Influence Mechanisms of Earth Pressure Balance Shield Tunneling Parameters on Chamber Pressure and Surface Settlement: A Theoretical and FDM-DEM Coupled Analysis

In earth pressure balance (EPB) shield tunneling, chamber pressure control is essential for maintaining excavation-face stability and limiting surface settlement. However, the influence mechanisms of key tunneling parameters on chamber pressure and ground response remain difficult to clarify when soil conditioning, cutterhead squeezing, muck discharge, and ground deformation are considered together. To address this issue, this study establishes a theoretical mechanical model for EPB shield tunneling and develops a calibrated three-dimensional FDM–DEM coupled numerical model based on the Jinan Metro Line 6 project. Triaxial and slump tests were used to calibrate the macro–micro parameters of unconditioned and foam-conditioned soil. The effects of tunneling speed, cutterhead speed, and screw conveyor speed on chamber pressure distribution and surface settlement were then analyzed. The results show that tunneling speed mainly affects the overall chamber pressure and face-support condition, screw conveyor speed controls muck discharge and pressure release, and cutterhead speed influences the spatial distribution of chamber pressure and settlement response. This study provides a theoretical and numerical basis for understanding chamber pressure evolution and coordinating tunneling parameters in EPB shield construction.