Synergistic effects of density, gradation, particle size, and particle shape on the water entry pressure of hydrophobized sands

This paper examines the specific role and interdependencies between soil density, particle size, particle shape, and gradation on the water entry pressure of hydrophobized sands. The tested granular materials include quartz sands of three size ranges, glass beads, and crushed glass. All granular materials were initially silanized with polydimethylsiloxane (PDMS) coatings to achieve the same intrinsic hydrophobicity. The water-ponding method was adopted to measure the water entry pressure in a comprehensive parametric study that consisted of 96 tests. Despite an acute sensitivity of the water entry pressure to relative density, the results revealed a more dominant effect of particle size. The largest water entry pressure (hydrophobized fine sand) was 14 times that of the lowest (hydrophobized coarse sand). Relatively higher water entry pressures were recorded with sands having larger coefficients of uniformity. A comparison between hydrophobized glass beads and crushed glass also revealed that rounded particles were less effective in retarding water infiltration in a dense state. A relationship, based on Jurin's law, was proposed for dense sands whereby the water entry pressure is obtained from the coefficient of uniformity, mean particle size, and particle shape.