Influence of the Cutterhead Configuration and Operation Parameters on the Face Stability of EPB Shield Tunnels in Dry Granular Soils

Abstract

This paper presents a study on the face stability of earth pressure balance (EPB) shield tunnels in dry granular soils using the discrete element model (DEM) method to replicate realistic excavation processes of the EPB machine. Analyses were conducted at different buried depths to determine the limit face pressures and the face failure model induced by the EPB shield machine with varying open ratios and rotation speeds of the cutterhead. The failure kinematics of the soil and the soil arching effect were also determined. The results showed that both the open ratio and the rotation speed of the cutterhead have significant effects on the stability of the face in terms of the failure kinematics, limit face pressures, and the soil arching effect. The failure zone was highly dependent on the open ratio, but it depended less on the rotation speed of the cutterhead. The stability of the face is overestimated when the excavation is conducted with a cutterhead that has a large open ratio, but it is underestimated when the excavation is conducted with a cutterhead that has a smaller open ratio. Ignoring the effect of the configuration of the cutterhead and the rotation speed results in unexpected and unrealistic results.