This paper aims to propose predictive equations for the small-strain shear modulus (Gmax) and small-strain damping ratio (Dmin) of a granulated mixture with plastic and nonplastic materials to reduce the dynamic energy of the ground. Polyurethane bead (PB) and glass bead (GB) were used as the plastic and nonplastic materials, respectively. 180 resonant-column tests were conducted with various conditions affecting the dynamic properties, such as nonplastic particle content (PC), void ratio (e), particle-size ratio (sr), and mean effective confining pressure (σm′). The results showed thatGmaxandDmin, respectively, increased and decreased asedecreased with increasingσm′of material mixtures. In addition,Gmaxdecreased with an increase in PC, whereasDminincreased. It was also found thatsrof materials affected the changes inGmaxandDmin. With an increase insr,Gmaxincreased whileDmindecreased because small particles do not hinder the behavior of large particles as the size of larger particles increases. Finally, based on the results, new equations for estimatingGmaxandDminof a granulated mixture with PB and GB were proposed as functions of PC,e, median grain size (D50), andσm′.