# Dynamic Response and Rock Damage of Different Shapes of Cavities under Blasting Loads
## 4 Numerical Simulation Study on the Response and Fracture Characteristics of Cavity Blasting
### Three-Dimensional Numerical Modeling and Damage Characteristics of Cavities
The damage situations of different cross-sectional cavity numerical models under blasting are shown in Figure 13. From Figure 13, it can be seen that the shape of the blast cavity within the rock mass model has not changed significantly with the variation in the shape of the cavity cross-section. This indicates that these conditions are set at a considerable distance, and they have little effect on the compressive and shearing destructive actions in the blasting crushing zone. At the five free surfaces near the explosive, under the action of blasting, there have been obvious tensile failure cracks, and these cracks exhibit variations in shape under different conditions. Figure 13: _Cont._  
To analyze the effects of blasting further statistically under different conditions, the information files from the simulations can be used to count the unit failure in the rock mass model. This allows us to understand the development of rock mass damage and the final damage effects during the rock blasting simulation process. Table 5 shows the number of failed units and the ratio of failed units to the total number of units for all models up to 20 ms, reflecting the impact of different conditions on the rock mass damage effects. The proportion of failed units in the parallelepiped cavity is slightly greater than that of the conical cavity and much greater than that of the circular cavity. Additionally, the proportion of failed units in the intact model is less than that of the parallelepiped and conical cavities but greater than that of the circular cavity. This means that the circular cavity absorbs more blast energy, hinders rock mass damage, and reduces the degree of rock mass destruction, while the parallelepiped and conical cavities promote rock mass damage. This is because parallelepiped and conical shapes have significant dynamic stress concentration at their corners, which induces damage and fractures in the cavities. From Figure 13, it can be observed that the cracks produced by the parallelepiped and conical cavities connect with the blasting crushing zone area, and the main cracks in the parallelepiped and conical cavities are more likely to be more likely  
cavities occur on the blast-facing side, which is consistent with the results of the two-dimensional numerical model. However, due to the larger effective incoming area of the parallelepiped compared to the conical, the area between the blastholes and the cavities experiences significant reflection and scattering of stress waves, thereby intensifying the damage to the rock mass in that area. Moreover, the average block sizes of the spherical, conical, and parallelepiped cavities in the experimental results are consistent with the numerical simulation results. This indicates that the spherical cavity hinders the blast stress wave from damaging the rock mass, while the conical and parallelepiped cavities promote the blasting damage to the rock mass.