As a new type of cementitious material

polymers have been widely applied in water conservancy and geotechnical engineering due to its fast cementation speed

high strength

light weight and high flexibility. As a polymer-containing composite

the constitutive model for polymerized rockfill materials remains inadequately studied. To characterize the mechanical behavior of polymerized rockfill materials more comprehensively

we develop a plasticity constitutive model that accommodates non-associated plastic flow

based on fractional-order calculus. The model introduces a modified mean stress that accounts for the polymer gelation effect and unifies the critical-state parameters across different polymer contents. It adopts a two-parameter yield surface and embeds the state parameters

defined by the modified mean stress

into the stress-dilatancy relation and the plastic modulus. Consequently

a stress fractional order plasticity constitutive model for polymerized rockfill materials with state dependence is established. Comparison of model predictions with experimental results shows that the proposed stress-fractional-order plasticity constitutive model effectively captures the strain-hardening and shear-shrinkage behavior of polymerized rockfill materials under drained shear conditions.