Study on creep properties of weak layer rock of slope under damage coupling

Based on the fractional order calculus theory and Weibull distribution, the fractional order nonlinear creep constitutive equation of green mudstone in the weak interlayer of slope under the combined action of initial damage and creep damage is established. In order to investigate the effect of damage degree on creep mechanical parameters and creep parameters, as well as the superiority of the improved creep model, creep tests were conducted on green mudstone samples with different initial damage degrees. The fractional order nonlinear creep damage coupling model outperforms the other two theoretical models in accurately describing the three stages of creep. The stress and damage variables in the constitutive equation will change the initial strain value of the creep curve. The fractional derivative and damage factor affect the shape of the creep curve, that is, change the time when the rock enters the third stage of creep. Therefore, to accurately predict the entire creep process of green mudstone, it is necessary to add fractional derivatives and damage factors to the creep model. This study is of great significance for analyzing the initial failure of slope creep under long-term gravity action and also provides a basis for predicting slope stability under coupled failure.