Study on load characteristics and crown displacement deformation prediction of arched tunnels under multi-point explosion

Multi-point simultaneous detonation typically involves the interaction of multiple shock waves, which leads to the formation of complex shock wave systems and presents significant risks to the safety of urban underground spaces. To investigate the dynamic response characteristics of underground tunnel structures under multi-point explosions, this study employs scaled model experiments, numerical simulations, and theoretical analysis to examine the pressure distribution and vibration deformation patterns of arched tunnel structures under various explosive configurations. The results show that as the spacing between explosives increases, both the pressure field and the structural dynamic response initially increase before decreasing. Compared to a single concentrated charge of equivalent mass, the pressure amplification effect in the medium and far field of a seven-point explosion can reach 3–6 times, while the peak displacement at the tunnel crown increases by 2–5 times, significantly intensifying the vibration deformation effects on the structure. Moreover, the interaction of multiple shock waves accelerates the transition from spherical waves to planar waves, with increasing explosive spacing further optimizing the wave system structure of the resulting shock waves. A dynamic calculation model for underground arched tunnel structures under seven-point explosive loading is also developed, capable of predicting the extreme displacement values at the tunnel crown for any given explosive spacing. The maximum deviation from experimental data is less than 17%, and a method for determining the optimal explosive spacing under the most adverse structural conditions is proposed. This study provides valuable insights for the protection of underground civil engineering structures.