Effect of clay content on the shear strength of clay-sand mixture

This paper investigates the effect of clay content on the shear strength of clay-sand mixtures. Bentonite and Jumunjin sand were mixed to prepare clay-sand mixtures with varying clay contents of 5, 10, 15, 20, 25 and 30%. The shear strength of clay-sand mixture was measured using direct shear tests and angle of repose tests in dry condition. The angle of repose of the clay-sand mixture was measured to be greater than that of pure sand for the studied range of clay contents. Likewise, the internal friction angle of the clay-sand mixture was measured to be higher than that of pure sand, reaching a peak at the clay content of 10%. Theoretically, the behavior of the clay-sand mixtures was to be governed by large size particles at clay contents smaller than 23.5%, which agrees well with the visual inspection on the mixtures. At clay content of 25.1% or greater, where the contribution of large particle was theoretically assumed to be none, the results from the angle of repose tests were significantly scattered, indicating that the clay started playing a key role in the behavior of mixtures.