Shear creep test and creep damage model study of mud shale under impact disturbance

The rock is in a creeping state for a long time under stress, and the impact disturbance effect generated during the mine blasting and mining process will accelerate the accumulation of rock damage, which seriously threatens the stability of the mine slope. Taking the shale in the soft interlayer of the slope of Huangshan limestone mine as the research object, the creep mechanical characteristics of the mud shale under the influence of impact disturbance were analyzed by carrying out shear creep tests under different impact energies and different impact times, and the secant modulus method was introduced to quantify the impact damage, and the evolution law of impact damage was analyzed. By introducing the Weibull distribution function to characterize the stress damage factor, and deriving the stress-impact coupling damage factor from the generalized damage theory, then introducing the impact damage degree and correction coefficient to improve the viscous element according to the change analysis of the viscosity coefficient, and finally substituting the coupled damage factor and impact damage improvement element into the Nishihara model, a new creep damage model is established. According to the experimental results, the differential evolution algorithm is used and the parameters of the model are identified by relying on the 1stopt global optimization software. Based on the above research, the following results are obtained: with the increase of impact energy and impact frequency, the long-term strength and total creep time of mud shale gradually decrease, the impact damage degree also increases, and its failure characteristics gradually change from brittle failure to typical plastic failure; under low shear stress level, the sensitivity of mud shale to impact disturbance is low, but with the increase of shear stress level, the sensitivity of shale to impact disturbance also increases, and the impact damage degree increases faster; the model fitting data matches the experimental data is high, and the creep damage model can better describe the creep characteristics of mud shale under impact disturbance. The research results can provide a theoretical basis for disaster prevention monitoring and stability analysis of mine slopes.