DIRECT SHEAR TESTING ON A ROCKFILL MATERIAL

In order to investigate the possible effects of two main factors (stress level and wetting) on a rockfill material, a number of medium-scale direct shear tests have been conducted with different stress levels in dry, saturated, and dry-saturated conditions. The results suggest that despite the similar trend of the strength and stiffness parameters related to the stress level in the three conditions, wetting decreases the strength and stiffness parameters of the material. In addition, the results of the dry-saturated tests showed that saturation of the dry specimens (modeling the first impounding of dry-constructed rockfill dams) decreases shear stresses and imposes sudden settlements on the material. This phenomenon is named saturation collapse in the literature. In addition, a comparison of the tests results with the results of the triaxial tests conducted on the same material indicates comparatively higher predictions by the direct shear tests.