Water-entry pressure and friction angle in an artificially synthesized water-repellent silty soil

Water-repellent soils possess unique hydraulic and mechanical behaviours that confer large potential for their use in geotechnical applications because particle-scale surface-wettability characteristics significantly influence macroscale manifestations. This study examined the hydraulic and mechanical behavior of an artificially created water-repellent silty soil with four different concentrations of a reactive organo-silane solution. A series of laboratory tests was performed that included measurements of waterdroplet penetration time (WDPT), water-entry pressure (WEP), flow rate, and friction angle. Experimental results showed that the artificial treatment produced a unique range of porosity values depending on the concentration and that the WDPT and WEP increased with decreasing porosity and increasing concentration. A gravimetric fraction of 40% water-repellent particles was sufficient for bulk soils to exhibit water repellency. The flow rate of specimens with a high concentration of reactive organo-silane tended to be high due to the resulting high degree of saturation on water permeation. In contrast, friction angles tended to decrease with increasing concentration of organo-silane solution under dry conditions and remained quasi-constant on wetting, regardless of the degree of saturation.