Abstract: To investigate the creep characteristics of loess, we conducted consolidation–drainage triaxial creep tests on undisturbed Malan loess at different moisture contents, while monitoring axial, radial, and volumetric deformations throughout. The test results show that the creep deformation of Malan loess with different moisture contents is characterized by axial compression, radial expansion, volume compression, and then axial accelerated compression, radial accelerated expansion, and volume accelerated compression to damage. Based on the mechanical response and microstructural evolution of loess under creep, we conclude that creep macroscopically reduces loess strength and increases deformation, while microscopically causing structural damage to the soil. The mechanism involves three synergistic effects—water-induced reduction of interparticle resistance, load-induced space release, and time-dependent processes—that promote creep-slip of soil particles. Based on memory-dependent derivatives and damage mechanics, we propose a creep-damage constitutive model. The applicability of the new model has been verified by fitting the theoretical model to the creep test data. These results deepen our understanding of loess creep and have practical value for the long-term safety assessment of loess engineering.

Key words: consolidation-drainage triaxial creep test, creep deformation characteristics, memory-dependent derivatives, creep damage constitutive model