Three-dimensional large-deformation modelling of active face failure incorporating dynamic cutterhead-soil interaction during EPB shield tunnelling

Earth Pressure Balance (EPB) tunnelling approach plays a vital role in the construction of underground infrastructure in densely populated urban environments. However, one of its most critical challenges is ensuring tunnel face stability during excavation, particularly in soft soils. Face instability can lead to severe ground deformation and potential hazards such as collapse. Traditional analytical and numerical studies often overlook the dynamic cutterhead-soil interaction, simplifying the excavation process and potentially underestimating failure risks. To address this gap, the present study develops a robust three-dimensional Coupled Eulerian–Lagrangian (CEL) large-deformation computational framework to investigate the active failure mechanisms of tunnel faces incorporate dynamic cutterhead-soil interaction. The CEL approach effectively captures the complex large strain behavior of clayey soils excavated by the rotating cutterhead, by combining the advantages of Eulerian and Lagrangian descriptions. The model explicitly incorporates key excavation variables—including cutterhead rotation, opening ratio (ζ), and tunnel cover depth—and systematically evaluates their effects on face support pressure re-quirements and failure mechanisms. Results reveal that dynamic excavation significantly alters the stress distribution and deformation patterns at the tunnel face. Neglecting these effects can lead to overestimated face stability, posing serious risks to construction safety. Among the inves-tigated parameters, the cutterhead opening ratio emerges as a particularly influential factor: smaller opening ratios provide enhanced mechanical confinement and lead to more stable face conditions, whereas larger opening ratios facilitate greater soil inflow and compromise face in-tegrity. The proposed CEL computational framework not only advances the understanding of tun-nel face behavior under realistic EPB excavation scenarios but also enables more efficient cutter-head design and more reliable support pressure control in practice. These findings offer valuable insights for minimizing ground disturbance and enhancing operational safety during practical EPB shield tunnelling in clayey ground.