For combined lock and navigable tunnel structures,the discharge from the lock can induce unsteady flow propagation within the tunnel,complicating the coupling effects among vessels,water bodies,and sidewalls,thereby posing greater challenges to the determination of tunnel dimensions.Taking the 1,000-ton-class navigable tunnel of the Shatuo Second Line on the Wujiang River as the study subject,a 120 normal physical model combined with self-propelled vessel models is employed to conduct experiments on hydraulic characteristics of unsteady flow.The study systematically monitors water level fluctuations,spatiotemporal distribution of flow velocity,and evolution characteristics of flow patterns in the tunnel and connected open channel under both still water conditions and lock discharge impacts,and analyzes the influence laws of unsteady flow on vessel navigation.The experimental results show that during discharge,the peak values of water level and flow velocity occur synchronously,exhibiting a single-peak feature of instantaneous surge and rapid decay.After discharge completion and gate opening,the water waves in the tunnel rapidly flatten without persistent oscillation,which means the interference to navigation is short-term.Additionally,installing a flow-stabilizing trough inside the tunnel can effectively suppress wave height and water level fluctuations.There is no significant difference in vessel navigation parameters compared to still water conditions.A bank speed of 1.0 m/s is recommended to ensure safe navigation.