Abstract: In this paper, direct shear tests were performed to study the influence of various degrees of saturation and clay contents on the shear strength of soil samples collected from a wind farm in Shandong Province. The test results showed that the shear stress-shear displacement relationship under the condition of a low degree of saturation was strain softening, and the strain hardening under a high degree of saturation. In addition to this, the plasticity of the cohesive soil sample increases with the increase in clay contents. With the increase in the degree of saturation, the cohesive forces among soil particles decrease which results in the decrease in shear strength of silty soil samples. Further, with the increase in clay contents, the shear strength of silty soil samples at first increases and then decreases, which is affected by the angle of internal friction. Overall, the clay content is an important factor that controls the effect of degree of saturation on the shear strength of finegrained soils.

Key words: fine-grained soils, degree of saturation, clay content, shear stress-shear displacement relationship, shear strength