Abstract: The rice husk ash, which is environmental friendly waste-recycling, can strengthen the soil. Triaxial tests were conducted to study the stress-strain properties, strength characteristics, and variation characteristics at different strain levels including the elastic modulus, deviator stress and reinforcement strength ratio of rice husk ash mixed clay with different proportions of rice husk ash and its reinforced soil. The test results show that the maximum dry density of the mixed soil reduces significantly and the optimum moisture obviously increases with the increase of rice husk ash content. The content of rice hush ash has a great influence on the shear strength of the reinforced soil, and rice husk ash-soil mixture’ s initial tangent modulus and peak stress that addition of 10%?15% rice husk ash is recommended as the maximum. Compared with geotextile reinforced rice-husk-ash mixed soil, higher deviatoric stress and shear strength are observed on specimens with geogrid, and this trend is more obvious with the increase of the number of reinforcement layers. It also shows that the inflection point of the stress-strain curve is more prominent with the increase of the number of reinforcement layers. The elastic modulus of the mixture material depends on the content of rice husk ash, the type and layers of reinforcement. After adding the rice husk ash, the elastic modulus of the soil increases significantly, and it increases 1.5 times in better content when reinforced by geogrid, both rice husk ash and the reinforcement can effectively strengthen the soils. As the number of reinforced layer increases, the reinforcement strength of rice husk ash-soil mixture increases significantly but has little relation with the confining pressure.

Key words: rice husk ash, triaxial test, reinforced soil, stress-strain, strength