Cumulative damage effect and stability analysis of the rock slope with a locked segment under cyclic blasting

There are many microcracks and micropores in the rock, which will initiate, propagate, and coalescence under dynamic loading, leading to rock instability and failure. When blasting excavation is carried out, the retained rock mass will be subjected to the dynamic loading generated by cyclic blasting, resulting in cumulative damage, which will lead to the reduction of the rock mass strength, and even failure. In order to simulate this physical process, the existing rock dynamic damage constitutive model, which could perfectly describe the rock dynamic damage induced by blasting, was embedded into FLAC through secondary development to analyze the cumulative damage of rock mass under cyclic blasting. And then it was adopted to simulate the damage effect and stability of the rock slope with the locked segment under cyclic blasting. The stability of the slope under cyclic blasting was determined by the displacement criterion method, and the safety factor of the slope after each blasting was obtained by the strength reduction method. Finally, the relationship between the failure mode and stability of the slope and the location of the locked segment was discussed by analyzing the damage, displacement field, and safety factor of the numerical models for different locations of the locked segment in the soft interlayer. The results show that the slope stability gradually decreases with increasing the number of cyclic blasting after considering the cumulative damage effect of the rock slope. For the rock slope with the locked segment, the damage of the locked segment firstly occurs at both ends, and then propagates to the middle, in which the rock mass shows a progressive failure mode. Because the cumulative damage of the rock slope is considered, the safety factor of the slope will decrease after each blasting. When the cumulative damage is not considered, the safety factor of the slope is basically unchanged. The failure mode of the rock slope with a locked segment under cyclic blasting is the combination of dynamic tensile failure and shear failure caused by rock mass slip. The location of the locked segment in the weak interlayer affects the failure mode and stability of the slope. Therefore, when carrying out similar engineering activities, the cumulative damage effect of rock mass should be considered to avoid engineering accidents.