Shear strength assessment of a well-graded clean sand

ABSTRACT: Shear strength of soil depends on various factors including the grain size distribution, stress level and the moisture content of the soil. This paper presents an investigation of the shear strength of a well-graded clean sand using direct shear tests. Tests are performed with varying normal stresses from 12.5 kPa to 400 kPa and varying moisture contents from 0 to 6%. A total of 80 direct shear tests are conducted which showed that the peak friction angle is influenced by normal stress levels and the moisture contents of the samples. The peak shear stress to normal stress ratio is higher at lower normal stress, which decreases with the increase of stress levels. The decrease of the stress ratio is higher for the moist sands than the dry sands. The dry unit weight of the sand is generally decreased with the increase of moisture content, which may contribute to the reduction of the friction angle for moist sands. The rate of shear displacement is varied to examine the effects on the shearing response of the sand. The shearing response of the sand is not found to depend significantly on the rate of shearing displacement within the range investigated.