Effect of grading characteristics on the undrained shear strength of sand: review with new evidences

In this paper, the shear strength of saturated pure sand and sand-silt mixture is evaluated by monotonic undrained triaxial tests that were carried out on reconstituted specimens at same relative densities and a constant confining pressure (sigma (3) = 300 kPa). The test results were used to conclude on the effect of low non-plastic contents (0-20 %) and grading characteristics on the liquefaction resistance of the sand. The test results indicate that the undrained residual strength reduced with the increase of non-plastic fine content. Also, shear strength of gap-graded sand mixed with low non-plastic fine content increases with decrease in effective size (D (50)). In other words, in this state, we can use the D (50) as a parameter to control of silty sand's undrained resistance. Besides, the undrained residual strength of pure sand specimens with same effective size increases due to increase of coefficient of uniformity (C (u)).