Effects of Grain Size and Grading on Dynamic Shear Moduli of Sands

Abstract

Resonant-column tests were performed intending to clarify the effects of grain size distribution on shear moduli of normally consolidated disturbed sands for shear strain ranging from 10 -6 to 10 -4 . The sands tested are clean sands which are uniform and do not contain fine particles, natural sands which are not uniform and contain fine particles and other artificially graded sands. The test results indicate the followings. Shear moduli of the clean sands tested at strain levels of γ = 10 -6 , 10 -5 and 10 -4 are expressed approximately by the similar empirical equations irrespectively of grain shape and grain size. For the sands other than clean sands, however, shear moduli decrease with the increase in uniformity coefficient and also decrease with the increase in the content of fine particles. Therefore it is concluded that in estimating shear moduli of ordinary natural sands which are not so uniform and contain fine particles, it is preferable to conduct resonant-column tests on the sands of interest. When tests are not conducted, the effects of grain size distribution on shear moduli should be taken into account.