Liquefaction susceptibility study of sandy soils: effect of low plastic fines

The objective of this paper is to present a study on the mechanical behavior of three Algerian sands through cyclic triaxial tests with focus on the effect of the fines content. The particularity of this study is to keep the amount of the sand material matrix as a constant parameter for the entire range of fines content. This choice was considered due to the difficulty to determine experimentally the maximum and minimum void ratios of soil mixtures for fines content exceeding 15 %. The materials used in this investigation are originated from two different regions (Chlef and Boumerdes) in northern Algeria and are known for their higher seismicity levels. By varying the cyclic stress ratios and the proportion of fines contained naturally in the sand, a series of cyclic triaxial tests were carried out on reconstituted samples with a density index of 0.5 and an initial confining pressure of 100 kPa, on a servocontrolled dynamic machine with a sinusoidal frequency signal of 0.05 Hz and alternated symmetrical cycles. Comparing the clean and natural sands, the test results indicate that the presence of fines influences significantly the liquefaction resistance. Indeed, the fines content increases the liquefaction resistance for Zemmouri sand, decreases or stabilizes it for the Rass and Chlef sands, respectively. The effect of fines on the Chlef and Rass sands is in good agreement with the published literature, where the liquefaction resistance decreases to a threshold value and then increases with the increase of the fines content. This study can be used in soil classification and determination of liquefaction potential of seismic areas with smaller amounts of fines.