Abstract: To explore the water flow diffusion process of floods in semi-enclosed underground spaces, a coupling method based on smoothed particle hydrodynamics (SPH) and discrete element method (DEM) is employed to simulate the dynamic process of flood invasion into underground bus stations. Then, a physical model experiment and numerical simulation are conducted to calibrate and validate the SPH-DEM coupling method, and the results demonstrate that the proposed method can effectively simulate the physical and mechanical processes of flood invasion into underground spaces. On this basis, the flood diffusion and evolution patterns in semi-enclosed underground space under two simulation conditions, floods from station hall and tunnel entrances, are examined, and the dynamic responses of various vehicles are analyzed. The research results indicate that: (1) In semi-enclosed underground spaces, private cars are subject to higher risks compared to buses. (2) Architectural environment around the vehicles significantly influences the evacuation and escape. (3) The specific location of the vehicles is a primary factor affecting the efficiency of evacuation and escape.

Key words: smoothed particle hydrodynamics and discrete element method coupling method, underground space, large-scale simulation, flood disaster, underground bus station