Dynamic behaviour and constitutive relationship of saturated fly ash-modified loess

The dynamic stress-strain relationship of a saturated loess modified using different fly ash contents is studied based on dynamic triaxial tests. The relationship between the dynamic behaviour and fly ash content is determined. Combined with SEM test results, the seismic-resistant mechanism of the fly ash-modified loess is analysed. The results show that the dynamic constitutive relationship of saturated fly ash-modified loess obeys the hyperbolic model. The model parameter a is minimum when the fly ash content is 20%. However, with the increase in the fly ash content, the model parameter b decreases, and the dynamic modulus of the modified loess is increased, whereas the damping ratio is reduced. When the weight proportion of fly ash is approximately 25%, the increase in the dynamic modulus and the decrease in the damping ratio with the increase in the dynamic strain tend to be slow. With the increase in the fly ash content, the flocculent cement content and the numbers of fine and micro pores in the modified loess are obviously increased. The improved liquefaction resistance of the loess is largely attributed to the increase in the inter-particle strength and the significant decrease in the number of large pores.