Abstract: The low recycling rate of ever increasing waste tire has brought about severe environmental problems. In this research we prepared mixed soil samples by adding waste tire rubber powder into red clay, and examined the compaction strength, shear strength and permeability of the mixed soils with varied rubber powder content (0%, 3%, 8%, 15%, 25%) and water content via standard light compaction test, equivalent compaction test, direct shear test and penetration test. Results unveiled that (1) the maximum dry density of red clay mixed with rubber powder was lower than that of original red clay, and the maximum dry density decreased with the increase of rubber powder content. (2) With the growth of rubber powder content, the optimum water content augmented in standard compaction test but reduced in equivalent compaction test. (3) When rubber powder content was lower than 15%, both the shear strength and internal friction angle of the mixed soil climbed with the increase of rubber powder content, showing strain hardening features. (4) In standard compaction test, when rubber powder content was 8%, the permeability rate of mixed soil rarely changed, while when rubber powder content was 15%, the permeability rate soared with an increasing rate of 97.3%. The research findings offer reference for the recycling of waste rubber powder and the engineering application of modifying red clay with rubber powder.

Key words: red clay, rubber powder, compaction characteristics, dry density, direct shear test, permeability