Abstract: The creep characteristics of fillers in water transportation engineering are related to the long-term stability of dock foundations. However, limited studies focused on the creep model of sandstone and mudstone fillers. To construct a constitutive model that can accurately describe the creep characteristics of sandstone and mudstone fillers, shear creep tests were conducted under different mix ratio conditions. Based on experimental results, the basic model is determined, and a new fractional order creep model considering time-dependent damage is constructed by combining Riemann-Liouville fractional calculus operator theory and damage mechanics theory. Model validation analysis found that as the content of mudstone particles increases, the long-term strength of sandstone and mudstone fillers gradually decreases, promoting the development of filler damage. Sensitivity analysis reveals that the model parameters η_α1, η_α2, α₁, and α₂ influence the model response in descending order of sensitivity: η_α2>η_α1>α₂,> α₁. The simulated values of the new model are consistent with the experimental data of sandstone and mudstone fillers, with an average R² of 0.99, proving the feasibility and rationality of the new model. This achievement provides the valuable insight for understanding the creep characteristics of sandstone and mudstone fillers and the long-term stability of dock foundations.