Abstract: The shear properties of composite soil mixing clay with rubber particle of scrap are investigated by using direct shear apparatus Shear Trac-II. Effects of the scrap rubber particle contents and particle size on the shear strength of composite soil are analyzed. The relationships between shear strength indexes and rubber particle contents or particle sizes are established. Besides, compaction properties of composite soil are studied by light compaction tests. Results indicate that maximum dry densities and optimum water contents of composite soil decrease gradually with the increase of rubber particle contents. However, the reduction tendency significantly decreases when rubber particle content exceeds 15%. When rubber particle content is 40%, shear strength of composite soil reaches the highest increasing by 20%~40% compared with pure clay soil. Furthermore, increasing particle size could significantly enhance the shear strength of composite soil when particle contents are less than 20%. Additionally, cohesion of composite soil increases firstly and then decreases with the increase of particle contents, whereas internal friction angle increases gradually . During the shearing process, soil sample exhibits a property of shear shrinkage at first and then shear dilation. And shear dilation is obvious for composite soil mixed with large size particle in low vertical pressures.

Key words: rubber particle of scrap tire, clay, composite soil, rubber particle content, compaction characteristics, shear strength