Shear strength characteristics of sand-gravel mixtures

Abstract

Most of the previous constitutive models used for investigation of the shear behavior of sandy soils have been developed without consideration of the oversize particles. The size of experimental samples is an important limitation in this case. In this research a laboratory study has been planned to investigate the shear strength of sandy soils containing different gravel contents. The tests conducted using a large scale direct shear apparatus with a 300 mm x 300 mm x 170 mm shear box. All the tests have been performed on dry samples in drained condition. The gravel contents of 20, 40 and 60 percent were used in sample preparation. The tests conducted in three different densities of 35, 60 and 85 percent and three different surcharges of 150, 300 and 450 kN/m². It was observed that the increase in gravel content and relative density results to an increase in the shear strength and dilation of the mixture. However, the gravel content has a more visible effect on the shear strength rather than the relative density. The brittleness and softening of the shear behavior also increases as the gravel content increases in the mixture. It was determined that the minimum void ratio of the mixture is a useful parameter to investigate the effects of gravel grains on the shear strength of sandy soil. The effect of overburden pressure on this relationship was also considered in this study.