Experimental Study on the Shearing Behavior of Saturated Silty Soils Based on Ring-Shear Tests

The shearing behavior of saturated silty soils has been examined extensively by performing undrained and partially drained (the upper drainage valve of the shear box was open during shearing) ring-shear tests on mixtures of a sandy silt with different loess contents. By performing tests at different initial void ratios, the shear behavior of these silty soils at different initial void ratios is presented and discussed. Undrained-shear-test results showed that the liquefaction phenomena in ring-shear tests were limited within the shear zone; for a given void ratio or interfine void ratio, both the peak and steady-state shear strengths decreased with increase of loess content. The partially drained shear tests revealed that a great reduction in the shear strength could result after the shear failure, due to the buildup of excess pore-water pressure within the shear zone; the magnitude of reduction in shear strength after failure was affected by the initial void ratio, the shear speed after failure, as well as the loess content in the sample. For a given void ratio or interfine void ratio, with increase of loess content, the drained peak shear strength became smaller, while the brittleness index became greater. It was also found that due to localized shearing, the permeability of the soil within the shear box after drained shearing could be three orders of magnitude smaller than before shearing.