Spatial motion patterns and force transmission characteristics of muck particles in EPB shield tunneling: An FDM–DEM coupling analysis

This is the authors' abstract. We don't add key points for this paper.

• A novel gradient stress strategy using a rigid wall boundary is proposed, greatly improving DEM-FDM simulation accuracy. • A refined DEM-FDM tunneling model is established, simulating soil conditioning in the chamber and ahead of the cutterhead. • Pressure distribution and load transfer in the chamber and at the face are revealed; full-chamber under-pressure mode is advised. • Muck particle movement during EPB tunneling is studied; clogging zones ahead of and inside the chamber are identified. Earth pressure balance (EPB) shield tunneling in sandy cobble strata often encounters challenges such as muck stagnation, severe tool wear, difficulties in chamber pressure control, and low excavation efficiency. To address these issues, this study proposes a novel gradient stress construction strategy based on rigid wall boundaries by integrating the finite difference method (FDM) and the discrete element method (DEM), and establishes a refined FDM–DEM coupled shield tunneling model. Using this model, the pressure distribution and load transfer mechanisms at the excavation face and within the chamber, as well as the motion trajectories, velocities, and spatial distribution of muck particles, are analyzed in detail. The results indicate that: (1) The pressure at the cutterhead spokes is lower than that at the cutterhead openings; the muck pressure within the chamber exhibits significant radial gradient variations, with distinct differences between the left and right sides. (2) The average pressure in the upper regions of both the left and right sides of the chamber is nearly equal, with a stable pressure transmission coefficient of approximately 0.8. An under-pressure advancement strategy is recommended to avoid ground heave. (3) The muck particles follow spiral trajectories, forming dual-vortex stagnation zones in the central region of the cutterhead (0–0.2 D , where D denotes the cutterhead diameter) and the support column region of the chamber (0–0.25 D ). The installation of radial mixing rods on the cutterhead shaft is suggested to improve muck flowability. This study provides new insights for optimizing cutterhead and chamber design, offering significant implications for enhancing the efficiency of shield tunneling construction.