Analysis of dynamic disturbance and multistage shear creep damage evolution law of the weak intercalated layers in slope under the influence of coupled damage effect

Based on the damage characteristics of multistage shear creep in weak intercalated layers (carbonaceous mud shale) of slopes under the influence of dynamic disturbance, the effective bearing area method was used. A new coupled damage equation (dynamic disturbance damage, shear creep damage, and initial damage) was established through further derivation, and its applicability was demonstrated. The calculation method for the relevant coupled damage degrees was also provided. Furthermore, by targeting the three coupled damage factors and extending the Kachanov damage law, a time-dependent damage evolution equation for weak intercalated layers under the influence of the three coupled damage effects was established. The influence of different dynamic disturbance intensities on the evolution of multistage shear creep damage in weak intercalated layers of slopes under the influence of coupled damage effects was analysed. The results show that the damage to the rock mass caused by dynamic disturbance mainly occurs in the low-frequency stage (40–80 Hz). The instantaneous damage caused by dynamic disturbance to the shear plane of weak intercalated layers is not only affected by the intensity of the dynamic disturbance but also limited by the magnitude of the shear creep load. The influence of the dynamic disturbance intensity on the entire process of multistage shear creep damage of weak intercalated layers was analysed. With increasing of dynamic disturbance intensity, the cumulative coupled damage at the end of shear creep at all levels gradually exhibits linear evolution. The time-dependent coupling damage evolution process of weak intercalated layers was quantitatively characterized.