Abstract: Widely-graded soil is a good anti-seepage filling material for core of earth dams and embankment, and its impermeability is determined by its hydraulic properties. For the same soil, compaction is the primary factor that controls its hydraulic properties. In this study, the effect of compaction on hydraulic properties of a widely-graded soil is studied by laboratory tests, and through data analysis, the hydraulic property model is established, which is based on the effect of compaction. The results demonstrate that the higher the degree of compaction, the less macropores between particles of the soil, the higher the air-entry-value of the soil, the lower the saturated permeability coefficient. A prediction model of osmotic suction is proposed and it can accurately describe the changing principle of osmotic suction for unsaturated soil upon drying. The air-entry-value of the soil has linear relationship with the relative compaction on semi-log coordinate, and saturated permeability coefficient has linear relationship with the dry density on semi-log coordinate. An experiential model among air-entry-value, saturated permeability coefficient, unsaturated permeability coefficient and relative compaction is established, also an experiential calculation formula for soil-water characteristic curve (SWCC) of widely-graded soil is established, which has general applicability.

Key words: unsaturated soil, relative compaction, soil-water characteristics curve(SWCC), saturated permeability coefficient, soil hydraulic conductivity function