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| Theoretical and experimental study on the spalling law of tunnels subjected to underground explosion |
| LI Jie，XU Tianhan，FAN Pengxian，LI Gan，JI Yuguo，ZHAO Yuetang |
| (State Key Laboratory of Explosion and Impact and Disaster Prevention and Mitigation，Army Engineering University of PLA，Nanjing，Jiangsu 210007，China) |
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Abstract Spalling is a primary failure mode observed in underground tunnels exposed to explosion waves. The spalling laws of underground tunnels in homogeneous hard rock and fractured rock masses were analyzed using a one-dimensional wave model and a block instability model，respectively. The calculation formulas for spalling block size，spalling velocity，and critical scaled distance for spalling under different conditions were obtained. Existing explosion tests of underground tunnels were analyzed using the proposed theoretical methods. To obtain real spalling data and verify the calculating theory，a prototype explosion experiment was conducted on a U-shaped tunnel in granite. The experiment revealed the spalling damage phenomenon of the tunnel at a scaled distance of 1.03 m/kg1/3，and measured the peak particle velocities at the tunnel top，the ejection velocities of spalling blocks，and the irreversible displacements of the tunnel wall. The measured results are in good agreement with the theoretical calculation results，which verified the scientific reliability of the theoretical method.
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