Modifying the mechanical properties of sand by using different hydrophobic conditions

Constructing a hydrophobic barrier structure is an effective means in reducing rainwater infiltration and maintaining the stability of earthen structures. The hydraulic properties of hydrophobized soil have been widely explored. However, effects of hydrophobic coating formation on the soil particle surface on the soil mechanical properties for the design and analysis of the barrier structure remain unclear. Thus, this study measures the mechanical properties (compressibility, shearing, and dilatancy) of a silica sand hydrophobized by dimethyldichlorosilane (DMDCS) to varying hydrophobic conditions, including the DMDCS content and the percentage of treatment (i.e., the mass proportion of hydrophobic mass among total mass). Test results reveal that (1) compressibility is unaffected when DMDCS content is less than 10%, and it is a function of degree of saturation ( S ) when the percentage of treatment is less than 100%; (2) the shearing mechanism switches from strain softening to strain hardening beyond a threshold DMDCS content because of the switching of shearing contacts between particles to between coatings; (3) the shear stress mobilized in 50%-treated sand lies in between that of the untreated and 100%-treated sand because of the presence of particle–coating contacts; (4) the peak friction angle declines with the increase in DMDCS content and is S -dependent for 50%-treated sand; and (5) soil dilatancy decreases significantly beyond a threshold DMDCS content of 0.05% or a threshold percentage of treatment of 50%.