Abstract: Considering the two-dimensional seepage effect of chamber of earth pressure balance shield, the spewing problem of earth pressure balance shield is analyzed by using an analytical method. The seepage field of chamber is divided into two regions, and the water head of the chamber is obtained in the form of an explicit hierarchical solution by using the method of separation variables and combining the conditions of continuity between regions. The flow in the screw conveyor is regarded as one-dimensional seepage, and the analytical solution of the seepage field of the shield is obtained based on the water flow and head continuity conditions at the intersection of the chamber and the screw conveyor. The analytical solutions of the seepage field of the chamber and the screw conveyor are compared with the numerical software calculation results and test results respectively, and the results are in good agreement to verify the correctness of the solution. Analyzing the impact of shield and soil parameters on the screw conveyor discharge water flow and water pressure, it is found that a water pressure difference of 0 between the inside and outside of the soil discharge port of the screw conveyor, there is an approximately linear relationship between the screw conveyor water flow and water pressure and water head at cutter surface center; increasing the length of the screw conveyor and inclination angle, and reducing the diameter of the screw conveyor are conducive to prevent spewing. Based on the existing research results of the spewing, a typical shield spewing discriminant map is given. Through discriminating the shield spewing example, and comparing it with the spewing discrimination results of one-dimensional analytical solution of the shield, it is proved that discrimination based on this analytical solution is more accurate.

Key words: earth pressure balance shield (EPBS), spewing, groundwater flow, water pressure, screw conveyor