Investigation of Cyclic Behavior of Silty Sand Soils Using Cyclic Simple Shear Test Under Constant Volume Conditions

The study of cyclic behavior of sandy soils during seismic load application has been one of the most important geotechnical issues in previous decades and is still one of the most geotechnical challenging seismic aspects among researchers. In the earthquake state, the soil is under initial constant normal stress and the shear stresses due to the earthquake on the sample change direction regularly, and as a result, the directions of cyclic changing the main effective stresses the soil sample is accessible. In this research, cyclic simple shear responses for different combinations of clean silicate sandy soil and non-plastic fine content of silt have been evaluated in order to understand such soils. The experiments were performed at cyclic stress ratios of 0.15 (CSR = 0.15) and confine pressures of 50, 100 and 150 KPa. Constant volume cyclic Simple shear tests on clean sand samples have shown that by increasing the non-plastic fines content to 30% by weight of the sample, the shear strain decreases and then the shear strain increases but the shear strain of the sand with 40% silt is less than the clean sand. The results showed that the liquefaction resistance of clean sand soil under the same conditions is higher than the silty sand soil. Also, with increasing confine pressure, the soil liquefaction resistance increases in all silt percentages.