Effect of grain-size distribution on cyclic strength of granular soils

Earthquakes are quite frequent in Japan. Liquefaction cases are often reported in the grounds which were not thought of liquefiable previously because they included larger gravel fraction or fine fraction. In this study, effect of soil gradation characteristics has examined in detail considering their critical role. The cyclic strength properties of the fill materials consisting of various gradation were investigated by using five soils with D-max = 2 mm and two, D-max = 19 mm from different sites in Hyogo prefecture, Japan. By preparing the test samples at the degree of compaction of 85%, 90% and 95%, based on the recommended values for various embankment types in the field, undrained cyclic triaxial tests were conducted in order to evaluate the liquefaction resistance of each soil type. Results show that increase of cyclic strength against the dry density was largely affected by the fines content (F-c) and average particle size (D-50) among others, of the tested soils.