Numerical Simulation of the Dynamic Responses and Cumulative Damage of Underground Caverns under Multiple Explosions

Attacking underground caverns with earth-penetrating bombs usually involves multiple explosions in succession. To assess the dynamic responses and cumulative damage of underground caverns under multiple explosions, based on a reduced-scale physical model test, the modified Riedel–Hiermaier–Thoma (RHT) model in the finite-element software LS-DYNA is used to build an underground cavern model that encounters four explosions above the vault. The characteristics of the stress wave attenuation and the evolution laws for the cumulative damage of the surrounding rock in the process of the four explosions are presented. Also, the displacement of the vault, the strain of the cavern wall, and the damage of a rock bolt-supported cavern and an unanchored cavern are compared. The results indicate that the peak pressure is attenuated increasingly in the latter three explosions. The circumferential strain of the cavern wall changes from tensile to compressive from the vault to the corner. The damage of the surrounding rock on the left and right sides of the explosion source is attenuated with increasing distance from the explosion source, and the attenuation curve has a reverse “S” shape. Moreover, the attenuation rate of the curve decreases with each explosion. Multiple explosions do not affect the size of the crushed zone, but they do increase the range of the fracture zone. With each explosion, the cumulative damage of the surrounding rock increases irreversibly, but the damage increment decreases. The cumulative damage of the surrounding rock exhibits a highly nonlinear relationship with successive explosions, and the effect of the rock bolt reinforcement becomes more obvious with successive explosions. Accordingly, the present research results offer a reference for antiexplosion design and support the optimization of underground engineering.