Abstract: 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.

Key words: polymerized rockfill materials, fractional order, plasticity constitutive model, modified mean stress, state-dependent