Tunnel leakage facilitates the transport of sand particles into the tunnel, initiating suffusion. Although train vibrations significantly influence particle-fluid interactions around tunnels, their impact on suffusion remains incompletely understood. This study employs an improved discrete element method (DEM) coupled with the pore network method (PNM) to simulate suffusion in gap-graded soil under both vibratory and static conditions. Results suggest that vibration exacerbates the suffusion around tunnels, resulting in more mass loss compared to static case. The force chains around the defect seam are continuously undermined and reconfigured under the influence of vibration. Vibration significantly reduces the number of stable force chains in the soil, decreasing the potential for pore clogging. The findings of this study offer crucial insights into suffusion under vibration from force-chain evolution perspective, and provide a foundation for developing erosion constitutive laws.