Correlations between water-entry value and its affecting factors for hydrophobic soil: A review

Hydrophobic soil has been proposed to be adopted as an infiltration barrier for geostructures because a water-entry value needs to be reached to wet hydrophobic soil. The Washburn equation was initially proposed to estimate the capillary height of hydrophilic soil (contact angles lower than 90 degrees), thus it is doubtful that whether one can use it for hydrophobic soil (contact angles larger than 90 degrees) without modification. Current studies show poor estimations of water-entry value by adopting the Washburn equation. This paper aims to conduct a review on the affecting factors of water-entry value for hydrophobic soil. Data from the literature are collected, reinterpreted and analysed with reference to existing theories. At the end of this review, research gaps which may be worth investigating are given.