Modeling the Creep Behavior of Sliding Zone Carbonaceous Shale Subjected to Dry–Wet Cycles Using a Fractional Derivative Approach

The long-term effects of dry–wet cycles induced by seasonal rainfall significantly influence the creep behavior of sliding zone soft rocks, contributing to landslide occurrence. Understanding this aspect is crucial for predicting and mitigating long-term slope instability. This study investigates the Mohuandang landslide, conducting shear creep tests on carbonaceous shale under dry–wet cycles. A quantitative approach was introduced, incorporating a fractional derivative to modify the Burgers model and develop an improved creep equation. Model validity was verified through experimental data. The key findings are as follows: (1) At low deviatoric stress levels (within the viscoelastic stage), creep deformation exhibits a nonlinear increase under dry–wet cycles, leading to a progressive reduction in long-term strength. (2) The modified creep model effectively captures the creep behavior of the sliding zone under the influence of dry–wet cycle-induced damage. (3) The damage evolution characteristics exhibit clear physical significance. These results provide theoretical insights and practical guidance for landslide prediction and risk management in regions subjected to dry–wet cycles induced by seasonal rainfall.