A comparative study on the undrained shear strength results of fall cone and vane shear tests in sand–clay mixtures

Abstract

This paper presents an intensive series of laboratory testing results from vane shear and fall cone tests that were conducted on various clay–sand mixtures to understand the link between these methods which are often used for determining the undrained shear strength (su). Three different gradations (2.0–1.0 mm, 1.0–0.6 mm, and 0.6–0.3 mm) of rounded and angular sands were mixed with low-plasticity clay at ratios of 0%, 10%, 20%, 30%, 40%, and 50%. The results of the tests demonstrated that the su values obtained from the vane shear tests were found to be always higher than those obtained from the fall cone tests. It was shown that the sand content used in the mixtures changed the su parameters of the specimens significantly. The results indicated that the su values were significantly influenced by grading characteristics of the sands (d10, d20, d30, d50, d60, cu, cc). The values of su were lower for the samples that had a larger size of sand grains. Finally, shape characteristics of the sand grains were found to be effective on the results. The samples with angular sand grains have higher su values than the samples with rounded sand grains, for all gradations employed in the present study.