Effects of nonplastic fines on static liquefaction of sands

Undrained triaxial compression tests were performed on reconstituted samples of Nevada and Ottawa sands with systematic variations in the fines content (particles smaller than 0.074 mm in diameter) to evaluate the effect of the finer fraction on the static liquefaction potential under monotonic loading. The fines were nonplastic. The results clearly show that the presence of fines can greatly increase the potential for static liquefaction of all four clean base sands using the dry funnel deposition technique. The fines appear to create a particle structure in the soil which is highly compressible, enhancing the potential for liquefaction, even though the density of the soil increases. Increasing the fines content of a clean sand can have the effect of increasing the potential for liquefaction up to a certain maximum level at which the behavior of the fines dominate the undrained soil behavior. At this point the potential for liquefaction tends to become constant with respect to relative density. It was found that complete static liquefaction could occur at a relative density greater than 60% at high fines contents.