Analysis of the dynamic response mechanism of utility tunnel structures with rainwater relief cabins under explosion shock waves

The utility tunnel is a critical urban infrastructure that supports stable city operations. Its complex internal layout makes it vulnerable to accidents, especially explosions, which can trigger system failures and endanger lives and property. Traditional designs use isolated cabins and pressure relief openings to reduce explosion impacts, but their protection is limited. This study proposes a new relief cabin structure that uses the rainwater storage cabin as an active chamber. A pressure relief plate directs the explosion shock wave into the water-filled cabin, reducing its destructive force. Using the Lagrange algorithm, Eulerian grids, and the multi-material ALE method, the paper analyzes how gas explosion shock waves propagate through air and water in the tunnel. An LS-DYNA-based 3D finite element model simulates shock wave transmission through water to the tunnel base and adjacent cabins. The damage, failure modes, and dynamic responses of concrete structures under shock loading are analyzed. Results show the new design outperforms traditional layouts in explosion mitigation, improving tunnel safety and resilience. This work supports engineering design and theoretical research for urban underground infrastructure.