Establishing selection criteria of water repellent sandy soils for use in impervious layer of engineered slope

In this study, the selection criteria of water-repellent sandy soils for use in the impervious layer of engineered slopes were examined. First, the hydrophobization of six kinds of sandy soils was performed via the silane treatment. Laboratory experiments to assess hydrophobicity and water-shielding performance—namely the water drop penetration time (WDPT) test, the contact-angle measurement test, and the water infiltration head (WIH) test—were conducted. Based on the required thickness and the required particle number of water-repellent soils, the mean particle sizes of sandy soils that achieved acceptable water-shielding performance were determined. It was found that a C_c value of less than 1.0 or a D₄₀ value of less than 2.0 mm allowed good water-shielding performance in sandy soils. Lastly, some of the measured WIH values agreed with the results estimated by the capillary rise model, and the application of the particle size to this model was discussed.