Influence of non-plastic silt content on seismic liquefaction of sands

Earthquakes are one of the important problems of Turkey because of being in a seismically active region. During earthquakes, loose, saturated, cohesionless soils could significantly lose their shear strength because of great excess pore water pressures generated and act like fluid, which is called soil liquefaction. Liquefaction is one of the most significant and worth researching phenomena in geotechnical engineering and it has been studied by researchers for decades. Liquefaction occurs mostly on sandy soils, but the soils in situ include a certain amount of silt. In this study, the effects of non-plastic silt contents on the liquefaction potential of sands were investigated experimentally at the Soil Mechanics Laboratory of Yeditepe University. The clean sand was mixed with silt at three different fines contents (i.e. FC = 5 percent, 15 percent, and 35 percent). Cyclic Direct Simple Shear (CDSS) tests were performed on each soil under 100 kPa vertical effective stress at a wide range of different relative densities (Dr) and under three different cyclic stress ratios (i.e. CSR = 0.1, 0.12 and 0.14). The results were compared with that of the clean sand (i.e. FC = 0%), and the change in the seismic liquefaction potential was investigated. In conclusion, it was observed that liquefaction resistance of silty sands with 5 percent fines content is greater than the resistance of clean sand and liquefaction resistance of silty sands with 35 percent fines content is smaller than the resistance of clean sands. In addition, it has been observed that liquefaction resistance of silty sands with 15 percent fines content decreases on soils where the relative density is less than 45 percent compared to the resistance of clean sands and liquefaction resistance of silty sands with 15 percent fines content increases on soils where the relative density is higher than 45 percent compared to the resistance of clean sands.