The Effect of Hydraulic Hysteresis on the Shear Strength of Clayey Soils under Partially Saturated States

摘要

Hydraulic hysteresis is a common phenomenon in unsaturated soils. The soil-water retention curve from the drying process is different from the one from the wetting process due to the effect of hydraulic hysteresis. The soil strength is strongly affected by the soil-water characteristics. Hence, hydraulic hysteresis can have an important effect on the shear strength of a soil. The direct shear tests under the drying and wetting conditions were done to explore the effect mechanism of the hydraulic paths on the shear strength of clayey soils. The results show that shear strengths of the clayey soils have the obviously peak values at low water contents for the drying paths. And the strain softening characteristics of the clayey soils are exhibited. However, the strain hardening is exhibited under high water content conditions for the drying paths. The strain hardening is always occurred for the wetting paths. The shear strengths of the clayey soils are obviously different from the wetting and drying paths although the water content of the samples and loaded normal stress are the same. The shear strength loss ratio, η is introduced to quantify the difference of shear strength of clayey soils under different hydraulic paths. The shear strength loss ratio is between 8% and 18%, which shows that hydraulic hysteresis has an important influence on the shear strength of clayey soils.