unsaturated conditions. The effectiveness of two capillary barriers in laterally diverting water was tested. The barriers were 7 m long and 1.2 m thick, built on a 10% slope. One had a homogeneous fine layer, while the fine layer of the other was layered to increase its ability to divert water laterally. The barriers were first subjected to constant infiltration (10 mm/day) followed by exposure to ambient climatic conditions. The layered capillary barrier was successful in laterally diverting water near the interface and did not permit any water to enter the coarse layer. In contrast, the homogeneous capillary barrier failed over its entire length. These results indicate that a significant lateral diversion capacity can be designed into capillary barriers, greatly increasing their effectiveness.