Abstract
Capillary barrier (CB) refers to a soil layer structure composing of a sand layer over a gravel layer used as a rainwater infiltration control technique for preventing seepage. The CB effect results mainly from differences in water-holding capacity and permeability between the sand layer and the gravel layer. Experimental verification of the CB effect requires that the CB layer interface be flat. Trying to achieve flatness, however, the soil layer interface over a large area at a real construction site would not only greatly affect the construction schedule and cost but also pose a quality control challenge. In order to put the CB structure to practical use, it is very important to quantify the CB effect, or the degree of influence of nonflatness of the CB layer interface on diversion length. In view of this, this study compared the CB diversion length in the case where the CB interface is flat, which was determined in the authors' previous study, and the CB diversion length in the case where the layer interface is not completely flat, which has now been investigated through newly conducted experiments. The results thus obtained reveal that although under the limited condition of regularly shaped (sinusoidal) nonflatness, nonflatness of the interface of a sand layer and a crushed seashell layer would not affect diversion length, etc. (the CB effect would not be lost) if the nonflatness is regularly shaped and is within about 30 mm, which is likely to be encountered in practical conditions.
