Abstract: Large-scale triaxial tests are conducted on sand specimens mixed with 20% fly ash under different consolidation and drainage conditions to investigate the behavior of fly ash and sand mixtures. The stress-strain behavior of fly ash and sand mixture with different reinforcements and different spacings between layers of reinforcement under different consolidation and drainage conditions is examined. Test results reveal that the shear performance of fly ash and sand mixture is the optimum under unconsolidated undrained condition. The effectiveness of tire reinforcement is the best,followed by triaxial geogrid,biaxial geogrid and geocell reinforcement. The corresponding coefficient of reinforcement effect and principal stress difference at failure both increase with the reducing of the spacing between reinforcement layers. Nevertheless,the spacing between reinforcement layers should not be too small; the reinforcement effect is good when the spacing is 20 cm. In addition, as confining pressure increases,the deviatoric stress at failure increases, while the corresponding reinforcement effect shrinks.The aforementioned results revealed the mechanical properties of reinforced fly ash-sand mixture under triaxial test, hence serving as theoretical basis for the application of fly ash-sand mixture.

Key words: fly ash and sand mixture, reinforced soil, large-scale triaxial test, shear strength, reinforcing effect