A series of strain-controlled cyclic triaxial tests were performed on Firoozkuh sand-silt mixtures with wide ranges of fines content (FC), relative density (Dr), and effective confining stress ( sigma c ') to investigate their liquefaction resistance in terms of capacity energy (Wliq). Also, several cyclic test results from previous studies were collected and reanalyzed. The results showed that Dr could be used as a proper parameter to define soil density state for predicting Wliq of clean sands and sand-silt mixtures when FC is greater than dispersing fines content (FCdis). However, due to the complicated role of FC in coarse-fine assemblies, no universal relationship between Wliq and FC has been reported for the soil mixtures when FC is less than the threshold fines content (FCth). Therefore, the concept of equivalent granular void ratio ( e & lowast;) was used to capture the coarse-fine interactions in such mixtures. It was also found that the fines contribution factor (b), which is the fraction of fines participating in load transfer, is dependent on Dr, as well as particle size disparity ratio (chi) and FC, neglected in previous studies. Finally, a new model was proposed for the prediction of the b value and also a unique relationship between e & lowast; and Wliq was obtained for all mixtures of specified sand and silt where FC <= FCth.