Face stability analysis of longitudinally inclined shield tunnel considering the effect of tensile strength cut-off and pore water pressure

• The study addresses the face stability of longitudinally inclined shield tunnels, a critical issue not well covered by previous research that mainly focused on horizontal tunnels. • A novel failure mechanism is constructed using the spatial discretization technique and modified by the tensile strength cut-off criterion, enabling more accurate stability analysis. • Pore water pressure is integrated as an external force in the virtual work equation, allowing computation of the critical chamber pressure for shield machines. • The proposed approach was validated against FLAC3D numerical simulations, confirming its effectiveness and practical relevance for engineering design.