Small strain stiffness of granular materials containing fines

Abstract

The paper presents the application of equivalent granular void ratio e* to predict the maximum stiffness of coarse particles containing low and high amounts of fines contents. A series of resonant column and compression wave velocity tests were conducted simultaneously on dense and loose specimens containing 0, 10, 20, 30, 40 and 50 gravimetric percentages of fine particles to measure the small strain moduli (Gmax, Mmax and Emax) of the mixtures. Samples were prepared by the moist tamping method and subjected to isotropic confining pressure levels of 50, 100, 150 and 200kPa. For the “fines-in-coarse” mixtures, Micro-CT scanning showed that some fine particles were active in the force chain network. This means that the contribution of fines in the force chains must be taken into account. The contribution of fines in the “fines-in-coarse” mixtures and the contribution of coarses in the “coarse-in-fines” mixtures were captured through the concept of equivalent granular void ratio e*. e was replaced by e* in Hardin’s relationship in the small strain region. The results revealed that Hardin׳s relationship is adequate for predicting maximum elastic moduli if e is replaced by e* in the void ratio function. However, the accuracy of the predicted maximum stiffness depends on the accuracy of the equivalent granular void ratio, e*.