Abstract

A meter-scale experimental system (2-m high by 2-m deep by 3-m wide) was used to investigate the behavior of water in a model system consisting of two unconsolidated sediment layers separated by a layer containing discrete flow channels. Stainless steel tubes were inserted vertically through a clayey matrix to represent the discrete flow-channel layer. The experimental system was well characterized, and results from water infiltration experiments were analyzed. A time series of water arrival at a network of 86 probes located in the unconsolidated sediment layers is presented, as well as water pressure histories at specific locations. Some probes were located at opposite ends of the flow channels to assess water migration through the discrete flow-channel layer. Analyses of the experimental results focused on capillary break phenomenon at the interface between the overlying unconsolidated layer and the underlying discrete flow channels. Dissimilar water pressure histories were measured at probes near the upper boundary of the discrete flow-channel layer, suggesting varied and complex water flow behavior. At some locations, a steady or periodic “leaking” of water through the discrete flow channels appeared to occur, contrary to capillary break theory. The authors advocate larger-scale experiments to advance our understanding and ability to model fluid flow across a wide range of spatial and temporal scales.

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