Synthesizing Hydrophobic Sand and Comparison of Shear Strength Properties with Hydrophilic Sand

Soil can become hydrophobic following wildfires, oil-spills, or due to the presence of organic substances. While this phenomenon has been widely observed by researchers, there is little information regarding the shear strength properties of hydrophobic soil to date; therefore, this study investigated the shear strength of artificially hydrophobized sand particles. Hydrophobic particles were created by coating Ottawa sand particles with organic silane to form water repellent films around the particles. Direct shear tests were conducted at multiple normal stresses for the naturally hydrophilic and artificially hydrophobic sands under dry and submerged conditions. In the dry condition, the hydrophobic sand showed an average 26% reduction in peak shear stress, with the angle of friction reducing from 36.9 to 29.7° compared to the hydrophilic sand. The average peak shear stress reduction was 34%, with the angle of friction reducing from 38.7 to 26.1° in the submerged test. These results indicate that particle hydrophobicity reduces shear strength. This study highlights that with the increasing number of disasters that results in soil hydrophobicity, more research is needed on the strength properties of hydrophobic soils.