Influences of fines content on cyclic resistance ratio of fines-sand-gravel mixtures

In the available researches on the cyclic resistance ratio (CRR) of saturated sand-gravel mixtures, the factors such as gravel content, sample preparation method, relative density and consolidation stress ratio have been considered. However, because of some reasons, the fines content (FC) has rarely been studied. The influences of the fines content on CRR of fines-sand-gravel mixtures are studied based on a series of undrained cyclic triaxial tests. According to the theory of particle contact state, the fines-sand-gravel mixtures are divided into coarse-like soils, fines-like soils and in-transition soils. "Cyclic mobility" and "cyclic liquefaction" are introduced to describe the cyclic failure process of coarse-like soils, fines-like soils and in-transition soils, and the criteria for the evaluation of cyclic failure of mixtures are proposed. The test results show that CRR of mixtures decreases with the increase of FC when FC is less than 30%, thereafter, it starts to increase, and CRR is the weakest when FC is 30%. Also, the analysis shows that CRR of mixtures decreases with the increase of ek, when FC < 25% or FC > 35%, ek can serve as a proper index to uniquely evaluate CRR of fines-sand-gravel mixtures, and an exponential relationship between the decrease in CRR and the increase in ek is then obtained.