Dynamic behavior and constitutive model of rice husk ash-stabilized loess under freeze–thaw and traffic loading

A series of dynamic triaxial tests was conducted using a global digital system temperature-controlled bidirectional dynamic triaxial system to meet the need for reliable dynamic design parameters of rice husk ash (RHA)-modified loess subgrades in cold regions subjected to the coupled effects of repeated freeze–thaw cycles and traffic-induced dynamic loading. The effects of RHA content and freeze–thaw cycles on dynamic stress–strain behavior, dynamic elastic modulus, normalized dynamic elastic modulus, and damping ratio were systematically investigated. On the basis of the experimental results, a dynamic constitutive model for RHA-modified loess was established. Results indicated that increasing the RHA content substantially enhanced the dynamic stress, dynamic elastic modulus, and normalized dynamic elastic modulus of the modified loess and reduced the damping ratio. Under conditions with coupled freeze–thaw cycling and dynamic loading, the degradation induced by freeze–thaw cycling and traffic loading acted synergistically, resulting in a pronounced deterioration of the dynamic properties of the soil. The findings not only elucidate the improvement mechanism of RHA in the dynamic behavior of loess and the degradation mechanism associated with freeze–thaw cycling but also demonstrate that the proposed constitutive model accurately captures the dynamic response of modified loess under complex loading conditions. This study provides a theoretical basis and technical reference for frost-resistant design, dynamic response analysis, and engineering optimization of loess subgrades in cold regions.