Investigating and comparing the resistance characteristics of sandy soils with changing the percentage of moisture and fine-grained characteristics

In nature, sandy soils are rarely clean and often contain some clay and silt. These fines grain have a significant effect on the resistance and dilation behavior of sandy soils. Therefore, in this study, resistance and dilation behavior of sand mixture with fine grains such as silt and clay using a small scale direct shear test have been studied. Tests are conducted on specimens of sand with various fine content ranging from 0 to 40%, density of 30, 60 and 90 percent and the samples are subjected to three normal stresses 0.5, 1.0 and 1.5 kg/cm2 with two percent of optimum and saturation moisture. The test results show with increase in percentage of fine grains, the shear strength of sandy soil decrease and with increase in percentage of clay the shear strength decreases further. Also, dilation angle and angle of friction decreases with increase fine grains content and cohesion parameter increases with increase fine grains, Of course, it more increases with increase clay content and the rate of change of the cohesion parameter increases with increasing fine-grained percentage.