Hydromechanical behaviour of hydrophobised soils of varying degrees of saturation: a comprehensive review

Artificially hydrophobised soil has been recently considered as an alternative engineering material that may be used to reduce water (or rainfall) infiltration and hence to enhance the geotechnical performance and stability of earthen structures such as slope and landfill covers. Thorough research has been conducted to study the hydrological behaviour and properties of hydrophobised soil in the last four decades. Mechanical properties of this kind of material has received some attention only since 2011, focusing on how hydrophobisation may affect the shearing behaviour and shear strength parameters including friction angle. Knowledge on the effects of hydrophobisation on other hydromechanical properties of soil that are relevant to geotechnical engineering applications is lacking. This paper therefore aims to conduct a comprehensive review and carry out some reinterpretation of selected literature with references to existing theories or frameworks of soil mechanics. Attempts are made to generalise and highlight not only the shearing behaviour, but also dilatancy, compressibility and stiffness of hydrophobised soil. Research gaps that may be worth exploring are given after the review.