Abstract: The rheological properties of rockfill materials are a primary factor contributing to the post-construction settlement of a rockfill dam, and improving compaction quality can reduce such settlement effectively. In this study, large-scale triaxial creep tests are conducted on rockfill specimens with different initial void ratios. We develop a compaction state-dependent final rheological model considering the void ratio effect, and examine the influence of compaction quality on the long-term deformation of a rockfill dam. The results indicate the rheological behavior of rockfill materials depends significantly on the compaction state－the smaller the initial void ratio, the bigger the attenuation rate of creep velocity and the smaller the final creep deformation. The dilatancy equation of the modified Cam-clay model well describes the rheological dilatancy relationship of rockfill materials, and the rheological critical dilatancy stress ratio decreases exponentially with the void ratio. Our final rheological model, equipped with 5 parameters, can uniformly characterize the final rheological behavior of rockfill materials under different compaction states; It is applicable to refined simulations of the effect of spatial variability in compaction quality on the long-term deformation of a rockfill dam. Compaction quality imposes a remarkable influence on the post-construction settlement of rockfill dams－the larger the initial void ratio, the more significant the increase in settlement, while the growth of downstream displacement is relatively smaller.

Key words: earth-rock dam, rockfill material, rheological property, initial void ratio, deformation prediction