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    Hydromechanical behavior of unsaturated artificially-hydrophobized sand: Compression, shearing, and dilatancy

    Year: 2021

    Journal: Eng. Geol., Volume 291, SEP 20

    Authors: Zhou, Zheng; Leung, Anthony Kwan; Zhu, Wei Jun; Li, Yuan Yuan

    Organizations: National Natural Science Foundation of China (NSFC) [51922112]; Research Grants Council of the Hong Kong Special Administrative Region, China [CRF/C6006-20G, AoE/E-603/18]

    Keywords: Hydrophobic soil; Wettability; Shear strength; Compressibility; Dilatancy; Unsaturated soil

    Artificially-hydrophobized soil has been used in geotechnical applications, such as slope stabilization. This application requires a thorough understanding of the soil's hydromechanical properties to inform stability assessment. The shearing behavior of dry and fully saturated hydrophobized sand has been extensively investigated in the literature. Yet, knowledge on the effects of unsaturation on the soil's hydmmechanical properties is scarce. Thus, how hydrophobic coating affects geotechnical properties such as compressibility and stress-dilatancy relation is unclear. This study conducted a comprehensive and systematic test program to, for the first time, quantify the hydromechanical properties of unsaturated hydrophobized Toyoura sand under wide ranges of confining pressure (25-300 kPa) and degrees of saturation (S; 0%-100%). The sand was hydrophobized by dichlorodimethylsilane (DMDCS). Constant-water-content shearing tests and compression tests were performed using the direct-shear box and oedometer apparatus, respectively. The test results revealed that the hydrophobic coating (i) made the compressibility index, swelling index, and peak friction angle independent of S; (ii) switched the sand's stress-strain behavior from strain-softening to strain-hardening at any degree of saturation; (iii) made the low-stress nonlinearity associated with sand dilatancy almost vanish; and (iv) made the peak friction angle to be practically independent of stress.
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