Abstract
Water-repellent soils have been known to cause finger-like wetting pattern. The objectives of this study are to measure some wettability indices and water characteristics for sands of mixed wettablity and to discuss relationships between the indices and the water characteristics. The WDPT (Water Drop Penetration Time) indicated the sands to be wettable or water-repellent, but it did not correspond to the water-entry pressure which is considered to show the degree of water-repellency. On the other hand, apparent contact angles measured by capillary rise method and sessile drop method showed good correlation with the water-entry pressure. Cassie’s equation was found to give good estimations of the apparent contact angles for the sands of mixed wettability. Soil water characteristic curves showed clear transitions from hydrophilic domains to less hydrophilic or hydrophobic domains corresponding to the apparent contact angles. Furthermore, it was found that magnitude of soil-water hysteresis for the sand was affected by its wettability.