Numerical Simulation Of The Dynamic Responses And Damage Of Underground Cavern Under Multiple Explosion Sources

Underground caverns are often subjected to multiple explosions, and the stress wave interaction caused by multiple explosion sources is very complicated. To evaluate the effects of possible explosions around an underground cavern, based on a similarity model test, the finite element software LS-DYNA3D was utilized to analyze the dynamic responses and damage of underground cavern under seven combinations of concentrated charge explosion sources in three places, including the side of the vault, side arch, and sidewall. The propagation law of the blast-induced wave, the formation mechanism of the crack, and the displacement distribution characteristics of the surrounding rock were presented, and the damage of the cavern was described according to the peak displacement and peak particle velocity (PPV) of the measurement points located on the cavern wall. Besides, the effects of rock bolt reinforcement on the anti-blast performance of the cavern were also studied. The research results indicate that when the compressive wave propagates to the free surfaces of the ground and cavern, it will reflect and generate the tensile wave, and then the tensile wave will cause spalling in the surrounding rock. Due to the interaction of the tensile wave, different forms of crack will occur in the surrounding rock. The main difference of the crack distribution between the single explosion source cases and multiple explosion sources cases lies in the middle part of the two explosion sources. The stress wave intensity, peak displacement, and PPV of the surrounding rock at the superposition of stress waves are obviously larger than those of other rock mass. The peak displacement, PPV, and damage of the surrounding rock increase with the increasing explosion source number. Furthermore, the damage assessment of the cavern evaluated by the single degree of freedom (SDOF) method agrees well with the result of the PPV empirical damage criteria. Compared with the unanchored cavern, the peak displacement of the bolt-supported cavern is significantly reduced, and the crack development changes from transverse to axial along the rock bolt direction in the reinforced area, and the blast resistant performance of the surrounding rock is improved. The research results can provide valuable references and basis for the anti-explosion design of underground defensive projects.