EFFECTS OF GROUND RUBBER ON COMPRESSIBILITY，SHRINKAGE AND HYDRAULIC CONDUCTIVITY OF KAOLIN SOILS

Used as a modified material, the waste tire granulated rubber is expected to enhance the effectiveness of liner system in landfill and extend the utilization of the tire waste. The mechanical and hydraulic properties tests of waste tire ground rubber and Kaolin soil mixtures are conducted. The effects of ground rubber on the compressibility, shrinkage and hydraulic conductivity properties are studied. As the rubber mixing content increases, the hydraulic conductivity, coefficient of compressibility, swelling index, coefficient of consolidation, and volumetric shrinkage ratio increase. The Kaolin soil and the mixtures are medium compressibility soils. The unconfined compressive strengths are greater than 200kPa, and the volumetric shrinkage ratios are less than the threshold strain of 4%. Under the pressure of 50kPa and 200kPa, the hydraulic conductivities are less than 1.0×10^-7cm·s^-1,which meets the requirement of compacted clay liner in the specification. In contrast to the 30mesh ground rubber, the mixtures of 12mesh ground rubber and Kaolin soil have smaller compressibility and swelling index, and larger consolidation coefficient. It is also found out that the size of the ground rubber has insignificant effect on unconfined compressive strength, shrinkage and hydraulic conductivity of the mixtures. Overall, the mixture with the size of 12-mesh and the rubber content of 25% is the optimal design scheme for using as a landfill liner material.