# 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
### Parameter Calibration and Cavity Stress Response
Finally, when the incident wave and the reflected wave produced by the right side's free surface acted on the cavity together, a significant compression strain also appeared on the opposite side, but it was still smaller than that on the side facing the blast. Additionally, the strain near the four sides of the parallelepiped was much greater than the strain within the cavity itself. In summary, during the plastic stage, the parallelepiped cavity is prone to develop cracks first at the four corners of the parallelepiped, which then gradually propagate to the four sides, thus initiating structural failure. As shown in Figure 10a, the propagation of stress waves to the conical cavity resulted in significant scattering. The stress waves were bifurcated by the corners facing the blast, propagating along the edges of the conical cavity to the right. Between the blasthole and the conical cavity, a larger conical region appeared with high effective stress, and the corners facing the blast exhibited significant dynamic stress concentration. Subsequently, the reflected waves generated by the free surface interacted with the incident waves simultaneously on the conical cavity, causing significant stress concentration at the three corners of the conical cavity, with the effective stress at the corner facing the blast being greater than that at the other two corners. From Figure 10b, it can be observed that when the blast stress wave reached the cavity, a significant compression strain appeared at the corner facing the blast. As the stress wave propagated, both edges of the side facing the blast also showed a considerable compression strain. Finally, when both the incident wave and the reflected wave acted on the conical cavity simultaneously, a region of significant compression strain appeared at the two corners opposite the blast, but no such strain was observed near the edges on the opposite side. Therefore, during the plastic stage, the conical cavity is prone to damage and failure at the three corners and the two sides adjacent to the blast, with most of the energy being consumed by the rock mass of the cavity on the side facing the blast, thereby protecting the structure of the cavity on the opposite side. The comprehensive analysis reveals that different cross-sectional shapes have a significant impact on the propagation of blast stress waves and the characteristics of stress and strain changes around the cavity. The circular cavity, due to its curvature, experiences only transient stress concentration at the top and bottom, and the effective strain throughout the process is far greater than that of the parallelepiped or conical cavities. This indicates that the circular cavity absorbs a large amount of blast energy for structural deformation of the cavity and subsequent cavity damage, thus reducing the energy used for the destruction of the surrounding rock mass. Therefore, the circular cavity serves as a better blast-resistant effect on the surrounding rock mass. Furthermore, both the parallelepiped and conical cavities exhibit significant stress concentration at the corners, with the effective strain of the conical cavity being less than that of the parallelepiped cavity due to the larger effective impact area of the parallelepiped cavity. However, because of the tip effect of the conical, the effective stress at the corner facing the wave is much greater than that of the parallelepiped.