Abstract: ［Objective］ During shield tunneling in water-bearing sand layers, due to abundant groundwater and high soil permeability, screw conveyors are highly prone to blowout incidents. If control measures are inadequate, serious construction safety accidents may occur. Therefore, it is essential to study a blowout risk assessment method for screw conveyors in EPB (earth pressure balance) shield tunneling through water-bearing sandy strata. ［Method］ A pressure gradient model of the excavation chamber and screw conveyor is established, simplifying the water flow channel in EPB shield to a two-dimensional plane problem. Based on Darcy′s law, fluid in the pressure chamber is considered to undergo two-dimensional Darcy flow through a porous medium, while the fluid in the screw conveyor will undergo one-dimensional Darcy flow. By incorporating boundary conditions, a combined finite difference-analytical solution method is applied to calculate the head-discharge curve at the screw conveyor outlet under specified water pressure conditions in the soil chamber. A blowout risk classification method for screw conveyors is proposed. Four critical states and five risk zones are defined according to water height and inflow volume at the screw conveyor outlet, they are classified as Level Ⅰ, Ⅱ, Ⅲ, and Ⅳ risk zones, and a safety zone respectively. A classification standard and zoning-grading method for blowout risk of screw conveyors is established. Taking the shield interval between Lyuboyuan Station and Binjiang Park Station on Nanjing Metro Line 9 as an example, which crosses the Yangtze River floodplain area, a screw conveyor blowout risk level classification is carried out on the interval, forming a risk unit chain for blowout assessment. ［Result & Conclusion］ In this shield interval, six construction unit chains with varying screw conveyor blowout risk levels are identified, covering three risk levels. Among which, the segment of Level I risk measures approximately 408 m, Level II about 463 m, and the no-risk zone about 241 m, accounting for 36.69%, 41.64%, and 21.67% of the total length, respectively. Given the high blowout risk and long construction distance during the interval construction, differentiated anti-blowout measures should be adopted for different risk levels to ensure safe and efficient shield tunneling.